[PATCH] Revert "drm/amd/display: Fix AMDGPU_MAX_BL_LEVEL value"

[Alex Deucher]

On Mon, Jul 21, 2025 at 3:15 PM Limonciello, Mario
<Mario.Limonciello at amd.com> wrote:
>
> On 7/21/25 8:43 AM, Mario Limonciello wrote:
> > From: Mario Limonciello <mario.limonciello at 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 at vger.kernel.org
> > Link: https://lore.kernel.org/amd-gfx/0f094c4b-d2a3-42cd-824c-dc2858a5618d@kernel.org/T/#m69f875a7e69aa22df3370b3e3a9e69f4a61fdaf2
> > Signed-off-by: Mario Limonciello <mario.limonciello at 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.

With that fixed, the patch is:
Acked-by: Alex Deucher <alexander.deucher at amd.com>