Commit 578df37b authored by Mario Limonciello's avatar Mario Limonciello Committed by Alex Deucher
Browse files

drm/amd/display: Add support for custom brightness curve 



Some systems specify in the firmware a brightness curve that better
reflects the characteristics of the panel used. This is done in the
form of data points and matching luminance percentage.

When converting a userspace requested brightness value use that curve
to convert to a firmware intended brightness value.

Reviewed-by: default avatarAlex Hung <alex.hung@amd.com>
Link: https://lore.kernel.org/r/20250228185145.186319-5-mario.limonciello@amd.com


Signed-off-by: default avatarMario Limonciello <mario.limonciello@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent f25c0f0d

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

+25 −0
Original line number Diff line number Diff line
@@ -4750,10 +4750,35 @@ static u32 convert_brightness_from_user(const struct amdgpu_dm_backlight_caps *c 
					uint32_t brightness)

{

	unsigned int min, max;

	u8 prev_signal = 0, prev_lum = 0;



	if (!get_brightness_range(caps, &min, &max))

		return brightness;



	for (int i = 0; i < caps->data_points; i++) {

		u8 signal, lum;



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

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



		/*

		 * brightness == signal: luminance is percent numerator

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

		 * brightness > signal: find next data point

		 */

		if (brightness < signal)

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

							   (brightness - prev_signal),

							   signal - prev_signal);

		else if (brightness > signal) {

			prev_signal = signal;

			prev_lum = lum;

			continue;

		}

		brightness = DIV_ROUND_CLOSEST(lum * brightness, 101);

		break;

	}



	// Rescale 0..255 to min..max

	return min + DIV_ROUND_CLOSEST((max - min) * brightness,

				       AMDGPU_MAX_BL_LEVEL);