From: Mario Limonciello Date: Mon, 29 Jun 2026 20:27:00 +0000 (-0500) Subject: drm/amd/display: Fix backlight max_brightness to match exported range X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f1b5d8f9cc54ae8a2567ac126867ae488e1bf625;p=thirdparty%2Fkernel%2Flinux.git drm/amd/display: Fix backlight max_brightness to match exported range [Why] FWTS autobrightness fails on eDP panels because actual_brightness can read higher than the advertised max_brightness (e.g. 63576 vs 62451). The conversion helpers expose the firmware PWM range to userspace as [0..max]. But max_brightness is advertised as (max - min), which is smaller. So reading the level can return a value above max_brightness. This regressed in commit 4b61b8a39051 ("drm/amd/display: Add debugging message for brightness caps"), which changed max_brightness to (max - min) and undid commit 8dbd72cb7900 ("drm/amd/display: Export full brightness range to userspace"). [How] Advertise max_brightness as max, and scale the initial AC/DC brightness against max too. Update the KUnit expectations to match. Fixes: 4b61b8a39051 ("drm/amd/display: Add debugging message for brightness caps") Reviewed-by: Alex Hung Signed-off-by: Mario Limonciello Signed-off-by: George Zhang Signed-off-by: Alex Deucher (cherry picked from commit bd9e2b5b0473c75abc0f4134dfe79ecbfb16610d) Cc: stable@vger.kernel.org --- 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 18145d78334f..ff337de44f7a 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -5563,11 +5563,11 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector) caps = &dm->backlight_caps[aconnector->bl_idx]; if (get_brightness_range(caps, &min, &max)) { if (power_supply_is_system_supplied() > 0) - props.brightness = DIV_ROUND_CLOSEST((max - min) * caps->ac_level, 100); + props.brightness = DIV_ROUND_CLOSEST(max * caps->ac_level, 100); else - props.brightness = DIV_ROUND_CLOSEST((max - min) * caps->dc_level, 100); + props.brightness = DIV_ROUND_CLOSEST(max * caps->dc_level, 100); /* min is zero, so max needs to be adjusted */ - props.max_brightness = max - min; + props.max_brightness = max; drm_dbg(drm, "Backlight caps: min: %d, max: %d, ac %d, dc %d\n", min, max, caps->ac_level, caps->dc_level); } else