Re: [PATCH 01/12] drm/i915/dp: Refactor FEC support check in intel_dp_supports_dsc

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

On Wed, 20 Nov 2024, Ankit Nautiyal <ankit.k.nautiyal@intel.com> wrote:
> Forward Error Correction is required for DP if we are using DSC but
> is optional for eDP.
>
> Currently the helper intel_dp_supports_dsc checks if fec_enable is set for
> DP or not. The helper is called after fec_enable is set in crtc_state.
>
> Instead of this a better approach would be to:
> first, call intel_dp_supports_dsc to check for DSC support
> (along with FEC requirement for DP) and then set fec_enable for DP
> (if not already set) in crtc_state.
>
> To achieve this, remove the check for fec_enable in the helper and instead
> check for FEC support for DP. With this change the helper
> intel_dp_supports_dsc can be called earlier and return early if DSC is
> not supported. The structure intel_dp is added to the helper to get the
> FEC support for DP.
>
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c     | 8 +++++---
>  drivers/gpu/drm/i915/display/intel_dp.h     | 3 ++-
>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 5 +++--
>  3 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 053a9a4182e7..db9ddbcdd159 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -1632,13 +1632,15 @@ bool intel_dp_supports_fec(struct intel_dp *intel_dp,
>  		drm_dp_sink_supports_fec(connector->dp.fec_capability);
>  }
>  
> -bool intel_dp_supports_dsc(const struct intel_connector *connector,
> +bool intel_dp_supports_dsc(struct intel_dp *intel_dp,
> +			   const struct intel_connector *connector,
>  			   const struct intel_crtc_state *crtc_state)
>  {
>  	if (!intel_dp_has_dsc(connector))
>  		return false;
>  
> -	if (intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DP) && !crtc_state->fec_enable)
> +	if (intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DP) &&
> +	    !intel_dp_supports_fec(intel_dp, connector, crtc_state))
>  		return false;
>  
>  	return intel_dsc_source_support(crtc_state);
> @@ -2376,7 +2378,7 @@ int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
>  		 intel_dp_supports_fec(intel_dp, connector, pipe_config) &&
>  		 !intel_dp_is_uhbr(pipe_config));
>  
> -	if (!intel_dp_supports_dsc(connector, pipe_config))
> +	if (!intel_dp_supports_dsc(intel_dp, connector, pipe_config))
>  		return -EINVAL;
>  
>  	if (!intel_dp_dsc_supports_format(connector, pipe_config->output_format))
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
> index 48f10876be65..4ae54e9718ce 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.h
> +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> @@ -170,7 +170,8 @@ bool intel_dp_supports_fec(struct intel_dp *intel_dp,
>  			   const struct intel_connector *connector,
>  			   const struct intel_crtc_state *pipe_config);
>  
> -bool intel_dp_supports_dsc(const struct intel_connector *connector,
> +bool intel_dp_supports_dsc(struct intel_dp *intel_dp,
> +			   const struct intel_connector *connector,
>  			   const struct intel_crtc_state *crtc_state);
>  
>  u32 intel_dp_dsc_nearest_valid_bpp(struct drm_i915_private *i915, u32 bpp, u32 pipe_bpp);
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index f058360a2641..0662736849ac 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -498,12 +498,13 @@ adjust_limits_for_dsc_hblank_expansion_quirk(const struct intel_connector *conne
>  	struct intel_display *display = to_intel_display(connector);
>  	const struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
>  	int min_bpp_x16 = limits->link.min_bpp_x16;
> +	struct intel_dp *intel_dp = connector->mst_port;

Maybe better to pass in intel_dp here too for clarity. The caller has it
from to_primary_dp().

BR,
Jani.

>  
>  	if (!hblank_expansion_quirk_needs_dsc(connector, crtc_state, limits))
>  		return true;
>  
>  	if (!dsc) {
> -		if (intel_dp_supports_dsc(connector, crtc_state)) {
> +		if (intel_dp_supports_dsc(intel_dp, connector, crtc_state)) {
>  			drm_dbg_kms(display->drm,
>  				    "[CRTC:%d:%s][CONNECTOR:%d:%s] DSC needed by hblank expansion quirk\n",
>  				    crtc->base.base.id, crtc->base.name,
> @@ -648,7 +649,7 @@ static int mst_stream_compute_config(struct intel_encoder *encoder,
>  			    str_yes_no(ret), str_yes_no(joiner_needs_dsc),
>  			    str_yes_no(intel_dp->force_dsc_en));
>  
> -		if (!intel_dp_supports_dsc(connector, pipe_config))
> +		if (!intel_dp_supports_dsc(intel_dp, connector, pipe_config))
>  			return -EINVAL;
>  
>  		if (!mst_stream_compute_config_limits(intel_dp, connector,

-- 
Jani Nikula, Intel