[PATCH 2/4] drm/i915: Adjust LUT rounding rules

[Borah, Chaitanya Kumar]

Hello Ville,

> -----Original Message-----
> From: dri-devel <dri-devel-bounces at lists.freedesktop.org> On Behalf Of Ville
> Syrjala
> Sent: Friday, October 13, 2023 6:44 PM
> To: intel-gfx at lists.freedesktop.org
> Cc: dri-devel at lists.freedesktop.org
> Subject: [PATCH 2/4] drm/i915: Adjust LUT rounding rules
> 
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> drm_color_lut_extract() rounding was changed to follow the OpenGL int<-
> >float conversion rules. Adjust intel_color_lut_pack() to match.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_color.c | 14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_color.c
> b/drivers/gpu/drm/i915/display/intel_color.c
> index 2a2a163ea652..b01f463af861 100644
> --- a/drivers/gpu/drm/i915/display/intel_color.c
> +++ b/drivers/gpu/drm/i915/display/intel_color.c
> @@ -785,14 +785,12 @@ static void chv_assign_csc(struct intel_crtc_state
> *crtc_state)
>  /* convert hw value with given bit_precision to lut property val */  static u32
> intel_color_lut_pack(u32 val, int bit_precision)  {

Is this operation unique to Intel. Should there be a drm helper for this?

Regards

Chaitanya

> -	u32 max = 0xffff >> (16 - bit_precision);
> -
> -	val = clamp_val(val, 0, max);
> -
> -	if (bit_precision < 16)
> -		val <<= 16 - bit_precision;
> -
> -	return val;
> +	if (bit_precision > 16)
> +		return DIV_ROUND_CLOSEST_ULL(mul_u32_u32(val, (1 << 16)
> - 1),
> +					     (1 << bit_precision) - 1);
> +	else
> +		return DIV_ROUND_CLOSEST(val * ((1 << 16) - 1),
> +					 (1 << bit_precision) - 1);
>  }
> 
>  static u32 i9xx_lut_8(const struct drm_color_lut *color)
> --
> 2.41.0