On Mon, Dec 28, 2020 at 04:42:30PM +0200, Andy Shevchenko wrote:
> On Mon, Dec 28, 2020 at 07:19:49PM +0800, Brad Campbell wrote:
> > G'day Andy,
> >
> > Commit 306c54d0edb6ba94d39877524dddebaad7770cf2 in kernel 5.9 breaks
> > usb-audio on my machine.
> >
> > I have a 2011 iMac with a pair of Apple Thunderbolt displays. Both Thunderbolt
> > displays have internal usb-audio devices. This patch causes the audio to stutter
> > terribly. Reverting it resolves the issue on any kernel up to and
> > including 5.10.3.
> >
> > Booting with pci=nomsi fixes the audio issues, but causes all sorts of
> > other problems (like broken Thunderbolt display routing), so that's a non-starter.
> >
> > The usb audio devices would appear to be on the Pericom USB controllers in the displays.
> > It wouldn't be the first peculiarity I've had on this machine due to the early Thunderbolt
> > implementation.
> >
> > The issue is pretty much identical with the sound card on both monitors.
>
> Thanks for the report!
>
> Funny that previous mail in my mailbox is exactly about this issue for
> PI7C9X440SL, i.e. fix [1] I made for v5.11 and Sasha ported to v5.10
> (mentioned previous mail). Can you try to apply [1] and confirm issue gone?
>
> [1]: f83c37941e88 ("PCI: Disable MSI for Pericom PCIe-USB adapter")
For your convenience the URL to the actual commit:
https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/commit/?id=f83c37941e88
--
With Best Regards,
Andy Shevchenko
