From: Anthony Koo <anthony....@amd.com>
[Why]
The PWL backlight curve is used by the firmware to convert between
brightness and linear PWM value.
Driver has a backlight LUT, but the firmware holds a PWL curve and
interpolates between points.
The calculations are incorrect leading to slightly off backlight values
being programmed.
[How]
Fix the PWL backlight curve threshold/offset calculations
Signed-off-by: Anthony Koo <anthony....@amd.com>
Reviewed-by: Josip Pavic <josip.pa...@amd.com>
Acked-by: Anson Jacob <anson.ja...@amd.com>
---
drivers/gpu/drm/amd/display/modules/power/power_helpers.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/display/modules/power/power_helpers.c
b/drivers/gpu/drm/amd/display/modules/power/power_helpers.c
index 3d4c66933f51..6270ecbd2438 100644
--- a/drivers/gpu/drm/amd/display/modules/power/power_helpers.c
+++ b/drivers/gpu/drm/amd/display/modules/power/power_helpers.c
@@ -266,7 +266,7 @@ static void fill_backlight_transform_table_v_2_2(struct
dmcu_iram_parameters par
* format U4.10.
*/
for (i = 1; i+1 < num_entries; i++) {
- lut_index = (params.backlight_lut_array_size - 1) * i /
(num_entries - 1);
+ lut_index = DIV_ROUNDUP((i * params.backlight_lut_array_size),
num_entries);
ASSERT(lut_index < params.backlight_lut_array_size);
table->backlight_thresholds[i] = (big_endian) ?
--
2.25.1
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