On Thu, Dec 15, 2022 at 8:38 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote: > > On Thu, Dec 15, 2022 at 8:20 PM Limonciello, Mario > <Mario.Limonciello@xxxxxxx> wrote: > > > > [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 > > Thanks for letting me know! > > I'll queue it up for 6.2-rc next week. Done now, thanks!
