From bd9e2b5b0473c75abc0f4134dfe79ecbfb16610d Mon Sep 17 00:00:00 2001 From: Mario Limonciello Date: Mon, 29 Jun 2026 15:27:00 -0500 Subject: [PATCH] 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 --- .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.c | 6 +++--- .../display/amdgpu_dm/tests/amdgpu_dm_backlight_test.c | 8 ++++---- 2 files changed, 7 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.c index 11d54897a894..ca60c72855fd 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.c @@ -407,12 +407,12 @@ void amdgpu_dm_backlight_fill_props(const struct amdgpu_dm_backlight_caps *caps, if (get_brightness_range(caps, &min, &max)) { if (is_system_supplied) - props->brightness = DIV_ROUND_CLOSEST((max - min) * caps->ac_level, + props->brightness = DIV_ROUND_CLOSEST(max * caps->ac_level, 100); else - props->brightness = DIV_ROUND_CLOSEST((max - min) * caps->dc_level, + props->brightness = DIV_ROUND_CLOSEST(max * caps->dc_level, 100); - props->max_brightness = max - min; + props->max_brightness = max; } else { props->brightness = MAX_BACKLIGHT_LEVEL; props->max_brightness = MAX_BACKLIGHT_LEVEL; diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_backlight_test.c b/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_backlight_test.c index adb896022a27..8ebc0f263e3e 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_backlight_test.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_backlight_test.c @@ -799,8 +799,8 @@ static void dm_test_backlight_fill_props_ac_linear(struct kunit *test) amdgpu_dm_backlight_fill_props(&caps, true, false, &props); KUNIT_EXPECT_EQ(test, props.brightness, - DIV_ROUND_CLOSEST((max - min) * caps.ac_level, 100)); - KUNIT_EXPECT_EQ(test, props.max_brightness, max - min); + DIV_ROUND_CLOSEST(max * caps.ac_level, 100)); + KUNIT_EXPECT_EQ(test, props.max_brightness, max); KUNIT_EXPECT_EQ(test, props.scale, BACKLIGHT_SCALE_LINEAR); KUNIT_EXPECT_EQ(test, props.type, BACKLIGHT_RAW); } @@ -825,8 +825,8 @@ static void dm_test_backlight_fill_props_dc_nonlinear(struct kunit *test) amdgpu_dm_backlight_fill_props(&caps, false, true, &props); KUNIT_EXPECT_EQ(test, props.brightness, - DIV_ROUND_CLOSEST((max - min) * caps.dc_level, 100)); - KUNIT_EXPECT_EQ(test, props.max_brightness, max - min); + DIV_ROUND_CLOSEST(max * caps.dc_level, 100)); + KUNIT_EXPECT_EQ(test, props.max_brightness, max); KUNIT_EXPECT_EQ(test, props.scale, BACKLIGHT_SCALE_NON_LINEAR); KUNIT_EXPECT_EQ(test, props.type, BACKLIGHT_RAW); }