[Intel-gfx] [PATCH v2 2/2] drm/i915/color: Downscale degamma lut values read from hardware

[Shankar, Uma]

> -----Original Message-----
> From: Borah, Chaitanya Kumar <chaitanya.kumar.borah at intel.com>
> Sent: Monday, July 10, 2023 7:13 PM
> To: intel-gfx at lists.freedesktop.org
> Cc: jani.nikula at linux.intel.com; Shankar, Uma <uma.shankar at intel.com>; Borah,
> Chaitanya Kumar <chaitanya.kumar.borah at intel.com>
> Subject: [PATCH v2 2/2] drm/i915/color: Downscale degamma lut values read from
> hardware
> 
> For MTL and beyond, convert back the 24 bit lut values read from HW to 16 bit
> values to maintain parity with userspace values. This way we avoid pipe config
> mismatch for pre-csc lut values.
> 
> v2: Add helper function to downscale values (Jani)

Change looks ok to me.
Reviewed-by: Uma Shankar <uma.shankar at intel.com>

> Signed-off-by: Chaitanya Kumar Borah <chaitanya.kumar.borah at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_color.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_color.c
> b/drivers/gpu/drm/i915/display/intel_color.c
> index 15ada7fada96..41666e778c03 100644
> --- a/drivers/gpu/drm/i915/display/intel_color.c
> +++ b/drivers/gpu/drm/i915/display/intel_color.c
> @@ -3456,6 +3456,14 @@ static struct drm_property_blob
> *glk_read_degamma_lut(struct intel_crtc *crtc)
>  	for (i = 0; i < lut_size; i++) {
>  		u32 val = intel_de_read_fw(dev_priv, PRE_CSC_GAMC_DATA(pipe));
> 
> +		/*
> +		 * For MTL and beyond, convert back the 24 bit lut values
> +		 * read from HW to 16 bit values to maintain parity with
> +		 * userspace values
> +		 */
> +		if (DISPLAY_VER(dev_priv) >= 14)
> +			val = change_lut_val_precision(val, 16, 24);
> +
>  		lut[i].red = val;
>  		lut[i].green = val;
>  		lut[i].blue = val;
> --
> 2.25.1