Reviewed-by: Alex Hung <alex.hung@xxxxxxx>
On 2/28/25 11:51, Mario Limonciello wrote:
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.
Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
.../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 25 +++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 61d626914590..b252c67f2bc4 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4759,10 +4759,35 @@ 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);
