Commit de63b055 authored by Mario Limonciello's avatar Mario Limonciello Committed by Alex Deucher
Browse files

drm/amd/display: Optimize custom brightness curve interpolation 



[Why]
Custom brightness curve works by walking through all data points one
by one.  When the brightness value is at either extreme this is a lot
of data points to walk.  This is especially noticeable when moving a
brightness slider around how it can lag.

[How]
Bisect the data points to find the closest for interpolation.

Reviewed-by: default avatarAlex Hung <alex.hung@amd.com>
Signed-off-by: default avatarMario Limonciello <mario.limonciello@amd.com>
Signed-off-by: default avatarAlex Hung <alex.hung@amd.com>
Tested-by: default avatarDan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 002a6120

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

+38 −26
Original line number Diff line number Diff line
@@ -4817,8 +4817,8 @@ static void convert_custom_brightness(const struct amdgpu_dm_backlight_caps *cap 
				      uint32_t *user_brightness)

{

	u32 brightness = scale_input_to_fw(min, max, *user_brightness);

	u8 prev_signal = 0, prev_lum = 0;

	int i = 0;

	u8 lower_signal, upper_signal, upper_lum, lower_lum, lum;

	int left, right;



	if (amdgpu_dc_debug_mask & DC_DISABLE_CUSTOM_BRIGHTNESS_CURVE)

		return;
@@ -4826,32 +4826,44 @@ static void convert_custom_brightness(const struct amdgpu_dm_backlight_caps *cap 
	if (!caps->data_points)

		return;



	/* choose start to run less interpolation steps */

	if (caps->luminance_data[caps->data_points/2].input_signal > brightness)

		i = caps->data_points/2;

	do {

		u8 signal = caps->luminance_data[i].input_signal;

		u8 lum = caps->luminance_data[i].luminance;

	left = 0;

	right = caps->data_points - 1;

	while (left <= right) {

		int mid = left + (right - left) / 2;

		u8 signal = caps->luminance_data[mid].input_signal;



		/*

		 * brightness == signal: luminance is percent numerator

		 * brightness < signal: interpolate between previous and current luminance numerator

		 * brightness > signal: find next data point

		 */

		if (brightness > signal) {

			prev_signal = signal;

			prev_lum = lum;

			i++;

			continue;

		/* Exact match found */

		if (signal == brightness) {

			lum = caps->luminance_data[mid].luminance;

			goto scale;

		}



		if (signal < brightness)

			left = mid + 1;

		else

			right = mid - 1;

	}

		if (brightness < signal)

			lum = prev_lum + DIV_ROUND_CLOSEST((lum - prev_lum) *

							   (brightness - prev_signal),

							   signal - prev_signal);



	/* verify bound */

	if (left >= caps->data_points)

		left = caps->data_points - 1;



	/* At this point, left > right */

	lower_signal = caps->luminance_data[right].input_signal;

	upper_signal = caps->luminance_data[left].input_signal;

	lower_lum = caps->luminance_data[right].luminance;

	upper_lum = caps->luminance_data[left].luminance;



	/* interpolate */

	if (right == left || !lower_lum)

		lum = upper_lum;

	else

		lum = lower_lum + DIV_ROUND_CLOSEST((upper_lum - lower_lum) *

						    (brightness - lower_signal),

						    upper_signal - lower_signal);

scale:

	*user_brightness = scale_fw_to_input(min, max,

					     DIV_ROUND_CLOSEST(lum * brightness, 101));

		return;

	} while (i < caps->data_points);

}



static u32 convert_brightness_from_user(const struct amdgpu_dm_backlight_caps *caps,