Re: [Intel-gfx] [PATCH 2/2] drm/i915/hdmi: Prune unsupported modes as per HDMI2.1 spec

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, May 09, 2022 at 03:01:30PM +0530, Ankit Nautiyal wrote:
> As per Sec 7.8.1 of HDMI2.1 spec, sources that support modes:
> 4K100, 4K120, 8K50, 8K60 must support these modes in at least one of
> the below formats:
> i) uncompressed FRL, 420 format and min of 10 bpc, or
> ii) compressed FRL, 444 format and min of 10 bpc.
> 
> Since FRL and DSC are not supported natively with HDMI, the above
> modes must be pruned as per the spec, and is a requirement for the
> HDMI2.1 compliance test.
> 
> This patch adds a condition to check for the modes with clock
> requirement more than 2376 MHz (1188 MHz with 420 format),
> and prune them if none of the above two formats are supported.

Wy are we trying to pass HDMI-2.1 tests on a device that
doesn't even support HDMI-2.1? 

> 
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_hdmi.c | 48 +++++++++++++++++++++++
>  1 file changed, 48 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
> index 1ae09431f53a..2ee1262f6427 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> @@ -1940,6 +1940,44 @@ static bool intel_hdmi_sink_bpc_possible(struct drm_connector *connector,
>  	}
>  }
>  
> +/*
> + * HDMI2.1 Sec7.8.1
> + * Support requirement for 4K100, 4K120, 8K50, and 8K60.
> + *
> + * The modes with timings same as above modes are supported only with min of 10 bpc
> + * along with:
> + *
> + * i) 444 format only with FRL mode support with DSC
> + * ii) 420 format only with FRL mode without DSC.
> + */
> +static bool
> +intel_hdmi21_bpc_possible(struct drm_connector *connector,
> +			  int clock, int bpc, bool ycbcr420_output,
> +			  bool frl, bool dsc)
> +{
> +	const struct drm_display_info *info = &connector->display_info;
> +	const struct drm_hdmi_info *hdmi = &info->hdmi;
> +
> +	int pixel_clock = ycbcr420_output ? clock * 2 : clock;
> +
> +	if (pixel_clock < 2376000)
> +		return true;
> +
> +	if (!frl)
> +		return false;
> +
> +	if (dsc && bpc > hdmi->dsc_cap.bpc_supported)
> +		return false;
> +
> +	if (!ycbcr420_output && !dsc)
> +		return false;
> +
> +	if (bpc < 10)
> +		return false;
> +
> +	return true;
> +}
> +
>  static enum drm_mode_status
>  intel_hdmi_mode_clock_valid(struct drm_connector *connector, int clock,
>  			    bool has_hdmi_sink, bool ycbcr420_output)
> @@ -1948,6 +1986,13 @@ intel_hdmi_mode_clock_valid(struct drm_connector *connector, int clock,
>  	struct intel_hdmi *hdmi = intel_attached_hdmi(to_intel_connector(connector));
>  	enum drm_mode_status status = MODE_OK;
>  	int bpc;
> +	bool frl, dsc;
> +
> +	/*
> +	 * FRL and DSC not supported for HDMI from source as of now.
> +	 */
> +	frl = false;
> +	dsc = false;
>  
>  	/*
>  	 * Try all color depths since valid port clock range
> @@ -1963,6 +2008,9 @@ intel_hdmi_mode_clock_valid(struct drm_connector *connector, int clock,
>  		if (!intel_hdmi_sink_bpc_possible(connector, bpc, has_hdmi_sink, ycbcr420_output))
>  			continue;
>  
> +		if (!intel_hdmi21_bpc_possible(connector, clock, bpc, ycbcr420_output, frl, dsc))
> +			continue;
> +
>  		status = hdmi_port_clock_valid(hdmi, tmds_clock, true, has_hdmi_sink);
>  		if (status == MODE_OK)
>  			return MODE_OK;
> -- 
> 2.25.1

-- 
Ville Syrjälä
Intel