Re: [PATCH v2] Bluetooth: btusb: check conditions before enabling USB ALT 3 for WBS

[Luiz Augusto von Dentz <luiz.dentz@gmail.com>]

Hi Pasi, Pauli,

On Tue, Aug 10, 2021 at 9:50 AM Pasi Kärkkäinen <pasik@iki.fi> wrote:
>
> Hello Marcel,
>
> On Fri, Jul 23, 2021 at 02:19:09PM +0200, Marcel Holtmann wrote:
> > Hi Pauli,
> >
> > > Some USB BT adapters don't satisfy the MTU requirement mentioned in
> > > commit e848dbd364ac ("Bluetooth: btusb: Add support USB ALT 3 for WBS")
> > > and have ALT 3 setting that produces no/garbled audio. Some adapters
> > > with larger MTU were also reported to have problems with ALT 3.
> > >
> > > Add a flag and check it and MTU before selecting ALT 3, falling back to
> > > ALT 1. Enable the flag for Realtek, restoring the previous behavior for
> > > non-Realtek devices.
> > >
> > > Tested with USB adapters (mtu<72, no/garbled sound with ALT3, ALT1
> > > works) BCM20702A1 0b05:17cb, CSR8510A10 0a12:0001, and (mtu>=72, ALT3
> > > works) RTL8761BU 0bda:8771, Intel AX200 8087:0029 (after disabling
> > > ALT6). Also got reports for (mtu>=72, ALT 3 reported to produce bad
> > > audio) Intel 8087:0a2b.
> > >
> > > Signed-off-by: Pauli Virtanen <pav@iki.fi>
> > > Fixes: e848dbd364ac ("Bluetooth: btusb: Add support USB ALT 3 for WBS")
> >
> > before I will apply this, I need Tested-by or Ack-by people that confirm that this fixes their issues now.
> >
>
> Is v3 ok/enough? It has one Tested-by.
> It would probably be good to send v4 anyway with CC stable@kernel.org ..
>
>
> Thanks,
>
> -- Pasi
>
> >
> > > ---
> > >
> > > Changes in v2:
> > > - Explain magic number 72 in a comment; didn't add the table for them,
> > >  because it's not used elsewhere and we need just one number from it.
> > > - Add flag for ALT3 support, restoring the behavior
> > >  for non-Realtek devices the same as before e848dbd364ac, due to
> > >  the problems reported on an Intel adapter. Don't have the device
> > >  myself.
> > >
> > > drivers/bluetooth/btusb.c | 22 ++++++++++++++--------
> > > 1 file changed, 14 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
> > > index 6d23308119d1..5cec719f6cba 100644
> > > --- a/drivers/bluetooth/btusb.c
> > > +++ b/drivers/bluetooth/btusb.c
> > > @@ -516,6 +516,7 @@ static const struct dmi_system_id btusb_needs_reset_resume_table[] = {
> > > #define BTUSB_HW_RESET_ACTIVE       12
> > > #define BTUSB_TX_WAIT_VND_EVT       13
> > > #define BTUSB_WAKEUP_DISABLE        14
> > > +#define BTUSB_ALT3_OK_FOR_WBS      15
> >
> > Rename this to BTUSB_USE_ALT3_FOR_WBS.
> >
> > >
> > > struct btusb_data {
> > >     struct hci_dev       *hdev;
> > > @@ -1748,16 +1749,20 @@ static void btusb_work(struct work_struct *work)
> > >                     /* Bluetooth USB spec recommends alt 6 (63 bytes), but
> > >                      * many adapters do not support it.  Alt 1 appears to
> > >                      * work for all adapters that do not have alt 6, and
> > > -                    * which work with WBS at all.
> > > +                    * which work with WBS at all.  Some devices prefer
> > > +                    * alt 3 (HCI payload >= 60 Bytes let air packet
> > > +                    * data satisfy 60 bytes), requiring
> > > +                    * MTU >= 3 (packets) * 25 (size) - 3 (headers) = 72
> > > +                    * see also Core spec 5, vol 4, B 2.1.1 & Table 2.1.
> > >                      */
> > > -                   new_alts = btusb_find_altsetting(data, 6) ? 6 : 1;
> > > -                   /* Because mSBC frames do not need to be aligned to the
> > > -                    * SCO packet boundary. If support the Alt 3, use the
> > > -                    * Alt 3 for HCI payload >= 60 Bytes let air packet
> > > -                    * data satisfy 60 bytes.
> > > -                    */
> > > -                   if (new_alts == 1 && btusb_find_altsetting(data, 3))
> > > +                   if (btusb_find_altsetting(data, 6))
> > > +                           new_alts = 6;
> > > +                   else if (test_bit(BTUSB_ALT3_OK_FOR_WBS, &data->flags) &&
> > > +                            hdev->sco_mtu >= 72 &&
> > > +                            btusb_find_altsetting(data, 3))
> >
> > This is whitespace damaged.

Ive fixed this and made it fit in 80 columns by reordering the checks.

> >
> > >                             new_alts = 3;
> > > +                   else
> > > +                           new_alts = 1;
> > >             }
> > >
> > >             if (btusb_switch_alt_setting(hdev, new_alts) < 0)
> > > @@ -4733,6 +4738,7 @@ static int btusb_probe(struct usb_interface *intf,
> > >              * (DEVICE_REMOTE_WAKEUP)
> > >              */
> > >             set_bit(BTUSB_WAKEUP_DISABLE, &data->flags);
> > > +           set_bit(BTUSB_ALT3_OK_FOR_WBS, &data->flags);
> > >     }
> >
> > Regards
> >
> > Marcel

Applied, thanks.


-- 
Luiz Augusto von Dentz