[Public] > -----Original Message----- > From: Limonciello, Mario <Mario.Limonciello@xxxxxxx> > Sent: Thursday, December 8, 2022 10:42 > To: Rafael J . Wysocki <rafael@xxxxxxxxxx>; Deucher, Alexander > <Alexander.Deucher@xxxxxxx>; Hans de Goede > <hdegoede@xxxxxxxxxx> > Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx; Daniel > Dadap <ddadap@xxxxxxxxxx>; Limonciello, Mario > <Mario.Limonciello@xxxxxxx> > Subject: [PATCH v3 0/3] Adjust ACPI video detection fallback path > > In kernel 6.1 the backlight registration code was overhauled so that > at most one backlight device got registered. As part of this change > there was code added to still allow making an acpi_video0 device if the > BIOS contained backlight control methods but no native or vendor drivers > registered. > > Even after the overhaul this fallback logic is failing on the BIOS from > a number of motherboard manufacturers supporting Ryzen APUs. > What happens is the amdgpu driver finishes registration and as expected > doesn't create a backlight control device since no eDP panels are connected > to a desktop. > > Then 8 seconds later the ACPI video detection code creates an > acpi_video0 device that is non-operational. GNOME then creates a > backlight slider. > > To avoid this situation from happening make two sets of changes: > > Prevent desktop problems w/ fallback logic > ------------------------------------------ > 1) Add support for the video detect code to let native drivers cancel the > fallback logic if they didn't find a panel. > > This is done this way so that if another driver decides that the ACPI > mechanism is still needed it can instead directly call the registration > function. > > 2) Add code to amdgpu to notify the ACPI video detection code that no panel > was detected on an APU. > > Disable fallback logic by default > --------------------------------- > This fallback logic was introduced to prevent regressions in the backlight > overhaul. As it has been deemed unnecessary by Hans explicitly disable the > timeout. If this turns out to be mistake and this part is reverted, the > other patches for preventing desktop problems will avoid regressions on > desktops. > > Mario Limonciello (3): > ACPI: video: Allow GPU drivers to report no panels > drm/amd/display: Report to ACPI video if no panels were found > ACPI: video: Don't enable fallback path for creating ACPI backlight by > default > > drivers/acpi/acpi_video.c | 17 ++++++++++++----- > .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 4 ++++ > include/acpi/video.h | 2 ++ > 3 files changed, 18 insertions(+), 5 deletions(-) > > -- > 2.34.1 FYI, besides me, this series also tested successfully by one of the reporters to the Red Hat bugzilla. https://bugzilla.redhat.com/show_bug.cgi?id=1783786#c8
