From: Wesley Cheng <quic_wcheng@quicinc.com>
To: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
<srinivas.kandagatla@linaro.org>, <mathias.nyman@intel.com>,
<perex@perex.cz>, <lgirdwood@gmail.com>, <andersson@kernel.org>,
<krzysztof.kozlowski+dt@linaro.org>, <gregkh@linuxfoundation.org>,
<Thinh.Nguyen@synopsys.com>, <broonie@kernel.org>,
<bgoswami@quicinc.com>, <tiwai@suse.com>, <robh+dt@kernel.org>,
<agross@kernel.org>
Cc: <devicetree@vger.kernel.org>, <alsa-devel@alsa-project.org>,
<linux-arm-msm@vger.kernel.org>, <linux-usb@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <quic_jackp@quicinc.com>,
<quic_plai@quicinc.com>
Subject: Re: [RFC PATCH v2 09/22] ASoC: qcom: qdsp6: Introduce USB AFE port to q6dsp
Date: Thu, 2 Feb 2023 17:23:46 -0800 [thread overview]
Message-ID: <a494e063-f0a0-2a71-5b7b-cb247efa245c@quicinc.com> (raw)
In-Reply-To: <de03c6b1-b6d6-0045-ea60-6ae800913e95@linux.intel.com>
Hi Pierre,
On 1/31/2023 7:02 PM, Pierre-Louis Bossart wrote:
>
>
> On 1/31/23 20:40, Wesley Cheng wrote:
>> Hi Pierre,
>>
>> On 1/30/2023 3:59 PM, Pierre-Louis Bossart wrote:
>>>
>>>
>>> On 1/30/23 16:54, Wesley Cheng wrote:
>>>> Hi Pierre,
>>>>
>>>> On 1/26/2023 7:38 AM, Pierre-Louis Bossart wrote:
>>>>>
>>>>>
>>>>> On 1/25/23 21:14, Wesley Cheng wrote:
>>>>>> The QC ADSP is able to support USB playback endpoints, so that the
>>>>>> main
>>>>>> application processor can be placed into lower CPU power modes. This
>>>>>> adds
>>>>>> the required AFE port configurations and port start command to
>>>>>> start an
>>>>>> audio session.
>>>>>>
>>>>>> Specifically, the QC ADSP can support all potential endpoints that are
>>>>>> exposed by the audio data interface. This includes, feedback
>>>>>> endpoints
>>>>>> (both implicit and explicit) as well as the isochronous (data)
>>>>>> endpoints.
>>>>>> The size of audio samples sent per USB frame (microframe) will be
>>>>>> adjusted
>>>>>> based on information received on the feedback endpoint.
>>>>>
>>>>> I think you meant "support all potential endpoint types"
>>>>>
>>>>> It's likely that some USB devices have more endpoints than what the DSP
>>>>> can handle, no?
>>>>>
>>>>
>>>> True, as we discussed before, we only handle the endpoints for the audio
>>>> interface. Other endpoints, such as HID, or control is still handled by
>>>> the main processor.
>>>
>>> The number of isoc/audio endpoints can be larger than 1 per direction,
>>> it's not uncommon for a USB device to have multiple connectors on the
>>> front side for instruments, mics, monitor speakers, you name it. Just
>>> google 'motu' or 'rme usb' and you'll see examples of USB devices that
>>> are very different from plain vanilla headsets.
>>>
>>
>> Thanks for the reference.
>>
>> I tried to do some research on the RME USB audio devices, and they
>> mentioned that they do have a "class compliant mode," which is for
>> compatibility w/ Linux hosts. I didn't see a vendor specific USB SND
>> driver matching the USB VID/PID either, so I am assuming that it uses
>> the USB SND driver as is.(and that Linux doesn't currently support their
>> vendor specific mode) In that case, the device should conform to the
>> UAC2.0 spec (same statement seen on UAC3.0), which states in Section
>> 4.9.1 Standard AS Interface Descriptor Table 4-26:
>>
>> "4 bNumEndpoints 1 Number Number of endpoints used by this
>> interface (excluding endpoint 0). Must be
>> either 0 (no data endpoint), 1 (data
>> endpoint) or 2 (data and explicit feedback
>> endpoint)."
>>
>> So each audio streaming interface should only have 1 data and
>> potentially 1 feedback. However, this device does expose a large number
>> of channels (I saw up to 18 channels), which the USB backend won't be
>> able to support. I still need to check how ASoC behaves if I pass in a
>> profile that the backend can't support.
>>
>> Maybe in the non-class compliant/vendor based class driver, they have
>> the support for multiple EPs per data interface? I don't have one of
>> these devices on hand, so I can't confirm that.
>
> Look at Figure 3-1 in the UAC2 spec, it shows it's perfectly legal to
> have multiple Audio Streaming interfaces - but one Audio Control
> interface only.
>
> The fact that there is a restriction to 1 or 2 endpoints per Audio
> Streaming interface does not really matter if in the end there are
> multiple endpoints and concurrent isoc transfers happening to/from the
> same USB device.
So the reason I wanted to mention the max number of EPs within the audio
streaming descriptor is because the USB SND driver currently creates
streams based off of the number of AS desc:
static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
{
...
for (i = 0; i < assoc->bInterfaceCount; i++) {
int intf = assoc->bFirstInterface + i;
if (intf != ctrlif)
snd_usb_create_stream(chip, ctrlif, intf);
}
"assoc" is the audio control interface desc. In the end, when userspace
initiates a playback session, it operates on the streams created (which
contains at max 1 isoc and 1 feedback ep)
In short, the audio DSP doesn't need to consider handling more than 1
isoc ep (and potentially 1 feedback). I believe that each audio stream
creates a separate PCM device, so userspace is still free to attempt to
activate another audio stream. I believe # of PCM devices created
matches the # of streams, so when userspace does activate another
session, it would be on an entirely different substream, and can be
handled through the USB SND (non-offload) path. If attempted to open
the substream used by the offload path, then we would reject is based on
the new change.
Thanks
Wesley Cheng
next prev parent reply other threads:[~2023-02-03 1:24 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-26 3:14 [RFC PATCH v2 00/22] Introduce QC USB SND audio offloading support Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 01/22] xhci: fix event ring segment table related masks and variables in header Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 02/22] xhci: remove xhci_test_trb_in_td_math early development check Wesley Cheng
2023-01-26 7:48 ` Greg KH
2023-01-26 3:14 ` [RFC PATCH v2 03/22] xhci: Refactor interrupter code for initial multi interrupter support Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 04/22] xhci: Add support to allocate several interrupters Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 05/22] usb: xhci: Add XHCI APIs to support USB offloading Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 06/22] usb: host: xhci-mem: Cleanup pending secondary event ring events Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 07/22] ASoC: Add SOC USB APIs for adding an USB backend Wesley Cheng
2023-01-26 15:32 ` Pierre-Louis Bossart
2023-01-30 22:36 ` Wesley Cheng
2023-01-28 13:26 ` Greg KH
2023-01-29 6:54 ` Zhou Furong
2023-01-29 7:09 ` Greg KH
2023-01-30 8:34 ` Zhou Furong
2023-01-30 9:27 ` Greg KH
2023-02-10 22:46 ` Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 08/22] ASoC: dt-bindings: Add USB_RX port Wesley Cheng
2023-01-26 11:55 ` Krzysztof Kozlowski
2023-01-30 21:52 ` Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 09/22] ASoC: qcom: qdsp6: Introduce USB AFE port to q6dsp Wesley Cheng
2023-01-26 15:07 ` Srinivas Kandagatla
2023-01-26 15:38 ` Pierre-Louis Bossart
2023-01-30 22:54 ` Wesley Cheng
2023-01-30 23:59 ` Pierre-Louis Bossart
2023-02-01 2:40 ` Wesley Cheng
2023-02-01 3:02 ` Pierre-Louis Bossart
2023-02-03 1:23 ` Wesley Cheng [this message]
2023-02-03 1:44 ` Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 10/22] ASoC: qdsp6: q6afe: Increase APR timeout Wesley Cheng
2023-01-26 15:09 ` Srinivas Kandagatla
2023-01-26 3:14 ` [RFC PATCH v2 11/22] ASoC: qcom: Add USB backend ASoC driver for Q6 Wesley Cheng
2023-01-26 15:44 ` Pierre-Louis Bossart
2023-01-30 22:59 ` Wesley Cheng
2023-01-30 23:50 ` Pierre-Louis Bossart
2023-01-26 16:35 ` Srinivas Kandagatla
2023-01-26 3:14 ` [RFC PATCH v2 12/22] sound: usb: card: Introduce USB SND platform op callbacks Wesley Cheng
2023-01-26 15:50 ` Pierre-Louis Bossart
2023-01-30 23:00 ` Wesley Cheng
2023-01-28 13:28 ` Greg KH
2023-02-10 22:49 ` Wesley Cheng
2023-02-28 2:59 ` Wesley Cheng
2023-02-28 7:30 ` Greg KH
2023-02-28 9:19 ` Wesley Cheng
2023-02-28 15:29 ` Greg KH
2023-02-20 17:11 ` Albert Wang
2023-01-26 3:14 ` [RFC PATCH v2 13/22] sound: usb: Export USB SND APIs for modules Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 14/22] dt-bindings: usb: dwc3: Add snps,num-hc-interrupters definition Wesley Cheng
2023-01-26 12:01 ` Krzysztof Kozlowski
2023-01-30 22:02 ` Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 15/22] usb: dwc3: Add DT parameter to specify maximum number of interrupters Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 16/22] sound: usb: Introduce QC USB SND offloading support Wesley Cheng
2023-01-26 16:07 ` Pierre-Louis Bossart
2023-01-28 13:32 ` Greg KH
2023-02-11 0:03 ` Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 17/22] sound: usb: card: Check for support for requested audio format Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 18/22] sound: soc: soc-usb: Add PCM format check API for USB backend Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 19/22] sound: soc: qcom: qusb6: Ensure PCM format is supported by USB audio device Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 20/22] sound: usb: Prevent starting of audio stream if in use Wesley Cheng
2023-01-26 16:12 ` Pierre-Louis Bossart
2023-02-07 1:15 ` Wesley Cheng
2023-02-07 13:29 ` Pierre-Louis Bossart
2023-02-11 9:52 ` Wesley Cheng
2023-02-13 15:22 ` Pierre-Louis Bossart
2023-02-13 20:12 ` Wesley Cheng
2023-01-26 3:14 ` [RFC PATCH v2 21/22] ASoC: dt-bindings: Add Q6USB backend bindings Wesley Cheng
2023-01-26 12:03 ` Krzysztof Kozlowski
2023-01-26 16:01 ` Srinivas Kandagatla
2023-01-26 3:14 ` [RFC PATCH v2 22/22] ASoC: dt-bindings: Update example for enabling USB offload on SM8250 Wesley Cheng
2023-01-26 12:05 ` Krzysztof Kozlowski
2023-01-26 9:23 ` [RFC PATCH v2 00/22] Introduce QC USB SND audio offloading support Mathias Nyman
2023-01-30 21:51 ` Wesley Cheng
2023-01-26 16:22 ` Pierre-Louis Bossart
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