[+cc stable@vger.kernel.org]

Hi,

On Sat, Feb 06, 2021 at 04:56:53PM +0100, Sjoerd Simons wrote:
> On Fri, Dec 18, 2020 at 10:23:08PM +0100, Marcel Holtmann wrote:
> > Hi Trent,
> > 
> > > When alt mode 6 is not available, fallback to the kernel <= 5.7 behavior
> > > of always using alt mode 1.
> > > 
> > > Prior to kernel 5.8, btusb would always use alt mode 1 for WBS (Wide
> > > Band Speech aka mSBC aka transparent SCO).  In commit baac6276c0a9
> > > ("Bluetooth: btusb: handle mSBC audio over USB Endpoints") this
> > > was changed to use alt mode 6, which is the recommended mode in the
> > > Bluetooth spec (Specifications of the Bluetooth System, v5.0, Vol 4.B
> > > §2.2.1).  However, many if not most BT USB adapters do not support alt
> > > mode 6.  In fact, I have been unable to find any which do.
> 
> > patch has been applied to bluetooth-next tree.
> 
> For easier application to the stable tree(s) this should probably get:
>   Fixes: baac6276c0a9 ("Bluetooth: btusb: handle mSBC audio over USB Endpoints")
> 
> In my testing this indeed fixes mSBC audio with both a Belkin (Broadcom
> BCM20702A, 050d:065a) and an Intel Bluetooth (8087:0a2b) adapters.
> 
>   Tested-By: Sjoerd Simons <sjoerd@collabora.com>

Tested on Intel AX200 Bluetooth (8087:0029):

Tested-by: Sebastian Reichel <sre@kernel.org>

The patch has been merged to Linus' tree today and I think it should
be applied to the 5.10 tree, which is used by Debian. This patch is
required to use BT headset with bidirectional-audio in acceptable
quality (That also requires proper userspace software, e.g. pipewire
0.3.22, which Sjoerd uploaded to Debian experimental).

Patch applies cleanly on 5.10.

Thanks,

-- Sebastian