Yes, this is still needed. f1b5d8f9cc54 fixes the advertised max_brightness mismatch by restoring the full userspace range [0..max].
The issue fixed by this patch is different: the custom brightness curve input is still normalized by (max - min). On panels with a non-zero PWM minimum, valid userspace requests near the top of the [0..max] range can therefore produce a curve input above 255. On my panel, min=3084 and max=65535. Without this patch, requests above the upper boundary caused the backlight to drop dark; with this patch, the full range maps into [0..255] and the issue no longer reproduces. I also tested with the f1b5d8f9cc54 semantics present, so the regression is still present without this change. чт, 13 авг. 2026 г. в 22:45, Mario Limonciello <[email protected]>: > > > On 8/13/26 12:09, Akhmed Zhitaev wrote: > > 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; > > > > Is this still needed with > > "drm/amd/display: Fix backlight max_brightness to match exported range" > > > https://github.com/torvalds/linux/commit/f1b5d8f9cc54ae8a2567ac126867ae488e1bf625 >
