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

From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
	micklorain@protonmail.com
Subject: Re: [PATCH v1 1/1] PCI: Enable INTx quirk for ATI PCIe-USB adapter
Date: Wed, 16 Mar 2022 12:27:57 +0200	[thread overview]
Message-ID: <YjG7rZ11PP3vWz89@smile.fi.intel.com> (raw)
In-Reply-To: <20220315202231.GA629970@bhelgaas>

On Tue, Mar 15, 2022 at 03:22:31PM -0500, Bjorn Helgaas wrote:
> 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.

But IIUC MSI is _not_ disabled. That's why I have issued this version of the
patch with different commit message. Did I misunderstand something?

-- 
With Best Regards,
Andy Shevchenko