drm/i915/display/tgl: Fix the order of the step to turn transcoder clock off

For TGL the step to turn off the transcoder clock was moved to after
the complete shutdown of DDI. Only the MST slave transcoders should
disable the clock before that.

v2:
- Adding last_mst_stream to intel_mst_post_disable_dp, make code more
easy to read and is similar to first_mst_stream in
intel_mst_pre_enable_dp()(Ville's idea)
- Calling intel_ddi_disable_pipe_clock() for GEN12+ right
intel_disable_ddi_buf() as stated in BSpec(Ville)

BSpec: 49190
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191205210350.96795-2-jose.souza@intel.com

drivers/gpu/drm/i915/display/intel_ddi.c

@@ -3807,11 +3807,19 @@ static void intel_ddi_post_disable_dp(struct intel_encoder *encoder,
 	 */
 	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_OFF);
 
-	if (!is_mst)
+	if (INTEL_GEN(dev_priv) < 12 && !is_mst)
 		intel_ddi_disable_pipe_clock(old_crtc_state);
 
 	intel_disable_ddi_buf(encoder, old_crtc_state);
 
+	/*
+	 * From TGL spec: "If single stream or multi-stream master transcoder:
+	 * Configure Transcoder Clock select to direct no clock to the
+	 * transcoder"
+	 */
+	if (INTEL_GEN(dev_priv) >= 12)
+		intel_ddi_disable_pipe_clock(old_crtc_state);
+
 	intel_edp_panel_vdd_on(intel_dp);
 	intel_edp_panel_off(intel_dp);
 

drivers/gpu/drm/i915/display/intel_dp_mst.c

@@ -235,7 +235,20 @@ static void intel_mst_post_disable_dp(struct intel_encoder *encoder,
 	struct intel_dp *intel_dp = &intel_dig_port->dp;
 	struct intel_connector *connector =
 		to_intel_connector(old_conn_state->connector);
+	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
+	bool last_mst_stream;
 
+	intel_dp->active_mst_links--;
+	last_mst_stream = intel_dp->active_mst_links == 0;
+
+	/*
+	 * From TGL spec: "If multi-stream slave transcoder: Configure
+	 * Transcoder Clock Select to direct no clock to the transcoder"
+	 *
+	 * From older GENs spec: "Configure Transcoder Clock Select to direct
+	 * no clock to the transcoder"
+	 */
+	if (INTEL_GEN(dev_priv) < 12 || !last_mst_stream)
 		intel_ddi_disable_pipe_clock(old_crtc_state);
 
 	/* this can fail */
@@ -252,13 +265,10 @@ static void intel_mst_post_disable_dp(struct intel_encoder *encoder,
 	drm_dp_send_power_updown_phy(&intel_dp->mst_mgr, connector->port,
 				     false);
 
-	intel_dp->active_mst_links--;
-
 	intel_mst->connector = NULL;
-	if (intel_dp->active_mst_links == 0) {
+	if (last_mst_stream)
 		intel_dig_port->base.post_disable(&intel_dig_port->base,
 						  old_crtc_state, NULL);
-	}
 
 	DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);
 }