From: Jani Nikula <jani.nikula@intel.com>
Date: Thu, 26 Apr 2018 11:25:29 +0300
Subject: drm/i915/dp: abstract link config selection
Git-commit: 3acd115d08f70615debd5a8d37a8b97dc17a9cbb
Patch-mainline: v4.18-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

For now, there's just the one link config selection, optimizing for slow
and wide link. No functional changes.

Keep the debug logging in the caller, to avoid duplication later on if
alternative link confing selection gets added.

v2: Improved commit message

Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/64848b76bf90d6ceecd7ec6b5add28531e0b1a41.1524730974.git.jani.nikula@intel.com

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/i915/intel_dp.c |   81 ++++++++++++++++++++++++----------------
 1 file changed, 50 insertions(+), 31 deletions(-)

--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1704,6 +1704,42 @@ static bool intel_edp_compare_alt_mode(s
 	return bres;
 }
 
+/* Optimize link config in order: max bpp, min clock, min lanes */
+static bool
+intel_dp_compute_link_config_wide(struct intel_dp *intel_dp,
+				  struct intel_crtc_state *pipe_config,
+				  const struct link_config_limits *limits)
+{
+	struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
+	int bpp, clock, lane_count;
+	int mode_rate, link_clock, link_avail;
+
+	for (bpp = limits->max_bpp; bpp >= limits->min_bpp; bpp -= 2 * 3) {
+		mode_rate = intel_dp_link_required(adjusted_mode->crtc_clock,
+						   bpp);
+
+		for (clock = limits->min_clock; clock <= limits->max_clock; clock++) {
+			for (lane_count = limits->min_lane_count;
+			     lane_count <= limits->max_lane_count;
+			     lane_count <<= 1) {
+				link_clock = intel_dp->common_rates[clock];
+				link_avail = intel_dp_max_data_rate(link_clock,
+								    lane_count);
+
+				if (mode_rate <= link_avail) {
+					pipe_config->lane_count = lane_count;
+					pipe_config->pipe_bpp = bpp;
+					pipe_config->port_clock = link_clock;
+
+					return true;
+				}
+			}
+		}
+	}
+
+	return false;
+}
+
 static bool
 intel_dp_compute_link_config(struct intel_encoder *encoder,
 			     struct intel_crtc_state *pipe_config)
@@ -1711,8 +1747,6 @@ intel_dp_compute_link_config(struct inte
 	struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
 	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
 	struct link_config_limits limits;
-	int bpp, clock, lane_count;
-	int mode_rate, link_avail, link_clock;
 	int common_len;
 
 	common_len = intel_dp_common_len_rate_limit(intel_dp,
@@ -1766,37 +1800,22 @@ intel_dp_compute_link_config(struct inte
 		      intel_dp->common_rates[limits.max_clock],
 		      limits.max_bpp, adjusted_mode->crtc_clock);
 
-	for (bpp = limits.max_bpp; bpp >= limits.min_bpp; bpp -= 2 * 3) {
-		mode_rate = intel_dp_link_required(adjusted_mode->crtc_clock,
-						   bpp);
-
-		for (clock = limits.min_clock; clock <= limits.max_clock; clock++) {
-			for (lane_count = limits.min_lane_count;
-			     lane_count <= limits.max_lane_count;
-			     lane_count <<= 1) {
-
-				link_clock = intel_dp->common_rates[clock];
-				link_avail = intel_dp_max_data_rate(link_clock,
-								    lane_count);
-
-				if (mode_rate <= link_avail) {
-					goto found;
-				}
-			}
-		}
-	}
-
-	return false;
-
-found:
-	pipe_config->lane_count = lane_count;
-	pipe_config->pipe_bpp = bpp;
-	pipe_config->port_clock = intel_dp->common_rates[clock];
+	/*
+	 * Optimize for slow and wide. This is the place to add alternative
+	 * optimization policy.
+	 */
+	if (!intel_dp_compute_link_config_wide(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, bpp);
-	DRM_DEBUG_KMS("DP link bw required %i available %i\n",
-		      mode_rate, link_avail);
+		      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;
 }