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drm/amd/display: set minimum abm backlight level

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[Why]
A lot of the time, the backlight characteristic curve maps min backlight
to a non-zero value.
But there are cases where we want the curve to intersect at 0.
In this scenario even if OS never asks to set 0% backlight, the ABM
reduction can result in backlight being lowered close to 0.
This particularly can cause problems in some LED drivers, and in
general just looks like backlight is completely off.

[How]
Add default cap to disallow backlight from dropping below 1%
even after ABM reduction is applied.

Signed-off-by: Anthony Koo <Anthony.Koo@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Anthony Koo
2019-08-29 10:49:12 -04:00
committed by Alex Deucher
parent 799c5b9cb9
commit 2ad0cdf9e2
3 changed files with 48 additions and 33 deletions
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5
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
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@@ -942,6 +942,11 @@ static int dm_late_init(void *handle)
params.backlight_lut_array_size = 16;
params.backlight_lut_array = linear_lut;
/* Min backlight level after ABM reduction, Don't allow below 1%
* 0xFFFF x 0.01 = 0x28F
*/
params.min_abm_backlight = 0x28F;
/* todo will enable for navi10 */
if (adev->asic_type <= CHIP_RAVEN) {
ret = dmcu_load_iram(dmcu, params);