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")
> | +-04.0-[39-69]----00.0-[3a-44]--+-00.0-[3b-3d]----00.0-[3c-3d]----03.0-[3d]--+-00.0 Pericom Semiconductor PI7C9X442SL USB OHCI Controller
> | | | +-00.1 Pericom Semiconductor PI7C9X442SL USB OHCI Controller
> | | | \-00.2 Pericom Semiconductor PI7C9X442SL USB EHCI Controller
> | +-05.0-[6a-9a]----00.0-[6b-72]--+-00.0-[6c-6e]----00.0-[6d-6e]----03.0-[6e]--+-00.0 Pericom Semiconductor PI7C9X442SL USB OHCI Controller
> | | | +-00.1 Pericom Semiconductor PI7C9X442SL USB OHCI Controller
> | | | \-00.2 Pericom Semiconductor PI7C9X442SL USB EHCI Controller
--
With Best Regards,
Andy Shevchenko
