Re: [PATCH v1 1/1] PCI: Enable INTx quirk for ATI PCIe-USB adapter

Bjorn Helgaas
2022-03-15T20:22:37Z

On Tue, Mar 15, 2022 at 12:09:08PM +0200, Andy Shevchenko wrote:
> On Mon, Mar 14, 2022 at 02:42:53PM -0500, Bjorn Helgaas wrote:
> > On Mon, Mar 14, 2022 at 12:14:48PM +0200, Andy Shevchenko wrote:
> > > ATI PCIe-USB adapter advertises MSI, but it doesn't work if INTx is disabled.
> > > Enable the respective quirk as it's done for other ATI devices on this chipset,
> > >
> > > Fixes: 306c54d0edb6 ("usb: hcd: Try MSI interrupts on PCI devices")
> >
> > This is interesting because there must be a TON of these AMD/ATI SB600
> > USB devices in the field, and 306c54d0edb6 was merged in July 2020 and
> > appeared in v5.9.
> >
> > So why would we only get a report now, in February 2022? Is there
> > some change more recent than 306c54d0edb6 that exposed this problem?
>
> I think it's a rhetorical question. To me it's as simple as the latency
> between getting the change into the kernel.
>
> However, I'm a bit worried that in case of ATI there are not so many
> platforms that are kept up-to-dated.

This would be a rhetorical question if I were not interested in the
answer but asking only to make a point. That's not the case at all.

If these SB600 USB devices stopped working in v5.9 (October 2020),
that would affect lots of keyboards and mice, and I would be surprised
if we didn't hear about it until February, 2022.

I looked through https://github.com/linuxhw/Dmesg, and there are at
least 40 dmesg logs from v5.9 or later with SB600 USB, so I'm
still a little skeptical that 306c54d0edb6 by itself is enough to
explain this.

Anyway, I applied this to pci/msi for v5.18 with the following commit
log:

PCI: Disable broken MSI on ATI SB600 USB adapters

Some ATI SB600 USB adapters advertise MSI, but MSI doesn't work if INTx is
disabled. Disable MSI on these adapters.