On Tue, Jul 12, 2022 at 3:40 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > Typically the acpi_video driver will initialize before amdgpu, which > used to cause /sys/class/backlight/acpi_video0 to get registered and then > amdgpu would register its own amdgpu_bl# device later. After which > the drivers/acpi/video_detect.c code unregistered the acpi_video0 device > to avoid there being 2 backlight devices. > > This means that userspace used to briefly see 2 devices and the > disappearing of acpi_video0 after a brief time confuses the systemd > backlight level save/restore code, see e.g.: > https://bbs.archlinux.org/viewtopic.php?id=269920 > > To fix this the ACPI video code has been modified to make backlight class > device registration a separate step, relying on the drm/kms driver to > ask for the acpi_video backlight registration after it is done setting up > its native backlight device. > > Add a call to the new acpi_video_register_backlight() when amdgpu skips > registering its own backlight device because of either the firmware_flags > or the acpi_video_get_backlight_type() return value. This ensures that > if the acpi_video backlight device should be used, it will be available > before the amdgpu drm_device gets registered with userspace. > > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> > --- > drivers/gpu/drm/amd/amdgpu/atombios_encoders.c | 9 +++++++-- > drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 ++ > 2 files changed, 9 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c b/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c > index abf209e36fca..45cd9268b426 100644 > --- a/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c > +++ b/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c > @@ -184,11 +184,11 @@ void amdgpu_atombios_encoder_init_backlight(struct amdgpu_encoder *amdgpu_encode > return; > > if (!(adev->mode_info.firmware_flags & ATOM_BIOS_INFO_BL_CONTROLLED_BY_GPU)) > - return; > + goto register_acpi_backlight; > > if (!acpi_video_backlight_use_native()) { > DRM_INFO("Skipping amdgpu atom DIG backlight registration\n"); > - return; > + goto register_acpi_backlight; > } > > pdata = kmalloc(sizeof(struct amdgpu_backlight_privdata), GFP_KERNEL); > @@ -225,6 +225,11 @@ void amdgpu_atombios_encoder_init_backlight(struct amdgpu_encoder *amdgpu_encode > error: > kfree(pdata); > return; > + > +register_acpi_backlight: > + /* Try registering an ACPI video backlight device instead. */ > + acpi_video_register_backlight(); > + return; Can drop the return here. Either way, Acked-by: Alex Deucher <alexander.deucher@xxxxxxx> > } > > void > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > index 3b03a95e59a8..a667e66a9842 100644 > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > @@ -4054,6 +4054,8 @@ amdgpu_dm_register_backlight_device(struct amdgpu_display_manager *dm) > > if (!acpi_video_backlight_use_native()) { > DRM_INFO("Skipping amdgpu DM backlight registration\n"); > + /* Try registering an ACPI video backlight device instead. */ > + acpi_video_register_backlight(); > return; > } > > -- > 2.36.0 >
