[Intel-gfx] [PATCH 6/7] drm/i915: Find fallback link rate/lane count

[Manasi Navare]

If link training fails, then we need to fallback to lower
link rate first and if link training fails at RBR, then
fallback to lower lane count.

Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c  | 28 ++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_drv.h |  6 ++++++
 2 files changed, 34 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 39116c8..369b5ce 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -303,6 +303,34 @@ static int intel_dp_link_rate_index(struct intel_dp *intel_dp,
 	return -1;
 }
 
+void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
+					     int link_rate, uint8_t lane_count)
+{
+	int common_rates[DP_MAX_SUPPORTED_RATES] = {};
+	int common_len;
+	int link_rate_index = -1;
+
+	if (!intel_dp->link_train_failed)
+		return;
+
+	common_len = intel_dp_common_rates(intel_dp, common_rates);
+	link_rate_index = intel_dp_link_rate_index(intel_dp,
+						   common_rates,
+						   link_rate);
+	if (link_rate_index > 0) {
+		intel_dp->fallback_link_rate_index = link_rate_index - 1;
+		intel_dp->fallback_link_rate = common_rates[intel_dp->fallback_link_rate_index];
+		intel_dp->fallback_lane_count = intel_dp_max_lane_count(intel_dp);
+	} else if (lane_count > 1) {
+		intel_dp->fallback_link_rate_index = common_len -1;
+		intel_dp->fallback_link_rate = common_rates[intel_dp->fallback_link_rate_index];
+		intel_dp->fallback_lane_count = lane_count - 1;
+	} else {
+		DRM_ERROR ("Link Training Unsuccessful\n");
+		intel_dp->link_train_failed = false;
+	}
+}
+
 static enum drm_mode_status
 intel_dp_mode_valid(struct drm_connector *connector,
 		    struct drm_display_mode *mode)
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index f6fe05a..c6789ee 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -890,6 +890,10 @@ struct intel_dp {
 	uint32_t DP;
 	int link_rate;
 	uint8_t lane_count;
+	int fallback_link_rate;
+	uint8_t fallback_lane_count;
+	int fallback_link_rate_index;
+	bool link_train_failed;
 	uint8_t sink_count;
 	bool link_mst;
 	bool has_audio;
@@ -1402,6 +1406,8 @@ int intel_dp_set_link_status_property(struct drm_connector *connector,
 void intel_dp_set_link_params(struct intel_dp *intel_dp,
 			      int link_rate, uint8_t lane_count,
 			      bool link_mst);
+void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
+					     int link_rate, uint8_t lane_count);
 void intel_dp_start_link_train(struct intel_dp *intel_dp);
 void intel_dp_stop_link_train(struct intel_dp *intel_dp);
 void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
-- 
1.9.1