AMDGPU_DM_DEFAULT_MIN_BACKLIGHT was set to the value of 12 to ensure no display backlight will flicker at low user brightness settings. However this value is quite bright, so for devices that do not implement the ACPI ATIF ATIF_FUNCTION_QUERY_BRIGHTNESS_TRANSFER_CHARACTERISTICS functionality the user cannot set the brightness to a low level even if the display would support such a low PWM.
This ATIF feature is not implemented on for example AMD grunt chromebooks.
Signed-off-by: Evan Benn evanbenn@chromium.org
--- I could not find a justification for the reason for the value. It has caused some noticable regression for users: https://bugzilla.kernel.org/show_bug.cgi?id=203439
Maybe this can be either user controlled or userspace configured, but preventing users from turning their backlight dim seems wrong.
Also reviewed here: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2...
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
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 573cf17262da..0129bd69b94e 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -3151,7 +3151,7 @@ static int amdgpu_dm_mode_config_init(struct amdgpu_device *adev) return 0; }
-#define AMDGPU_DM_DEFAULT_MIN_BACKLIGHT 12 +#define AMDGPU_DM_DEFAULT_MIN_BACKLIGHT 0 #define AMDGPU_DM_DEFAULT_MAX_BACKLIGHT 255 #define AUX_BL_DEFAULT_TRANSITION_TIME_MS 50