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

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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: Alex Hung <alex.hung@amd.com>
Link: https://lore.kernel.org/r/20250228185145.186319-5-mario.limonciello@amd.com
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Mario Limonciello
2025-02-28 12:51:44 -06:00
committed by Alex Deucher
parent f25c0f0d4f
commit 578df37b1b
1 changed files with 25 additions and 0 deletions
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25
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
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@@ -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);