Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Glenn Schmottlach]

Hi Ruslan -

> I applied your patches, but WIN10 still can't recognize it well.
> The UAC1 is OK for WIN10 with the below same configuration.
> Any debug information you would like to know to check it?

> if [ "$FUNC" =3D=3D "uac2" ]; then
> mkdir functions/$FUNC".0"
> echo 2 > functions/$FUNC".0"/p_ssize
> echo 48000 > functions/$FUNC".0"/p_srate
> echo 3 > functions/$FUNC".0"/p_chmask
>
> echo 2 > functions/$FUNC".0"/c_ssize
> echo 48000 > functions/$FUNC".0"/c_srate
> echo 3 > functions/$FUNC".0"/c_chmask
> #echo 4 > functions/$FUNC".0"/req_number
> ln -s functions/$FUNC".0" configs/c.1
> echo high-speed > /sys/kernel/config/usb_gadget/g1/max_speed

I too applied your patch and configured my UAC2 gadget with the
following pertinent parameters:

mkdir -p "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0"
echo "${req_number:-4}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/req_number"
echo "${c_ssize:-4}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_ssize"
echo "${c_srate:-48000}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_srate"
echo "${c_chmask:-0xFFFFFFFF}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_chmask"
echo "${c_sync:-adaptive}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_sync"
echo "${p_ssize:-4}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_ssize"
echo "${p_srate:-48000}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_srate"
echo "${p_chmask:-0xFFFFFFFF}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_chmask"

Unfortunately, under Windows 10 I get the following error loading the driver:

This device cannot start. ( Problem Code 10)
Problem Status: C0440022

So the generic Windows (Thesycon) UAC2 driver appears to fail loading
the Linux UAC2 gadget device. Can you share with us your configuration
or how you tested this with Windows 10? I tested audio capture with
another Linux PC running Audacity and it was correctly detected and
seemed to work. I'm hoping it's a simple misconfiguration issue. Can
you offer suggestions?

Thanks,

Glenn

[PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Ruslan Bilovol]

Current UAC2 gadget implements capture/sync paths
as two USB ISO ASYNC endpoints (IN and OUT).

This violates USB spec which says that ISO ASYNC OUT endpoint
should have feedback companion endpoint.
See USB2.0 spec  "5.12.4.1 Synchronization Type": asynchronous
sink provides explicit feedback (isochronous pipe).
Interesting that for ISO ASYNC *IN* endpoint respective
feedback isn't required since source provides implicit
feedforward (data stream).

While it's not an issue if UAC2 Gadget is connected to
Linux host (Linux ignores missing feedback endpoint),
with other hosts like Windows or MacOS the UAC2 Gadget
isn't enumerated due to missing feedback endpoint.

This patch series adds feedback endpoint support to
UAC2 function, new control to UAC2 mixer which can
be used by userspace tools (like alsaloop from alsa-utils)
for updating feedback frequency reported to the host.
This is useful for usecases when UAC2 Gadget's audio
samples are played to another codec or audio card
with its own internal freerunning clock so host can
be notified that more/less samples are required.

The alsaloop tool requires some (relatively small)
modifications in order to start support driving
feedback frequency through UAC2 mixer control.
That change will be sent as a separate patch
to ALSA community.

Also added ability to switch ISO ASYNC OUT endpoint into
adaptive endpoint which doesn't require feedback endpoint
(as per USB spec).

Ruslan Bilovol (3):
  usb: gadget: f_uac2/u_audio: add feedback endpoint support
  usb: gadget: f_uac2: add adaptive sync support for capture
  usb: gadget: u_audio: add real feedback implementation

 Documentation/ABI/testing/configfs-usb-gadget-uac2 |   1 +
 Documentation/usb/gadget-testing.rst               |   1 +
 drivers/usb/gadget/function/f_uac2.c               | 118 ++++++++++-
 drivers/usb/gadget/function/u_audio.c              | 217 ++++++++++++++++++++-
 drivers/usb/gadget/function/u_audio.h              |  10 +
 drivers/usb/gadget/function/u_uac2.h               |   2 +
 6 files changed, 345 insertions(+), 4 deletions(-)

-- 
1.9.1

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Peter Chen]

On 20-11-08 02:18:28, Ruslan Bilovol wrote:
> Current UAC2 gadget implements capture/sync paths
> as two USB ISO ASYNC endpoints (IN and OUT).
> 
> This violates USB spec which says that ISO ASYNC OUT endpoint
> should have feedback companion endpoint.
> See USB2.0 spec  "5.12.4.1 Synchronization Type": asynchronous
> sink provides explicit feedback (isochronous pipe).
> Interesting that for ISO ASYNC *IN* endpoint respective
> feedback isn't required since source provides implicit
> feedforward (data stream).
> 
> While it's not an issue if UAC2 Gadget is connected to
> Linux host (Linux ignores missing feedback endpoint),
> with other hosts like Windows or MacOS the UAC2 Gadget
> isn't enumerated due to missing feedback endpoint.
> 
> This patch series adds feedback endpoint support to
> UAC2 function, new control to UAC2 mixer which can
> be used by userspace tools (like alsaloop from alsa-utils)
> for updating feedback frequency reported to the host.
> This is useful for usecases when UAC2 Gadget's audio
> samples are played to another codec or audio card
> with its own internal freerunning clock so host can
> be notified that more/less samples are required.
> 
> The alsaloop tool requires some (relatively small)
> modifications in order to start support driving
> feedback frequency through UAC2 mixer control.
> That change will be sent as a separate patch
> to ALSA community.
> 
> Also added ability to switch ISO ASYNC OUT endpoint into
> adaptive endpoint which doesn't require feedback endpoint
> (as per USB spec).
> 
> Ruslan Bilovol (3):
>   usb: gadget: f_uac2/u_audio: add feedback endpoint support
>   usb: gadget: f_uac2: add adaptive sync support for capture
>   usb: gadget: u_audio: add real feedback implementation

Hi Ruslan,

I applied your patches, but WIN10 still can't recognize it well.
The UAC1 is OK for WIN10 with the below same configuration.
Any debug information you would like to know to check it?


if [ "$FUNC" == "uac2" ]; then
mkdir functions/$FUNC".0"
echo 2 > functions/$FUNC".0"/p_ssize
echo 48000 > functions/$FUNC".0"/p_srate
echo 3 > functions/$FUNC".0"/p_chmask

echo 2 > functions/$FUNC".0"/c_ssize
echo 48000 > functions/$FUNC".0"/c_srate
echo 3 > functions/$FUNC".0"/c_chmask
#echo 4 > functions/$FUNC".0"/req_number
ln -s functions/$FUNC".0" configs/c.1
echo high-speed > /sys/kernel/config/usb_gadget/g1/max_speed
fi

-- 

Thanks,
Peter Chen

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Ruslan Bilovol]

On Wed, Nov 11, 2020 at 11:30 AM Peter Chen <peter.chen@nxp.com> wrote:
>
> On 20-11-08 02:18:28, Ruslan Bilovol wrote:
> > Current UAC2 gadget implements capture/sync paths
> > as two USB ISO ASYNC endpoints (IN and OUT).
> >
> > This violates USB spec which says that ISO ASYNC OUT endpoint
> > should have feedback companion endpoint.
> > See USB2.0 spec  "5.12.4.1 Synchronization Type": asynchronous
> > sink provides explicit feedback (isochronous pipe).
> > Interesting that for ISO ASYNC *IN* endpoint respective
> > feedback isn't required since source provides implicit
> > feedforward (data stream).
> >
> > While it's not an issue if UAC2 Gadget is connected to
> > Linux host (Linux ignores missing feedback endpoint),
> > with other hosts like Windows or MacOS the UAC2 Gadget
> > isn't enumerated due to missing feedback endpoint.
> >
> > This patch series adds feedback endpoint support to
> > UAC2 function, new control to UAC2 mixer which can
> > be used by userspace tools (like alsaloop from alsa-utils)
> > for updating feedback frequency reported to the host.
> > This is useful for usecases when UAC2 Gadget's audio
> > samples are played to another codec or audio card
> > with its own internal freerunning clock so host can
> > be notified that more/less samples are required.
> >
> > The alsaloop tool requires some (relatively small)
> > modifications in order to start support driving
> > feedback frequency through UAC2 mixer control.
> > That change will be sent as a separate patch
> > to ALSA community.
> >
> > Also added ability to switch ISO ASYNC OUT endpoint into
> > adaptive endpoint which doesn't require feedback endpoint
> > (as per USB spec).
> >
> > Ruslan Bilovol (3):
> >   usb: gadget: f_uac2/u_audio: add feedback endpoint support
> >   usb: gadget: f_uac2: add adaptive sync support for capture
> >   usb: gadget: u_audio: add real feedback implementation
>
> Hi Ruslan,
>
> I applied your patches, but WIN10 still can't recognize it well.
> The UAC1 is OK for WIN10 with the below same configuration.
> Any debug information you would like to know to check it?
>
>
> if [ "$FUNC" == "uac2" ]; then
> mkdir functions/$FUNC".0"
> echo 2 > functions/$FUNC".0"/p_ssize
> echo 48000 > functions/$FUNC".0"/p_srate
> echo 3 > functions/$FUNC".0"/p_chmask
>
> echo 2 > functions/$FUNC".0"/c_ssize
> echo 48000 > functions/$FUNC".0"/c_srate
> echo 3 > functions/$FUNC".0"/c_chmask
> #echo 4 > functions/$FUNC".0"/req_number
> ln -s functions/$FUNC".0" configs/c.1
> echo high-speed > /sys/kernel/config/usb_gadget/g1/max_speed
> fi
>

Hmm... I just tested below config and it works fine with my Win10.
The only thing I noticed is Windows doesn't enable UAC2 gadget
by default, but this can be done from Win10 sound settings

--------------------------------->8--------------------------------------
mkdir cfg
mount none cfg -t configfs
mkdir cfg/usb_gadget/g1
cd cfg/usb_gadget/g1
mkdir configs/c.1
mkdir functions/uac2.0

# 44.1 kHz sample rate
echo 44100 > functions/uac2.0/c_srate
echo 44100 > functions/uac2.0/p_srate

mkdir strings/0x409
mkdir configs/c.1/strings/0x409
echo 0x0101 > idProduct
echo 0x1d6b > idVendor
echo my-serial-num > strings/0x409/serialnumber
echo my-manufacturer > strings/0x409/manufacturer
echo "Test gadget" > strings/0x409/product
echo "Conf 1" > configs/c.1/strings/0x409/configuration
echo 120 > configs/c.1/MaxPower
ln -s functions/uac2.0 configs/c.1
echo musb-hdrc.0 > UDC
--------------------------------->8--------------------------------------

Thanks,
Ruslan

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Glenn Schmottlach]

On Thu, Nov 12, 2020 at 6:20 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
>
> On Wed, Nov 11, 2020 at 11:30 AM Peter Chen <peter.chen@nxp.com> wrote:
> >
> > On 20-11-08 02:18:28, Ruslan Bilovol wrote:
> > > Current UAC2 gadget implements capture/sync paths
> > > as two USB ISO ASYNC endpoints (IN and OUT).
> > >
> > > This violates USB spec which says that ISO ASYNC OUT endpoint
> > > should have feedback companion endpoint.
> > > See USB2.0 spec  "5.12.4.1 Synchronization Type": asynchronous
> > > sink provides explicit feedback (isochronous pipe).
> > > Interesting that for ISO ASYNC *IN* endpoint respective
> > > feedback isn't required since source provides implicit
> > > feedforward (data stream).
> > >
> > > While it's not an issue if UAC2 Gadget is connected to
> > > Linux host (Linux ignores missing feedback endpoint),
> > > with other hosts like Windows or MacOS the UAC2 Gadget
> > > isn't enumerated due to missing feedback endpoint.
> > >
> > > This patch series adds feedback endpoint support to
> > > UAC2 function, new control to UAC2 mixer which can
> > > be used by userspace tools (like alsaloop from alsa-utils)
> > > for updating feedback frequency reported to the host.
> > > This is useful for usecases when UAC2 Gadget's audio
> > > samples are played to another codec or audio card
> > > with its own internal freerunning clock so host can
> > > be notified that more/less samples are required.
> > >
> > > The alsaloop tool requires some (relatively small)
> > > modifications in order to start support driving
> > > feedback frequency through UAC2 mixer control.
> > > That change will be sent as a separate patch
> > > to ALSA community.
> > >
> > > Also added ability to switch ISO ASYNC OUT endpoint into
> > > adaptive endpoint which doesn't require feedback endpoint
> > > (as per USB spec).
> > >
> > > Ruslan Bilovol (3):
> > >   usb: gadget: f_uac2/u_audio: add feedback endpoint support
> > >   usb: gadget: f_uac2: add adaptive sync support for capture
> > >   usb: gadget: u_audio: add real feedback implementation
> >
> > Hi Ruslan,
> >
> > I applied your patches, but WIN10 still can't recognize it well.
> > The UAC1 is OK for WIN10 with the below same configuration.
> > Any debug information you would like to know to check it?
> >
> >
> > if [ "$FUNC" == "uac2" ]; then
> > mkdir functions/$FUNC".0"
> > echo 2 > functions/$FUNC".0"/p_ssize
> > echo 48000 > functions/$FUNC".0"/p_srate
> > echo 3 > functions/$FUNC".0"/p_chmask
> >
> > echo 2 > functions/$FUNC".0"/c_ssize
> > echo 48000 > functions/$FUNC".0"/c_srate
> > echo 3 > functions/$FUNC".0"/c_chmask
> > #echo 4 > functions/$FUNC".0"/req_number
> > ln -s functions/$FUNC".0" configs/c.1
> > echo high-speed > /sys/kernel/config/usb_gadget/g1/max_speed
> > fi
> >
>
> Hmm... I just tested below config and it works fine with my Win10.
> The only thing I noticed is Windows doesn't enable UAC2 gadget
> by default, but this can be done from Win10 sound settings
>
> --------------------------------->8--------------------------------------
> mkdir cfg
> mount none cfg -t configfs
> mkdir cfg/usb_gadget/g1
> cd cfg/usb_gadget/g1
> mkdir configs/c.1
> mkdir functions/uac2.0
>
> # 44.1 kHz sample rate
> echo 44100 > functions/uac2.0/c_srate
> echo 44100 > functions/uac2.0/p_srate
>
> mkdir strings/0x409
> mkdir configs/c.1/strings/0x409
> echo 0x0101 > idProduct
> echo 0x1d6b > idVendor
> echo my-serial-num > strings/0x409/serialnumber
> echo my-manufacturer > strings/0x409/manufacturer
> echo "Test gadget" > strings/0x409/product
> echo "Conf 1" > configs/c.1/strings/0x409/configuration
> echo 120 > configs/c.1/MaxPower
> ln -s functions/uac2.0 configs/c.1
> echo musb-hdrc.0 > UDC
> --------------------------------->8--------------------------------------
>
> Thanks,
> Ruslan

Hi Ruslan -

With your configuration (above) Win10 was able to recognize and load
the driver. What appears to prevent my configuration from loading is
the fact that I selected 48K as my sample rate and my capture/playback
channel mask includes more than two (2) channels. If I take your
configuration and change the sample rate (c_srate/p_srate) to 48000
Windows will fail to load the driver. Likewise, setting the
c_chmask/p_chmask to 7 (three channels) will also cause the driver to
fail to load.

You mentioned there is an option in Win10 Sound Settings to "enable"
UAC2 by default. I cannot find that option and I wonder if this is
what is preventing me from changing the sample rate or channel mask?
Could Windows be treating my audio gadget as a UAC1 device rather than
a fully multi-channel audio device (even though the usbaudio2.sys
driver is loaded)? Have you tried other configurations to verify your
Win10 box supports more than two channels and a 44.1K sample rate? I
look forward to your feedback and any suggestions you might offer.

Thanks,

Glenn

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Ruslan Bilovol]

On Fri, Nov 13, 2020 at 5:35 PM Glenn Schmottlach
<gschmottlach@gmail.com> wrote:
>
> On Thu, Nov 12, 2020 at 6:20 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
> >
> > On Wed, Nov 11, 2020 at 11:30 AM Peter Chen <peter.chen@nxp.com> wrote:
> > >
> > > On 20-11-08 02:18:28, Ruslan Bilovol wrote:
> > > > Current UAC2 gadget implements capture/sync paths
> > > > as two USB ISO ASYNC endpoints (IN and OUT).
> > > >
> > > > This violates USB spec which says that ISO ASYNC OUT endpoint
> > > > should have feedback companion endpoint.
> > > > See USB2.0 spec  "5.12.4.1 Synchronization Type": asynchronous
> > > > sink provides explicit feedback (isochronous pipe).
> > > > Interesting that for ISO ASYNC *IN* endpoint respective
> > > > feedback isn't required since source provides implicit
> > > > feedforward (data stream).
> > > >
> > > > While it's not an issue if UAC2 Gadget is connected to
> > > > Linux host (Linux ignores missing feedback endpoint),
> > > > with other hosts like Windows or MacOS the UAC2 Gadget
> > > > isn't enumerated due to missing feedback endpoint.
> > > >
> > > > This patch series adds feedback endpoint support to
> > > > UAC2 function, new control to UAC2 mixer which can
> > > > be used by userspace tools (like alsaloop from alsa-utils)
> > > > for updating feedback frequency reported to the host.
> > > > This is useful for usecases when UAC2 Gadget's audio
> > > > samples are played to another codec or audio card
> > > > with its own internal freerunning clock so host can
> > > > be notified that more/less samples are required.
> > > >
> > > > The alsaloop tool requires some (relatively small)
> > > > modifications in order to start support driving
> > > > feedback frequency through UAC2 mixer control.
> > > > That change will be sent as a separate patch
> > > > to ALSA community.
> > > >
> > > > Also added ability to switch ISO ASYNC OUT endpoint into
> > > > adaptive endpoint which doesn't require feedback endpoint
> > > > (as per USB spec).
> > > >
> > > > Ruslan Bilovol (3):
> > > >   usb: gadget: f_uac2/u_audio: add feedback endpoint support
> > > >   usb: gadget: f_uac2: add adaptive sync support for capture
> > > >   usb: gadget: u_audio: add real feedback implementation
> > >
> > > Hi Ruslan,
> > >
> > > I applied your patches, but WIN10 still can't recognize it well.
> > > The UAC1 is OK for WIN10 with the below same configuration.
> > > Any debug information you would like to know to check it?
> > >
> > >
> > > if [ "$FUNC" == "uac2" ]; then
> > > mkdir functions/$FUNC".0"
> > > echo 2 > functions/$FUNC".0"/p_ssize
> > > echo 48000 > functions/$FUNC".0"/p_srate
> > > echo 3 > functions/$FUNC".0"/p_chmask
> > >
> > > echo 2 > functions/$FUNC".0"/c_ssize
> > > echo 48000 > functions/$FUNC".0"/c_srate
> > > echo 3 > functions/$FUNC".0"/c_chmask
> > > #echo 4 > functions/$FUNC".0"/req_number
> > > ln -s functions/$FUNC".0" configs/c.1
> > > echo high-speed > /sys/kernel/config/usb_gadget/g1/max_speed
> > > fi
> > >
> >
> > Hmm... I just tested below config and it works fine with my Win10.
> > The only thing I noticed is Windows doesn't enable UAC2 gadget
> > by default, but this can be done from Win10 sound settings
> >
> > --------------------------------->8--------------------------------------
> > mkdir cfg
> > mount none cfg -t configfs
> > mkdir cfg/usb_gadget/g1
> > cd cfg/usb_gadget/g1
> > mkdir configs/c.1
> > mkdir functions/uac2.0
> >
> > # 44.1 kHz sample rate
> > echo 44100 > functions/uac2.0/c_srate
> > echo 44100 > functions/uac2.0/p_srate
> >
> > mkdir strings/0x409
> > mkdir configs/c.1/strings/0x409
> > echo 0x0101 > idProduct
> > echo 0x1d6b > idVendor
> > echo my-serial-num > strings/0x409/serialnumber
> > echo my-manufacturer > strings/0x409/manufacturer
> > echo "Test gadget" > strings/0x409/product
> > echo "Conf 1" > configs/c.1/strings/0x409/configuration
> > echo 120 > configs/c.1/MaxPower
> > ln -s functions/uac2.0 configs/c.1
> > echo musb-hdrc.0 > UDC
> > --------------------------------->8--------------------------------------
> >
> > Thanks,
> > Ruslan
>
> Hi Ruslan -
>
> With your configuration (above) Win10 was able to recognize and load
> the driver. What appears to prevent my configuration from loading is
> the fact that I selected 48K as my sample rate and my capture/playback
> channel mask includes more than two (2) channels. If I take your
> configuration and change the sample rate (c_srate/p_srate) to 48000
> Windows will fail to load the driver. Likewise, setting the
> c_chmask/p_chmask to 7 (three channels) will also cause the driver to
> fail to load.
>
> You mentioned there is an option in Win10 Sound Settings to "enable"
> UAC2 by default. I cannot find that option and I wonder if this is
> what is preventing me from changing the sample rate or channel mask?
> Could Windows be treating my audio gadget as a UAC1 device rather than
> a fully multi-channel audio device (even though the usbaudio2.sys
> driver is loaded)? Have you tried other configurations to verify your
> Win10 box supports more than two channels and a 44.1K sample rate? I
> look forward to your feedback and any suggestions you might offer.
>

I was able to reproduce the issue and prepared a patch below, please
try it and see if it fixes the issue.

Maximum data rates that I used were (AFAIR) 8 channel 192kHz/32bit,
but there is another issue with high data rate if someone uses so many
channels, very high sampling frequency or sample size that data can't
fit into allowed (by USB spec) max packet size of endpoint. In this case
need to decrease bInterval of endpoint.
I test it in a high-performance audio case so always use a minimal possible
bInterval (set to '1').
Of course in the future that need to be calculated dynamically depending on
the UAC2 settings

Please test patches below and see it it helps

---------------------------------------------8<----------------------------------------
From 51516435bbf2486574ec7bc9fd4726677cd474a4 Mon Sep 17 00:00:00 2001
From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
Date: Sun, 22 Nov 2020 21:05:38 +0200
Subject: [PATCH] usb: gadget: f_uac2: always increase endpoint max_packet_size
 by one audio slot

As per UAC2 Audio Data Formats spec (2.3.1.1 USB Packets),
if the sampling rate is a constant, the allowable variation
of number of audio slots per virtual frame is +/- 1 audio slot.

It means that endpoint should be able to accept/send +1 audio
slot.

Previous endpoint max_packet_size calculation code
was adding sometimes +1 audio slot due to DIV_ROUND_UP
behaviour which was rounding up to closest integer.
However this doesn't work if the numbers are divisible.

It had no any impact with Linux hosts which ignore
this issue, but in case of more strict Windows it
caused rejected enumeration

Thus always add +1 audio slot to endpoint's max packet size

Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
---
 drivers/usb/gadget/function/f_uac2.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/function/f_uac2.c
b/drivers/usb/gadget/function/f_uac2.c
index ebdb2a1..1698587 100644
--- a/drivers/usb/gadget/function/f_uac2.c
+++ b/drivers/usb/gadget/function/f_uac2.c
@@ -486,7 +486,7 @@ static void set_ep_max_packet_size(const struct
f_uac2_opts *uac2_opts,
  }

  max_packet_size = num_channels(chmask) * ssize *
- DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1)));
+ ((srate / (factor / (1 << (ep_desc->bInterval - 1)))) + 1);

  if (!is_playback && (uac2_opts->c_sync == USB_ENDPOINT_SYNC_ASYNC))
  max_packet_size = max_packet_size * FBACK_FREQ_MAX / 100;
-- 
1.9.1


---------------------------------------------8<----------------------------------------
From c8f2f2b414af672ec40841e75fb1ea761ae29122 Mon Sep 17 00:00:00 2001
From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
Date: Sun, 16 Feb 2020 22:40:23 +0200
Subject: [PATCH] usb: gadget: f_uac2: change bInterval to 1 for
 8ch/24bit/44.1kHz

With bInterval=4 one audio slot in case of 8ch/24bit/44.1kHz
exeeds MaxPacket size of ISO endpoint (>1024) and can't be
transferred in time.
USB spec ("5.6.3 Isochronous Transfer Packet Size Constraints")
says if we need to transfer more than 1024 it is a high speed, high
bandwidth endpoint and should have bInterval=1.

In the future, bInterval should be dynamically calculated
depending on bandwith requirementes

Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
---
 drivers/usb/gadget/function/f_uac2.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_uac2.c
b/drivers/usb/gadget/function/f_uac2.c
index 3633df6..fb9b875 100644
--- a/drivers/usb/gadget/function/f_uac2.c
+++ b/drivers/usb/gadget/function/f_uac2.c
@@ -281,7 +281,7 @@ enum {

  .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
  .wMaxPacketSize = cpu_to_le16(1024),
- .bInterval = 4,
+ .bInterval = 1,
 };

 /* CS AS ISO OUT Endpoint */
@@ -358,7 +358,7 @@ enum {

  .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
  .wMaxPacketSize = cpu_to_le16(1024),
- .bInterval = 4,
+ .bInterval = 1,
 };

 /* CS AS ISO IN Endpoint */
-- 
1.9.1


---------------------------------------------8<----------------------------------------

Thanks,
Ruslan

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Glenn Schmottlach]

On Sun, Nov 22, 2020 at 2:52 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
>
> On Fri, Nov 13, 2020 at 5:35 PM Glenn Schmottlach
> <gschmottlach@gmail.com> wrote:
> >
> > On Thu, Nov 12, 2020 at 6:20 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
> > >
> > > On Wed, Nov 11, 2020 at 11:30 AM Peter Chen <peter.chen@nxp.com> wrote:
> > > >
> > > > On 20-11-08 02:18:28, Ruslan Bilovol wrote:
> > > > > Current UAC2 gadget implements capture/sync paths
> > > > > as two USB ISO ASYNC endpoints (IN and OUT).
> > > > >
> > > > > This violates USB spec which says that ISO ASYNC OUT endpoint
> > > > > should have feedback companion endpoint.
> > > > > See USB2.0 spec  "5.12.4.1 Synchronization Type": asynchronous
> > > > > sink provides explicit feedback (isochronous pipe).
> > > > > Interesting that for ISO ASYNC *IN* endpoint respective
> > > > > feedback isn't required since source provides implicit
> > > > > feedforward (data stream).
> > > > >
> > > > > While it's not an issue if UAC2 Gadget is connected to
> > > > > Linux host (Linux ignores missing feedback endpoint),
> > > > > with other hosts like Windows or MacOS the UAC2 Gadget
> > > > > isn't enumerated due to missing feedback endpoint.
> > > > >
> > > > > This patch series adds feedback endpoint support to
> > > > > UAC2 function, new control to UAC2 mixer which can
> > > > > be used by userspace tools (like alsaloop from alsa-utils)
> > > > > for updating feedback frequency reported to the host.
> > > > > This is useful for usecases when UAC2 Gadget's audio
> > > > > samples are played to another codec or audio card
> > > > > with its own internal freerunning clock so host can
> > > > > be notified that more/less samples are required.
> > > > >
> > > > > The alsaloop tool requires some (relatively small)
> > > > > modifications in order to start support driving
> > > > > feedback frequency through UAC2 mixer control.
> > > > > That change will be sent as a separate patch
> > > > > to ALSA community.
> > > > >
> > > > > Also added ability to switch ISO ASYNC OUT endpoint into
> > > > > adaptive endpoint which doesn't require feedback endpoint
> > > > > (as per USB spec).
> > > > >
> > > > > Ruslan Bilovol (3):
> > > > >   usb: gadget: f_uac2/u_audio: add feedback endpoint support
> > > > >   usb: gadget: f_uac2: add adaptive sync support for capture
> > > > >   usb: gadget: u_audio: add real feedback implementation
> > > >
> > > > Hi Ruslan,
> > > >
> > > > I applied your patches, but WIN10 still can't recognize it well.
> > > > The UAC1 is OK for WIN10 with the below same configuration.
> > > > Any debug information you would like to know to check it?
> > > >
> > > >
> > > > if [ "$FUNC" == "uac2" ]; then
> > > > mkdir functions/$FUNC".0"
> > > > echo 2 > functions/$FUNC".0"/p_ssize
> > > > echo 48000 > functions/$FUNC".0"/p_srate
> > > > echo 3 > functions/$FUNC".0"/p_chmask
> > > >
> > > > echo 2 > functions/$FUNC".0"/c_ssize
> > > > echo 48000 > functions/$FUNC".0"/c_srate
> > > > echo 3 > functions/$FUNC".0"/c_chmask
> > > > #echo 4 > functions/$FUNC".0"/req_number
> > > > ln -s functions/$FUNC".0" configs/c.1
> > > > echo high-speed > /sys/kernel/config/usb_gadget/g1/max_speed
> > > > fi
> > > >
> > >
> > > Hmm... I just tested below config and it works fine with my Win10.
> > > The only thing I noticed is Windows doesn't enable UAC2 gadget
> > > by default, but this can be done from Win10 sound settings
> > >
> > > --------------------------------->8--------------------------------------
> > > mkdir cfg
> > > mount none cfg -t configfs
> > > mkdir cfg/usb_gadget/g1
> > > cd cfg/usb_gadget/g1
> > > mkdir configs/c.1
> > > mkdir functions/uac2.0
> > >
> > > # 44.1 kHz sample rate
> > > echo 44100 > functions/uac2.0/c_srate
> > > echo 44100 > functions/uac2.0/p_srate
> > >
> > > mkdir strings/0x409
> > > mkdir configs/c.1/strings/0x409
> > > echo 0x0101 > idProduct
> > > echo 0x1d6b > idVendor
> > > echo my-serial-num > strings/0x409/serialnumber
> > > echo my-manufacturer > strings/0x409/manufacturer
> > > echo "Test gadget" > strings/0x409/product
> > > echo "Conf 1" > configs/c.1/strings/0x409/configuration
> > > echo 120 > configs/c.1/MaxPower
> > > ln -s functions/uac2.0 configs/c.1
> > > echo musb-hdrc.0 > UDC
> > > --------------------------------->8--------------------------------------
> > >
> > > Thanks,
> > > Ruslan
> >
> > Hi Ruslan -
> >
> > With your configuration (above) Win10 was able to recognize and load
> > the driver. What appears to prevent my configuration from loading is
> > the fact that I selected 48K as my sample rate and my capture/playback
> > channel mask includes more than two (2) channels. If I take your
> > configuration and change the sample rate (c_srate/p_srate) to 48000
> > Windows will fail to load the driver. Likewise, setting the
> > c_chmask/p_chmask to 7 (three channels) will also cause the driver to
> > fail to load.
> >
> > You mentioned there is an option in Win10 Sound Settings to "enable"
> > UAC2 by default. I cannot find that option and I wonder if this is
> > what is preventing me from changing the sample rate or channel mask?
> > Could Windows be treating my audio gadget as a UAC1 device rather than
> > a fully multi-channel audio device (even though the usbaudio2.sys
> > driver is loaded)? Have you tried other configurations to verify your
> > Win10 box supports more than two channels and a 44.1K sample rate? I
> > look forward to your feedback and any suggestions you might offer.
> >
>
> I was able to reproduce the issue and prepared a patch below, please
> try it and see if it fixes the issue.
>
> Maximum data rates that I used were (AFAIR) 8 channel 192kHz/32bit,
> but there is another issue with high data rate if someone uses so many
> channels, very high sampling frequency or sample size that data can't
> fit into allowed (by USB spec) max packet size of endpoint. In this case
> need to decrease bInterval of endpoint.
> I test it in a high-performance audio case so always use a minimal possible
> bInterval (set to '1').
> Of course in the future that need to be calculated dynamically depending on
> the UAC2 settings
>
> Please test patches below and see it it helps
>
> ---------------------------------------------8<----------------------------------------
> From 51516435bbf2486574ec7bc9fd4726677cd474a4 Mon Sep 17 00:00:00 2001
> From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> Date: Sun, 22 Nov 2020 21:05:38 +0200
> Subject: [PATCH] usb: gadget: f_uac2: always increase endpoint max_packet_size
>  by one audio slot
>
> As per UAC2 Audio Data Formats spec (2.3.1.1 USB Packets),
> if the sampling rate is a constant, the allowable variation
> of number of audio slots per virtual frame is +/- 1 audio slot.
>
> It means that endpoint should be able to accept/send +1 audio
> slot.
>
> Previous endpoint max_packet_size calculation code
> was adding sometimes +1 audio slot due to DIV_ROUND_UP
> behaviour which was rounding up to closest integer.
> However this doesn't work if the numbers are divisible.
>
> It had no any impact with Linux hosts which ignore
> this issue, but in case of more strict Windows it
> caused rejected enumeration
>
> Thus always add +1 audio slot to endpoint's max packet size
>
> Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> ---
>  drivers/usb/gadget/function/f_uac2.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/function/f_uac2.c
> b/drivers/usb/gadget/function/f_uac2.c
> index ebdb2a1..1698587 100644
> --- a/drivers/usb/gadget/function/f_uac2.c
> +++ b/drivers/usb/gadget/function/f_uac2.c
> @@ -486,7 +486,7 @@ static void set_ep_max_packet_size(const struct
> f_uac2_opts *uac2_opts,
>   }
>
>   max_packet_size = num_channels(chmask) * ssize *
> - DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1)));
> + ((srate / (factor / (1 << (ep_desc->bInterval - 1)))) + 1);
>
>   if (!is_playback && (uac2_opts->c_sync == USB_ENDPOINT_SYNC_ASYNC))
>   max_packet_size = max_packet_size * FBACK_FREQ_MAX / 100;
> --
> 1.9.1
>
>
> ---------------------------------------------8<----------------------------------------
> From c8f2f2b414af672ec40841e75fb1ea761ae29122 Mon Sep 17 00:00:00 2001
> From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> Date: Sun, 16 Feb 2020 22:40:23 +0200
> Subject: [PATCH] usb: gadget: f_uac2: change bInterval to 1 for
>  8ch/24bit/44.1kHz
>
> With bInterval=4 one audio slot in case of 8ch/24bit/44.1kHz
> exeeds MaxPacket size of ISO endpoint (>1024) and can't be
> transferred in time.
> USB spec ("5.6.3 Isochronous Transfer Packet Size Constraints")
> says if we need to transfer more than 1024 it is a high speed, high
> bandwidth endpoint and should have bInterval=1.
>
> In the future, bInterval should be dynamically calculated
> depending on bandwith requirementes
>
> Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> ---
>  drivers/usb/gadget/function/f_uac2.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/f_uac2.c
> b/drivers/usb/gadget/function/f_uac2.c
> index 3633df6..fb9b875 100644
> --- a/drivers/usb/gadget/function/f_uac2.c
> +++ b/drivers/usb/gadget/function/f_uac2.c
> @@ -281,7 +281,7 @@ enum {
>
>   .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
>   .wMaxPacketSize = cpu_to_le16(1024),
> - .bInterval = 4,
> + .bInterval = 1,
>  };
>
>  /* CS AS ISO OUT Endpoint */
> @@ -358,7 +358,7 @@ enum {
>
>   .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
>   .wMaxPacketSize = cpu_to_le16(1024),
> - .bInterval = 4,
> + .bInterval = 1,
>  };
>
>  /* CS AS ISO IN Endpoint */
> --
> 1.9.1
>
>
> ---------------------------------------------8<----------------------------------------
>
> Thanks,
> Ruslan

Hi Ruslan -

I have had some mixed success with your additional patches. First, the
UAC2 gadget does correctly register with Windows 10 but only for 1-31
channels. For a fully specified channel map (32 channels):

c_chmask = 0xFFFFFFFF    ( Does not load)
p_chmask = 0xFFFFFFFF   ( Does not load)

the driver fails to load (code=10). This seems similar to the prior
problem. Could there be another off-by-one problem here?

With a 31 channel mask the Windows 10 usbaudio2.sys loads successfully, e.g.

c_chmask = 0x7FFFFFFF (loads)
p_chmask = 0x7FFFFFFF (loads)

Once Windows 10 loads the driver successfully, however, I can't seem
to select the device through Audacity on Windows. The device appears
in the Windows "Device Manager" under "Sound, video and game
controllers -> Source/Sink". How are you testing audio
playback/capture under Windows? Perhaps my test approach is wrong?

I used the same approach on my Linux host where the USB UAC2 device
appears as an ALSA device and I use speaker-test on the target
(BeagleBone Black) to play and then capture the audio using Audacity
on the Linux host. I was hoping to do the same or something similar
under Windows.

Below is the script I've been using on the target to configure my UAC2 device:

mkdir -p "/sys/kernel/config/usb_gadget/g_multi"
echo "${idVendor:-0x11F5}" > "/sys/kernel/config/usb_gadget/g_multi/idVendor"
echo "${idProduct:-0x0009}" > "/sys/kernel/config/usb_gadget/g_multi/idProduct"
echo "${bcdDevice:-0x0001}" > "/sys/kernel/config/usb_gadget/g_multi/bcdDevice"
echo "${bDeviceClass:-0x00}" >
"/sys/kernel/config/usb_gadget/g_multi/bDeviceClass"
echo "${bDeviceSubClass:-0x00}" >
"/sys/kernel/config/usb_gadget/g_multi/bDeviceSubClass"
echo "${bDeviceProtocol:-0x00}" >
"/sys/kernel/config/usb_gadget/g_multi/bDeviceProtocol"
echo "${bcdUSB:-0x0200}" > "/sys/kernel/config/usb_gadget/g_multi/bcdUSB"
echo "${bMaxPacketSize0:-0x00}" >
"/sys/kernel/config/usb_gadget/g_multi/bMaxPacketSize0"
mkdir -p "/sys/kernel/config/usb_gadget/g_multi/strings/0x409"
echo "${serialnumber:-000000000000}" >
"/sys/kernel/config/usb_gadget/g_multi/strings/0x409/serialnumber"
echo "${product:-UAC2}" >
"/sys/kernel/config/usb_gadget/g_multi/strings/0x409/product"
echo "${manufacturer:-www.acme.com}" >
"/sys/kernel/config/usb_gadget/g_multi/strings/0x409/manufacturer"
mkdir -p "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0"
echo "${req_number:-4}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/req_number"
echo "${c_ssize:-4}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_ssize"
echo "${c_srate:-48000}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_srate"
echo "${c_chmask:-0x00000003}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_chmask"
echo "${c_sync:-asynchronous}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_sync"
echo "${p_ssize:-4}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_ssize"
echo "${p_srate:-48000}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_srate"
echo "${p_chmask:-0x00000003}" >
"/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_chmask"
mkdir -p "/sys/kernel/config/usb_gadget/g_multi/configs/c.1"
echo "${bmAttributes:-0x80}" >
"/sys/kernel/config/usb_gadget/g_multi/configs/c.1/bmAttributes"
echo "${MaxPower:-500}" >
"/sys/kernel/config/usb_gadget/g_multi/configs/c.1/MaxPower"
mkdir -p "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/strings/0x409"
echo "${configuration:-BeagleBone Composite}" >
"/sys/kernel/config/usb_gadget/g_multi/configs/c.1/strings/0x409/configuration"
ln -s "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0"
"/sys/kernel/config/usb_gadget/g_multi/configs/c.1/uac2.usb0"
mkdir -p "/sys/kernel/config/usb_gadget/g_multi/os_desc"
ln -s "//sys/kernel/config/usb_gadget/g_multi/configs/c.1"
"/sys/kernel/config/usb_gadget/g_multi/os_desc/c.1"
echo "${qw_sign:-MSFT100}" >
"/sys/kernel/config/usb_gadget/g_multi/os_desc/qw_sign"
echo "${b_vendor_code:-0x00}" >
"/sys/kernel/config/usb_gadget/g_multi/os_desc/b_vendor_code"
echo "${use:-1}" > "/sys/kernel/config/usb_gadget/g_multi/os_desc/use"

basename /sys/class/udc/* > /sys/kernel/config/usb_gadget/g_multi/UDC

This is only a two channel playback/capture configuration. I hoped to
get this working under Windows before increasing my channel count to a
full 32 channel mask with a 48K sample rate.

I look forward to hearing your suggestions and possibly pointing out
where I've gone astray.

Thanks,

Glenn

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Ruslan Bilovol]

On Wed, Nov 25, 2020 at 9:29 PM Glenn Schmottlach
<gschmottlach@gmail.com> wrote:
>
> On Sun, Nov 22, 2020 at 2:52 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
> >
> > On Fri, Nov 13, 2020 at 5:35 PM Glenn Schmottlach
> > <gschmottlach@gmail.com> wrote:
> > >
> > > On Thu, Nov 12, 2020 at 6:20 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
> > > >
> > > > On Wed, Nov 11, 2020 at 11:30 AM Peter Chen <peter.chen@nxp.com> wrote:
> > > > >
> > > > > On 20-11-08 02:18:28, Ruslan Bilovol wrote:
> > > > > > Current UAC2 gadget implements capture/sync paths
> > > > > > as two USB ISO ASYNC endpoints (IN and OUT).
> > > > > >
> > > > > > This violates USB spec which says that ISO ASYNC OUT endpoint
> > > > > > should have feedback companion endpoint.
> > > > > > See USB2.0 spec  "5.12.4.1 Synchronization Type": asynchronous
> > > > > > sink provides explicit feedback (isochronous pipe).
> > > > > > Interesting that for ISO ASYNC *IN* endpoint respective
> > > > > > feedback isn't required since source provides implicit
> > > > > > feedforward (data stream).
> > > > > >
> > > > > > While it's not an issue if UAC2 Gadget is connected to
> > > > > > Linux host (Linux ignores missing feedback endpoint),
> > > > > > with other hosts like Windows or MacOS the UAC2 Gadget
> > > > > > isn't enumerated due to missing feedback endpoint.
> > > > > >
> > > > > > This patch series adds feedback endpoint support to
> > > > > > UAC2 function, new control to UAC2 mixer which can
> > > > > > be used by userspace tools (like alsaloop from alsa-utils)
> > > > > > for updating feedback frequency reported to the host.
> > > > > > This is useful for usecases when UAC2 Gadget's audio
> > > > > > samples are played to another codec or audio card
> > > > > > with its own internal freerunning clock so host can
> > > > > > be notified that more/less samples are required.
> > > > > >
> > > > > > The alsaloop tool requires some (relatively small)
> > > > > > modifications in order to start support driving
> > > > > > feedback frequency through UAC2 mixer control.
> > > > > > That change will be sent as a separate patch
> > > > > > to ALSA community.
> > > > > >
> > > > > > Also added ability to switch ISO ASYNC OUT endpoint into
> > > > > > adaptive endpoint which doesn't require feedback endpoint
> > > > > > (as per USB spec).
> > > > > >
> > > > > > Ruslan Bilovol (3):
> > > > > >   usb: gadget: f_uac2/u_audio: add feedback endpoint support
> > > > > >   usb: gadget: f_uac2: add adaptive sync support for capture
> > > > > >   usb: gadget: u_audio: add real feedback implementation
> > > > >
> > > > > Hi Ruslan,
> > > > >
> > > > > I applied your patches, but WIN10 still can't recognize it well.
> > > > > The UAC1 is OK for WIN10 with the below same configuration.
> > > > > Any debug information you would like to know to check it?
> > > > >
> > > > >
> > > > > if [ "$FUNC" == "uac2" ]; then
> > > > > mkdir functions/$FUNC".0"
> > > > > echo 2 > functions/$FUNC".0"/p_ssize
> > > > > echo 48000 > functions/$FUNC".0"/p_srate
> > > > > echo 3 > functions/$FUNC".0"/p_chmask
> > > > >
> > > > > echo 2 > functions/$FUNC".0"/c_ssize
> > > > > echo 48000 > functions/$FUNC".0"/c_srate
> > > > > echo 3 > functions/$FUNC".0"/c_chmask
> > > > > #echo 4 > functions/$FUNC".0"/req_number
> > > > > ln -s functions/$FUNC".0" configs/c.1
> > > > > echo high-speed > /sys/kernel/config/usb_gadget/g1/max_speed
> > > > > fi
> > > > >
> > > >
> > > > Hmm... I just tested below config and it works fine with my Win10.
> > > > The only thing I noticed is Windows doesn't enable UAC2 gadget
> > > > by default, but this can be done from Win10 sound settings
> > > >
> > > > --------------------------------->8--------------------------------------
> > > > mkdir cfg
> > > > mount none cfg -t configfs
> > > > mkdir cfg/usb_gadget/g1
> > > > cd cfg/usb_gadget/g1
> > > > mkdir configs/c.1
> > > > mkdir functions/uac2.0
> > > >
> > > > # 44.1 kHz sample rate
> > > > echo 44100 > functions/uac2.0/c_srate
> > > > echo 44100 > functions/uac2.0/p_srate
> > > >
> > > > mkdir strings/0x409
> > > > mkdir configs/c.1/strings/0x409
> > > > echo 0x0101 > idProduct
> > > > echo 0x1d6b > idVendor
> > > > echo my-serial-num > strings/0x409/serialnumber
> > > > echo my-manufacturer > strings/0x409/manufacturer
> > > > echo "Test gadget" > strings/0x409/product
> > > > echo "Conf 1" > configs/c.1/strings/0x409/configuration
> > > > echo 120 > configs/c.1/MaxPower
> > > > ln -s functions/uac2.0 configs/c.1
> > > > echo musb-hdrc.0 > UDC
> > > > --------------------------------->8--------------------------------------
> > > >
> > > > Thanks,
> > > > Ruslan
> > >
> > > Hi Ruslan -
> > >
> > > With your configuration (above) Win10 was able to recognize and load
> > > the driver. What appears to prevent my configuration from loading is
> > > the fact that I selected 48K as my sample rate and my capture/playback
> > > channel mask includes more than two (2) channels. If I take your
> > > configuration and change the sample rate (c_srate/p_srate) to 48000
> > > Windows will fail to load the driver. Likewise, setting the
> > > c_chmask/p_chmask to 7 (three channels) will also cause the driver to
> > > fail to load.
> > >
> > > You mentioned there is an option in Win10 Sound Settings to "enable"
> > > UAC2 by default. I cannot find that option and I wonder if this is
> > > what is preventing me from changing the sample rate or channel mask?
> > > Could Windows be treating my audio gadget as a UAC1 device rather than
> > > a fully multi-channel audio device (even though the usbaudio2.sys
> > > driver is loaded)? Have you tried other configurations to verify your
> > > Win10 box supports more than two channels and a 44.1K sample rate? I
> > > look forward to your feedback and any suggestions you might offer.
> > >
> >
> > I was able to reproduce the issue and prepared a patch below, please
> > try it and see if it fixes the issue.
> >
> > Maximum data rates that I used were (AFAIR) 8 channel 192kHz/32bit,
> > but there is another issue with high data rate if someone uses so many
> > channels, very high sampling frequency or sample size that data can't
> > fit into allowed (by USB spec) max packet size of endpoint. In this case
> > need to decrease bInterval of endpoint.
> > I test it in a high-performance audio case so always use a minimal possible
> > bInterval (set to '1').
> > Of course in the future that need to be calculated dynamically depending on
> > the UAC2 settings
> >
> > Please test patches below and see it it helps
> >
> > ---------------------------------------------8<----------------------------------------
> > From 51516435bbf2486574ec7bc9fd4726677cd474a4 Mon Sep 17 00:00:00 2001
> > From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > Date: Sun, 22 Nov 2020 21:05:38 +0200
> > Subject: [PATCH] usb: gadget: f_uac2: always increase endpoint max_packet_size
> >  by one audio slot
> >
> > As per UAC2 Audio Data Formats spec (2.3.1.1 USB Packets),
> > if the sampling rate is a constant, the allowable variation
> > of number of audio slots per virtual frame is +/- 1 audio slot.
> >
> > It means that endpoint should be able to accept/send +1 audio
> > slot.
> >
> > Previous endpoint max_packet_size calculation code
> > was adding sometimes +1 audio slot due to DIV_ROUND_UP
> > behaviour which was rounding up to closest integer.
> > However this doesn't work if the numbers are divisible.
> >
> > It had no any impact with Linux hosts which ignore
> > this issue, but in case of more strict Windows it
> > caused rejected enumeration
> >
> > Thus always add +1 audio slot to endpoint's max packet size
> >
> > Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > ---
> >  drivers/usb/gadget/function/f_uac2.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/gadget/function/f_uac2.c
> > b/drivers/usb/gadget/function/f_uac2.c
> > index ebdb2a1..1698587 100644
> > --- a/drivers/usb/gadget/function/f_uac2.c
> > +++ b/drivers/usb/gadget/function/f_uac2.c
> > @@ -486,7 +486,7 @@ static void set_ep_max_packet_size(const struct
> > f_uac2_opts *uac2_opts,
> >   }
> >
> >   max_packet_size = num_channels(chmask) * ssize *
> > - DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1)));
> > + ((srate / (factor / (1 << (ep_desc->bInterval - 1)))) + 1);
> >
> >   if (!is_playback && (uac2_opts->c_sync == USB_ENDPOINT_SYNC_ASYNC))
> >   max_packet_size = max_packet_size * FBACK_FREQ_MAX / 100;
> > --
> > 1.9.1
> >
> >
> > ---------------------------------------------8<----------------------------------------
> > From c8f2f2b414af672ec40841e75fb1ea761ae29122 Mon Sep 17 00:00:00 2001
> > From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > Date: Sun, 16 Feb 2020 22:40:23 +0200
> > Subject: [PATCH] usb: gadget: f_uac2: change bInterval to 1 for
> >  8ch/24bit/44.1kHz
> >
> > With bInterval=4 one audio slot in case of 8ch/24bit/44.1kHz
> > exeeds MaxPacket size of ISO endpoint (>1024) and can't be
> > transferred in time.
> > USB spec ("5.6.3 Isochronous Transfer Packet Size Constraints")
> > says if we need to transfer more than 1024 it is a high speed, high
> > bandwidth endpoint and should have bInterval=1.
> >
> > In the future, bInterval should be dynamically calculated
> > depending on bandwith requirementes
> >
> > Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > ---
> >  drivers/usb/gadget/function/f_uac2.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/usb/gadget/function/f_uac2.c
> > b/drivers/usb/gadget/function/f_uac2.c
> > index 3633df6..fb9b875 100644
> > --- a/drivers/usb/gadget/function/f_uac2.c
> > +++ b/drivers/usb/gadget/function/f_uac2.c
> > @@ -281,7 +281,7 @@ enum {
> >
> >   .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
> >   .wMaxPacketSize = cpu_to_le16(1024),
> > - .bInterval = 4,
> > + .bInterval = 1,
> >  };
> >
> >  /* CS AS ISO OUT Endpoint */
> > @@ -358,7 +358,7 @@ enum {
> >
> >   .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
> >   .wMaxPacketSize = cpu_to_le16(1024),
> > - .bInterval = 4,
> > + .bInterval = 1,
> >  };
> >
> >  /* CS AS ISO IN Endpoint */
> > --
> > 1.9.1
> >
> >
> > ---------------------------------------------8<----------------------------------------
> >
> > Thanks,
> > Ruslan
>
> Hi Ruslan -
>
> I have had some mixed success with your additional patches. First, the

That's good news, thanks for testing!

> UAC2 gadget does correctly register with Windows 10 but only for 1-31
> channels. For a fully specified channel map (32 channels):
>
> c_chmask = 0xFFFFFFFF    ( Does not load)
> p_chmask = 0xFFFFFFFF   ( Does not load)
>
> the driver fails to load (code=10). This seems similar to the prior
> problem. Could there be another off-by-one problem here?
>
> With a 31 channel mask the Windows 10 usbaudio2.sys loads successfully, e.g.
>
> c_chmask = 0x7FFFFFFF (loads)
> p_chmask = 0x7FFFFFFF (loads)

That's correct behavior. UAC2 spec says that bits D27..D30 are reserved.
Also bit D31 is mutually exclusive with other bits and means 'raw data'.
It means that with current UAC2 gadget implementation you can enable
only 27 channels.

It seems like it's possible to add more channels by adding more audio
clusters but that requires UAC2 driver modifications. Also it's not clear
whether it's implemented in Host OS drivers

I personally tested as many as 8x8 playback/capture channels simultaneously.

>
> Once Windows 10 loads the driver successfully, however, I can't seem
> to select the device through Audacity on Windows. The device appears
> in the Windows "Device Manager" under "Sound, video and game
> controllers -> Source/Sink". How are you testing audio
> playback/capture under Windows? Perhaps my test approach is wrong?

You need to go to sound settings -> manage sound devices and enable
UAC2 gadget there, after that it will appear in the system.

I also used Audacity for testing this and it works fine for me

Thanks,
Ruslan

>
> I used the same approach on my Linux host where the USB UAC2 device
> appears as an ALSA device and I use speaker-test on the target
> (BeagleBone Black) to play and then capture the audio using Audacity
> on the Linux host. I was hoping to do the same or something similar
> under Windows.
>
> Below is the script I've been using on the target to configure my UAC2 device:
>
> mkdir -p "/sys/kernel/config/usb_gadget/g_multi"
> echo "${idVendor:-0x11F5}" > "/sys/kernel/config/usb_gadget/g_multi/idVendor"
> echo "${idProduct:-0x0009}" > "/sys/kernel/config/usb_gadget/g_multi/idProduct"
> echo "${bcdDevice:-0x0001}" > "/sys/kernel/config/usb_gadget/g_multi/bcdDevice"
> echo "${bDeviceClass:-0x00}" >
> "/sys/kernel/config/usb_gadget/g_multi/bDeviceClass"
> echo "${bDeviceSubClass:-0x00}" >
> "/sys/kernel/config/usb_gadget/g_multi/bDeviceSubClass"
> echo "${bDeviceProtocol:-0x00}" >
> "/sys/kernel/config/usb_gadget/g_multi/bDeviceProtocol"
> echo "${bcdUSB:-0x0200}" > "/sys/kernel/config/usb_gadget/g_multi/bcdUSB"
> echo "${bMaxPacketSize0:-0x00}" >
> "/sys/kernel/config/usb_gadget/g_multi/bMaxPacketSize0"
> mkdir -p "/sys/kernel/config/usb_gadget/g_multi/strings/0x409"
> echo "${serialnumber:-000000000000}" >
> "/sys/kernel/config/usb_gadget/g_multi/strings/0x409/serialnumber"
> echo "${product:-UAC2}" >
> "/sys/kernel/config/usb_gadget/g_multi/strings/0x409/product"
> echo "${manufacturer:-www.acme.com}" >
> "/sys/kernel/config/usb_gadget/g_multi/strings/0x409/manufacturer"
> mkdir -p "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0"
> echo "${req_number:-4}" >
> "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/req_number"
> echo "${c_ssize:-4}" >
> "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_ssize"
> echo "${c_srate:-48000}" >
> "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_srate"
> echo "${c_chmask:-0x00000003}" >
> "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_chmask"
> echo "${c_sync:-asynchronous}" >
> "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_sync"
> echo "${p_ssize:-4}" >
> "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_ssize"
> echo "${p_srate:-48000}" >
> "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_srate"
> echo "${p_chmask:-0x00000003}" >
> "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_chmask"
> mkdir -p "/sys/kernel/config/usb_gadget/g_multi/configs/c.1"
> echo "${bmAttributes:-0x80}" >
> "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/bmAttributes"
> echo "${MaxPower:-500}" >
> "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/MaxPower"
> mkdir -p "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/strings/0x409"
> echo "${configuration:-BeagleBone Composite}" >
> "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/strings/0x409/configuration"
> ln -s "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0"
> "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/uac2.usb0"
> mkdir -p "/sys/kernel/config/usb_gadget/g_multi/os_desc"
> ln -s "//sys/kernel/config/usb_gadget/g_multi/configs/c.1"
> "/sys/kernel/config/usb_gadget/g_multi/os_desc/c.1"
> echo "${qw_sign:-MSFT100}" >
> "/sys/kernel/config/usb_gadget/g_multi/os_desc/qw_sign"
> echo "${b_vendor_code:-0x00}" >
> "/sys/kernel/config/usb_gadget/g_multi/os_desc/b_vendor_code"
> echo "${use:-1}" > "/sys/kernel/config/usb_gadget/g_multi/os_desc/use"
>
> basename /sys/class/udc/* > /sys/kernel/config/usb_gadget/g_multi/UDC
>
> This is only a two channel playback/capture configuration. I hoped to
> get this working under Windows before increasing my channel count to a
> full 32 channel mask with a 48K sample rate.
>
> I look forward to hearing your suggestions and possibly pointing out
> where I've gone astray.
>
> Thanks,
>
> Glenn

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Glenn Schmottlach]

On Sat, Nov 28, 2020 at 6:26 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
>
> On Wed, Nov 25, 2020 at 9:29 PM Glenn Schmottlach
> <gschmottlach@gmail.com> wrote:
> >
> > On Sun, Nov 22, 2020 at 2:52 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
> > >
> > > On Fri, Nov 13, 2020 at 5:35 PM Glenn Schmottlach
> > > <gschmottlach@gmail.com> wrote:
> > > >
> > > > On Thu, Nov 12, 2020 at 6:20 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
> > > > >
> > > > > On Wed, Nov 11, 2020 at 11:30 AM Peter Chen <peter.chen@nxp.com> wrote:
> > > > > >
> > > > > > On 20-11-08 02:18:28, Ruslan Bilovol wrote:
> > > > > > > Current UAC2 gadget implements capture/sync paths
> > > > > > > as two USB ISO ASYNC endpoints (IN and OUT).
> > > > > > >
> > > > > > > This violates USB spec which says that ISO ASYNC OUT endpoint
> > > > > > > should have feedback companion endpoint.
> > > > > > > See USB2.0 spec  "5.12.4.1 Synchronization Type": asynchronous
> > > > > > > sink provides explicit feedback (isochronous pipe).
> > > > > > > Interesting that for ISO ASYNC *IN* endpoint respective
> > > > > > > feedback isn't required since source provides implicit
> > > > > > > feedforward (data stream).
> > > > > > >
> > > > > > > While it's not an issue if UAC2 Gadget is connected to
> > > > > > > Linux host (Linux ignores missing feedback endpoint),
> > > > > > > with other hosts like Windows or MacOS the UAC2 Gadget
> > > > > > > isn't enumerated due to missing feedback endpoint.
> > > > > > >
> > > > > > > This patch series adds feedback endpoint support to
> > > > > > > UAC2 function, new control to UAC2 mixer which can
> > > > > > > be used by userspace tools (like alsaloop from alsa-utils)
> > > > > > > for updating feedback frequency reported to the host.
> > > > > > > This is useful for usecases when UAC2 Gadget's audio
> > > > > > > samples are played to another codec or audio card
> > > > > > > with its own internal freerunning clock so host can
> > > > > > > be notified that more/less samples are required.
> > > > > > >
> > > > > > > The alsaloop tool requires some (relatively small)
> > > > > > > modifications in order to start support driving
> > > > > > > feedback frequency through UAC2 mixer control.
> > > > > > > That change will be sent as a separate patch
> > > > > > > to ALSA community.
> > > > > > >
> > > > > > > Also added ability to switch ISO ASYNC OUT endpoint into
> > > > > > > adaptive endpoint which doesn't require feedback endpoint
> > > > > > > (as per USB spec).
> > > > > > >
> > > > > > > Ruslan Bilovol (3):
> > > > > > >   usb: gadget: f_uac2/u_audio: add feedback endpoint support
> > > > > > >   usb: gadget: f_uac2: add adaptive sync support for capture
> > > > > > >   usb: gadget: u_audio: add real feedback implementation
> > > > > >
> > > > > > Hi Ruslan,
> > > > > >
> > > > > > I applied your patches, but WIN10 still can't recognize it well.
> > > > > > The UAC1 is OK for WIN10 with the below same configuration.
> > > > > > Any debug information you would like to know to check it?
> > > > > >
> > > > > >
> > > > > > if [ "$FUNC" == "uac2" ]; then
> > > > > > mkdir functions/$FUNC".0"
> > > > > > echo 2 > functions/$FUNC".0"/p_ssize
> > > > > > echo 48000 > functions/$FUNC".0"/p_srate
> > > > > > echo 3 > functions/$FUNC".0"/p_chmask
> > > > > >
> > > > > > echo 2 > functions/$FUNC".0"/c_ssize
> > > > > > echo 48000 > functions/$FUNC".0"/c_srate
> > > > > > echo 3 > functions/$FUNC".0"/c_chmask
> > > > > > #echo 4 > functions/$FUNC".0"/req_number
> > > > > > ln -s functions/$FUNC".0" configs/c.1
> > > > > > echo high-speed > /sys/kernel/config/usb_gadget/g1/max_speed
> > > > > > fi
> > > > > >
> > > > >
> > > > > Hmm... I just tested below config and it works fine with my Win10.
> > > > > The only thing I noticed is Windows doesn't enable UAC2 gadget
> > > > > by default, but this can be done from Win10 sound settings
> > > > >
> > > > > --------------------------------->8--------------------------------------
> > > > > mkdir cfg
> > > > > mount none cfg -t configfs
> > > > > mkdir cfg/usb_gadget/g1
> > > > > cd cfg/usb_gadget/g1
> > > > > mkdir configs/c.1
> > > > > mkdir functions/uac2.0
> > > > >
> > > > > # 44.1 kHz sample rate
> > > > > echo 44100 > functions/uac2.0/c_srate
> > > > > echo 44100 > functions/uac2.0/p_srate
> > > > >
> > > > > mkdir strings/0x409
> > > > > mkdir configs/c.1/strings/0x409
> > > > > echo 0x0101 > idProduct
> > > > > echo 0x1d6b > idVendor
> > > > > echo my-serial-num > strings/0x409/serialnumber
> > > > > echo my-manufacturer > strings/0x409/manufacturer
> > > > > echo "Test gadget" > strings/0x409/product
> > > > > echo "Conf 1" > configs/c.1/strings/0x409/configuration
> > > > > echo 120 > configs/c.1/MaxPower
> > > > > ln -s functions/uac2.0 configs/c.1
> > > > > echo musb-hdrc.0 > UDC
> > > > > --------------------------------->8--------------------------------------
> > > > >
> > > > > Thanks,
> > > > > Ruslan
> > > >
> > > > Hi Ruslan -
> > > >
> > > > With your configuration (above) Win10 was able to recognize and load
> > > > the driver. What appears to prevent my configuration from loading is
> > > > the fact that I selected 48K as my sample rate and my capture/playback
> > > > channel mask includes more than two (2) channels. If I take your
> > > > configuration and change the sample rate (c_srate/p_srate) to 48000
> > > > Windows will fail to load the driver. Likewise, setting the
> > > > c_chmask/p_chmask to 7 (three channels) will also cause the driver to
> > > > fail to load.
> > > >
> > > > You mentioned there is an option in Win10 Sound Settings to "enable"
> > > > UAC2 by default. I cannot find that option and I wonder if this is
> > > > what is preventing me from changing the sample rate or channel mask?
> > > > Could Windows be treating my audio gadget as a UAC1 device rather than
> > > > a fully multi-channel audio device (even though the usbaudio2.sys
> > > > driver is loaded)? Have you tried other configurations to verify your
> > > > Win10 box supports more than two channels and a 44.1K sample rate? I
> > > > look forward to your feedback and any suggestions you might offer.
> > > >
> > >
> > > I was able to reproduce the issue and prepared a patch below, please
> > > try it and see if it fixes the issue.
> > >
> > > Maximum data rates that I used were (AFAIR) 8 channel 192kHz/32bit,
> > > but there is another issue with high data rate if someone uses so many
> > > channels, very high sampling frequency or sample size that data can't
> > > fit into allowed (by USB spec) max packet size of endpoint. In this case
> > > need to decrease bInterval of endpoint.
> > > I test it in a high-performance audio case so always use a minimal possible
> > > bInterval (set to '1').
> > > Of course in the future that need to be calculated dynamically depending on
> > > the UAC2 settings
> > >
> > > Please test patches below and see it it helps
> > >
> > > ---------------------------------------------8<----------------------------------------
> > > From 51516435bbf2486574ec7bc9fd4726677cd474a4 Mon Sep 17 00:00:00 2001
> > > From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > > Date: Sun, 22 Nov 2020 21:05:38 +0200
> > > Subject: [PATCH] usb: gadget: f_uac2: always increase endpoint max_packet_size
> > >  by one audio slot
> > >
> > > As per UAC2 Audio Data Formats spec (2.3.1.1 USB Packets),
> > > if the sampling rate is a constant, the allowable variation
> > > of number of audio slots per virtual frame is +/- 1 audio slot.
> > >
> > > It means that endpoint should be able to accept/send +1 audio
> > > slot.
> > >
> > > Previous endpoint max_packet_size calculation code
> > > was adding sometimes +1 audio slot due to DIV_ROUND_UP
> > > behaviour which was rounding up to closest integer.
> > > However this doesn't work if the numbers are divisible.
> > >
> > > It had no any impact with Linux hosts which ignore
> > > this issue, but in case of more strict Windows it
> > > caused rejected enumeration
> > >
> > > Thus always add +1 audio slot to endpoint's max packet size
> > >
> > > Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > > ---
> > >  drivers/usb/gadget/function/f_uac2.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/usb/gadget/function/f_uac2.c
> > > b/drivers/usb/gadget/function/f_uac2.c
> > > index ebdb2a1..1698587 100644
> > > --- a/drivers/usb/gadget/function/f_uac2.c
> > > +++ b/drivers/usb/gadget/function/f_uac2.c
> > > @@ -486,7 +486,7 @@ static void set_ep_max_packet_size(const struct
> > > f_uac2_opts *uac2_opts,
> > >   }
> > >
> > >   max_packet_size = num_channels(chmask) * ssize *
> > > - DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1)));
> > > + ((srate / (factor / (1 << (ep_desc->bInterval - 1)))) + 1);
> > >
> > >   if (!is_playback && (uac2_opts->c_sync == USB_ENDPOINT_SYNC_ASYNC))
> > >   max_packet_size = max_packet_size * FBACK_FREQ_MAX / 100;
> > > --
> > > 1.9.1
> > >
> > >
> > > ---------------------------------------------8<----------------------------------------
> > > From c8f2f2b414af672ec40841e75fb1ea761ae29122 Mon Sep 17 00:00:00 2001
> > > From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > > Date: Sun, 16 Feb 2020 22:40:23 +0200
> > > Subject: [PATCH] usb: gadget: f_uac2: change bInterval to 1 for
> > >  8ch/24bit/44.1kHz
> > >
> > > With bInterval=4 one audio slot in case of 8ch/24bit/44.1kHz
> > > exeeds MaxPacket size of ISO endpoint (>1024) and can't be
> > > transferred in time.
> > > USB spec ("5.6.3 Isochronous Transfer Packet Size Constraints")
> > > says if we need to transfer more than 1024 it is a high speed, high
> > > bandwidth endpoint and should have bInterval=1.
> > >
> > > In the future, bInterval should be dynamically calculated
> > > depending on bandwith requirementes
> > >
> > > Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > > ---
> > >  drivers/usb/gadget/function/f_uac2.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/usb/gadget/function/f_uac2.c
> > > b/drivers/usb/gadget/function/f_uac2.c
> > > index 3633df6..fb9b875 100644
> > > --- a/drivers/usb/gadget/function/f_uac2.c
> > > +++ b/drivers/usb/gadget/function/f_uac2.c
> > > @@ -281,7 +281,7 @@ enum {
> > >
> > >   .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
> > >   .wMaxPacketSize = cpu_to_le16(1024),
> > > - .bInterval = 4,
> > > + .bInterval = 1,
> > >  };
> > >
> > >  /* CS AS ISO OUT Endpoint */
> > > @@ -358,7 +358,7 @@ enum {
> > >
> > >   .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
> > >   .wMaxPacketSize = cpu_to_le16(1024),
> > > - .bInterval = 4,
> > > + .bInterval = 1,
> > >  };
> > >
> > >  /* CS AS ISO IN Endpoint */
> > > --
> > > 1.9.1
> > >
> > >
> > > ---------------------------------------------8<----------------------------------------
> > >
> > > Thanks,
> > > Ruslan
> >
> > Hi Ruslan -
> >
> > I have had some mixed success with your additional patches. First, the
>
> That's good news, thanks for testing!
>
> > UAC2 gadget does correctly register with Windows 10 but only for 1-31
> > channels. For a fully specified channel map (32 channels):
> >
> > c_chmask = 0xFFFFFFFF    ( Does not load)
> > p_chmask = 0xFFFFFFFF   ( Does not load)
> >
> > the driver fails to load (code=10). This seems similar to the prior
> > problem. Could there be another off-by-one problem here?
> >
> > With a 31 channel mask the Windows 10 usbaudio2.sys loads successfully, e.g.
> >
> > c_chmask = 0x7FFFFFFF (loads)
> > p_chmask = 0x7FFFFFFF (loads)
>
> That's correct behavior. UAC2 spec says that bits D27..D30 are reserved.
> Also bit D31 is mutually exclusive with other bits and means 'raw data'.
> It means that with current UAC2 gadget implementation you can enable
> only 27 channels.
>
> It seems like it's possible to add more channels by adding more audio
> clusters but that requires UAC2 driver modifications. Also it's not clear
> whether it's implemented in Host OS drivers
>
> I personally tested as many as 8x8 playback/capture channels simultaneously.
>
> >
> > Once Windows 10 loads the driver successfully, however, I can't seem
> > to select the device through Audacity on Windows. The device appears
> > in the Windows "Device Manager" under "Sound, video and game
> > controllers -> Source/Sink". How are you testing audio
> > playback/capture under Windows? Perhaps my test approach is wrong?
>
> You need to go to sound settings -> manage sound devices and enable
> UAC2 gadget there, after that it will appear in the system.
>
> I also used Audacity for testing this and it works fine for me
>
> Thanks,
> Ruslan
>
> >
> > I used the same approach on my Linux host where the USB UAC2 device
> > appears as an ALSA device and I use speaker-test on the target
> > (BeagleBone Black) to play and then capture the audio using Audacity
> > on the Linux host. I was hoping to do the same or something similar
> > under Windows.
> >
> > Below is the script I've been using on the target to configure my UAC2 device:
> >
> > mkdir -p "/sys/kernel/config/usb_gadget/g_multi"
> > echo "${idVendor:-0x11F5}" > "/sys/kernel/config/usb_gadget/g_multi/idVendor"
> > echo "${idProduct:-0x0009}" > "/sys/kernel/config/usb_gadget/g_multi/idProduct"
> > echo "${bcdDevice:-0x0001}" > "/sys/kernel/config/usb_gadget/g_multi/bcdDevice"
> > echo "${bDeviceClass:-0x00}" >
> > "/sys/kernel/config/usb_gadget/g_multi/bDeviceClass"
> > echo "${bDeviceSubClass:-0x00}" >
> > "/sys/kernel/config/usb_gadget/g_multi/bDeviceSubClass"
> > echo "${bDeviceProtocol:-0x00}" >
> > "/sys/kernel/config/usb_gadget/g_multi/bDeviceProtocol"
> > echo "${bcdUSB:-0x0200}" > "/sys/kernel/config/usb_gadget/g_multi/bcdUSB"
> > echo "${bMaxPacketSize0:-0x00}" >
> > "/sys/kernel/config/usb_gadget/g_multi/bMaxPacketSize0"
> > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/strings/0x409"
> > echo "${serialnumber:-000000000000}" >
> > "/sys/kernel/config/usb_gadget/g_multi/strings/0x409/serialnumber"
> > echo "${product:-UAC2}" >
> > "/sys/kernel/config/usb_gadget/g_multi/strings/0x409/product"
> > echo "${manufacturer:-www.acme.com}" >
> > "/sys/kernel/config/usb_gadget/g_multi/strings/0x409/manufacturer"
> > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0"
> > echo "${req_number:-4}" >
> > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/req_number"
> > echo "${c_ssize:-4}" >
> > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_ssize"
> > echo "${c_srate:-48000}" >
> > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_srate"
> > echo "${c_chmask:-0x00000003}" >
> > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_chmask"
> > echo "${c_sync:-asynchronous}" >
> > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_sync"
> > echo "${p_ssize:-4}" >
> > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_ssize"
> > echo "${p_srate:-48000}" >
> > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_srate"
> > echo "${p_chmask:-0x00000003}" >
> > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_chmask"
> > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/configs/c.1"
> > echo "${bmAttributes:-0x80}" >
> > "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/bmAttributes"
> > echo "${MaxPower:-500}" >
> > "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/MaxPower"
> > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/strings/0x409"
> > echo "${configuration:-BeagleBone Composite}" >
> > "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/strings/0x409/configuration"
> > ln -s "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0"
> > "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/uac2.usb0"
> > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/os_desc"
> > ln -s "//sys/kernel/config/usb_gadget/g_multi/configs/c.1"
> > "/sys/kernel/config/usb_gadget/g_multi/os_desc/c.1"
> > echo "${qw_sign:-MSFT100}" >
> > "/sys/kernel/config/usb_gadget/g_multi/os_desc/qw_sign"
> > echo "${b_vendor_code:-0x00}" >
> > "/sys/kernel/config/usb_gadget/g_multi/os_desc/b_vendor_code"
> > echo "${use:-1}" > "/sys/kernel/config/usb_gadget/g_multi/os_desc/use"
> >
> > basename /sys/class/udc/* > /sys/kernel/config/usb_gadget/g_multi/UDC
> >
> > This is only a two channel playback/capture configuration. I hoped to
> > get this working under Windows before increasing my channel count to a
> > full 32 channel mask with a 48K sample rate.
> >
> > I look forward to hearing your suggestions and possibly pointing out
> > where I've gone astray.
> >
> > Thanks,
> >
> > Glenn

Hi Ruslan -

Thanks for the feedback but unfortunately I've experienced mixed
results with the gadget UAC2 driver on both Windows/Linux. Let me
describe my environment. My host platform is either a Linux Ubuntu
18.04 or Windows 10 laptop while the target environment is a
BeagleBone Black (Linux beaglebone 5.4.74-g9574bba32a #1 PREEMPT). I'm
testing two different scenarios:

Scenario #1:
BeagleBone Black (BBB) runs speaker-test generating a single channel
(S32_LE) audio stream containing a 1KHz tone with a 48K sample rate,
e.g.

> speaker-test -D hw:1,0 -r 48000 -c 1 -f 1000 -F S32_LE -t sine

The host laptop is running Audacity and recording the tone over the
UAC2 adapter. On the Linux host the capture is correct and the tone is
bit-perfect. On the Windows 10 the capture contains numerous missing
samples which translates into a lot of audible pops and clicks.

Scenario #2:
The Linux/Windows host plays a single channel, 48K, S32_LE 1K sine
tone to the target using either Audacity (on Windows) or 'aplay' (on
Linux), e.g.

> aplay -D hw:4,0 -c 1  -r 48000 -t wav  tone_1k.wav  (Linux)

On the BBB target I use 'arecord' to record the tone to a RAM disk and
then copy the recorded file back to the host where I can verify the
quality of the recording. In both instances (e.g. using either Windows
or Linux for playback) the recording on the target results in a
captured file with missing samples and audible pops/clicks. In this
scenario the UAC2 gadget is configured with c_sync == asynchronous. I
wouldn't expect things to improve with c_sync == adaptive since you
mentioned in your patch that it always reports back the nominal
frequency to the host from the feedback endpoint.

Do you have any suggestions that might explain (the above) behavior.
Can you describe your test environment in more detail so that I can
perhaps re-create it? What Linux target are you using with your tests?
You mentioned you tested an 8x8 playback/capture scenario. Can you
provide any details of how you performed this test and the method you
used to confirm the audio quality for the capture/playback?

Thanks for any insights you might be able to offer . . .

Glenn

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Glenn Schmottlach]

On Tue, Dec 1, 2020 at 4:43 PM Glenn Schmottlach <gschmottlach@gmail.com> wrote:
>
> On Sat, Nov 28, 2020 at 6:26 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
> >
> > On Wed, Nov 25, 2020 at 9:29 PM Glenn Schmottlach
> > <gschmottlach@gmail.com> wrote:
> > >
> > > On Sun, Nov 22, 2020 at 2:52 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
> > > >
> > > > On Fri, Nov 13, 2020 at 5:35 PM Glenn Schmottlach
> > > > <gschmottlach@gmail.com> wrote:
> > > > >
> > > > > On Thu, Nov 12, 2020 at 6:20 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
> > > > > >
> > > > > > On Wed, Nov 11, 2020 at 11:30 AM Peter Chen <peter.chen@nxp.com> wrote:
> > > > > > >
> > > > > > > On 20-11-08 02:18:28, Ruslan Bilovol wrote:
> > > > > > > > Current UAC2 gadget implements capture/sync paths
> > > > > > > > as two USB ISO ASYNC endpoints (IN and OUT).
> > > > > > > >
> > > > > > > > This violates USB spec which says that ISO ASYNC OUT endpoint
> > > > > > > > should have feedback companion endpoint.
> > > > > > > > See USB2.0 spec  "5.12.4.1 Synchronization Type": asynchronous
> > > > > > > > sink provides explicit feedback (isochronous pipe).
> > > > > > > > Interesting that for ISO ASYNC *IN* endpoint respective
> > > > > > > > feedback isn't required since source provides implicit
> > > > > > > > feedforward (data stream).
> > > > > > > >
> > > > > > > > While it's not an issue if UAC2 Gadget is connected to
> > > > > > > > Linux host (Linux ignores missing feedback endpoint),
> > > > > > > > with other hosts like Windows or MacOS the UAC2 Gadget
> > > > > > > > isn't enumerated due to missing feedback endpoint.
> > > > > > > >
> > > > > > > > This patch series adds feedback endpoint support to
> > > > > > > > UAC2 function, new control to UAC2 mixer which can
> > > > > > > > be used by userspace tools (like alsaloop from alsa-utils)
> > > > > > > > for updating feedback frequency reported to the host.
> > > > > > > > This is useful for usecases when UAC2 Gadget's audio
> > > > > > > > samples are played to another codec or audio card
> > > > > > > > with its own internal freerunning clock so host can
> > > > > > > > be notified that more/less samples are required.
> > > > > > > >
> > > > > > > > The alsaloop tool requires some (relatively small)
> > > > > > > > modifications in order to start support driving
> > > > > > > > feedback frequency through UAC2 mixer control.
> > > > > > > > That change will be sent as a separate patch
> > > > > > > > to ALSA community.
> > > > > > > >
> > > > > > > > Also added ability to switch ISO ASYNC OUT endpoint into
> > > > > > > > adaptive endpoint which doesn't require feedback endpoint
> > > > > > > > (as per USB spec).
> > > > > > > >
> > > > > > > > Ruslan Bilovol (3):
> > > > > > > >   usb: gadget: f_uac2/u_audio: add feedback endpoint support
> > > > > > > >   usb: gadget: f_uac2: add adaptive sync support for capture
> > > > > > > >   usb: gadget: u_audio: add real feedback implementation
> > > > > > >
> > > > > > > Hi Ruslan,
> > > > > > >
> > > > > > > I applied your patches, but WIN10 still can't recognize it well.
> > > > > > > The UAC1 is OK for WIN10 with the below same configuration.
> > > > > > > Any debug information you would like to know to check it?
> > > > > > >
> > > > > > >
> > > > > > > if [ "$FUNC" == "uac2" ]; then
> > > > > > > mkdir functions/$FUNC".0"
> > > > > > > echo 2 > functions/$FUNC".0"/p_ssize
> > > > > > > echo 48000 > functions/$FUNC".0"/p_srate
> > > > > > > echo 3 > functions/$FUNC".0"/p_chmask
> > > > > > >
> > > > > > > echo 2 > functions/$FUNC".0"/c_ssize
> > > > > > > echo 48000 > functions/$FUNC".0"/c_srate
> > > > > > > echo 3 > functions/$FUNC".0"/c_chmask
> > > > > > > #echo 4 > functions/$FUNC".0"/req_number
> > > > > > > ln -s functions/$FUNC".0" configs/c.1
> > > > > > > echo high-speed > /sys/kernel/config/usb_gadget/g1/max_speed
> > > > > > > fi
> > > > > > >
> > > > > >
> > > > > > Hmm... I just tested below config and it works fine with my Win10.
> > > > > > The only thing I noticed is Windows doesn't enable UAC2 gadget
> > > > > > by default, but this can be done from Win10 sound settings
> > > > > >
> > > > > > --------------------------------->8--------------------------------------
> > > > > > mkdir cfg
> > > > > > mount none cfg -t configfs
> > > > > > mkdir cfg/usb_gadget/g1
> > > > > > cd cfg/usb_gadget/g1
> > > > > > mkdir configs/c.1
> > > > > > mkdir functions/uac2.0
> > > > > >
> > > > > > # 44.1 kHz sample rate
> > > > > > echo 44100 > functions/uac2.0/c_srate
> > > > > > echo 44100 > functions/uac2.0/p_srate
> > > > > >
> > > > > > mkdir strings/0x409
> > > > > > mkdir configs/c.1/strings/0x409
> > > > > > echo 0x0101 > idProduct
> > > > > > echo 0x1d6b > idVendor
> > > > > > echo my-serial-num > strings/0x409/serialnumber
> > > > > > echo my-manufacturer > strings/0x409/manufacturer
> > > > > > echo "Test gadget" > strings/0x409/product
> > > > > > echo "Conf 1" > configs/c.1/strings/0x409/configuration
> > > > > > echo 120 > configs/c.1/MaxPower
> > > > > > ln -s functions/uac2.0 configs/c.1
> > > > > > echo musb-hdrc.0 > UDC
> > > > > > --------------------------------->8--------------------------------------
> > > > > >
> > > > > > Thanks,
> > > > > > Ruslan
> > > > >
> > > > > Hi Ruslan -
> > > > >
> > > > > With your configuration (above) Win10 was able to recognize and load
> > > > > the driver. What appears to prevent my configuration from loading is
> > > > > the fact that I selected 48K as my sample rate and my capture/playback
> > > > > channel mask includes more than two (2) channels. If I take your
> > > > > configuration and change the sample rate (c_srate/p_srate) to 48000
> > > > > Windows will fail to load the driver. Likewise, setting the
> > > > > c_chmask/p_chmask to 7 (three channels) will also cause the driver to
> > > > > fail to load.
> > > > >
> > > > > You mentioned there is an option in Win10 Sound Settings to "enable"
> > > > > UAC2 by default. I cannot find that option and I wonder if this is
> > > > > what is preventing me from changing the sample rate or channel mask?
> > > > > Could Windows be treating my audio gadget as a UAC1 device rather than
> > > > > a fully multi-channel audio device (even though the usbaudio2.sys
> > > > > driver is loaded)? Have you tried other configurations to verify your
> > > > > Win10 box supports more than two channels and a 44.1K sample rate? I
> > > > > look forward to your feedback and any suggestions you might offer.
> > > > >
> > > >
> > > > I was able to reproduce the issue and prepared a patch below, please
> > > > try it and see if it fixes the issue.
> > > >
> > > > Maximum data rates that I used were (AFAIR) 8 channel 192kHz/32bit,
> > > > but there is another issue with high data rate if someone uses so many
> > > > channels, very high sampling frequency or sample size that data can't
> > > > fit into allowed (by USB spec) max packet size of endpoint. In this case
> > > > need to decrease bInterval of endpoint.
> > > > I test it in a high-performance audio case so always use a minimal possible
> > > > bInterval (set to '1').
> > > > Of course in the future that need to be calculated dynamically depending on
> > > > the UAC2 settings
> > > >
> > > > Please test patches below and see it it helps
> > > >
> > > > ---------------------------------------------8<----------------------------------------
> > > > From 51516435bbf2486574ec7bc9fd4726677cd474a4 Mon Sep 17 00:00:00 2001
> > > > From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > > > Date: Sun, 22 Nov 2020 21:05:38 +0200
> > > > Subject: [PATCH] usb: gadget: f_uac2: always increase endpoint max_packet_size
> > > >  by one audio slot
> > > >
> > > > As per UAC2 Audio Data Formats spec (2.3.1.1 USB Packets),
> > > > if the sampling rate is a constant, the allowable variation
> > > > of number of audio slots per virtual frame is +/- 1 audio slot.
> > > >
> > > > It means that endpoint should be able to accept/send +1 audio
> > > > slot.
> > > >
> > > > Previous endpoint max_packet_size calculation code
> > > > was adding sometimes +1 audio slot due to DIV_ROUND_UP
> > > > behaviour which was rounding up to closest integer.
> > > > However this doesn't work if the numbers are divisible.
> > > >
> > > > It had no any impact with Linux hosts which ignore
> > > > this issue, but in case of more strict Windows it
> > > > caused rejected enumeration
> > > >
> > > > Thus always add +1 audio slot to endpoint's max packet size
> > > >
> > > > Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > > > ---
> > > >  drivers/usb/gadget/function/f_uac2.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/usb/gadget/function/f_uac2.c
> > > > b/drivers/usb/gadget/function/f_uac2.c
> > > > index ebdb2a1..1698587 100644
> > > > --- a/drivers/usb/gadget/function/f_uac2.c
> > > > +++ b/drivers/usb/gadget/function/f_uac2.c
> > > > @@ -486,7 +486,7 @@ static void set_ep_max_packet_size(const struct
> > > > f_uac2_opts *uac2_opts,
> > > >   }
> > > >
> > > >   max_packet_size = num_channels(chmask) * ssize *
> > > > - DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1)));
> > > > + ((srate / (factor / (1 << (ep_desc->bInterval - 1)))) + 1);
> > > >
> > > >   if (!is_playback && (uac2_opts->c_sync == USB_ENDPOINT_SYNC_ASYNC))
> > > >   max_packet_size = max_packet_size * FBACK_FREQ_MAX / 100;
> > > > --
> > > > 1.9.1
> > > >
> > > >
> > > > ---------------------------------------------8<----------------------------------------
> > > > From c8f2f2b414af672ec40841e75fb1ea761ae29122 Mon Sep 17 00:00:00 2001
> > > > From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > > > Date: Sun, 16 Feb 2020 22:40:23 +0200
> > > > Subject: [PATCH] usb: gadget: f_uac2: change bInterval to 1 for
> > > >  8ch/24bit/44.1kHz
> > > >
> > > > With bInterval=4 one audio slot in case of 8ch/24bit/44.1kHz
> > > > exeeds MaxPacket size of ISO endpoint (>1024) and can't be
> > > > transferred in time.
> > > > USB spec ("5.6.3 Isochronous Transfer Packet Size Constraints")
> > > > says if we need to transfer more than 1024 it is a high speed, high
> > > > bandwidth endpoint and should have bInterval=1.
> > > >
> > > > In the future, bInterval should be dynamically calculated
> > > > depending on bandwith requirementes
> > > >
> > > > Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > > > ---
> > > >  drivers/usb/gadget/function/f_uac2.c | 4 ++--
> > > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/usb/gadget/function/f_uac2.c
> > > > b/drivers/usb/gadget/function/f_uac2.c
> > > > index 3633df6..fb9b875 100644
> > > > --- a/drivers/usb/gadget/function/f_uac2.c
> > > > +++ b/drivers/usb/gadget/function/f_uac2.c
> > > > @@ -281,7 +281,7 @@ enum {
> > > >
> > > >   .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
> > > >   .wMaxPacketSize = cpu_to_le16(1024),
> > > > - .bInterval = 4,
> > > > + .bInterval = 1,
> > > >  };
> > > >
> > > >  /* CS AS ISO OUT Endpoint */
> > > > @@ -358,7 +358,7 @@ enum {
> > > >
> > > >   .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
> > > >   .wMaxPacketSize = cpu_to_le16(1024),
> > > > - .bInterval = 4,
> > > > + .bInterval = 1,
> > > >  };
> > > >
> > > >  /* CS AS ISO IN Endpoint */
> > > > --
> > > > 1.9.1
> > > >
> > > >
> > > > ---------------------------------------------8<----------------------------------------
> > > >
> > > > Thanks,
> > > > Ruslan
> > >
> > > Hi Ruslan -
> > >
> > > I have had some mixed success with your additional patches. First, the
> >
> > That's good news, thanks for testing!
> >
> > > UAC2 gadget does correctly register with Windows 10 but only for 1-31
> > > channels. For a fully specified channel map (32 channels):
> > >
> > > c_chmask = 0xFFFFFFFF    ( Does not load)
> > > p_chmask = 0xFFFFFFFF   ( Does not load)
> > >
> > > the driver fails to load (code=10). This seems similar to the prior
> > > problem. Could there be another off-by-one problem here?
> > >
> > > With a 31 channel mask the Windows 10 usbaudio2.sys loads successfully, e.g.
> > >
> > > c_chmask = 0x7FFFFFFF (loads)
> > > p_chmask = 0x7FFFFFFF (loads)
> >
> > That's correct behavior. UAC2 spec says that bits D27..D30 are reserved.
> > Also bit D31 is mutually exclusive with other bits and means 'raw data'.
> > It means that with current UAC2 gadget implementation you can enable
> > only 27 channels.
> >
> > It seems like it's possible to add more channels by adding more audio
> > clusters but that requires UAC2 driver modifications. Also it's not clear
> > whether it's implemented in Host OS drivers
> >
> > I personally tested as many as 8x8 playback/capture channels simultaneously.
> >
> > >
> > > Once Windows 10 loads the driver successfully, however, I can't seem
> > > to select the device through Audacity on Windows. The device appears
> > > in the Windows "Device Manager" under "Sound, video and game
> > > controllers -> Source/Sink". How are you testing audio
> > > playback/capture under Windows? Perhaps my test approach is wrong?
> >
> > You need to go to sound settings -> manage sound devices and enable
> > UAC2 gadget there, after that it will appear in the system.
> >
> > I also used Audacity for testing this and it works fine for me
> >
> > Thanks,
> > Ruslan
> >
> > >
> > > I used the same approach on my Linux host where the USB UAC2 device
> > > appears as an ALSA device and I use speaker-test on the target
> > > (BeagleBone Black) to play and then capture the audio using Audacity
> > > on the Linux host. I was hoping to do the same or something similar
> > > under Windows.
> > >
> > > Below is the script I've been using on the target to configure my UAC2 device:
> > >
> > > mkdir -p "/sys/kernel/config/usb_gadget/g_multi"
> > > echo "${idVendor:-0x11F5}" > "/sys/kernel/config/usb_gadget/g_multi/idVendor"
> > > echo "${idProduct:-0x0009}" > "/sys/kernel/config/usb_gadget/g_multi/idProduct"
> > > echo "${bcdDevice:-0x0001}" > "/sys/kernel/config/usb_gadget/g_multi/bcdDevice"
> > > echo "${bDeviceClass:-0x00}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/bDeviceClass"
> > > echo "${bDeviceSubClass:-0x00}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/bDeviceSubClass"
> > > echo "${bDeviceProtocol:-0x00}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/bDeviceProtocol"
> > > echo "${bcdUSB:-0x0200}" > "/sys/kernel/config/usb_gadget/g_multi/bcdUSB"
> > > echo "${bMaxPacketSize0:-0x00}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/bMaxPacketSize0"
> > > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/strings/0x409"
> > > echo "${serialnumber:-000000000000}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/strings/0x409/serialnumber"
> > > echo "${product:-UAC2}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/strings/0x409/product"
> > > echo "${manufacturer:-www.acme.com}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/strings/0x409/manufacturer"
> > > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0"
> > > echo "${req_number:-4}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/req_number"
> > > echo "${c_ssize:-4}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_ssize"
> > > echo "${c_srate:-48000}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_srate"
> > > echo "${c_chmask:-0x00000003}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_chmask"
> > > echo "${c_sync:-asynchronous}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_sync"
> > > echo "${p_ssize:-4}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_ssize"
> > > echo "${p_srate:-48000}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_srate"
> > > echo "${p_chmask:-0x00000003}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_chmask"
> > > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/configs/c.1"
> > > echo "${bmAttributes:-0x80}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/bmAttributes"
> > > echo "${MaxPower:-500}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/MaxPower"
> > > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/strings/0x409"
> > > echo "${configuration:-BeagleBone Composite}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/strings/0x409/configuration"
> > > ln -s "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0"
> > > "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/uac2.usb0"
> > > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/os_desc"
> > > ln -s "//sys/kernel/config/usb_gadget/g_multi/configs/c.1"
> > > "/sys/kernel/config/usb_gadget/g_multi/os_desc/c.1"
> > > echo "${qw_sign:-MSFT100}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/os_desc/qw_sign"
> > > echo "${b_vendor_code:-0x00}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/os_desc/b_vendor_code"
> > > echo "${use:-1}" > "/sys/kernel/config/usb_gadget/g_multi/os_desc/use"
> > >
> > > basename /sys/class/udc/* > /sys/kernel/config/usb_gadget/g_multi/UDC
> > >
> > > This is only a two channel playback/capture configuration. I hoped to
> > > get this working under Windows before increasing my channel count to a
> > > full 32 channel mask with a 48K sample rate.
> > >
> > > I look forward to hearing your suggestions and possibly pointing out
> > > where I've gone astray.
> > >
> > > Thanks,
> > >
> > > Glenn
>
> Hi Ruslan -
>
> Thanks for the feedback but unfortunately I've experienced mixed
> results with the gadget UAC2 driver on both Windows/Linux. Let me
> describe my environment. My host platform is either a Linux Ubuntu
> 18.04 or Windows 10 laptop while the target environment is a
> BeagleBone Black (Linux beaglebone 5.4.74-g9574bba32a #1 PREEMPT). I'm
> testing two different scenarios:
>
> Scenario #1:
> BeagleBone Black (BBB) runs speaker-test generating a single channel
> (S32_LE) audio stream containing a 1KHz tone with a 48K sample rate,
> e.g.
>
> > speaker-test -D hw:1,0 -r 48000 -c 1 -f 1000 -F S32_LE -t sine
>
> The host laptop is running Audacity and recording the tone over the
> UAC2 adapter. On the Linux host the capture is correct and the tone is
> bit-perfect. On the Windows 10 the capture contains numerous missing
> samples which translates into a lot of audible pops and clicks.
>
> Scenario #2:
> The Linux/Windows host plays a single channel, 48K, S32_LE 1K sine
> tone to the target using either Audacity (on Windows) or 'aplay' (on
> Linux), e.g.
>
> > aplay -D hw:4,0 -c 1  -r 48000 -t wav  tone_1k.wav  (Linux)
>
> On the BBB target I use 'arecord' to record the tone to a RAM disk and
> then copy the recorded file back to the host where I can verify the
> quality of the recording. In both instances (e.g. using either Windows
> or Linux for playback) the recording on the target results in a
> captured file with missing samples and audible pops/clicks. In this
> scenario the UAC2 gadget is configured with c_sync == asynchronous. I
> wouldn't expect things to improve with c_sync == adaptive since you
> mentioned in your patch that it always reports back the nominal
> frequency to the host from the feedback endpoint.
>
> Do you have any suggestions that might explain (the above) behavior.
> Can you describe your test environment in more detail so that I can
> perhaps re-create it? What Linux target are you using with your tests?
> You mentioned you tested an 8x8 playback/capture scenario. Can you
> provide any details of how you performed this test and the method you
> used to confirm the audio quality for the capture/playback?
>
> Thanks for any insights you might be able to offer . . .
>
> Glenn

Hi Ruslan -

This is a follow-up from my post yesterday. I recompiled my kernel
*WITHOUT* your UAC2 patches and repeated Scenario #2 where the Linux
PC plays a single channel tone to the BeagleBone Black where it's
recorded with 'arecord'. Yesterday, I recorded garbled audio on the
target but today, without any UAC2 kernel patches, the recorded audio
on the target is glitch-free and appears to be bit-perfect.

This experiment leads me to believe your patches may be inadvertently
corrupting the data-path. Have you been able to repeat my experiment
and either confirm or refute my findings? I am interested to learn
more how you tested your patches and whether it's something I can
recreate here.

Assuming we can sort out this data corruption issue, what are your
thoughts on how the Linux target device can properly provide the
Windows feedback endpoint with real frequency updates rather than the
constant nominal frequency. If I understood your patch notes correctly
it seems this is an outstanding issue that requires additional
attention. I'm a bit of a noob when it comes to how this might be
addressed.

Thanks for your continued insights and support . . .

Glenn

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Peter Chen]

On 20-12-02 17:04:47, Glenn Schmottlach wrote:
> On Tue, Dec 1, 2020 at 4:43 PM Glenn Schmottlach <gschmottlach@gmail.com> wrote:
> > Hi Ruslan -
> >
> > Thanks for the feedback but unfortunately I've experienced mixed
> > results with the gadget UAC2 driver on both Windows/Linux. Let me
> > describe my environment. My host platform is either a Linux Ubuntu
> > 18.04 or Windows 10 laptop while the target environment is a
> > BeagleBone Black (Linux beaglebone 5.4.74-g9574bba32a #1 PREEMPT). I'm
> > testing two different scenarios:
> >
> > Scenario #1:
> > BeagleBone Black (BBB) runs speaker-test generating a single channel
> > (S32_LE) audio stream containing a 1KHz tone with a 48K sample rate,
> > e.g.
> >
> > > speaker-test -D hw:1,0 -r 48000 -c 1 -f 1000 -F S32_LE -t sine
> >
> > The host laptop is running Audacity and recording the tone over the
> > UAC2 adapter. On the Linux host the capture is correct and the tone is
> > bit-perfect. On the Windows 10 the capture contains numerous missing
> > samples which translates into a lot of audible pops and clicks.
> >
> > Scenario #2:
> > The Linux/Windows host plays a single channel, 48K, S32_LE 1K sine
> > tone to the target using either Audacity (on Windows) or 'aplay' (on
> > Linux), e.g.
> >
> > > aplay -D hw:4,0 -c 1  -r 48000 -t wav  tone_1k.wav  (Linux)
> >
> > On the BBB target I use 'arecord' to record the tone to a RAM disk and
> > then copy the recorded file back to the host where I can verify the
> > quality of the recording. In both instances (e.g. using either Windows
> > or Linux for playback) the recording on the target results in a
> > captured file with missing samples and audible pops/clicks. In this
> > scenario the UAC2 gadget is configured with c_sync == asynchronous. I
> > wouldn't expect things to improve with c_sync == adaptive since you
> > mentioned in your patch that it always reports back the nominal
> > frequency to the host from the feedback endpoint.
> >
> > Do you have any suggestions that might explain (the above) behavior.
> > Can you describe your test environment in more detail so that I can
> > perhaps re-create it? What Linux target are you using with your tests?
> > You mentioned you tested an 8x8 playback/capture scenario. Can you
> > provide any details of how you performed this test and the method you
> > used to confirm the audio quality for the capture/playback?
> >
> > Thanks for any insights you might be able to offer . . .
> >
> > Glenn
> 
> Hi Ruslan -
> 
> This is a follow-up from my post yesterday. I recompiled my kernel
> *WITHOUT* your UAC2 patches and repeated Scenario #2 where the Linux
> PC plays a single channel tone to the BeagleBone Black where it's
> recorded with 'arecord'. Yesterday, I recorded garbled audio on the
> target but today, without any UAC2 kernel patches, the recorded audio
> on the target is glitch-free and appears to be bit-perfect.
> 
> This experiment leads me to believe your patches may be inadvertently
> corrupting the data-path. Have you been able to repeat my experiment
> and either confirm or refute my findings? I am interested to learn
> more how you tested your patches and whether it's something I can
> recreate here.
> 
> Assuming we can sort out this data corruption issue, what are your
> thoughts on how the Linux target device can properly provide the
> Windows feedback endpoint with real frequency updates rather than the
> constant nominal frequency. If I understood your patch notes correctly
> it seems this is an outstanding issue that requires additional
> attention. I'm a bit of a noob when it comes to how this might be
> addressed.
> 
> Thanks for your continued insights and support . . .
> 
> Glenn

Hi Glenn & Ruslan,

Do you know why WIN10 can't recognized UAC2 device if I configure the
sample rate as 48000HZ? Configuring sample rate as 44100HZ, the playback
function would work well at my platforms (chipidea IP), no glitch is
heard. At WIN10, I use Windows Media Player, at board side I use command: 

arecord -f cd -t wav -D hw:4,0 | aplay -f cd -Dplughw:3,0 &

From the USB Bus analyzer:

Feedback EP is scheduled every 1ms, there are nine 176-byte packets and one
180-byte packet among 10ms transfers.

-- 

Thanks,
Peter Chen

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Glenn Schmottlach]

On Thu, Dec 3, 2020 at 5:09 AM Peter Chen <peter.chen@nxp.com> wrote:
>
> On 20-12-02 17:04:47, Glenn Schmottlach wrote:
> > On Tue, Dec 1, 2020 at 4:43 PM Glenn Schmottlach <gschmottlach@gmail.com> wrote:
> > > Hi Ruslan -
> > >
> > > Thanks for the feedback but unfortunately I've experienced mixed
> > > results with the gadget UAC2 driver on both Windows/Linux. Let me
> > > describe my environment. My host platform is either a Linux Ubuntu
> > > 18.04 or Windows 10 laptop while the target environment is a
> > > BeagleBone Black (Linux beaglebone 5.4.74-g9574bba32a #1 PREEMPT). I'm
> > > testing two different scenarios:
> > >
> > > Scenario #1:
> > > BeagleBone Black (BBB) runs speaker-test generating a single channel
> > > (S32_LE) audio stream containing a 1KHz tone with a 48K sample rate,
> > > e.g.
> > >
> > > > speaker-test -D hw:1,0 -r 48000 -c 1 -f 1000 -F S32_LE -t sine
> > >
> > > The host laptop is running Audacity and recording the tone over the
> > > UAC2 adapter. On the Linux host the capture is correct and the tone is
> > > bit-perfect. On the Windows 10 the capture contains numerous missing
> > > samples which translates into a lot of audible pops and clicks.
> > >
> > > Scenario #2:
> > > The Linux/Windows host plays a single channel, 48K, S32_LE 1K sine
> > > tone to the target using either Audacity (on Windows) or 'aplay' (on
> > > Linux), e.g.
> > >
> > > > aplay -D hw:4,0 -c 1  -r 48000 -t wav  tone_1k.wav  (Linux)
> > >
> > > On the BBB target I use 'arecord' to record the tone to a RAM disk and
> > > then copy the recorded file back to the host where I can verify the
> > > quality of the recording. In both instances (e.g. using either Windows
> > > or Linux for playback) the recording on the target results in a
> > > captured file with missing samples and audible pops/clicks. In this
> > > scenario the UAC2 gadget is configured with c_sync == asynchronous. I
> > > wouldn't expect things to improve with c_sync == adaptive since you
> > > mentioned in your patch that it always reports back the nominal
> > > frequency to the host from the feedback endpoint.
> > >
> > > Do you have any suggestions that might explain (the above) behavior.
> > > Can you describe your test environment in more detail so that I can
> > > perhaps re-create it? What Linux target are you using with your tests?
> > > You mentioned you tested an 8x8 playback/capture scenario. Can you
> > > provide any details of how you performed this test and the method you
> > > used to confirm the audio quality for the capture/playback?
> > >
> > > Thanks for any insights you might be able to offer . . .
> > >
> > > Glenn
> >
> > Hi Ruslan -
> >
> > This is a follow-up from my post yesterday. I recompiled my kernel
> > *WITHOUT* your UAC2 patches and repeated Scenario #2 where the Linux
> > PC plays a single channel tone to the BeagleBone Black where it's
> > recorded with 'arecord'. Yesterday, I recorded garbled audio on the
> > target but today, without any UAC2 kernel patches, the recorded audio
> > on the target is glitch-free and appears to be bit-perfect.
> >
> > This experiment leads me to believe your patches may be inadvertently
> > corrupting the data-path. Have you been able to repeat my experiment
> > and either confirm or refute my findings? I am interested to learn
> > more how you tested your patches and whether it's something I can
> > recreate here.
> >
> > Assuming we can sort out this data corruption issue, what are your
> > thoughts on how the Linux target device can properly provide the
> > Windows feedback endpoint with real frequency updates rather than the
> > constant nominal frequency. If I understood your patch notes correctly
> > it seems this is an outstanding issue that requires additional
> > attention. I'm a bit of a noob when it comes to how this might be
> > addressed.
> >
> > Thanks for your continued insights and support . . .
> >
> > Glenn
>
> Hi Glenn & Ruslan,
>
> Do you know why WIN10 can't recognized UAC2 device if I configure the
> sample rate as 48000HZ? Configuring sample rate as 44100HZ, the playback
> function would work well at my platforms (chipidea IP), no glitch is
> heard. At WIN10, I use Windows Media Player, at board side I use command:
>
> arecord -f cd -t wav -D hw:4,0 | aplay -f cd -Dplughw:3,0 &
>
> From the USB Bus analyzer:
>
> Feedback EP is scheduled every 1ms, there are nine 176-byte packets and one
> 180-byte packet among 10ms transfers.
>
> --
>
> Thanks,
> Peter Chen

Hi Peter -

I have not experienced the issue you are reporting. My configuration
uses a 48Khz sample rate exclusively and Windows 10 appears to
recognize the UAC2 device properly with all of Ruslan's patches. I
have not done any serious testing at the 44.1KHz rate so I don't
recall if that is recognized correctly on my Windows 10 box.

It looks like you've established a UAC2 loopback on your target board.
How are you verifying the captured audio on the Window 10 PC? I didn't
realize Windows Media Player allows you to both playback and capture
from the same (UAC2) device simultaneously.

Thanks,

Glenn

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Ruslan Bilovol]

On Thu, Dec 3, 2020 at 12:09 PM Peter Chen <peter.chen@nxp.com> wrote:
>
> On 20-12-02 17:04:47, Glenn Schmottlach wrote:
> > On Tue, Dec 1, 2020 at 4:43 PM Glenn Schmottlach <gschmottlach@gmail.com> wrote:
> > > Hi Ruslan -
> > >
> > > Thanks for the feedback but unfortunately I've experienced mixed
> > > results with the gadget UAC2 driver on both Windows/Linux. Let me
> > > describe my environment. My host platform is either a Linux Ubuntu
> > > 18.04 or Windows 10 laptop while the target environment is a
> > > BeagleBone Black (Linux beaglebone 5.4.74-g9574bba32a #1 PREEMPT). I'm
> > > testing two different scenarios:
> > >
> > > Scenario #1:
> > > BeagleBone Black (BBB) runs speaker-test generating a single channel
> > > (S32_LE) audio stream containing a 1KHz tone with a 48K sample rate,
> > > e.g.
> > >
> > > > speaker-test -D hw:1,0 -r 48000 -c 1 -f 1000 -F S32_LE -t sine
> > >
> > > The host laptop is running Audacity and recording the tone over the
> > > UAC2 adapter. On the Linux host the capture is correct and the tone is
> > > bit-perfect. On the Windows 10 the capture contains numerous missing
> > > samples which translates into a lot of audible pops and clicks.
> > >
> > > Scenario #2:
> > > The Linux/Windows host plays a single channel, 48K, S32_LE 1K sine
> > > tone to the target using either Audacity (on Windows) or 'aplay' (on
> > > Linux), e.g.
> > >
> > > > aplay -D hw:4,0 -c 1  -r 48000 -t wav  tone_1k.wav  (Linux)
> > >
> > > On the BBB target I use 'arecord' to record the tone to a RAM disk and
> > > then copy the recorded file back to the host where I can verify the
> > > quality of the recording. In both instances (e.g. using either Windows
> > > or Linux for playback) the recording on the target results in a
> > > captured file with missing samples and audible pops/clicks. In this
> > > scenario the UAC2 gadget is configured with c_sync == asynchronous. I
> > > wouldn't expect things to improve with c_sync == adaptive since you
> > > mentioned in your patch that it always reports back the nominal
> > > frequency to the host from the feedback endpoint.
> > >
> > > Do you have any suggestions that might explain (the above) behavior.
> > > Can you describe your test environment in more detail so that I can
> > > perhaps re-create it? What Linux target are you using with your tests?
> > > You mentioned you tested an 8x8 playback/capture scenario. Can you
> > > provide any details of how you performed this test and the method you
> > > used to confirm the audio quality for the capture/playback?
> > >
> > > Thanks for any insights you might be able to offer . . .
> > >
> > > Glenn
> >
> > Hi Ruslan -
> >
> > This is a follow-up from my post yesterday. I recompiled my kernel
> > *WITHOUT* your UAC2 patches and repeated Scenario #2 where the Linux
> > PC plays a single channel tone to the BeagleBone Black where it's
> > recorded with 'arecord'. Yesterday, I recorded garbled audio on the
> > target but today, without any UAC2 kernel patches, the recorded audio
> > on the target is glitch-free and appears to be bit-perfect.
> >
> > This experiment leads me to believe your patches may be inadvertently
> > corrupting the data-path. Have you been able to repeat my experiment
> > and either confirm or refute my findings? I am interested to learn
> > more how you tested your patches and whether it's something I can
> > recreate here.
> >
> > Assuming we can sort out this data corruption issue, what are your
> > thoughts on how the Linux target device can properly provide the
> > Windows feedback endpoint with real frequency updates rather than the
> > constant nominal frequency. If I understood your patch notes correctly
> > it seems this is an outstanding issue that requires additional
> > attention. I'm a bit of a noob when it comes to how this might be
> > addressed.
> >
> > Thanks for your continued insights and support . . .
> >
> > Glenn
>
> Hi Glenn & Ruslan,
>
> Do you know why WIN10 can't recognized UAC2 device if I configure the
> sample rate as 48000HZ? Configuring sample rate as 44100HZ, the playback
> function would work well at my platforms (chipidea IP), no glitch is
> heard. At WIN10, I use Windows Media Player, at board side I use command:

That's known issue, Windows is more strict with UAC2 descriptors, try to apply
my patch "usb: gadget: f_uac2: always increase endpoint max_packet_size
by one audio slot" that I shared in this email:
https://www.spinics.net/lists/linux-usb/msg205077.html

Thanks,
Ruslan

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Peter Chen]

[-- Attachment #1: Type: text/plain, Size: 5574 bytes --]

On 20-12-10 14:59:24, Ruslan Bilovol wrote:
> On Thu, Dec 3, 2020 at 12:09 PM Peter Chen <peter.chen@nxp.com> wrote:
> >
> > On 20-12-02 17:04:47, Glenn Schmottlach wrote:
> > > On Tue, Dec 1, 2020 at 4:43 PM Glenn Schmottlach <gschmottlach@gmail.com> wrote:
> > > > Hi Ruslan -
> > > >
> > > > Thanks for the feedback but unfortunately I've experienced mixed
> > > > results with the gadget UAC2 driver on both Windows/Linux. Let me
> > > > describe my environment. My host platform is either a Linux Ubuntu
> > > > 18.04 or Windows 10 laptop while the target environment is a
> > > > BeagleBone Black (Linux beaglebone 5.4.74-g9574bba32a #1 PREEMPT). I'm
> > > > testing two different scenarios:
> > > >
> > > > Scenario #1:
> > > > BeagleBone Black (BBB) runs speaker-test generating a single channel
> > > > (S32_LE) audio stream containing a 1KHz tone with a 48K sample rate,
> > > > e.g.
> > > >
> > > > > speaker-test -D hw:1,0 -r 48000 -c 1 -f 1000 -F S32_LE -t sine
> > > >
> > > > The host laptop is running Audacity and recording the tone over the
> > > > UAC2 adapter. On the Linux host the capture is correct and the tone is
> > > > bit-perfect. On the Windows 10 the capture contains numerous missing
> > > > samples which translates into a lot of audible pops and clicks.
> > > >
> > > > Scenario #2:
> > > > The Linux/Windows host plays a single channel, 48K, S32_LE 1K sine
> > > > tone to the target using either Audacity (on Windows) or 'aplay' (on
> > > > Linux), e.g.
> > > >
> > > > > aplay -D hw:4,0 -c 1  -r 48000 -t wav  tone_1k.wav  (Linux)
> > > >
> > > > On the BBB target I use 'arecord' to record the tone to a RAM disk and
> > > > then copy the recorded file back to the host where I can verify the
> > > > quality of the recording. In both instances (e.g. using either Windows
> > > > or Linux for playback) the recording on the target results in a
> > > > captured file with missing samples and audible pops/clicks. In this
> > > > scenario the UAC2 gadget is configured with c_sync == asynchronous. I
> > > > wouldn't expect things to improve with c_sync == adaptive since you
> > > > mentioned in your patch that it always reports back the nominal
> > > > frequency to the host from the feedback endpoint.
> > > >
> > > > Do you have any suggestions that might explain (the above) behavior.
> > > > Can you describe your test environment in more detail so that I can
> > > > perhaps re-create it? What Linux target are you using with your tests?
> > > > You mentioned you tested an 8x8 playback/capture scenario. Can you
> > > > provide any details of how you performed this test and the method you
> > > > used to confirm the audio quality for the capture/playback?
> > > >
> > > > Thanks for any insights you might be able to offer . . .
> > > >
> > > > Glenn
> > >
> > > Hi Ruslan -
> > >
> > > This is a follow-up from my post yesterday. I recompiled my kernel
> > > *WITHOUT* your UAC2 patches and repeated Scenario #2 where the Linux
> > > PC plays a single channel tone to the BeagleBone Black where it's
> > > recorded with 'arecord'. Yesterday, I recorded garbled audio on the
> > > target but today, without any UAC2 kernel patches, the recorded audio
> > > on the target is glitch-free and appears to be bit-perfect.
> > >
> > > This experiment leads me to believe your patches may be inadvertently
> > > corrupting the data-path. Have you been able to repeat my experiment
> > > and either confirm or refute my findings? I am interested to learn
> > > more how you tested your patches and whether it's something I can
> > > recreate here.
> > >
> > > Assuming we can sort out this data corruption issue, what are your
> > > thoughts on how the Linux target device can properly provide the
> > > Windows feedback endpoint with real frequency updates rather than the
> > > constant nominal frequency. If I understood your patch notes correctly
> > > it seems this is an outstanding issue that requires additional
> > > attention. I'm a bit of a noob when it comes to how this might be
> > > addressed.
> > >
> > > Thanks for your continued insights and support . . .
> > >
> > > Glenn
> >
> > Hi Glenn & Ruslan,
> >
> > Do you know why WIN10 can't recognized UAC2 device if I configure the
> > sample rate as 48000HZ? Configuring sample rate as 44100HZ, the playback
> > function would work well at my platforms (chipidea IP), no glitch is
> > heard. At WIN10, I use Windows Media Player, at board side I use command:
> 
> That's known issue, Windows is more strict with UAC2 descriptors, try to apply
> my patch "usb: gadget: f_uac2: always increase endpoint max_packet_size
> by one audio slot" that I shared in this email:
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.spinics.net%2Flists%2Flinux-usb%2Fmsg205077.html&amp;data=04%7C01%7Cpeter.chen%40nxp.com%7C1c037c406a47423725e008d89d0b77c1%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637432019865845335%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=7jE6EEi4ZifLMVNgs3%2FygUkBjCrcIrtvIjX2%2FVwbwUM%3D&amp;reserved=0
> 

Better than before, the Device Manager could recognize this sound device,
But Windows Media Player can't play it, see attached.

Meanwhile, I find your proposal patch [1] is not based on your UAC2 patch which
changed bmAttributes as USB_ENDPOINT_XFER_ISOC only at descriptor.

[1] https://www.spinics.net/lists/linux-usb/msg205077.html
-- 

Thanks,
Peter Chen

[-- Attachment #2: wmp_can't_play.PNG --]
[-- Type: image/png, Size: 6717 bytes --]

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Ruslan Bilovol]

On Tue, Dec 1, 2020 at 11:44 PM Glenn Schmottlach
<gschmottlach@gmail.com> wrote:
>
> On Sat, Nov 28, 2020 at 6:26 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
> >
> > On Wed, Nov 25, 2020 at 9:29 PM Glenn Schmottlach
> > <gschmottlach@gmail.com> wrote:
> > >
> > > On Sun, Nov 22, 2020 at 2:52 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
> > > >
> > > > On Fri, Nov 13, 2020 at 5:35 PM Glenn Schmottlach
> > > > <gschmottlach@gmail.com> wrote:
> > > > >
> > > > > On Thu, Nov 12, 2020 at 6:20 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
> > > > > >
> > > > > > On Wed, Nov 11, 2020 at 11:30 AM Peter Chen <peter.chen@nxp.com> wrote:
> > > > > > >
> > > > > > > On 20-11-08 02:18:28, Ruslan Bilovol wrote:
> > > > > > > > Current UAC2 gadget implements capture/sync paths
> > > > > > > > as two USB ISO ASYNC endpoints (IN and OUT).
> > > > > > > >
> > > > > > > > This violates USB spec which says that ISO ASYNC OUT endpoint
> > > > > > > > should have feedback companion endpoint.
> > > > > > > > See USB2.0 spec  "5.12.4.1 Synchronization Type": asynchronous
> > > > > > > > sink provides explicit feedback (isochronous pipe).
> > > > > > > > Interesting that for ISO ASYNC *IN* endpoint respective
> > > > > > > > feedback isn't required since source provides implicit
> > > > > > > > feedforward (data stream).
> > > > > > > >
> > > > > > > > While it's not an issue if UAC2 Gadget is connected to
> > > > > > > > Linux host (Linux ignores missing feedback endpoint),
> > > > > > > > with other hosts like Windows or MacOS the UAC2 Gadget
> > > > > > > > isn't enumerated due to missing feedback endpoint.
> > > > > > > >
> > > > > > > > This patch series adds feedback endpoint support to
> > > > > > > > UAC2 function, new control to UAC2 mixer which can
> > > > > > > > be used by userspace tools (like alsaloop from alsa-utils)
> > > > > > > > for updating feedback frequency reported to the host.
> > > > > > > > This is useful for usecases when UAC2 Gadget's audio
> > > > > > > > samples are played to another codec or audio card
> > > > > > > > with its own internal freerunning clock so host can
> > > > > > > > be notified that more/less samples are required.
> > > > > > > >
> > > > > > > > The alsaloop tool requires some (relatively small)
> > > > > > > > modifications in order to start support driving
> > > > > > > > feedback frequency through UAC2 mixer control.
> > > > > > > > That change will be sent as a separate patch
> > > > > > > > to ALSA community.
> > > > > > > >
> > > > > > > > Also added ability to switch ISO ASYNC OUT endpoint into
> > > > > > > > adaptive endpoint which doesn't require feedback endpoint
> > > > > > > > (as per USB spec).
> > > > > > > >
> > > > > > > > Ruslan Bilovol (3):
> > > > > > > >   usb: gadget: f_uac2/u_audio: add feedback endpoint support
> > > > > > > >   usb: gadget: f_uac2: add adaptive sync support for capture
> > > > > > > >   usb: gadget: u_audio: add real feedback implementation
> > > > > > >
> > > > > > > Hi Ruslan,
> > > > > > >
> > > > > > > I applied your patches, but WIN10 still can't recognize it well.
> > > > > > > The UAC1 is OK for WIN10 with the below same configuration.
> > > > > > > Any debug information you would like to know to check it?
> > > > > > >
> > > > > > >
> > > > > > > if [ "$FUNC" == "uac2" ]; then
> > > > > > > mkdir functions/$FUNC".0"
> > > > > > > echo 2 > functions/$FUNC".0"/p_ssize
> > > > > > > echo 48000 > functions/$FUNC".0"/p_srate
> > > > > > > echo 3 > functions/$FUNC".0"/p_chmask
> > > > > > >
> > > > > > > echo 2 > functions/$FUNC".0"/c_ssize
> > > > > > > echo 48000 > functions/$FUNC".0"/c_srate
> > > > > > > echo 3 > functions/$FUNC".0"/c_chmask
> > > > > > > #echo 4 > functions/$FUNC".0"/req_number
> > > > > > > ln -s functions/$FUNC".0" configs/c.1
> > > > > > > echo high-speed > /sys/kernel/config/usb_gadget/g1/max_speed
> > > > > > > fi
> > > > > > >
> > > > > >
> > > > > > Hmm... I just tested below config and it works fine with my Win10.
> > > > > > The only thing I noticed is Windows doesn't enable UAC2 gadget
> > > > > > by default, but this can be done from Win10 sound settings
> > > > > >
> > > > > > --------------------------------->8--------------------------------------
> > > > > > mkdir cfg
> > > > > > mount none cfg -t configfs
> > > > > > mkdir cfg/usb_gadget/g1
> > > > > > cd cfg/usb_gadget/g1
> > > > > > mkdir configs/c.1
> > > > > > mkdir functions/uac2.0
> > > > > >
> > > > > > # 44.1 kHz sample rate
> > > > > > echo 44100 > functions/uac2.0/c_srate
> > > > > > echo 44100 > functions/uac2.0/p_srate
> > > > > >
> > > > > > mkdir strings/0x409
> > > > > > mkdir configs/c.1/strings/0x409
> > > > > > echo 0x0101 > idProduct
> > > > > > echo 0x1d6b > idVendor
> > > > > > echo my-serial-num > strings/0x409/serialnumber
> > > > > > echo my-manufacturer > strings/0x409/manufacturer
> > > > > > echo "Test gadget" > strings/0x409/product
> > > > > > echo "Conf 1" > configs/c.1/strings/0x409/configuration
> > > > > > echo 120 > configs/c.1/MaxPower
> > > > > > ln -s functions/uac2.0 configs/c.1
> > > > > > echo musb-hdrc.0 > UDC
> > > > > > --------------------------------->8--------------------------------------
> > > > > >
> > > > > > Thanks,
> > > > > > Ruslan
> > > > >
> > > > > Hi Ruslan -
> > > > >
> > > > > With your configuration (above) Win10 was able to recognize and load
> > > > > the driver. What appears to prevent my configuration from loading is
> > > > > the fact that I selected 48K as my sample rate and my capture/playback
> > > > > channel mask includes more than two (2) channels. If I take your
> > > > > configuration and change the sample rate (c_srate/p_srate) to 48000
> > > > > Windows will fail to load the driver. Likewise, setting the
> > > > > c_chmask/p_chmask to 7 (three channels) will also cause the driver to
> > > > > fail to load.
> > > > >
> > > > > You mentioned there is an option in Win10 Sound Settings to "enable"
> > > > > UAC2 by default. I cannot find that option and I wonder if this is
> > > > > what is preventing me from changing the sample rate or channel mask?
> > > > > Could Windows be treating my audio gadget as a UAC1 device rather than
> > > > > a fully multi-channel audio device (even though the usbaudio2.sys
> > > > > driver is loaded)? Have you tried other configurations to verify your
> > > > > Win10 box supports more than two channels and a 44.1K sample rate? I
> > > > > look forward to your feedback and any suggestions you might offer.
> > > > >
> > > >
> > > > I was able to reproduce the issue and prepared a patch below, please
> > > > try it and see if it fixes the issue.
> > > >
> > > > Maximum data rates that I used were (AFAIR) 8 channel 192kHz/32bit,
> > > > but there is another issue with high data rate if someone uses so many
> > > > channels, very high sampling frequency or sample size that data can't
> > > > fit into allowed (by USB spec) max packet size of endpoint. In this case
> > > > need to decrease bInterval of endpoint.
> > > > I test it in a high-performance audio case so always use a minimal possible
> > > > bInterval (set to '1').
> > > > Of course in the future that need to be calculated dynamically depending on
> > > > the UAC2 settings
> > > >
> > > > Please test patches below and see it it helps
> > > >
> > > > ---------------------------------------------8<----------------------------------------
> > > > From 51516435bbf2486574ec7bc9fd4726677cd474a4 Mon Sep 17 00:00:00 2001
> > > > From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > > > Date: Sun, 22 Nov 2020 21:05:38 +0200
> > > > Subject: [PATCH] usb: gadget: f_uac2: always increase endpoint max_packet_size
> > > >  by one audio slot
> > > >
> > > > As per UAC2 Audio Data Formats spec (2.3.1.1 USB Packets),
> > > > if the sampling rate is a constant, the allowable variation
> > > > of number of audio slots per virtual frame is +/- 1 audio slot.
> > > >
> > > > It means that endpoint should be able to accept/send +1 audio
> > > > slot.
> > > >
> > > > Previous endpoint max_packet_size calculation code
> > > > was adding sometimes +1 audio slot due to DIV_ROUND_UP
> > > > behaviour which was rounding up to closest integer.
> > > > However this doesn't work if the numbers are divisible.
> > > >
> > > > It had no any impact with Linux hosts which ignore
> > > > this issue, but in case of more strict Windows it
> > > > caused rejected enumeration
> > > >
> > > > Thus always add +1 audio slot to endpoint's max packet size
> > > >
> > > > Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > > > ---
> > > >  drivers/usb/gadget/function/f_uac2.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/usb/gadget/function/f_uac2.c
> > > > b/drivers/usb/gadget/function/f_uac2.c
> > > > index ebdb2a1..1698587 100644
> > > > --- a/drivers/usb/gadget/function/f_uac2.c
> > > > +++ b/drivers/usb/gadget/function/f_uac2.c
> > > > @@ -486,7 +486,7 @@ static void set_ep_max_packet_size(const struct
> > > > f_uac2_opts *uac2_opts,
> > > >   }
> > > >
> > > >   max_packet_size = num_channels(chmask) * ssize *
> > > > - DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1)));
> > > > + ((srate / (factor / (1 << (ep_desc->bInterval - 1)))) + 1);
> > > >
> > > >   if (!is_playback && (uac2_opts->c_sync == USB_ENDPOINT_SYNC_ASYNC))
> > > >   max_packet_size = max_packet_size * FBACK_FREQ_MAX / 100;
> > > > --
> > > > 1.9.1
> > > >
> > > >
> > > > ---------------------------------------------8<----------------------------------------
> > > > From c8f2f2b414af672ec40841e75fb1ea761ae29122 Mon Sep 17 00:00:00 2001
> > > > From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > > > Date: Sun, 16 Feb 2020 22:40:23 +0200
> > > > Subject: [PATCH] usb: gadget: f_uac2: change bInterval to 1 for
> > > >  8ch/24bit/44.1kHz
> > > >
> > > > With bInterval=4 one audio slot in case of 8ch/24bit/44.1kHz
> > > > exeeds MaxPacket size of ISO endpoint (>1024) and can't be
> > > > transferred in time.
> > > > USB spec ("5.6.3 Isochronous Transfer Packet Size Constraints")
> > > > says if we need to transfer more than 1024 it is a high speed, high
> > > > bandwidth endpoint and should have bInterval=1.
> > > >
> > > > In the future, bInterval should be dynamically calculated
> > > > depending on bandwith requirementes
> > > >
> > > > Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > > > ---
> > > >  drivers/usb/gadget/function/f_uac2.c | 4 ++--
> > > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/usb/gadget/function/f_uac2.c
> > > > b/drivers/usb/gadget/function/f_uac2.c
> > > > index 3633df6..fb9b875 100644
> > > > --- a/drivers/usb/gadget/function/f_uac2.c
> > > > +++ b/drivers/usb/gadget/function/f_uac2.c
> > > > @@ -281,7 +281,7 @@ enum {
> > > >
> > > >   .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
> > > >   .wMaxPacketSize = cpu_to_le16(1024),
> > > > - .bInterval = 4,
> > > > + .bInterval = 1,
> > > >  };
> > > >
> > > >  /* CS AS ISO OUT Endpoint */
> > > > @@ -358,7 +358,7 @@ enum {
> > > >
> > > >   .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
> > > >   .wMaxPacketSize = cpu_to_le16(1024),
> > > > - .bInterval = 4,
> > > > + .bInterval = 1,
> > > >  };
> > > >
> > > >  /* CS AS ISO IN Endpoint */
> > > > --
> > > > 1.9.1
> > > >
> > > >
> > > > ---------------------------------------------8<----------------------------------------
> > > >
> > > > Thanks,
> > > > Ruslan
> > >
> > > Hi Ruslan -
> > >
> > > I have had some mixed success with your additional patches. First, the
> >
> > That's good news, thanks for testing!
> >
> > > UAC2 gadget does correctly register with Windows 10 but only for 1-31
> > > channels. For a fully specified channel map (32 channels):
> > >
> > > c_chmask = 0xFFFFFFFF    ( Does not load)
> > > p_chmask = 0xFFFFFFFF   ( Does not load)
> > >
> > > the driver fails to load (code=10). This seems similar to the prior
> > > problem. Could there be another off-by-one problem here?
> > >
> > > With a 31 channel mask the Windows 10 usbaudio2.sys loads successfully, e.g.
> > >
> > > c_chmask = 0x7FFFFFFF (loads)
> > > p_chmask = 0x7FFFFFFF (loads)
> >
> > That's correct behavior. UAC2 spec says that bits D27..D30 are reserved.
> > Also bit D31 is mutually exclusive with other bits and means 'raw data'.
> > It means that with current UAC2 gadget implementation you can enable
> > only 27 channels.
> >
> > It seems like it's possible to add more channels by adding more audio
> > clusters but that requires UAC2 driver modifications. Also it's not clear
> > whether it's implemented in Host OS drivers
> >
> > I personally tested as many as 8x8 playback/capture channels simultaneously.
> >
> > >
> > > Once Windows 10 loads the driver successfully, however, I can't seem
> > > to select the device through Audacity on Windows. The device appears
> > > in the Windows "Device Manager" under "Sound, video and game
> > > controllers -> Source/Sink". How are you testing audio
> > > playback/capture under Windows? Perhaps my test approach is wrong?
> >
> > You need to go to sound settings -> manage sound devices and enable
> > UAC2 gadget there, after that it will appear in the system.
> >
> > I also used Audacity for testing this and it works fine for me
> >
> > Thanks,
> > Ruslan
> >
> > >
> > > I used the same approach on my Linux host where the USB UAC2 device
> > > appears as an ALSA device and I use speaker-test on the target
> > > (BeagleBone Black) to play and then capture the audio using Audacity
> > > on the Linux host. I was hoping to do the same or something similar
> > > under Windows.
> > >
> > > Below is the script I've been using on the target to configure my UAC2 device:
> > >
> > > mkdir -p "/sys/kernel/config/usb_gadget/g_multi"
> > > echo "${idVendor:-0x11F5}" > "/sys/kernel/config/usb_gadget/g_multi/idVendor"
> > > echo "${idProduct:-0x0009}" > "/sys/kernel/config/usb_gadget/g_multi/idProduct"
> > > echo "${bcdDevice:-0x0001}" > "/sys/kernel/config/usb_gadget/g_multi/bcdDevice"
> > > echo "${bDeviceClass:-0x00}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/bDeviceClass"
> > > echo "${bDeviceSubClass:-0x00}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/bDeviceSubClass"
> > > echo "${bDeviceProtocol:-0x00}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/bDeviceProtocol"
> > > echo "${bcdUSB:-0x0200}" > "/sys/kernel/config/usb_gadget/g_multi/bcdUSB"
> > > echo "${bMaxPacketSize0:-0x00}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/bMaxPacketSize0"
> > > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/strings/0x409"
> > > echo "${serialnumber:-000000000000}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/strings/0x409/serialnumber"
> > > echo "${product:-UAC2}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/strings/0x409/product"
> > > echo "${manufacturer:-www.acme.com}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/strings/0x409/manufacturer"
> > > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0"
> > > echo "${req_number:-4}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/req_number"
> > > echo "${c_ssize:-4}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_ssize"
> > > echo "${c_srate:-48000}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_srate"
> > > echo "${c_chmask:-0x00000003}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_chmask"
> > > echo "${c_sync:-asynchronous}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/c_sync"
> > > echo "${p_ssize:-4}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_ssize"
> > > echo "${p_srate:-48000}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_srate"
> > > echo "${p_chmask:-0x00000003}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0/p_chmask"
> > > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/configs/c.1"
> > > echo "${bmAttributes:-0x80}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/bmAttributes"
> > > echo "${MaxPower:-500}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/MaxPower"
> > > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/strings/0x409"
> > > echo "${configuration:-BeagleBone Composite}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/strings/0x409/configuration"
> > > ln -s "/sys/kernel/config/usb_gadget/g_multi/functions/uac2.usb0"
> > > "/sys/kernel/config/usb_gadget/g_multi/configs/c.1/uac2.usb0"
> > > mkdir -p "/sys/kernel/config/usb_gadget/g_multi/os_desc"
> > > ln -s "//sys/kernel/config/usb_gadget/g_multi/configs/c.1"
> > > "/sys/kernel/config/usb_gadget/g_multi/os_desc/c.1"
> > > echo "${qw_sign:-MSFT100}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/os_desc/qw_sign"
> > > echo "${b_vendor_code:-0x00}" >
> > > "/sys/kernel/config/usb_gadget/g_multi/os_desc/b_vendor_code"
> > > echo "${use:-1}" > "/sys/kernel/config/usb_gadget/g_multi/os_desc/use"
> > >
> > > basename /sys/class/udc/* > /sys/kernel/config/usb_gadget/g_multi/UDC
> > >
> > > This is only a two channel playback/capture configuration. I hoped to
> > > get this working under Windows before increasing my channel count to a
> > > full 32 channel mask with a 48K sample rate.
> > >
> > > I look forward to hearing your suggestions and possibly pointing out
> > > where I've gone astray.
> > >
> > > Thanks,
> > >
> > > Glenn
>
> Hi Ruslan -
>
> Thanks for the feedback but unfortunately I've experienced mixed
> results with the gadget UAC2 driver on both Windows/Linux. Let me
> describe my environment. My host platform is either a Linux Ubuntu
> 18.04 or Windows 10 laptop while the target environment is a
> BeagleBone Black (Linux beaglebone 5.4.74-g9574bba32a #1 PREEMPT). I'm
> testing two different scenarios:
>
> Scenario #1:
> BeagleBone Black (BBB) runs speaker-test generating a single channel
> (S32_LE) audio stream containing a 1KHz tone with a 48K sample rate,
> e.g.
>
> > speaker-test -D hw:1,0 -r 48000 -c 1 -f 1000 -F S32_LE -t sine
>
> The host laptop is running Audacity and recording the tone over the
> UAC2 adapter. On the Linux host the capture is correct and the tone is
> bit-perfect. On the Windows 10 the capture contains numerous missing
> samples which translates into a lot of audible pops and clicks.
>
> Scenario #2:
> The Linux/Windows host plays a single channel, 48K, S32_LE 1K sine
> tone to the target using either Audacity (on Windows) or 'aplay' (on
> Linux), e.g.
>
> > aplay -D hw:4,0 -c 1  -r 48000 -t wav  tone_1k.wav  (Linux)
>
> On the BBB target I use 'arecord' to record the tone to a RAM disk and
> then copy the recorded file back to the host where I can verify the
> quality of the recording. In both instances (e.g. using either Windows
> or Linux for playback) the recording on the target results in a
> captured file with missing samples and audible pops/clicks. In this
> scenario the UAC2 gadget is configured with c_sync == asynchronous. I
> wouldn't expect things to improve with c_sync == adaptive since you
> mentioned in your patch that it always reports back the nominal
> frequency to the host from the feedback endpoint.
>
> Do you have any suggestions that might explain (the above) behavior.
> Can you describe your test environment in more detail so that I can
> perhaps re-create it? What Linux target are you using with your tests?
> You mentioned you tested an 8x8 playback/capture scenario. Can you
> provide any details of how you performed this test and the method you
> used to confirm the audio quality for the capture/playback?

I also use BeagleBone black in my development.
I have two testing scenarios:
 1) BeagleBone PC loopback (e.g. redirect play->capture in BBB), here
     I play sine wave on PC to BBB and record back (simultaneously in
     Audacity), it looks like:
     Audiacity (PC playback) -> BBB capture -> alsaloop -> BBB playback ->
     Audacity (PC capture)
 2) I connect another USB audio card to BBB, and redirect audio samples
     from PC through BBB UAC2 audio gadget to USB audio card, this path
     looks like:
     PC playback) -> BBB capture -> alsaloop -> BBB USB audio card

With #1 I tested simultaneous 8x8ch 24bit 44.1 kHz loopback (also 4x4ch
and 2x2 ch)
With #2 it's limited to USB audio card I have (usually I do 2ch 16bit 44.1 or
48 kHz)

I see you use 32bit samples, I tested it a few times before on the previous
patch set versions.

Can you try to check 2ch 16bit 44.1 or 48 kHz? I'm thinking if this issue is
limited to some combination of sampling rate, channels and sample resolution

Thanks,
Ruslan

>
> Thanks for any insights you might be able to offer . . .
>
> Glenn

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Jerome Brunet]

On Sun 22 Nov 2020 at 20:51, Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:

> On Fri, Nov 13, 2020 at 5:35 PM Glenn Schmottlach
> <gschmottlach@gmail.com> wrote:
>>
>> On Thu, Nov 12, 2020 at 6:20 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
>> >
>> > On Wed, Nov 11, 2020 at 11:30 AM Peter Chen <peter.chen@nxp.com> wrote:
>> > >
>> > > On 20-11-08 02:18:28, Ruslan Bilovol wrote:
>> > > > Current UAC2 gadget implements capture/sync paths
>> > > > as two USB ISO ASYNC endpoints (IN and OUT).
>> > > >
>> > > > This violates USB spec which says that ISO ASYNC OUT endpoint
>> > > > should have feedback companion endpoint.
>> > > > See USB2.0 spec  "5.12.4.1 Synchronization Type": asynchronous
>> > > > sink provides explicit feedback (isochronous pipe).
>> > > > Interesting that for ISO ASYNC *IN* endpoint respective
>> > > > feedback isn't required since source provides implicit
>> > > > feedforward (data stream).
>> > > >
>> > > > While it's not an issue if UAC2 Gadget is connected to
>> > > > Linux host (Linux ignores missing feedback endpoint),
>> > > > with other hosts like Windows or MacOS the UAC2 Gadget
>> > > > isn't enumerated due to missing feedback endpoint.
>> > > >
>> > > > This patch series adds feedback endpoint support to
>> > > > UAC2 function, new control to UAC2 mixer which can
>> > > > be used by userspace tools (like alsaloop from alsa-utils)
>> > > > for updating feedback frequency reported to the host.
>> > > > This is useful for usecases when UAC2 Gadget's audio
>> > > > samples are played to another codec or audio card
>> > > > with its own internal freerunning clock so host can
>> > > > be notified that more/less samples are required.
>> > > >
>> > > > The alsaloop tool requires some (relatively small)
>> > > > modifications in order to start support driving
>> > > > feedback frequency through UAC2 mixer control.
>> > > > That change will be sent as a separate patch
>> > > > to ALSA community.
>> > > >
>> > > > Also added ability to switch ISO ASYNC OUT endpoint into
>> > > > adaptive endpoint which doesn't require feedback endpoint
>> > > > (as per USB spec).
>> > > >
>> > > > Ruslan Bilovol (3):
>> > > >   usb: gadget: f_uac2/u_audio: add feedback endpoint support
>> > > >   usb: gadget: f_uac2: add adaptive sync support for capture
>> > > >   usb: gadget: u_audio: add real feedback implementation
>> > >
>> > > Hi Ruslan,
>> > >
>> > > I applied your patches, but WIN10 still can't recognize it well.
>> > > The UAC1 is OK for WIN10 with the below same configuration.
>> > > Any debug information you would like to know to check it?
>> > >
>> > >
>> > > if [ "$FUNC" == "uac2" ]; then
>> > > mkdir functions/$FUNC".0"
>> > > echo 2 > functions/$FUNC".0"/p_ssize
>> > > echo 48000 > functions/$FUNC".0"/p_srate
>> > > echo 3 > functions/$FUNC".0"/p_chmask
>> > >
>> > > echo 2 > functions/$FUNC".0"/c_ssize
>> > > echo 48000 > functions/$FUNC".0"/c_srate
>> > > echo 3 > functions/$FUNC".0"/c_chmask
>> > > #echo 4 > functions/$FUNC".0"/req_number
>> > > ln -s functions/$FUNC".0" configs/c.1
>> > > echo high-speed > /sys/kernel/config/usb_gadget/g1/max_speed
>> > > fi
>> > >
>> >
>> > Hmm... I just tested below config and it works fine with my Win10.
>> > The only thing I noticed is Windows doesn't enable UAC2 gadget
>> > by default, but this can be done from Win10 sound settings
>> >
>> > --------------------------------->8--------------------------------------
>> > mkdir cfg
>> > mount none cfg -t configfs
>> > mkdir cfg/usb_gadget/g1
>> > cd cfg/usb_gadget/g1
>> > mkdir configs/c.1
>> > mkdir functions/uac2.0
>> >
>> > # 44.1 kHz sample rate
>> > echo 44100 > functions/uac2.0/c_srate
>> > echo 44100 > functions/uac2.0/p_srate
>> >
>> > mkdir strings/0x409
>> > mkdir configs/c.1/strings/0x409
>> > echo 0x0101 > idProduct
>> > echo 0x1d6b > idVendor
>> > echo my-serial-num > strings/0x409/serialnumber
>> > echo my-manufacturer > strings/0x409/manufacturer
>> > echo "Test gadget" > strings/0x409/product
>> > echo "Conf 1" > configs/c.1/strings/0x409/configuration
>> > echo 120 > configs/c.1/MaxPower
>> > ln -s functions/uac2.0 configs/c.1
>> > echo musb-hdrc.0 > UDC
>> > --------------------------------->8--------------------------------------
>> >
>> > Thanks,
>> > Ruslan
>>
>> Hi Ruslan -
>>
>> With your configuration (above) Win10 was able to recognize and load
>> the driver. What appears to prevent my configuration from loading is
>> the fact that I selected 48K as my sample rate and my capture/playback
>> channel mask includes more than two (2) channels. If I take your
>> configuration and change the sample rate (c_srate/p_srate) to 48000
>> Windows will fail to load the driver. Likewise, setting the
>> c_chmask/p_chmask to 7 (three channels) will also cause the driver to
>> fail to load.
>>
>> You mentioned there is an option in Win10 Sound Settings to "enable"
>> UAC2 by default. I cannot find that option and I wonder if this is
>> what is preventing me from changing the sample rate or channel mask?
>> Could Windows be treating my audio gadget as a UAC1 device rather than
>> a fully multi-channel audio device (even though the usbaudio2.sys
>> driver is loaded)? Have you tried other configurations to verify your
>> Win10 box supports more than two channels and a 44.1K sample rate? I
>> look forward to your feedback and any suggestions you might offer.
>>
>
> I was able to reproduce the issue and prepared a patch below, please
> try it and see if it fixes the issue.
>
> Maximum data rates that I used were (AFAIR) 8 channel 192kHz/32bit,
> but there is another issue with high data rate if someone uses so many
> channels, very high sampling frequency or sample size that data can't
> fit into allowed (by USB spec) max packet size of endpoint. In this case
> need to decrease bInterval of endpoint.
> I test it in a high-performance audio case so always use a minimal possible
> bInterval (set to '1').
> Of course in the future that need to be calculated dynamically depending on
> the UAC2 settings
>
> Please test patches below and see it it helps
>
> ---------------------------------------------8<----------------------------------------
> From 51516435bbf2486574ec7bc9fd4726677cd474a4 Mon Sep 17 00:00:00 2001
> From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> Date: Sun, 22 Nov 2020 21:05:38 +0200
> Subject: [PATCH] usb: gadget: f_uac2: always increase endpoint max_packet_size
>  by one audio slot
>
> As per UAC2 Audio Data Formats spec (2.3.1.1 USB Packets),
> if the sampling rate is a constant, the allowable variation
> of number of audio slots per virtual frame is +/- 1 audio slot.
>
> It means that endpoint should be able to accept/send +1 audio
> slot.
>
> Previous endpoint max_packet_size calculation code
> was adding sometimes +1 audio slot due to DIV_ROUND_UP
> behaviour which was rounding up to closest integer.
> However this doesn't work if the numbers are divisible.
>
> It had no any impact with Linux hosts which ignore
> this issue, but in case of more strict Windows it
> caused rejected enumeration
>
> Thus always add +1 audio slot to endpoint's max packet size
>
> Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> ---
>  drivers/usb/gadget/function/f_uac2.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/function/f_uac2.c
> b/drivers/usb/gadget/function/f_uac2.c
> index ebdb2a1..1698587 100644
> --- a/drivers/usb/gadget/function/f_uac2.c
> +++ b/drivers/usb/gadget/function/f_uac2.c
> @@ -486,7 +486,7 @@ static void set_ep_max_packet_size(const struct
> f_uac2_opts *uac2_opts,
>   }
>
>   max_packet_size = num_channels(chmask) * ssize *
> - DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1)));
> + ((srate / (factor / (1 << (ep_desc->bInterval - 1)))) + 1);
>
>   if (!is_playback && (uac2_opts->c_sync == USB_ENDPOINT_SYNC_ASYNC))
>   max_packet_size = max_packet_size * FBACK_FREQ_MAX / 100;

I think "reserving" 20% additional bandwidth is a bit extreme.
In the end, the purpose is composate the drift which appears between
different XTALs

Allocating bandwidth for 1 more sample than the stream should require
(49 instead of 48 for 48kHz with 4 bIntervals) should allow to
compensate any realistic drift, don't you think ?

> -- 
> 1.9.1
>
>
> ---------------------------------------------8<----------------------------------------
> From c8f2f2b414af672ec40841e75fb1ea761ae29122 Mon Sep 17 00:00:00 2001
> From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> Date: Sun, 16 Feb 2020 22:40:23 +0200
> Subject: [PATCH] usb: gadget: f_uac2: change bInterval to 1 for
>  8ch/24bit/44.1kHz
>
> With bInterval=4 one audio slot in case of 8ch/24bit/44.1kHz
> exeeds MaxPacket size of ISO endpoint (>1024) and can't be
> transferred in time.
> USB spec ("5.6.3 Isochronous Transfer Packet Size Constraints")
> says if we need to transfer more than 1024 it is a high speed, high
> bandwidth endpoint and should have bInterval=1.
>
> In the future, bInterval should be dynamically calculated
> depending on bandwith requirementes

Probably better to do it from the start to avoid breaking stuff for
people who have been using the gadget with the current badnwidth so far

>
> Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> ---
>  drivers/usb/gadget/function/f_uac2.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/f_uac2.c
> b/drivers/usb/gadget/function/f_uac2.c
> index 3633df6..fb9b875 100644
> --- a/drivers/usb/gadget/function/f_uac2.c
> +++ b/drivers/usb/gadget/function/f_uac2.c
> @@ -281,7 +281,7 @@ enum {
>
>   .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
>   .wMaxPacketSize = cpu_to_le16(1024),
> - .bInterval = 4,
> + .bInterval = 1,
>  };
>
>  /* CS AS ISO OUT Endpoint */
> @@ -358,7 +358,7 @@ enum {
>
>   .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
>   .wMaxPacketSize = cpu_to_le16(1024),
> - .bInterval = 4,
> + .bInterval = 1,
>  };
>
>  /* CS AS ISO IN Endpoint */

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Pavel Hofman]

Dne 26. 11. 20 v 14:16 Jerome Brunet napsal(a):
> 
>> Maximum data rates that I used were (AFAIR) 8 channel 192kHz/32bit,
>> but there is another issue with high data rate if someone uses so many
>> channels, very high sampling frequency or sample size that data can't
>> fit into allowed (by USB spec) max packet size of endpoint. In this case
>> need to decrease bInterval of endpoint.

Should anyone test the patches with RPi4 dwc2 as the gadget, please note 
the recently accepted patch 
https://patchwork.kernel.org/project/linux-usb/patch/e9e7d070-593c-122f-3a5c-2435bb147ab2@ivitera.com/ 
which allows using full 1024 bytes maxpacketsize on EP OUT. It is not an 
enumeration issue, but the old (= existing) RX FIFO size drops data with 
packet sizes above 960 bytes.

Thanks a lot for the great work.

Best regards,

Pavel.

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Ruslan Bilovol]

On Thu, Nov 26, 2020 at 3:44 PM Pavel Hofman <pavel.hofman@ivitera.com> wrote:
>
> Dne 26. 11. 20 v 14:16 Jerome Brunet napsal(a):
> >
> >> Maximum data rates that I used were (AFAIR) 8 channel 192kHz/32bit,
> >> but there is another issue with high data rate if someone uses so many
> >> channels, very high sampling frequency or sample size that data can't
> >> fit into allowed (by USB spec) max packet size of endpoint. In this case
> >> need to decrease bInterval of endpoint.
>
> Should anyone test the patches with RPi4 dwc2 as the gadget, please note
> the recently accepted patch
> https://patchwork.kernel.org/project/linux-usb/patch/e9e7d070-593c-122f-3a5c-2435bb147ab2@ivitera.com/
> which allows using full 1024 bytes maxpacketsize on EP OUT. It is not an
> enumeration issue, but the old (= existing) RX FIFO size drops data with
> packet sizes above 960 bytes.

Thanks for bringing this to our attention. Does it affect RPi 3 as well?
I'm going to test feedback feature on this board

Regards,
Ruslan

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Pavel Hofman]

Dne 04. 12. 20 v 15:39 Ruslan Bilovol napsal(a):
> On Thu, Nov 26, 2020 at 3:44 PM Pavel Hofman <pavel.hofman@ivitera.com> wrote:
>>
>> Dne 26. 11. 20 v 14:16 Jerome Brunet napsal(a):
>>>
>>>> Maximum data rates that I used were (AFAIR) 8 channel 192kHz/32bit,
>>>> but there is another issue with high data rate if someone uses so many
>>>> channels, very high sampling frequency or sample size that data can't
>>>> fit into allowed (by USB spec) max packet size of endpoint. In this case
>>>> need to decrease bInterval of endpoint.
>>
>> Should anyone test the patches with RPi4 dwc2 as the gadget, please note
>> the recently accepted patch
>> https://patchwork.kernel.org/project/linux-usb/patch/e9e7d070-593c-122f-3a5c-2435bb147ab2@ivitera.com/
>> which allows using full 1024 bytes maxpacketsize on EP OUT. It is not an
>> enumeration issue, but the old (= existing) RX FIFO size drops data with
>> packet sizes above 960 bytes.
> 
> Thanks for bringing this to our attention. Does it affect RPi 3 as well?
> I'm going to test feedback feature on this board

It configures the dwc2 IP of the broadcom which IIRC is in all RPis. The
affected files bcm283x-rpi-usb-otg.dtsi and
bcm283x-rpi-usb-peripheral.dtsi do not seem RPi4 specific. But I had
only RPi4 to analyze the problem and check the fix.

Ruslan, please what do you think about the existing behaviour of gaudio
in case of USB stream disconnection? The elapsed-period callback stops
being called and the user space will eventually time out. How about
closing the PCM stream immediately in case of a problem in the USB
layer? E.g. some SPDIF receivers do that in case of change in the
incoming samplerate
https://github.com/torvalds/linux/blob/master/sound/i2c/other/ak4117.c#L503
.

Thanks a lot for the great work.

With regards,

Pavel.

Re: [PATCH 0/3] UAC2 Gadget: feedback endpoint support

[Ruslan Bilovol]

On Thu, Nov 26, 2020 at 3:16 PM Jerome Brunet <jbrunet@baylibre.com> wrote:
>
>
> On Sun 22 Nov 2020 at 20:51, Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
>
> > On Fri, Nov 13, 2020 at 5:35 PM Glenn Schmottlach
> > <gschmottlach@gmail.com> wrote:
> >>
> >> On Thu, Nov 12, 2020 at 6:20 PM Ruslan Bilovol <ruslan.bilovol@gmail.com> wrote:
> >> >
> >> > On Wed, Nov 11, 2020 at 11:30 AM Peter Chen <peter.chen@nxp.com> wrote:
> >> > >
> >> > > On 20-11-08 02:18:28, Ruslan Bilovol wrote:
> >> > > > Current UAC2 gadget implements capture/sync paths
> >> > > > as two USB ISO ASYNC endpoints (IN and OUT).
> >> > > >
> >> > > > This violates USB spec which says that ISO ASYNC OUT endpoint
> >> > > > should have feedback companion endpoint.
> >> > > > See USB2.0 spec  "5.12.4.1 Synchronization Type": asynchronous
> >> > > > sink provides explicit feedback (isochronous pipe).
> >> > > > Interesting that for ISO ASYNC *IN* endpoint respective
> >> > > > feedback isn't required since source provides implicit
> >> > > > feedforward (data stream).
> >> > > >
> >> > > > While it's not an issue if UAC2 Gadget is connected to
> >> > > > Linux host (Linux ignores missing feedback endpoint),
> >> > > > with other hosts like Windows or MacOS the UAC2 Gadget
> >> > > > isn't enumerated due to missing feedback endpoint.
> >> > > >
> >> > > > This patch series adds feedback endpoint support to
> >> > > > UAC2 function, new control to UAC2 mixer which can
> >> > > > be used by userspace tools (like alsaloop from alsa-utils)
> >> > > > for updating feedback frequency reported to the host.
> >> > > > This is useful for usecases when UAC2 Gadget's audio
> >> > > > samples are played to another codec or audio card
> >> > > > with its own internal freerunning clock so host can
> >> > > > be notified that more/less samples are required.
> >> > > >
> >> > > > The alsaloop tool requires some (relatively small)
> >> > > > modifications in order to start support driving
> >> > > > feedback frequency through UAC2 mixer control.
> >> > > > That change will be sent as a separate patch
> >> > > > to ALSA community.
> >> > > >
> >> > > > Also added ability to switch ISO ASYNC OUT endpoint into
> >> > > > adaptive endpoint which doesn't require feedback endpoint
> >> > > > (as per USB spec).
> >> > > >
> >> > > > Ruslan Bilovol (3):
> >> > > >   usb: gadget: f_uac2/u_audio: add feedback endpoint support
> >> > > >   usb: gadget: f_uac2: add adaptive sync support for capture
> >> > > >   usb: gadget: u_audio: add real feedback implementation
> >> > >
> >> > > Hi Ruslan,
> >> > >
> >> > > I applied your patches, but WIN10 still can't recognize it well.
> >> > > The UAC1 is OK for WIN10 with the below same configuration.
> >> > > Any debug information you would like to know to check it?
> >> > >
> >> > >
> >> > > if [ "$FUNC" == "uac2" ]; then
> >> > > mkdir functions/$FUNC".0"
> >> > > echo 2 > functions/$FUNC".0"/p_ssize
> >> > > echo 48000 > functions/$FUNC".0"/p_srate
> >> > > echo 3 > functions/$FUNC".0"/p_chmask
> >> > >
> >> > > echo 2 > functions/$FUNC".0"/c_ssize
> >> > > echo 48000 > functions/$FUNC".0"/c_srate
> >> > > echo 3 > functions/$FUNC".0"/c_chmask
> >> > > #echo 4 > functions/$FUNC".0"/req_number
> >> > > ln -s functions/$FUNC".0" configs/c.1
> >> > > echo high-speed > /sys/kernel/config/usb_gadget/g1/max_speed
> >> > > fi
> >> > >
> >> >
> >> > Hmm... I just tested below config and it works fine with my Win10.
> >> > The only thing I noticed is Windows doesn't enable UAC2 gadget
> >> > by default, but this can be done from Win10 sound settings
> >> >
> >> > --------------------------------->8--------------------------------------
> >> > mkdir cfg
> >> > mount none cfg -t configfs
> >> > mkdir cfg/usb_gadget/g1
> >> > cd cfg/usb_gadget/g1
> >> > mkdir configs/c.1
> >> > mkdir functions/uac2.0
> >> >
> >> > # 44.1 kHz sample rate
> >> > echo 44100 > functions/uac2.0/c_srate
> >> > echo 44100 > functions/uac2.0/p_srate
> >> >
> >> > mkdir strings/0x409
> >> > mkdir configs/c.1/strings/0x409
> >> > echo 0x0101 > idProduct
> >> > echo 0x1d6b > idVendor
> >> > echo my-serial-num > strings/0x409/serialnumber
> >> > echo my-manufacturer > strings/0x409/manufacturer
> >> > echo "Test gadget" > strings/0x409/product
> >> > echo "Conf 1" > configs/c.1/strings/0x409/configuration
> >> > echo 120 > configs/c.1/MaxPower
> >> > ln -s functions/uac2.0 configs/c.1
> >> > echo musb-hdrc.0 > UDC
> >> > --------------------------------->8--------------------------------------
> >> >
> >> > Thanks,
> >> > Ruslan
> >>
> >> Hi Ruslan -
> >>
> >> With your configuration (above) Win10 was able to recognize and load
> >> the driver. What appears to prevent my configuration from loading is
> >> the fact that I selected 48K as my sample rate and my capture/playback
> >> channel mask includes more than two (2) channels. If I take your
> >> configuration and change the sample rate (c_srate/p_srate) to 48000
> >> Windows will fail to load the driver. Likewise, setting the
> >> c_chmask/p_chmask to 7 (three channels) will also cause the driver to
> >> fail to load.
> >>
> >> You mentioned there is an option in Win10 Sound Settings to "enable"
> >> UAC2 by default. I cannot find that option and I wonder if this is
> >> what is preventing me from changing the sample rate or channel mask?
> >> Could Windows be treating my audio gadget as a UAC1 device rather than
> >> a fully multi-channel audio device (even though the usbaudio2.sys
> >> driver is loaded)? Have you tried other configurations to verify your
> >> Win10 box supports more than two channels and a 44.1K sample rate? I
> >> look forward to your feedback and any suggestions you might offer.
> >>
> >
> > I was able to reproduce the issue and prepared a patch below, please
> > try it and see if it fixes the issue.
> >
> > Maximum data rates that I used were (AFAIR) 8 channel 192kHz/32bit,
> > but there is another issue with high data rate if someone uses so many
> > channels, very high sampling frequency or sample size that data can't
> > fit into allowed (by USB spec) max packet size of endpoint. In this case
> > need to decrease bInterval of endpoint.
> > I test it in a high-performance audio case so always use a minimal possible
> > bInterval (set to '1').
> > Of course in the future that need to be calculated dynamically depending on
> > the UAC2 settings
> >
> > Please test patches below and see it it helps
> >
> > ---------------------------------------------8<----------------------------------------
> > From 51516435bbf2486574ec7bc9fd4726677cd474a4 Mon Sep 17 00:00:00 2001
> > From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > Date: Sun, 22 Nov 2020 21:05:38 +0200
> > Subject: [PATCH] usb: gadget: f_uac2: always increase endpoint max_packet_size
> >  by one audio slot
> >
> > As per UAC2 Audio Data Formats spec (2.3.1.1 USB Packets),
> > if the sampling rate is a constant, the allowable variation
> > of number of audio slots per virtual frame is +/- 1 audio slot.
> >
> > It means that endpoint should be able to accept/send +1 audio
> > slot.
> >
> > Previous endpoint max_packet_size calculation code
> > was adding sometimes +1 audio slot due to DIV_ROUND_UP
> > behaviour which was rounding up to closest integer.
> > However this doesn't work if the numbers are divisible.
> >
> > It had no any impact with Linux hosts which ignore
> > this issue, but in case of more strict Windows it
> > caused rejected enumeration
> >
> > Thus always add +1 audio slot to endpoint's max packet size
> >
> > Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > ---
> >  drivers/usb/gadget/function/f_uac2.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/gadget/function/f_uac2.c
> > b/drivers/usb/gadget/function/f_uac2.c
> > index ebdb2a1..1698587 100644
> > --- a/drivers/usb/gadget/function/f_uac2.c
> > +++ b/drivers/usb/gadget/function/f_uac2.c
> > @@ -486,7 +486,7 @@ static void set_ep_max_packet_size(const struct
> > f_uac2_opts *uac2_opts,
> >   }
> >
> >   max_packet_size = num_channels(chmask) * ssize *
> > - DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1)));
> > + ((srate / (factor / (1 << (ep_desc->bInterval - 1)))) + 1);
> >
> >   if (!is_playback && (uac2_opts->c_sync == USB_ENDPOINT_SYNC_ASYNC))
> >   max_packet_size = max_packet_size * FBACK_FREQ_MAX / 100;
>
> I think "reserving" 20% additional bandwidth is a bit extreme.
> In the end, the purpose is composate the drift which appears between
> different XTALs

That isn't extreme, I checked snd-usb ALSA driver before selecting number
and it assumes the drift is between -25% ... +50% so +/-20% should work
fine here (see snd_usb_handle_sync_urb() in sound/usb/endpoint.c).

Since our UAC2 gadget is a kind of "reversed" USB audio card, that also
works fine with alsaloop connecting it to other audio cards in the system.

>
> Allocating bandwidth for 1 more sample than the stream should require
> (49 instead of 48 for 48kHz with 4 bIntervals) should allow to
> compensate any realistic drift, don't you think ?

With cheap USB Audio adapters I saw +/-100 Hz drift on 44100 Hz

Anyway I don't think this can cause any problem since it is OK as
per UAC2 spec and hosts (at least Linux) can handle such values

Thanks,
Ruslan

>
> > --
> > 1.9.1
> >
> >
> > ---------------------------------------------8<----------------------------------------
> > From c8f2f2b414af672ec40841e75fb1ea761ae29122 Mon Sep 17 00:00:00 2001
> > From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > Date: Sun, 16 Feb 2020 22:40:23 +0200
> > Subject: [PATCH] usb: gadget: f_uac2: change bInterval to 1 for
> >  8ch/24bit/44.1kHz
> >
> > With bInterval=4 one audio slot in case of 8ch/24bit/44.1kHz
> > exeeds MaxPacket size of ISO endpoint (>1024) and can't be
> > transferred in time.
> > USB spec ("5.6.3 Isochronous Transfer Packet Size Constraints")
> > says if we need to transfer more than 1024 it is a high speed, high
> > bandwidth endpoint and should have bInterval=1.
> >
> > In the future, bInterval should be dynamically calculated
> > depending on bandwith requirementes
>
> Probably better to do it from the start to avoid breaking stuff for
> people who have been using the gadget with the current badnwidth so far

That is an existing issue with UAC2 driver since its initial implementation,
I'm going to fix it in the near future as a separate patch. The issue is not
related to the feedback synchronization support patch.

I actually developed a few patches (not published yet) to check user
parameters and refuse to start UAC1/2 gadget if they are wrong
(currently UAC1/2 gagdet accepts incorrect parameters and then
silently fails to work correctly)

Thanks,
Ruslan

>
> >
> > Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> > ---
> >  drivers/usb/gadget/function/f_uac2.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/usb/gadget/function/f_uac2.c
> > b/drivers/usb/gadget/function/f_uac2.c
> > index 3633df6..fb9b875 100644
> > --- a/drivers/usb/gadget/function/f_uac2.c
> > +++ b/drivers/usb/gadget/function/f_uac2.c
> > @@ -281,7 +281,7 @@ enum {
> >
> >   .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
> >   .wMaxPacketSize = cpu_to_le16(1024),
> > - .bInterval = 4,
> > + .bInterval = 1,
> >  };
> >
> >  /* CS AS ISO OUT Endpoint */
> > @@ -358,7 +358,7 @@ enum {
> >
> >   .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
> >   .wMaxPacketSize = cpu_to_le16(1024),
> > - .bInterval = 4,
> > + .bInterval = 1,
> >  };
> >
> >  /* CS AS ISO IN Endpoint */
>