Re: [PATCH v8 07/19] drm/i915/dp: Compute DSC pipe config in atomic check

[Manasi Navare <manasi.d.navare@intel.com>]

On Fri, Nov 02, 2018 at 02:31:26PM -0700, Manasi Navare wrote:
> DSC params like the enable, compressed bpp, slice count and
> dsc_split are added to the intel_crtc_state. These parameters
> are set based on the requested mode and available link parameters
> during the pipe configuration in atomic check phase.
> These values are then later used to populate the remaining DSC
> and RC parameters before enbaling DSC in atomic commit.
> 
> v11:
> * Const crtc_state, reject DSC on DP without FEC (Ville)
> * Dont set dsc_split to false (Ville)
> v10:
> * Add a helper for dp_dsc support (Ville)
> * Set pipe_config to max bpp, link params for DSC for now (Ville)
> * Compute bpp - use dp dsc support helper (Ville)
> v9:
> * Rebase on top of drm-tip that now uses fast_narrow config
> for edp (Manasi)
> v8:
> * Check for DSC bpc not 0 (manasi)
> 
> v7:
> * Fix indentation in compute_m_n (Manasi)
> 
> v6 (From Gaurav):
> * Remove function call of intel_dp_compute_dsc_params() and
> invoke intel_dp_compute_dsc_params() in the patch where
> it is defined to fix compilation warning (Gaurav)
> 
> v5:
> Add drm_dsc_cfg in intel_crtc_state (Manasi)
> 
> v4:
> * Rebase on refactoring of intel_dp_compute_config on tip (Manasi)
> * Add a comment why we need to check PSR while enabling DSC (Gaurav)
> 
> v3:
> * Check PPR > max_cdclock to use 2 VDSC instances (Ville)
> 
> v2:
> * Add if-else for eDP/DP (Gaurav)
> 
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
> Cc: Gaurav K Singh <gaurav.k.singh@intel.com>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
> Acked-by: Jani Nikula <jani.nikula@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c |  20 +++-
>  drivers/gpu/drm/i915/intel_display.h |   3 +-
>  drivers/gpu/drm/i915/intel_dp.c      | 167 ++++++++++++++++++++++++---
>  drivers/gpu/drm/i915/intel_dp_mst.c  |   2 +-
>  4 files changed, 166 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index b219d5858160..477e53c37353 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -6442,7 +6442,7 @@ static int ironlake_fdi_compute_config(struct intel_crtc *intel_crtc,
>  
>  	pipe_config->fdi_lanes = lane;
>  
> -	intel_link_compute_m_n(pipe_config->pipe_bpp, lane, fdi_dotclock,
> +	intel_link_compute_m_n(pipe_config->pipe_bpp, 0, lane, fdi_dotclock,
>  			       link_bw, &pipe_config->fdi_m_n, false);
>  
>  	ret = ironlake_check_fdi_lanes(dev, intel_crtc->pipe, pipe_config);
> @@ -6679,17 +6679,25 @@ static void compute_m_n(unsigned int m, unsigned int n,
>  }
>  
>  void
> -intel_link_compute_m_n(int bits_per_pixel, int nlanes,
> +intel_link_compute_m_n(int bits_per_pixel, uint16_t compressed_bpp,
> +		       int nlanes,
>  		       int pixel_clock, int link_clock,
>  		       struct intel_link_m_n *m_n,
>  		       bool constant_n)
>  {
>  	m_n->tu = 64;
>  
> -	compute_m_n(bits_per_pixel * pixel_clock,
> -		    link_clock * nlanes * 8,
> -		    &m_n->gmch_m, &m_n->gmch_n,
> -		    constant_n);
> +	/* For DSC, Data M/N calculation uses compressed BPP */
> +	if (compressed_bpp)
> +		compute_m_n(compressed_bpp * pixel_clock,
> +			    link_clock * nlanes * 8,
> +			    &m_n->gmch_m, &m_n->gmch_n,
> +			    constant_n);
> +	else
> +		compute_m_n(bits_per_pixel * pixel_clock,
> +			    link_clock * nlanes * 8,
> +			    &m_n->gmch_m, &m_n->gmch_n,
> +			    constant_n);
>  
>  	compute_m_n(pixel_clock, link_clock,
>  		    &m_n->link_m, &m_n->link_n,
> diff --git a/drivers/gpu/drm/i915/intel_display.h b/drivers/gpu/drm/i915/intel_display.h
> index 5d50decbcbb5..b0b23e1e9392 100644
> --- a/drivers/gpu/drm/i915/intel_display.h
> +++ b/drivers/gpu/drm/i915/intel_display.h
> @@ -407,7 +407,8 @@ struct intel_link_m_n {
>  	     (__i)++) \
>  		for_each_if(plane)
>  
> -void intel_link_compute_m_n(int bpp, int nlanes,
> +void intel_link_compute_m_n(int bpp, uint16_t compressed_bpp,
> +			    int nlanes,
>  			    int pixel_clock, int link_clock,
>  			    struct intel_link_m_n *m_n,
>  			    bool constant_n);
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index b39b4bda8e40..58326fc9d935 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -47,6 +47,8 @@
>  
>  /* DP DSC small joiner has 2 FIFOs each of 640 x 6 bytes */
>  #define DP_DSC_MAX_SMALL_JOINER_RAM_BUFFER	61440
> +#define DP_DSC_MIN_SUPPORTED_BPC		8
> +#define DP_DSC_MAX_SUPPORTED_BPC		10
>  
>  /* DP DSC throughput values used for slice count calculations KPixels/s */
>  #define DP_DSC_PEAK_PIXEL_RATE			2720000
> @@ -1840,6 +1842,29 @@ struct link_config_limits {
>  	int min_bpp, max_bpp;
>  };
>  
> +static bool intel_dp_source_supports_dsc(struct intel_dp *intel_dp,
> +					 const struct intel_crtc_state *pipe_config)
> +{
> +	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
> +
> +	/* FIXME: FEC needed for external DP until then reject DSC on DP */
> +	if (!intel_dp_is_edp(intel_dp))
> +		return false;
> +
> +	return INTEL_GEN(dev_priv) >= 10 &&
> +		pipe_config->cpu_transcoder != TRANSCODER_A;
> +}
> +
> +static bool intel_dp_supports_dsc(struct intel_dp *intel_dp,
> +				  const struct intel_crtc_state *pipe_config)
> +{
> +	if (!intel_dp_source_supports_dsc(intel_dp, pipe_config) ||
> +	    !drm_dp_sink_supports_dsc(intel_dp->dsc_dpcd))
> +		return false;
> +
> +	return true;
> +}
> +
>  static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
>  				struct intel_crtc_state *pipe_config)
>  {
> @@ -1863,6 +1888,15 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
>  		}
>  	}
>  
> +	/* If DSC is supported, use the max value reported by panel */
> +	if (intel_dp_supports_dsc(intel_dp, pipe_config)) {
> +		bpc = min_t(u8,
> +			    drm_dp_dsc_sink_max_color_depth(intel_dp->dsc_dpcd),
> +			    DP_DSC_MAX_SUPPORTED_BPC);
> +		if (bpc)
> +			bpp = min(bpp, 3*bpc);

Ville, the problem with chosing the min between existing bpp and 3 * bpc (computed from DSC dpcd) is that EDID based bpc
might be lower and in case DSC is supported, the bpc value should be based on the dsc color depth and that should
override the value obtained from EDID.  This was confirmed from the VDSC programming documents obtained from
HW architecture folks

So i think it should still be if DSC supported use the bpc directly from min_t(u8, drm_dp_dsc_sink_max_color_depth(intel_dp->dsc_dpcd),DP_DSC_MAX_SUPPORTED_BPC);

Manasi

> +	}
> +
>  	return bpp;
>  }
>  
> @@ -1974,6 +2008,80 @@ intel_dp_compute_link_config_fast(struct intel_dp *intel_dp,
>  	return false;
>  }
>  
> +static bool intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
> +					struct intel_crtc_state *pipe_config,
> +					const struct link_config_limits *limits)
> +{
> +	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> +	struct drm_i915_private *dev_priv = to_i915(dig_port->base.base.dev);
> +	struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
> +	u16 dsc_max_output_bpp = 0;
> +	u8 dsc_dp_slice_count = 0;
> +
> +	if (!intel_dp_supports_dsc(intel_dp, pipe_config))
> +		return false;
> +
> +	/* DSC not supported for DSC sink BPC < 8 */
> +	if (limits->max_bpp < 3 * DP_DSC_MIN_SUPPORTED_BPC) {
> +		DRM_DEBUG_KMS("No DSC support for less than 8bpc\n");
> +		return false;
> +	}
> +
> +	/*
> +	 * For now enable DSC for max bpp, max link rate, max lane count.
> +	 * Optimize this later for the minimum possible link rate/lane count
> +	 * with DSC enabled for the requested mode.
> +	 */
> +	pipe_config->pipe_bpp = limits->max_bpp;
> +	pipe_config->port_clock = intel_dp->common_rates[limits->max_clock];
> +	pipe_config->lane_count = limits->max_lane_count;
> +
> +	if (intel_dp_is_edp(intel_dp)) {
> +		pipe_config->dsc_params.compressed_bpp =
> +			drm_edp_dsc_sink_output_bpp(intel_dp->dsc_dpcd) >> 4;
> +		pipe_config->dsc_params.slice_count =
> +			drm_dp_dsc_sink_max_slice_count(intel_dp->dsc_dpcd,
> +							true);
> +	} else {
> +		dsc_max_output_bpp =
> +			intel_dp_dsc_get_output_bpp(pipe_config->port_clock,
> +						    pipe_config->lane_count,
> +						    adjusted_mode->crtc_clock,
> +						    adjusted_mode->crtc_hdisplay);
> +		dsc_dp_slice_count =
> +			intel_dp_dsc_get_slice_count(intel_dp,
> +						     adjusted_mode->crtc_clock,
> +						     adjusted_mode->crtc_hdisplay);
> +		if (!(dsc_max_output_bpp && dsc_dp_slice_count)) {
> +			DRM_DEBUG_KMS("Compressed BPP/Slice Count not supported\n");
> +			return false;
> +		}
> +		pipe_config->dsc_params.compressed_bpp = dsc_max_output_bpp >> 4;
> +		pipe_config->dsc_params.slice_count = dsc_dp_slice_count;
> +	}
> +	/*
> +	 * VDSC engine operates at 1 Pixel per clock, so if peak pixel rate
> +	 * is greater than the maximum Cdclock and if slice count is even
> +	 * then we need to use 2 VDSC instances.
> +	 */
> +	if (adjusted_mode->crtc_clock > dev_priv->max_cdclk_freq) {
> +		if (pipe_config->dsc_params.slice_count > 1) {
> +			pipe_config->dsc_params.dsc_split = true;
> +		} else {
> +			DRM_DEBUG_KMS("Cannot split stream to use 2 VDSC instances\n");
> +			return false;
> +		}
> +	}
> +	pipe_config->dsc_params.compression_enable = true;
> +	DRM_DEBUG_KMS("DP DSC computed with Input Bpp = %d "
> +		      "Compressed Bpp = %d Slice Count = %d\n",
> +		      pipe_config->pipe_bpp,
> +		      pipe_config->dsc_params.compressed_bpp,
> +		      pipe_config->dsc_params.slice_count);
> +
> +	return true;
> +}
> +
>  static bool
>  intel_dp_compute_link_config(struct intel_encoder *encoder,
>  			     struct intel_crtc_state *pipe_config)
> @@ -1982,6 +2090,7 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>  	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
>  	struct link_config_limits limits;
>  	int common_len;
> +	bool ret = false;
>  
>  	common_len = intel_dp_common_len_rate_limit(intel_dp,
>  						    intel_dp->max_link_rate);
> @@ -1995,8 +2104,12 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>  	limits.min_lane_count = 1;
>  	limits.max_lane_count = intel_dp_max_lane_count(intel_dp);
>  
> -	limits.min_bpp = 6 * 3;
>  	limits.max_bpp = intel_dp_compute_bpp(intel_dp, pipe_config);
> +	if (intel_dp_supports_dsc(intel_dp, pipe_config) &&
> +	    limits.max_bpp >= DP_DSC_MIN_SUPPORTED_BPC*3)
> +		limits.min_bpp = DP_DSC_MIN_SUPPORTED_BPC * 3;
> +	else
> +		limits.min_bpp = 6 * 3;
>  
>  	if (intel_dp_is_edp(intel_dp) && intel_dp->edp_dpcd[0] < DP_EDP_14) {
>  		/*
> @@ -2020,7 +2133,7 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>  		      intel_dp->common_rates[limits.max_clock],
>  		      limits.max_bpp, adjusted_mode->crtc_clock);
>  
> -	if (intel_dp_is_edp(intel_dp)) {
> +	if (intel_dp_is_edp(intel_dp))
>  		/*
>  		 * Optimize for fast and narrow. eDP 1.3 section 3.3 and eDP 1.4
>  		 * section A.1: "It is recommended that the minimum number of
> @@ -2030,26 +2143,42 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>  		 * Note that we use the max clock and lane count for eDP 1.3 and
>  		 * earlier, and fast vs. wide is irrelevant.
>  		 */
> -		if (!intel_dp_compute_link_config_fast(intel_dp, pipe_config,
> -						       &limits))
> -			return false;
> -	} else {
> +		ret = intel_dp_compute_link_config_fast(intel_dp, pipe_config,
> +							&limits);
> +	else
>  		/* Optimize for slow and wide. */
> -		if (!intel_dp_compute_link_config_wide(intel_dp, pipe_config,
> -						       &limits))
> +		ret = intel_dp_compute_link_config_wide(intel_dp, pipe_config,
> +							&limits);
> +
> +	/* enable compression if the mode doesn't fit available BW */
> +	if (!ret) {
> +		if (!intel_dp_dsc_compute_config(intel_dp, pipe_config,
> +						 &limits))
>  			return false;
>  	}
>  
> -	DRM_DEBUG_KMS("DP lane count %d clock %d bpp %d\n",
> -		      pipe_config->lane_count, pipe_config->port_clock,
> -		      pipe_config->pipe_bpp);
> +	if (pipe_config->dsc_params.compression_enable) {
> +		DRM_DEBUG_KMS("DP lane count %d clock %d Input bpp %d Compressed bpp %d\n",
> +			      pipe_config->lane_count, pipe_config->port_clock,
> +			      pipe_config->pipe_bpp,
> +			      pipe_config->dsc_params.compressed_bpp);
>  
> -	DRM_DEBUG_KMS("DP link rate required %i available %i\n",
> -		      intel_dp_link_required(adjusted_mode->crtc_clock,
> -					     pipe_config->pipe_bpp),
> -		      intel_dp_max_data_rate(pipe_config->port_clock,
> -					     pipe_config->lane_count));
> +		DRM_DEBUG_KMS("DP link rate required %i available %i\n",
> +			      intel_dp_link_required(adjusted_mode->crtc_clock,
> +						     pipe_config->dsc_params.compressed_bpp),
> +			      intel_dp_max_data_rate(pipe_config->port_clock,
> +						     pipe_config->lane_count));
> +	} else {
> +		DRM_DEBUG_KMS("DP lane count %d clock %d bpp %d\n",
> +			      pipe_config->lane_count, pipe_config->port_clock,
> +			      pipe_config->pipe_bpp);
>  
> +		DRM_DEBUG_KMS("DP link rate required %i available %i\n",
> +			      intel_dp_link_required(adjusted_mode->crtc_clock,
> +						     pipe_config->pipe_bpp),
> +			      intel_dp_max_data_rate(pipe_config->port_clock,
> +						     pipe_config->lane_count));
> +	}
>  	return true;
>  }
>  
> @@ -2133,7 +2262,9 @@ intel_dp_compute_config(struct intel_encoder *encoder,
>  			intel_conn_state->broadcast_rgb == INTEL_BROADCAST_RGB_LIMITED;
>  	}
>  
> -	intel_link_compute_m_n(pipe_config->pipe_bpp, pipe_config->lane_count,
> +	intel_link_compute_m_n(pipe_config->pipe_bpp,
> +			       pipe_config->dsc_params.compressed_bpp,
> +			       pipe_config->lane_count,
>  			       adjusted_mode->crtc_clock,
>  			       pipe_config->port_clock,
>  			       &pipe_config->dp_m_n,
> @@ -2142,7 +2273,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
>  	if (intel_connector->panel.downclock_mode != NULL &&
>  		dev_priv->drrs.type == SEAMLESS_DRRS_SUPPORT) {
>  			pipe_config->has_drrs = true;
> -			intel_link_compute_m_n(pipe_config->pipe_bpp,
> +			intel_link_compute_m_n(pipe_config->pipe_bpp, 0,
>  					       pipe_config->lane_count,
>  					       intel_connector->panel.downclock_mode->clock,
>  					       pipe_config->port_clock,
> diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> index 8b71d64ebd9d..e02caedd443c 100644
> --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> @@ -90,7 +90,7 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
>  		}
>  	}
>  
> -	intel_link_compute_m_n(bpp, lane_count,
> +	intel_link_compute_m_n(bpp, 0, lane_count,
>  			       adjusted_mode->crtc_clock,
>  			       pipe_config->port_clock,
>  			       &pipe_config->dp_m_n,
> -- 
> 2.18.0
> 
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