Re: [Intel-gfx] [PATCH v2 2/3] drm/i915/xelpd: Enable Pipe Degamma

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 26 Nov 2021, Uma Shankar <uma.shankar@intel.com> wrote:
> Enable Pipe Degamma for XE_LPD. Extend the legacy implementation
> to incorparate the extended lut size for XE_LPD.
>
> v2: Added a helper for degamma lut size (Ville)
>
> Signed-off-by: Uma Shankar <uma.shankar@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_color.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_color.c b/drivers/gpu/drm/i915/display/intel_color.c
> index 42fe549ef6fe..de3ded1e327a 100644
> --- a/drivers/gpu/drm/i915/display/intel_color.c
> +++ b/drivers/gpu/drm/i915/display/intel_color.c
> @@ -808,6 +808,14 @@ static void bdw_load_luts(const struct intel_crtc_state *crtc_state)
>  	}
>  }
>  
> +static int glk_degamma_lut_size(struct drm_i915_private *i915)
> +{
> +	if (DISPLAY_VER(i915) >= 13)
> +		return 131;
> +	else
> +		return 35;
> +}
> +

Why do we have both a function with hardcoded values and device info
members for this?

BR,
Jani.

>  static void glk_load_degamma_lut(const struct intel_crtc_state *crtc_state)
>  {
>  	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
> @@ -827,8 +835,8 @@ static void glk_load_degamma_lut(const struct intel_crtc_state *crtc_state)
>  
>  	for (i = 0; i < lut_size; i++) {
>  		/*
> -		 * First 33 entries represent range from 0 to 1.0
> -		 * 34th and 35th entry will represent extended range
> +		 * First lut_size entries represent range from 0 to 1.0
> +		 * 3 additional lut entries will represent extended range
>  		 * inputs 3.0 and 7.0 respectively, currently clamped
>  		 * at 1.0. Since the precision is 16bit, the user
>  		 * value can be directly filled to register.
> @@ -844,7 +852,7 @@ static void glk_load_degamma_lut(const struct intel_crtc_state *crtc_state)
>  	}
>  
>  	/* Clamp values > 1.0. */
> -	while (i++ < 35)
> +	while (i++ < glk_degamma_lut_size(dev_priv))
>  		intel_de_write_fw(dev_priv, PRE_CSC_GAMC_DATA(pipe), 1 << 16);
>  
>  	intel_de_write_fw(dev_priv, PRE_CSC_GAMC_INDEX(pipe), 0);

-- 
Jani Nikula, Intel Open Source Graphics Center