> -----Original Message-----
> From: Borah, Chaitanya Kumar <chaitanya.kumar.borah@xxxxxxxxx>
> Sent: Monday, July 10, 2023 7:13 PM
> To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: jani.nikula@xxxxxxxxxxxxxxx; Shankar, Uma <uma.shankar@xxxxxxxxx>; Borah,
> Chaitanya Kumar <chaitanya.kumar.borah@xxxxxxxxx>
> 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@xxxxxxxxx>
> Signed-off-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@xxxxxxxxx>
> ---
> 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
