Re: [PATCH 46/50] drm/i915/dsc: Add intel_dsc_get_slice_config()

["Hogander, Jouni" <jouni.hogander@intel.com>]

On Thu, 2025-11-27 at 19:50 +0200, Imre Deak wrote:
> Add intel_dsc_get_slice_config() and move the logic to select a given
> slice configuration to that function from the configuration loop in
> intel_dp_dsc_get_slice_count(). The same functionality can be used by
> other outputs like DSI as well, done as a follow-up.
> 
> Signed-off-by: Imre Deak <imre.deak@intel.com>

Reviewed-by: Jouni Högander <jouni.hogander@intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_dp.c   | 22 ++++-------
>  drivers/gpu/drm/i915/display/intel_vdsc.c | 48
> +++++++++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_vdsc.h |  4 ++
>  3 files changed, 59 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index a4ff1ffc8f7d4..461f80bd54cbf 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -1029,28 +1029,20 @@ u8 intel_dp_dsc_get_slice_count(const struct
> intel_connector *connector,
>  	 * TGL+: 2x4 (TODO: Add support for this)
>  	 */
>  	for (slices_per_pipe = 1; slices_per_pipe <= 4;
> slices_per_pipe++) {
> -		int slices_per_line = slices_per_pipe *
> num_joined_pipes;
> +		struct intel_dsc_slice_config config;
> +		int slices_per_line;
>  
> -		/*
> -		 * 3 DSC Slices per pipe need 3 DSC engines, which
> is supported only
> -		 * with Ultrajoiner only for some platforms.
> -		 */
> -		if (slices_per_pipe == 3 &&
> -		    (!HAS_DSC_3ENGINES(display) || num_joined_pipes
> != 4))
> +		if (!intel_dsc_get_slice_config(display,
> +						num_joined_pipes,
> slices_per_pipe,
> +						&config))
>  			continue;
>  
> +		slices_per_line =
> intel_dsc_line_slice_count(&config);
> +
>  		if
> (!(drm_dp_dsc_slice_count_to_mask(slices_per_line) &
>  		      sink_slice_count_mask))
>  			continue;
>  
> -		 /*
> -		  * Bigjoiner needs small joiner to be enabled.
> -		  * So there should be at least 2 dsc slices per
> pipe,
> -		  * whenever bigjoiner is enabled.
> -		  */
> -		if (num_joined_pipes > 1 && slices_per_pipe < 2)
> -			continue;
> -
>  		if (mode_hdisplay % slices_per_line)
>  			continue;
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_vdsc.c
> b/drivers/gpu/drm/i915/display/intel_vdsc.c
> index 190ce567bc7fa..9910134d52653 100644
> --- a/drivers/gpu/drm/i915/display/intel_vdsc.c
> +++ b/drivers/gpu/drm/i915/display/intel_vdsc.c
> @@ -40,6 +40,54 @@ int intel_dsc_line_slice_count(const struct
> intel_dsc_slice_config *config)
>  	return config->pipes_per_line * config->streams_per_pipe *
> config->slices_per_stream;
>  }
>  
> +bool intel_dsc_get_slice_config(struct intel_display *display,
> +				int pipes_per_line, int
> slices_per_pipe,
> +				struct intel_dsc_slice_config
> *config)
> +{
> +	int streams_per_pipe;
> +
> +	/* TODO: Add support for 8 slices per pipe on TGL+. */
> +	switch (slices_per_pipe) {
> +	case 3:
> +		/*
> +		 * 3 DSC Slices per pipe need 3 DSC engines, which
> is supported only
> +		 * with Ultrajoiner only for some platforms.
> +		 */
> +		if (!HAS_DSC_3ENGINES(display) || pipes_per_line !=
> 4)
> +			return false;
> +
> +		streams_per_pipe = 3;
> +		break;
> +	case 4:
> +		/* TODO: Consider using 1 DSC engine stream x 4
> slices instead. */
> +	case 2:
> +		/* TODO: Consider using 1 DSC engine stream x 2
> slices instead. */
> +		streams_per_pipe = 2;
> +		break;
> +	case 1:
> +		 /*
> +		  * Bigjoiner needs small joiner to be enabled.
> +		  * So there should be at least 2 dsc slices per
> pipe,
> +		  * whenever bigjoiner is enabled.
> +		  */
> +		if (pipes_per_line > 1)
> +			return false;
> +
> +		streams_per_pipe = 1;
> +		break;
> +	default:
> +		MISSING_CASE(slices_per_pipe);
> +		return false;
> +	}
> +
> +	config->pipes_per_line = pipes_per_line;
> +	config->streams_per_pipe = streams_per_pipe;
> +	config->slices_per_stream = slices_per_pipe /
> streams_per_pipe;
> +
> +	return true;
> +}
> +
> +
>  static bool is_pipe_dsc(struct intel_crtc *crtc, enum transcoder
> cpu_transcoder)
>  {
>  	struct intel_display *display = to_intel_display(crtc);
> diff --git a/drivers/gpu/drm/i915/display/intel_vdsc.h
> b/drivers/gpu/drm/i915/display/intel_vdsc.h
> index e61116d5297c8..aeb17670307b1 100644
> --- a/drivers/gpu/drm/i915/display/intel_vdsc.h
> +++ b/drivers/gpu/drm/i915/display/intel_vdsc.h
> @@ -13,11 +13,15 @@ struct drm_printer;
>  enum transcoder;
>  struct intel_crtc;
>  struct intel_crtc_state;
> +struct intel_display;
>  struct intel_dsc_slice_config;
>  struct intel_encoder;
>  
>  bool intel_dsc_source_support(const struct intel_crtc_state
> *crtc_state);
>  int intel_dsc_line_slice_count(const struct intel_dsc_slice_config
> *config);
> +bool intel_dsc_get_slice_config(struct intel_display *display,
> +				int num_joined_pipes, int
> slice_per_pipe,
> +				struct intel_dsc_slice_config
> *config);
>  void intel_uncompressed_joiner_enable(const struct intel_crtc_state
> *crtc_state);
>  void intel_dsc_enable(const struct intel_crtc_state *crtc_state);
>  void intel_dsc_disable(const struct intel_crtc_state *crtc_state);