On 7/21/25 8:43 AM, Mario Limonciello wrote:

From: Mario Limonciello mario.limonciello@amd.com

This reverts commit 66abb996999de0d440a02583a6e70c2c24deab45. This broke custom brightness curves but it wasn't obvious because of other related changes. Custom brightness curves are always from a 0-255 input signal. The correct fix was to fix the default value which was done by [1].

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4412 Cc: stable@vger.kernel.org Link: https://lore.kernel.org/amd-gfx/0f094c4b-d2a3-42cd-824c-dc2858a5618d@kernel.... Signed-off-by: Mario Limonciello mario.limonciello@amd.com

---

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)

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 8e1405e9025ba..f3e407f31de11 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -4740,16 +4740,16 @@ static int get_brightness_range(const struct amdgpu_dm_backlight_caps *caps, return 1; } -/* Rescale from [min..max] to [0..MAX_BACKLIGHT_LEVEL] */ +/* Rescale from [min..max] to [0..AMDGPU_MAX_BL_LEVEL] */ static inline u32 scale_input_to_fw(int min, int max, u64 input) {

• return DIV_ROUND_CLOSEST_ULL(input * MAX_BACKLIGHT_LEVEL, max - min);

• return DIV_ROUND_CLOSEST_ULL(input * AMDGPU_MAX_BL_LEVEL, max - min); }

-/* Rescale from [0..MAX_BACKLIGHT_LEVEL] to [min..max] */ +/* Rescale from [0..AMDGPU_MAX_BL_LEVEL] to [min..max] */ static inline u32 scale_fw_to_input(int min, int max, u64 input) {

• return min + DIV_ROUND_CLOSEST_ULL(input * (max - min), MAX_BACKLIGHT_LEVEL);

• return min + DIV_ROUND_CLOSEST_ULL(input * (max - min), AMDGPU_MAX_BL_LEVEL); }

static void convert_custom_brightness(const struct amdgpu_dm_backlight_caps *caps, @@ -4977,7 +4977,7 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector) drm_dbg(drm, "Backlight caps: min: %d, max: %d, ac %d, dc %d\n", min, max, caps->ac_level, caps->dc_level); } else

• props.brightness = props.max_brightness = MAX_BACKLIGHT_LEVEL;
  

• props.brightness = props.max_brightness = AMDGPU_MAX_BL_LEVEL;
  

This bottom hunk doesn't need to revert, that one is fine. The other two need to be reverted though to fix this issue.