[RFC 2/4] drm/i915/dp: refactor DP MST detection and configuration

[Jani Nikula <jani.nikula@intel.com>]

Currently we've split MST capability detection in two places,
intel_dp_can_mst() and intel_dp_configure_mst(). They check essentially
the same things.

Move bulk of the work, including logging, to intel_dp_can_mst() and
rename it intel_dp_mst_detect(). Set intel_dp->is_mst there to avoid
duplicate work.

Rename intel_dp_configure_mst() to intel_dp_mst_configure(), and only
set the topology manager state there.

The main functional difference is that the DP_MSTM_CAP DPCD register is
now only read once at detect, unconditionally, and the MST support is
always logged. Everything else should remain the same.

Cc: Arun R Murthy <arun.r.murthy@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 36 ++++++++++---------------
 1 file changed, 14 insertions(+), 22 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 7af09f2c008d..e0b8ee6bde79 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -4004,23 +4004,15 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 					   intel_dp->downstream_ports) == 0;
 }
 
-static bool
-intel_dp_can_mst(struct intel_dp *intel_dp)
+static bool intel_dp_mst_detect(struct intel_dp *intel_dp)
 {
 	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
+	bool sink_can_mst = drm_dp_read_mst_cap(&intel_dp->aux, intel_dp->dpcd) == DP_MST_CAPABLE;
 
-	return i915->display.params.enable_dp_mst &&
+	intel_dp->is_mst = i915->display.params.enable_dp_mst &&
 		intel_dp_mst_source_support(intel_dp) &&
-		drm_dp_read_mst_cap(&intel_dp->aux, intel_dp->dpcd) == DP_MST_CAPABLE;
-}
-
-static void
-intel_dp_configure_mst(struct intel_dp *intel_dp)
-{
-	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
-	struct intel_encoder *encoder =
-		&dp_to_dig_port(intel_dp)->base;
-	bool sink_can_mst = drm_dp_read_mst_cap(&intel_dp->aux, intel_dp->dpcd) == DP_MST_CAPABLE;
+		sink_can_mst;
 
 	drm_dbg_kms(&i915->drm,
 		    "[ENCODER:%d:%s] MST support: port: %s, sink: %s, modparam: %s\n",
@@ -4029,14 +4021,14 @@ intel_dp_configure_mst(struct intel_dp *intel_dp)
 		    str_yes_no(sink_can_mst),
 		    str_yes_no(i915->display.params.enable_dp_mst));
 
-	if (!intel_dp_mst_source_support(intel_dp))
-		return;
-
-	intel_dp->is_mst = sink_can_mst &&
-		i915->display.params.enable_dp_mst;
+	return intel_dp->is_mst;
+}
 
-	drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr,
-					intel_dp->is_mst);
+static void intel_dp_mst_configure(struct intel_dp *intel_dp)
+{
+	if (intel_dp_mst_source_support(intel_dp))
+		drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr,
+						intel_dp->is_mst);
 }
 
 static bool
@@ -5387,7 +5379,7 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
 		connector_status_connected : connector_status_disconnected;
 	}
 
-	if (intel_dp_can_mst(intel_dp))
+	if (intel_dp_mst_detect(intel_dp))
 		return connector_status_connected;
 
 	/* If no HPD, poke DDC gently */
@@ -5706,7 +5698,7 @@ intel_dp_detect(struct drm_connector *connector,
 
 	intel_dp_detect_dsc_caps(intel_dp, intel_connector);
 
-	intel_dp_configure_mst(intel_dp);
+	intel_dp_mst_configure(intel_dp);
 
 	/*
 	 * TODO: Reset link params when switching to MST mode, until MST
-- 
2.39.2