radeon kernel driver not suppressing ACPI_VIDEO_NOTIFY_PROBE events when it should

[Alex Deucher]

On Wed, Jan 6, 2021 at 3:04 PM Hans de Goede <hdegoede at redhat.com> wrote:
>
> Hi,
>
> On 1/6/21 8:33 PM, Alex Deucher wrote:
> > On Wed, Jan 6, 2021 at 1:10 PM Hans de Goede <hdegoede at redhat.com> wrote:
> >>
> >> Hi,
> >>
> >> On 1/6/21 6:07 PM, Alex Deucher wrote:
> >>> On Wed, Jan 6, 2021 at 11:25 AM Hans de Goede <hdegoede at redhat.com> wrote:
> >>>>
> >>>> Hi All,
> >>>>
> >>>> I get Cc-ed on all Fedora kernel bugs and this one stood out to me:
> >>>>
> >>>> https://bugzilla.redhat.com/show_bug.cgi?id=1911763
> >>>>
> >>>> Since I've done a lot of work on the acpi-video code I thought I should
> >>>> take a look. I've managed to help the user with a kernel-commandline
> >>>> option which stops video.ko (the acpi-video kernel module) from emitting
> >>>> key-press events for ACPI_VIDEO_NOTIFY_PROBE events.
> >>>>
> >>>> This is on a Dell Vostro laptop with i915/radeon hybrid gfx.
> >>>>
> >>>> I was thinking about adding a DMI quirk for this, but from the brief time
> >>>> that I worked on nouveau (and specifically hybrid gfx setups) I know that
> >>>> these events get fired on hybrid gfx setups when the discrete GPU is
> >>>> powered down and something happens which requires the discrete GPUs drivers
> >>>> attention, like an external monitor being plugged into a connector handled
> >>>> by the dGPU (note that is not the case here).
> >>>>
> >>>> So I took a quick look at the radeon code and the radeon_atif_handler()
> >>>> function from drivers/gpu/drm/radeon/radeon_acpi.c. When successful that
> >>>> returns NOTIFY_BAD which suppresses the key-press.
> >>>>
> >>>> But in various cases it returns NOTIFY_DONE instead which does not
> >>>> suppress the key-press event. So I think that the spurious key-press events
> >>>> which the user is seeing should be avoided by this function returning
> >>>> NOTIFY_BAD.
> >>>>
> >>>> Specifically I'm wondering if we should not return
> >>>> NOTIFY_BAD when count == 0?   I guess this can cause problems if there
> >>>> are multiple GPUs, but we could check if the acpi-event is for the
> >>>> pci-device the radeon driver is bound to. This would require changing the
> >>>> acpi-notify code to also pass the acpi_device pointer as part of the
> >>>> acpi_bus_event but that should not be a problem.
> >>>>
> >>>
> >>> For A+A PX/HG systems, we'd want the notifications for both the dGPU
> >>> and the APU since some of the events are relevant to one or the other.
> >>> ATIF_DGPU_DISPLAY_EVENT is only relevant to the dGPU, while
> >>> ATIF_PANEL_BRIGHTNESS_CHANGE_REQUEST would be possibly relevant to
> >>> both (if there was a mux), but mainly the APU.
> >>> ATIF_SYSTEM_POWER_SOURCE_CHANGE_REQUEST would be relevant to both.
> >>> The other events have extended bits to determine which GPU the event
> >>> is targeted at.
> >>
> >> Right, but AFAIK on hybrid systems there are 2 ACPI video-bus devices,
> >> one for each of the iGPU and dGPU which is why I suggested passing
> >> the video-bus acpi_device as extra data in acpi_bus_event and then
> >> radeon_atif_handler() could check if the acpi_device is the companion
> >> device of the GPU. This assumes that events for GPU# will also
> >> originate from (through an ACPI ASL notify call) the ACPI video-bus
> >> which belongs to that GPU.
> >
> > That's not the case.  For PX/HG systems, ATIF is in the iGPU's
> > namespace, on dGPU only systems, ATIF is in the dGPU's namespace.
>
> That assumes and AMD iGPU + AMD dGPU I believe ?  The system on
> which the spurious ACPI_VIDEO_NOTIFY_PROBE events lead to spurious
> KEY_SWITCHVIDEOMODE key-presses being reported uses an Intel iGPU
> with an AMD dGPU. I don't have any hybrid gfx systems available for
> testing atm, but I believe that in this case there will be 2 ACPI
> video-busses, one for each GPU.

I think the ATIF method will be on the iGPU regardless of whether it's
intel or AMD.

>
> Note I'm not saying that that means that checking the originating
> ACPI device is the companion of the GPUs PCI-device is the solution
> here. But so far all I've heard from you is that that is not the
> solution, without you offering any alternative ideas / possible
> solutions to try for filtering out these spurious key-presses.

Sorry, I'm not really an ACPI expert.  I think returning NOTIFY_BAD is
fine for this specific case, but I don't know if it will break other
platforms.  That said, I don't recall seeing any other similar bugs,
so maybe this is something specific to this particular laptop.

Alex