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

[Bjorn Helgaas]

On Mon, Sep 30, 2019 at 06:36:12PM +0200, Karol Herbst wrote:
> On Mon, Sep 30, 2019 at 6:30 PM Mika Westerberg
> <mika.westerberg at linux.intel.com> wrote:
> >
> > 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)
> 
> afaik this is the case for essentially every laptop out there.

I think we should look into this a little bit.
acpi_ns_check_argument_types() checks the argument type and prints
this message, but AFAICT it doesn't actually fix anything or prevent
execution of the method, so I have no idea what happens when we
actually execute the _DSM.

If we execute this _DSM as part of power management, and the _DSM
doesn't work right, it would be no surprise that we have problems.

Maybe we could learn something by turning on ACPI_DB_PARSE output (see
Documentation/firmware-guide/acpi/debug.rst).

You must have an acpidump already from all your investigation.  Can
you put it somewhere, e.g., bugzilla.kernel.org, and include a URL?