drm/i915/dp: add functions for max common link rate and lane count

These are the theoretical maximums common for source and sink. These are
the maximums we should start with. They may be degraded in case of link
training failures, and the dynamic link values are stored separately.

Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/5088aca253c47dfa18251e1adb976aca1718f083.1491485983.git.jani.nikula@intel.com

drivers/gpu/drm/i915/intel_dp.c

@@ -161,22 +161,27 @@ static void intel_dp_set_sink_rates(struct intel_dp *intel_dp)
 	intel_dp->num_sink_rates = num_rates;
 }
 
-static int intel_dp_max_sink_rate(struct intel_dp *intel_dp)
+/* Theoretical max between source and sink */
+static int intel_dp_max_common_rate(struct intel_dp *intel_dp)
 {
-	return intel_dp->sink_rates[intel_dp->num_sink_rates - 1];
+	return intel_dp->common_rates[intel_dp->num_common_rates - 1];
 }
 
-static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
+/* Theoretical max between source and sink */
+static int intel_dp_max_common_lane_count(struct intel_dp *intel_dp)
 {
 	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
-	u8 source_max, sink_max;
-
-	source_max = intel_dig_port->max_lanes;
-	sink_max = intel_dp->max_link_lane_count;
+	int source_max = intel_dig_port->max_lanes;
+	int sink_max = drm_dp_max_lane_count(intel_dp->dpcd);
 
 	return min(source_max, sink_max);
 }
 
+static int intel_dp_max_lane_count(struct intel_dp *intel_dp)
+{
+	return intel_dp->max_link_lane_count;
+}
+
 int
 intel_dp_link_required(int pixel_clock, int bpp)
 {
@@ -329,7 +334,7 @@ int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
 		intel_dp->max_link_rate = intel_dp->common_rates[index - 1];
 		intel_dp->max_link_lane_count = lane_count;
 	} else if (lane_count > 1) {
-		intel_dp->max_link_rate = intel_dp_max_sink_rate(intel_dp);
+		intel_dp->max_link_rate = intel_dp_max_common_rate(intel_dp);
 		intel_dp->max_link_lane_count = lane_count >> 1;
 	} else {
 		DRM_ERROR("Link Training Unsuccessful\n");
@@ -4636,11 +4641,11 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
 		      yesno(drm_dp_tps3_supported(intel_dp->dpcd)));
 
 	if (intel_dp->reset_link_params) {
-		/* Set the max lane count for link */
-		intel_dp->max_link_lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
+		/* Initial max link lane count */
+		intel_dp->max_link_lane_count = intel_dp_max_common_lane_count(intel_dp);
 
-		/* Set the max link rate for link */
-		intel_dp->max_link_rate = intel_dp_max_sink_rate(intel_dp);
+		/* Initial max link rate */
+		intel_dp->max_link_rate = intel_dp_max_common_rate(intel_dp);
 
 		intel_dp->reset_link_params = false;
 	}