Custom brightness curves use an 8-bit input signal. After exporting the
full PWM range to userspace, the curve normalizer still divides requests
by the physical PWM span. On panels with a nonzero minimum PWM level,
this can produce a curve input greater than 255 and send an invalid
backlight level to DC.
Scale the userspace [0..max] range to the curve's [0..255] range
instead. This retains the full advertised range and keeps the reverse
readback conversion unchanged.
Fixes: 8dbd72cb7900 ("drm/amd/display: Export full brightness range to
userspace")
Cc: [email protected]
Signed-off-by: Akhmed Zhitaev <[email protected]>
---
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 8 ++++----
1 file changed, 4 insertions(+), 4 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 40d82a3ee..533c69f0b 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -5131,10 +5131,10 @@ static int get_brightness_range(const struct
amdgpu_dm_backlight_caps *caps,
return 1;
}
-/* Rescale from [min..max] to [0..AMDGPU_MAX_BL_LEVEL] */
-static inline u32 scale_input_to_fw(int min, int max, u64 input)
+/* Rescale userspace [0..max] to the firmware curve's [0..255]. */
+static inline u32 scale_input_to_fw(int max, u64 input)
{
- return DIV_ROUND_CLOSEST_ULL(input * AMDGPU_MAX_BL_LEVEL, max - min);
+ return DIV_ROUND_CLOSEST_ULL(input * AMDGPU_MAX_BL_LEVEL, max);
}
/* Rescale from [0..AMDGPU_MAX_BL_LEVEL] to [min..max] */
@@ -5147,7 +5147,7 @@ static void convert_custom_brightness(const struct
amdgpu_dm_backlight_caps *cap
unsigned int min, unsigned int max,
uint32_t *user_brightness)
{
- u32 brightness = scale_input_to_fw(min, max, *user_brightness);
+ u32 brightness = scale_input_to_fw(max, *user_brightness);
u8 lower_signal, upper_signal, upper_lum, lower_lum, lum;
int left, right;
--
2.55.0
