Flaky brightness on Renoir
hwentlan at amd.com
Wed May 20 21:52:50 UTC 2020
We've seen similar problems internally.
Michael, does this "fix" your issue?
Anthony, looks like smooth_brightness is problematic on (some) renoir
On 2020-05-20 5:47 p.m., Alex Deucher wrote:
> Adding some display people.
> On Wed, May 20, 2020 at 5:46 PM Alexander Monakov <amonakov at ispras.ru> wrote:
>> I have a laptop with the recent Renoir SoC. Screen brightness is
>> controlled via the amdgpu driver. Unfortunately it doesn't work
>> properly: brightness doesn't go below a certain threshold. In one
>> experiment I've found the threshold to be about 95 (of 255), which is
>> quite high.
>> There's a bugreport on the tracker from a person with the same laptop
>> model as mine that says that the threshold may vary from boot to boot.
>> So far I was able to find a workaround: avoiding
>> dmcu_set_backlight_level like in the patch below gives more reliable
>> backlight control (but at the expense of breaking "actual_brightness"
>> sysfs file, because it reads from DMCU registers).
>> What might be the problem and can I help investigate this further? Would
>> really like to see this work properly.
>> diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_abm.c b/drivers/gpu/drm/amd/display/dc/dce/dce_abm.c
>> index b8a3fc505c9b..3274b0d15893 100644
>> --- a/drivers/gpu/drm/amd/display/dc/dce/dce_abm.c
>> +++ b/drivers/gpu/drm/amd/display/dc/dce/dce_abm.c
>> @@ -428,7 +428,7 @@ static bool dce_abm_set_backlight_level_pwm(
>> backlight_pwm_u16_16, backlight_pwm_u16_16);
>> /* If DMCU is in reset state, DMCU is uninitialized */
>> - if (use_smooth_brightness)
>> + if (0 && use_smooth_brightness)
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>> amd-gfx at lists.freedesktop.org
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