[Intel-gfx] [PATCH 04/11] drm/i915/dp: Get optimal link config to have best compressed bpp

[Ankit Nautiyal <ankit.k.nautiyal@intel.com>]

Currently, we take the max lane, rate and pipe bpp, to get the maximum
compressed bpp possible. We then set the output bpp to this value.
This patch provides support to have max bpp, min rate and min lanes,
that can support the min compressed bpp.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 223 +++++++++++++++++++++---
 1 file changed, 200 insertions(+), 23 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 8ddbbada22ab..10f9292e1e0d 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -1461,6 +1461,187 @@ static int intel_dp_dsc_compute_params(struct intel_encoder *encoder,
 	return drm_dsc_compute_rc_parameters(vdsc_cfg);
 }
 
+static bool is_dsc_bw_sufficient(int link_rate, int lane_count, int compressed_bpp,
+				 const struct drm_display_mode *adjusted_mode)
+{
+	int mode_rate = intel_dp_link_required(adjusted_mode->crtc_clock, compressed_bpp);
+	int link_avail = intel_dp_max_data_rate(link_rate, lane_count);
+
+	return mode_rate <= link_avail;
+}
+
+static int dsc_compute_link_config(struct intel_dp *intel_dp,
+				   struct intel_crtc_state *pipe_config,
+				   struct link_config_limits *limits,
+				   int pipe_bpp,
+				   u16 compressed_bpp)
+{
+	const struct drm_display_mode *adjusted_mode =
+		&pipe_config->hw.adjusted_mode;
+	int link_rate, lane_count;
+	int dsc_max_bpp;
+	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
+	int i;
+
+	for (i = 0; i < intel_dp->num_common_rates; i++) {
+		link_rate = intel_dp_common_rate(intel_dp, i);
+		if (link_rate < limits->min_rate || link_rate > limits->max_rate)
+			continue;
+
+		for (lane_count = limits->min_lane_count;
+		     lane_count <= limits->max_lane_count;
+		     lane_count <<= 1) {
+			dsc_max_bpp = intel_dp_dsc_get_output_bpp_max(dev_priv,
+								      link_rate,
+								      lane_count,
+								      adjusted_mode->crtc_clock,
+								      adjusted_mode->crtc_hdisplay,
+								      pipe_config->bigjoiner_pipes,
+								      pipe_bpp);
+			if (compressed_bpp > dsc_max_bpp)
+				continue;
+
+			if (!is_dsc_bw_sufficient(link_rate, lane_count,
+						  compressed_bpp, adjusted_mode))
+				continue;
+
+			pipe_config->lane_count = lane_count;
+			pipe_config->port_clock = link_rate;
+
+			return 0;
+		}
+	}
+
+	return -EINVAL;
+}
+
+static u16 dsc_max_sink_compressed_bppx16(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE],
+					  struct intel_crtc_state *pipe_config,
+					  int bpc)
+{
+	u16 max_bpp = dsc_dpcd[DP_DSC_MAX_BITS_PER_PIXEL_LOW - DP_DSC_SUPPORT] |
+		     (dsc_dpcd[DP_DSC_MAX_BITS_PER_PIXEL_HI - DP_DSC_SUPPORT] &
+		      DP_DSC_MAX_BITS_PER_PIXEL_HI_MASK << DP_DSC_MAX_BITS_PER_PIXEL_HI_SHIFT);
+
+	if (max_bpp)
+		return max_bpp;
+	/*
+	 * If support not given in DPCD 67h, 68h use the Maximum Allowed bit rate
+	 * values as given in spec Table 2-157 DP v2.0
+	 */
+	switch (pipe_config->output_format) {
+	case INTEL_OUTPUT_FORMAT_RGB:
+	case INTEL_OUTPUT_FORMAT_YCBCR444:
+		return (3 * bpc) << 4;
+	case INTEL_OUTPUT_FORMAT_YCBCR420:
+		return (3 * (bpc / 2)) << 4;
+	default:
+		MISSING_CASE(pipe_config->output_format);
+		break;
+	}
+
+	return 0;
+}
+
+static u16 dsc_min_compressed_bppx16(struct intel_crtc_state *pipe_config)
+{
+	switch (pipe_config->output_format) {
+	case INTEL_OUTPUT_FORMAT_RGB:
+	case INTEL_OUTPUT_FORMAT_YCBCR444:
+		return 8 << 4;
+	case INTEL_OUTPUT_FORMAT_YCBCR420:
+		return 6 << 4;
+	default:
+		MISSING_CASE(pipe_config->output_format);
+		break;
+	}
+
+	return 0;
+}
+
+static int dsc_compute_compressed_bpp(struct intel_dp *intel_dp,
+				      struct intel_crtc_state *pipe_config,
+				      struct link_config_limits *limits,
+				      int pipe_bpp)
+{
+	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
+	u16 compressed_bpp;
+	int dsc_min_bpp, dsc_src_max_bpp, dsc_sink_max_bpp, dsc_max_bpp;
+	int ret;
+
+	dsc_min_bpp = max(dsc_min_compressed_bppx16(pipe_config) >> 4, 8);
+	if (DISPLAY_VER(dev_priv) <= 12)
+		dsc_src_max_bpp = 23;
+	else
+		dsc_src_max_bpp = 27;
+	dsc_sink_max_bpp = dsc_max_sink_compressed_bppx16(intel_dp->dsc_dpcd,
+							  pipe_config, pipe_bpp / 3) >> 4;
+
+	dsc_max_bpp = dsc_sink_max_bpp ? min(dsc_sink_max_bpp, dsc_src_max_bpp) : dsc_src_max_bpp;
+
+	for (compressed_bpp = dsc_max_bpp;
+	     compressed_bpp >= dsc_min_bpp;
+	     compressed_bpp--) {
+		ret = dsc_compute_link_config(intel_dp,
+					      pipe_config,
+					      limits,
+					      pipe_bpp,
+					      compressed_bpp);
+		if (ret == 0) {
+			pipe_config->dsc.compressed_bpp = compressed_bpp;
+			return 0;
+		}
+	}
+
+	return -EINVAL;
+}
+
+static int intel_dp_dsc_compute_pipe_bpp(struct intel_dp *intel_dp,
+					 struct intel_crtc_state *pipe_config,
+					 struct drm_connector_state *conn_state,
+					 struct link_config_limits *limits)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	u8 dsc_bpc[3] = {0};
+	u8 dsc_max_bpc, dsc_max_bpp;
+	u8 max_req_bpc = conn_state->max_requested_bpc;
+	int i, bpp, ret;
+	int num_bpc = drm_dp_dsc_sink_supported_input_bpcs(intel_dp->dsc_dpcd,
+							   dsc_bpc);
+
+	/* Max DSC Input BPC for ICL is 10 and for TGL+ is 12 */
+	if (DISPLAY_VER(i915) >= 12)
+		dsc_max_bpc = min_t(u8, 12, limits->max_bpp);
+	else
+		dsc_max_bpc = min_t(u8, 10, max_req_bpc);
+
+	dsc_max_bpp = min(dsc_max_bpc * 3, limits->max_bpp);
+
+	/*
+	 * Get the maximum DSC bpc that will be supported by any valid
+	 * link configuration and compressed bpp.
+	 */
+	for (i = 0; i < num_bpc; i++) {
+		bpp = dsc_bpc[i] * 3;
+
+		if (bpp < limits->min_bpp)
+			continue;
+
+		if (bpp > limits->max_bpp)
+			break;
+
+		ret = dsc_compute_compressed_bpp(intel_dp, pipe_config,
+						 limits, bpp);
+		if (ret == 0) {
+			pipe_config->pipe_bpp = bpp;
+
+			return 0;
+		}
+	}
+
+	return -EINVAL;
+}
+
 static int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
 				       struct intel_crtc_state *pipe_config,
 				       struct drm_connector_state *conn_state,
@@ -1505,17 +1686,11 @@ static int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
 		return -EINVAL;
 	}
 
-	pipe_config->pipe_bpp = pipe_bpp;
-
-	/*
-	 * For now enable DSC for 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->port_clock = limits->max_rate;
-	pipe_config->lane_count = limits->max_lane_count;
-
 	if (intel_dp_is_edp(intel_dp)) {
+		pipe_config->pipe_bpp = pipe_bpp;
+		pipe_config->port_clock = limits->max_rate;
+		pipe_config->lane_count = limits->max_lane_count;
+
 		pipe_config->dsc.compressed_bpp =
 			min_t(u16, drm_edp_dsc_sink_output_bpp(intel_dp->dsc_dpcd) >> 4,
 			      pipe_config->pipe_bpp);
@@ -1523,29 +1698,31 @@ static int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
 			drm_dp_dsc_sink_max_slice_count(intel_dp->dsc_dpcd,
 							true);
 	} else {
-		u16 dsc_max_output_bpp;
 		u8 dsc_dp_slice_count;
 
-		dsc_max_output_bpp =
-			intel_dp_dsc_get_output_bpp_max(dev_priv,
-							pipe_config->port_clock,
-							pipe_config->lane_count,
-							adjusted_mode->crtc_clock,
-							adjusted_mode->crtc_hdisplay,
-							pipe_config->bigjoiner_pipes,
-							pipe_bpp);
+		if (intel_dp->force_dsc_bpc &&
+		    intel_dp->force_dsc_bpc <= conn_state->max_requested_bpc)
+			ret = dsc_compute_compressed_bpp(intel_dp, pipe_config,
+							 limits, pipe_bpp);
+		else
+			ret = intel_dp_dsc_compute_pipe_bpp(intel_dp, pipe_config,
+							    conn_state, limits);
+		if (ret < 0) {
+			drm_dbg_kms(&dev_priv->drm,
+				    "Cannot support mode with DSC with any link config\n");
+			return ret;
+		}
+
 		dsc_dp_slice_count =
 			intel_dp_dsc_get_slice_count(intel_dp,
 						     adjusted_mode->crtc_clock,
 						     adjusted_mode->crtc_hdisplay,
 						     pipe_config->bigjoiner_pipes);
-		if (!dsc_max_output_bpp || !dsc_dp_slice_count) {
+		if (!dsc_dp_slice_count) {
 			drm_dbg_kms(&dev_priv->drm,
-				    "Compressed BPP/Slice Count not supported\n");
+				    "Slice Count not supported\n");
 			return -EINVAL;
 		}
-		pipe_config->dsc.compressed_bpp = min_t(u16, dsc_max_output_bpp,
-							pipe_config->pipe_bpp);
 		pipe_config->dsc.slice_count = dsc_dp_slice_count;
 	}
 
-- 
2.25.1