radeon kernel driver not suppressing ACPI_VIDEO_NOTIFY_PROBE events when it should

[Hans de Goede]

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.

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.

Regards,

Hans