[RFC PATCH] pci: prevent putting pcie devices into lower device states on certain intel bridges

[Mika Westerberg]

On Mon, Sep 30, 2019 at 06:05:14PM +0200, Karol Herbst wrote:
> still happens with your patch applied. The machine simply gets shut down.
> 
> dmesg can be found here:
> https://gist.githubusercontent.com/karolherbst/40eb091c7b7b33ef993525de660f1a3b/raw/2380e31f566e93e5ba7c87ef545420965d4c492c/gistfile1.txt

Looking your dmesg:

Sep 30 17:24:27 kernel: nouveau 0000:01:00.0: DRM: DCB version 4.1
Sep 30 17:24:27 kernel: nouveau 0000:01:00.0: DRM: MM: using COPY for buffer copies
Sep 30 17:24:27 kernel: [drm] Initialized nouveau 1.3.1 20120801 for 0000:01:00.0 on minor 1

I would assume it runtime suspends here. Then it wakes up because of PCI
access from userspace:

Sep 30 17:24:42 kernel: pci_raw_set_power_state: 56 callbacks suppressed
 
and for some reason it does not get resumed properly. There are also few
warnings from ACPI that might be relevant:

Sep 30 17:24:27 kernel: ACPI Warning: \_SB.PCI0.GFX0._DSM: Argument #4 type mismatch - Found [Buffer], ACPI requires [Package] (20190509/nsarguments-59)
Sep 30 17:24:27 kernel: ACPI Warning: \_SB.PCI0.PEG0.PEGP._DSM: Argument #4 type mismatch - Found [Buffer], ACPI requires [Package] (20190509/nsarguments-59)

This seems to be Dell XPS 9560 which I think has been around some time
already so I wonder why we only see issues now. Has it ever worked for
you or maybe there is a regression that causes it to happen now?