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drm/amd/display: Increase precision for backlight curve 

[Why]
We are currently losing precision when we convert from
16 bit --> 8 bit --> 16 bit.

[How]
We shouldn't down convert unnecessarily and lose precision.
Keep values at 16 bit and use directly.

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 2019-01-30 11:05:38 -05:00 committed by Alex Deucher
parent ce72741b53
commit c19bd82f8b
1 changed files with 4 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
drivers/gpu/drm/amd/display/modules/power/power_helpers.c
View File

@ -165,18 +165,11 @@ struct iram_table_v_2_2 {
};
#pragma pack(pop)
static uint16_t backlight_8_to_16(unsigned int backlight_8bit)
{
return (uint16_t)(backlight_8bit * 0x101);
}
static void fill_backlight_transform_table(struct dmcu_iram_parameters params,
struct iram_table_v_2 *table)
{
unsigned int i;
unsigned int num_entries = NUM_BL_CURVE_SEGS;
unsigned int query_input_8bit;
unsigned int query_output_8bit;
unsigned int lut_index;
table->backlight_thresholds[0] = 0;
@ -194,16 +187,13 @@ static void fill_backlight_transform_table(struct dmcu_iram_parameters params,
* format U4.10.
*/
for (i = 1; i+1 < num_entries; i++) {
query_input_8bit = DIV_ROUNDUP((i * 256), num_entries);
lut_index = (params.backlight_lut_array_size - 1) * i / (num_entries - 1);
ASSERT(lut_index < params.backlight_lut_array_size);
query_output_8bit = params.backlight_lut_array[lut_index] >> 8;
table->backlight_thresholds[i] =
backlight_8_to_16(query_input_8bit);
cpu_to_be16(DIV_ROUNDUP((i * 65536), num_entries));
table->backlight_offsets[i] =
backlight_8_to_16(query_output_8bit);
cpu_to_be16(params.backlight_lut_array[lut_index]);
}
}
@ -212,8 +202,6 @@ static void fill_backlight_transform_table_v_2_2(struct dmcu_iram_parameters par
{
unsigned int i;
unsigned int num_entries = NUM_BL_CURVE_SEGS;
unsigned int query_input_8bit;
unsigned int query_output_8bit;
unsigned int lut_index;
table->backlight_thresholds[0] = 0;
@ -231,16 +219,13 @@ 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++) {
query_input_8bit = DIV_ROUNDUP((i * 256), num_entries);
lut_index = (params.backlight_lut_array_size - 1) * i / (num_entries - 1);
ASSERT(lut_index < params.backlight_lut_array_size);
query_output_8bit = params.backlight_lut_array[lut_index] >> 8;
table->backlight_thresholds[i] =
backlight_8_to_16(query_input_8bit);
cpu_to_be16(DIV_ROUNDUP((i * 65536), num_entries));
table->backlight_offsets[i] =
backlight_8_to_16(query_output_8bit);
cpu_to_be16(params.backlight_lut_array[lut_index]);
}
}