[Intel-gfx] [PATCH] drm/i915: Only enable DFP 4:4:4->4:2:0 conversion when outputting YCbCr 4:4:4

[Jani Nikula]

On Mon, 11 Jan 2021, Ville Syrjala <ville.syrjala at linux.intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> Let's not enable the 4:4:4->4:2:0 conversion bit in the DFP unless we're
> actually outputting YCbCr 4:4:4. It would appear some protocol
> converters blindy consult this bit even when the source is outputting
> RGB, resulting in a visual mess.
>
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2914
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

Fixes: 181567aa9f0d ("drm/i915: Do YCbCr 444->420 conversion via DP protocol converters")
Cc: <stable at vger.kernel.org> # v5.10+

Right?

Reviewed-by: Jani Nikula <jani.nikula at intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 4f190a82d4ad..aa30ef9f6906 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -4368,8 +4368,8 @@ void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp,
>  		drm_dbg_kms(&i915->drm, "Failed to set protocol converter HDMI mode to %s\n",
>  			    enableddisabled(intel_dp->has_hdmi_sink));
>  
> -	tmp = intel_dp->dfp.ycbcr_444_to_420 ?
> -		DP_CONVERSION_TO_YCBCR420_ENABLE : 0;
> +	tmp = crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR444 &&
> +		intel_dp->dfp.ycbcr_444_to_420 ? DP_CONVERSION_TO_YCBCR420_ENABLE : 0;
>  
>  	if (drm_dp_dpcd_writeb(&intel_dp->aux,
>  			       DP_PROTOCOL_CONVERTER_CONTROL_1, tmp) != 1)

-- 
Jani Nikula, Intel Open Source Graphics Center