drm/i915: Fix BXT lane latency optimal setting with MST

Call the DDI .pre_pll_enable() hook from the MST code so that BXT gets
the correct lane latency optimal setting applied. And we obviously need
to compute the correct value, and read it out to keep the state checker
happy.

While at it drop the useless 'encoder' parameter to
bxt_ddi_phy_calc_lane_lat_optim_mask()

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171027134348.31190-1-ville.syrjala@linux.intel.com
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/gpu/drm/i915/i915_drv.h

@@ -4179,8 +4179,7 @@ bool bxt_ddi_phy_is_enabled(struct drm_i915_private *dev_priv,
 			    enum dpio_phy phy);
 bool bxt_ddi_phy_verify_state(struct drm_i915_private *dev_priv,
 			      enum dpio_phy phy);
-uint8_t bxt_ddi_phy_calc_lane_lat_optim_mask(struct intel_encoder *encoder,
-					     uint8_t lane_count);
+uint8_t bxt_ddi_phy_calc_lane_lat_optim_mask(uint8_t lane_count);
 void bxt_ddi_phy_set_lane_optim_mask(struct intel_encoder *encoder,
 				     uint8_t lane_lat_optim_mask);
 uint8_t bxt_ddi_phy_get_lane_lat_optim_mask(struct intel_encoder *encoder);

drivers/gpu/drm/i915/intel_ddi.c

@@ -2662,8 +2662,7 @@ static bool intel_ddi_compute_config(struct intel_encoder *encoder,
 
 	if (IS_GEN9_LP(dev_priv) && ret)
 		pipe_config->lane_lat_optim_mask =
-			bxt_ddi_phy_calc_lane_lat_optim_mask(encoder,
-							     pipe_config->lane_count);
+			bxt_ddi_phy_calc_lane_lat_optim_mask(pipe_config->lane_count);
 
 	intel_ddi_compute_min_voltage_level(dev_priv, pipe_config);
 

drivers/gpu/drm/i915/intel_dp_mst.c

@@ -88,6 +88,10 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
 
 	pipe_config->dp_m_n.tu = slots;
 
+	if (IS_GEN9_LP(dev_priv))
+		pipe_config->lane_lat_optim_mask =
+			bxt_ddi_phy_calc_lane_lat_optim_mask(pipe_config->lane_count);
+
 	intel_ddi_compute_min_voltage_level(dev_priv, pipe_config);
 
 	return true;
@@ -182,6 +186,20 @@ static void intel_mst_post_disable_dp(struct intel_encoder *encoder,
 	DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);
 }
 
+static void intel_mst_pre_pll_enable_dp(struct intel_encoder *encoder,
+					const struct intel_crtc_state *pipe_config,
+					const struct drm_connector_state *conn_state)
+{
+	struct intel_dp_mst_encoder *intel_mst = enc_to_mst(&encoder->base);
+	struct intel_digital_port *intel_dig_port = intel_mst->primary;
+	struct intel_dp *intel_dp = &intel_dig_port->dp;
+
+	if (intel_dp->active_mst_links == 0 &&
+	    intel_dig_port->base.pre_pll_enable)
+		intel_dig_port->base.pre_pll_enable(&intel_dig_port->base,
+						    pipe_config, NULL);
+}
+
 static void intel_mst_pre_enable_dp(struct intel_encoder *encoder,
 				    const struct intel_crtc_state *pipe_config,
 				    const struct drm_connector_state *conn_state)
@@ -311,6 +329,10 @@ static void intel_dp_mst_enc_get_config(struct intel_encoder *encoder,
 
 	intel_ddi_clock_get(&intel_dig_port->base, pipe_config);
 
+	if (IS_GEN9_LP(dev_priv))
+		pipe_config->lane_lat_optim_mask =
+			bxt_ddi_phy_get_lane_lat_optim_mask(encoder);
+
 	intel_ddi_compute_min_voltage_level(dev_priv, pipe_config);
 }
 
@@ -582,6 +604,7 @@ intel_dp_create_fake_mst_encoder(struct intel_digital_port *intel_dig_port, enum
 	intel_encoder->compute_config = intel_dp_mst_compute_config;
 	intel_encoder->disable = intel_mst_disable_dp;
 	intel_encoder->post_disable = intel_mst_post_disable_dp;
+	intel_encoder->pre_pll_enable = intel_mst_pre_pll_enable_dp;
 	intel_encoder->pre_enable = intel_mst_pre_enable_dp;
 	intel_encoder->enable = intel_mst_enable_dp;
 	intel_encoder->get_hw_state = intel_dp_mst_enc_get_hw_state;

drivers/gpu/drm/i915/intel_dpio_phy.c

@@ -567,8 +567,7 @@ bool bxt_ddi_phy_verify_state(struct drm_i915_private *dev_priv,
 }
 
 uint8_t
-bxt_ddi_phy_calc_lane_lat_optim_mask(struct intel_encoder *encoder,
-				     uint8_t lane_count)
+bxt_ddi_phy_calc_lane_lat_optim_mask(uint8_t lane_count)
 {
 	switch (lane_count) {
 	case 1: