Re: [PATCH v2] thunderbolt: fix PCI device class after powering up

["Łukasz Bartosik" <lb@semihalf.com>]

>
> Hi,
>
> On Fri, Jul 29, 2022 at 11:40:22AM +0200, Łukasz Bartosik wrote:
> > A thunderbolt
> > lspci -d 8086:9a1b -vmmknn
> > Slot: 00:0d.2
> > Class:        System peripheral [0880]
> > Vendor:       Intel Corporation [8086]
> > Device:       Tiger Lake-LP Thunderbolt 4 NHI #0 [9a1b]
> >
> > presents itself with PCI class 0x088000 after Chromebook boots.
> > lspci -s 00:0d.2 -xxx
> > 00:0d.2 System peripheral: Intel Corporation Tiger Lake-LP Thunderbolt 4
> > NHI #0 (rev 01)
> > 00: 86 80 1b 9a 00 00 10 00 01 00 80 08 00 00 00 00
> > ...
> >
> > However after thunderbolt is powered up in nhi_probe()
> > its class changes to 0x0c0340
> > lspci -s 00:0d.2 -xxx
> > 00:0d.2 System peripheral: Intel Corporation Tiger Lake-LP Thunderbolt 4
> > NHI #0 (rev 01)
> > 00: 86 80 1b 9a 06 04 10 00 01 40 03 0c 00 00 00 00
> > ...
> >
> > which leaves pci_dev structure with old class value
> > cat /sys/bus/pci/devices/0000:00:0d.2/class
> > 0x088000
>
> This is completely unexpected. Which Chromebook this is and have you
> tried to upgrade it to the latest?
>

This happens on a Tiger Lake based reference Chromebook platform.
The issue also happens on the latest ChromeOS image available for that platform.

> > This fix updates PCI device class in pci_dev structure after
> > thunderbolt is powered up.
>
> I think we need to understand why this happens in the first place before
> doing anything else.

If you have suggestions what else to check apart from what I already
did then please
let me know I will gladly do it.

Thanks,
Lukasz