From 6cec25f5b5660602b1953038cf40968b2d71c403 Mon Sep 17 00:00:00 2001 From: Mario Limonciello Date: Thu, 4 Sep 2025 13:49:35 -0500 Subject: [PATCH] drm/amd/display: Handle interpolation for first data point [Why] If the first data point for a custom brightness curve is not 0% luminance then the first few luminance values will be ignored. [How] Check signal is below first data point and if so do linear interpolation to 0 instead. Reviewed-by: Alex Hung Signed-off-by: Mario Limonciello Signed-off-by: Ivan Lipski Tested-by: Dan Wheeler Signed-off-by: Alex Deucher --- drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 10 ++++++++++ 1 file changed, 10 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 09427e0560559..271ea16151782 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -4828,6 +4828,16 @@ static void convert_custom_brightness(const struct amdgpu_dm_backlight_caps *cap if (!caps->data_points) return; + /* + * Handle the case where brightness is below the first data point + * Interpolate between (0,0) and (first_signal, first_lum) + */ + if (brightness < caps->luminance_data[0].input_signal) { + lum = DIV_ROUND_CLOSEST(caps->luminance_data[0].luminance * brightness, + caps->luminance_data[0].input_signal); + goto scale; + } + left = 0; right = caps->data_points - 1; while (left <= right) { -- 2.47.3