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Commit c19bd82f authored by Anthony Koo's avatar Anthony Koo Committed by Alex Deucher
Browse files

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: default avatarAnthony Koo <Anthony.Koo@amd.com>
Reviewed-by: default avatarAric Cyr <Aric.Cyr@amd.com>
Acked-by: default avatarLeo Li <sunpeng.li@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent ce72741b

drivers/gpu/drm/amd/display/modules/power/power_helpers.c

+4 −19
Original line number Diff line number Diff line
@@ -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]);

	}

}