Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
Pre-existing issues: - [High] Double scaling of the brightness value when a custom brightness curve is used, causing the minimum backlight level to be incorrectly raised. -- --- Patch [1]: [PATCH] drm/amd/display: Scale custom brightness curve from full range --- commit d7add749f0052e896a6fee3206021e51b2fd8540 Author: Akhmed Zhitaev <[email protected]> drm/amd/display: Scale custom brightness curve from full range This patch changes the input scaling for custom brightness curves to map the userspace [0..max] range to the curve's [0..255] range. This prevents generating a curve input greater than 255 for panels with a nonzero minimum PWM level. > 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 941c1a3128249..7908b15370845 100644 > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c [ ... ] > -/* 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] */ > @@ -5281,7 +5281,7 @@ 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; [Severity: High] This isn't a bug introduced by this patch, but does the current code double-scale the brightness when a custom brightness curve is used? Looking at scale_fw_to_input() in drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c, it maps the curve's [0..255] output 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), AMDGPU_MAX_BL_LEVEL); } This is used at the end of convert_custom_brightness(), meaning the output brightness value is returned in the [min..max] range. However, in convert_brightness_from_user(), the output gets rescaled again: convert_custom_brightness(caps, min, max, &brightness); // Rescale 0..max to min..max return min + DIV_ROUND_CLOSEST_ULL((u64)(max - min) * brightness, max); Because scale_fw_to_input() already mapped it to [min..max], and convert_brightness_from_user() rescales it to [min..max] again under the assumption that the value is in [0..max], the minimum offset is applied twice. Since this patch explicitly aims to fix the brightness scaling logic introduced by commit 8dbd72cb7900, should scale_fw_to_input() or convert_brightness_from_user() also be updated to avoid raising the minimum backlight level incorrectly for panels using custom brightness curves? -- Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=1
