drm/i915/dp: Factor out helpers to compute the link limits

Factor out helpers that DP / DP_MST encoders can use to compute the link
rate/lane count and bpp limits. A follow-up patch will call these to
recalculate the limits if DSC compression is required.
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230921195159.2646027-2-imre.deak@intel.com

drivers/gpu/drm/i915/display/intel_dp.c

@@ -2188,29 +2188,25 @@ int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
 	return 0;
 }
 
-static int
-intel_dp_compute_link_config(struct intel_encoder *encoder,
-			     struct intel_crtc_state *pipe_config,
-			     struct drm_connector_state *conn_state,
-			     bool respect_downstream_limits)
+static void
+intel_dp_compute_config_limits(struct intel_dp *intel_dp,
+			       struct intel_crtc_state *crtc_state,
+			       bool respect_downstream_limits,
+			       struct link_config_limits *limits)
 {
-	struct drm_i915_private *i915 = to_i915(encoder->base.dev);
-	struct intel_crtc *crtc = to_intel_crtc(pipe_config->uapi.crtc);
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
 	const struct drm_display_mode *adjusted_mode =
-		&pipe_config->hw.adjusted_mode;
-	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
-	struct link_config_limits limits;
-	bool joiner_needs_dsc = false;
-	int ret;
+		&crtc_state->hw.adjusted_mode;
 
-	limits.min_rate = intel_dp_common_rate(intel_dp, 0);
-	limits.max_rate = intel_dp_max_link_rate(intel_dp);
+	limits->min_rate = intel_dp_common_rate(intel_dp, 0);
+	limits->max_rate = intel_dp_max_link_rate(intel_dp);
 
-	limits.min_lane_count = 1;
-	limits.max_lane_count = intel_dp_max_lane_count(intel_dp);
+	limits->min_lane_count = 1;
+	limits->max_lane_count = intel_dp_max_lane_count(intel_dp);
 
-	limits.min_bpp = intel_dp_min_bpp(pipe_config->output_format);
-	limits.max_bpp = intel_dp_max_bpp(intel_dp, pipe_config, respect_downstream_limits);
+	limits->min_bpp = intel_dp_min_bpp(crtc_state->output_format);
+	limits->max_bpp = intel_dp_max_bpp(intel_dp, crtc_state,
+					   respect_downstream_limits);
 
 	if (intel_dp->use_max_params) {
 		/*
@@ -2221,16 +2217,35 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
 		 * configuration, and typically on older panels these
 		 * values correspond to the native resolution of the panel.
 		 */
-		limits.min_lane_count = limits.max_lane_count;
-		limits.min_rate = limits.max_rate;
+		limits->min_lane_count = limits->max_lane_count;
+		limits->min_rate = limits->max_rate;
 	}
 
-	intel_dp_adjust_compliance_config(intel_dp, pipe_config, &limits);
+	intel_dp_adjust_compliance_config(intel_dp, crtc_state, limits);
 
 	drm_dbg_kms(&i915->drm, "DP link computation with max lane count %i "
 		    "max rate %d max bpp %d pixel clock %iKHz\n",
-		    limits.max_lane_count, limits.max_rate,
-		    limits.max_bpp, adjusted_mode->crtc_clock);
+		    limits->max_lane_count, limits->max_rate,
+		    limits->max_bpp, adjusted_mode->crtc_clock);
+}
+
+static int
+intel_dp_compute_link_config(struct intel_encoder *encoder,
+			     struct intel_crtc_state *pipe_config,
+			     struct drm_connector_state *conn_state,
+			     bool respect_downstream_limits)
+{
+	struct drm_i915_private *i915 = to_i915(encoder->base.dev);
+	struct intel_crtc *crtc = to_intel_crtc(pipe_config->uapi.crtc);
+	const struct drm_display_mode *adjusted_mode =
+		&pipe_config->hw.adjusted_mode;
+	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
+	struct link_config_limits limits;
+	bool joiner_needs_dsc = false;
+	int ret;
+
+	intel_dp_compute_config_limits(intel_dp, pipe_config,
+				       respect_downstream_limits, &limits);
 
 	if (intel_dp_need_bigjoiner(intel_dp, adjusted_mode->crtc_hdisplay,
 				    adjusted_mode->crtc_clock))

drivers/gpu/drm/i915/display/intel_dp_mst.c

@@ -293,6 +293,35 @@ static int intel_dp_mst_update_slots(struct intel_encoder *encoder,
 	return 0;
 }
 
+static void
+intel_dp_mst_compute_config_limits(struct intel_dp *intel_dp,
+				   struct intel_crtc_state *crtc_state,
+				   struct link_config_limits *limits)
+{
+	/*
+	 * for MST we always configure max link bw - the spec doesn't
+	 * seem to suggest we should do otherwise.
+	 */
+	limits->min_rate = limits->max_rate =
+		intel_dp_max_link_rate(intel_dp);
+
+	limits->min_lane_count = limits->max_lane_count =
+		intel_dp_max_lane_count(intel_dp);
+
+	limits->min_bpp = intel_dp_min_bpp(crtc_state->output_format);
+	/*
+	 * FIXME: If all the streams can't fit into the link with
+	 * their current pipe_bpp we should reduce pipe_bpp across
+	 * the board until things start to fit. Until then we
+	 * limit to <= 8bpc since that's what was hardcoded for all
+	 * MST streams previously. This hack should be removed once
+	 * we have the proper retry logic in place.
+	 */
+	limits->max_bpp = min(crtc_state->pipe_bpp, 24);
+
+	intel_dp_adjust_compliance_config(intel_dp, crtc_state, limits);
+}
+
 static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
 				       struct intel_crtc_state *pipe_config,
 				       struct drm_connector_state *conn_state)
@@ -312,28 +341,7 @@ static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
 	pipe_config->output_format = INTEL_OUTPUT_FORMAT_RGB;
 	pipe_config->has_pch_encoder = false;
 
-	/*
-	 * for MST we always configure max link bw - the spec doesn't
-	 * seem to suggest we should do otherwise.
-	 */
-	limits.min_rate =
-	limits.max_rate = intel_dp_max_link_rate(intel_dp);
-
-	limits.min_lane_count =
-	limits.max_lane_count = intel_dp_max_lane_count(intel_dp);
-
-	limits.min_bpp = intel_dp_min_bpp(pipe_config->output_format);
-	/*
-	 * FIXME: If all the streams can't fit into the link with
-	 * their current pipe_bpp we should reduce pipe_bpp across
-	 * the board until things start to fit. Until then we
-	 * limit to <= 8bpc since that's what was hardcoded for all
-	 * MST streams previously. This hack should be removed once
-	 * we have the proper retry logic in place.
-	 */
-	limits.max_bpp = min(pipe_config->pipe_bpp, 24);
-
-	intel_dp_adjust_compliance_config(intel_dp, pipe_config, &limits);
+	intel_dp_mst_compute_config_limits(intel_dp, pipe_config, &limits);
 
 	ret = intel_dp_mst_compute_link_config(encoder, pipe_config,
 					       conn_state, &limits);