drm/i915: Pass a crtc state to ddi post_disable from MST code

Pass an old crtc state to intel_ddi_post_disable() from the MST code.

Note that this crtc state won't necessaitly match the one that was
passed to intel_ddi_pre_enable() if the first stream to be enabled isn't
the last stream to be disabled. But this is fine since the states should
be identical in every important way. This does mean people frobbing
the DDI pre_enable/post_disable hooks have to pay attention in what
parts of the state they consult.

The alternative would be to inline the relevant code into the MST code.
That is actually what we used to do for pre_enable before
commit e081c8463ac9 ("drm/i915: Remove duplicate DDI enabling logic
from MST path"). For post_disable we've always called the DDI hook.

v2: Pimp up the comments explaining the MST issues

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171027193128.14483-6-ville.syrjala@linux.intel.com
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/gpu/drm/i915/intel_ddi.c

@@ -2214,6 +2214,19 @@ static void intel_ddi_pre_enable(struct intel_encoder *encoder,
 	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
 	enum pipe pipe = crtc->pipe;
 
+	/*
+	 * When called from DP MST code:
+	 * - conn_state will be NULL
+	 * - encoder will be the main encoder (ie. mst->primary)
+	 * - the main connector associated with this port
+	 *   won't be active or linked to a crtc
+	 * - crtc_state will be the state of the first stream to
+	 *   be activated on this port, and it may not be the same
+	 *   stream that will be deactivated last, but each stream
+	 *   should have a state that is identical when it comes to
+	 *   the DP link parameteres
+	 */
+
 	WARN_ON(crtc_state->has_pch_encoder);
 
 	intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, true);
@@ -2254,12 +2267,7 @@ static void intel_ddi_post_disable_dp(struct intel_encoder *encoder,
 	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
 	struct intel_digital_port *dig_port = enc_to_dig_port(&encoder->base);
 	struct intel_dp *intel_dp = &dig_port->dp;
-	/*
-	 * old_crtc_state and old_conn_state are NULL when called from
-	 * DP_MST. The main connector associated with this port is never
-	 * bound to a crtc for MST.
-	 */
-	bool is_mst = !old_crtc_state;
+	bool is_mst = intel_crtc_has_type(old_crtc_state, INTEL_OUTPUT_DP_MST);
 
 	/*
 	 * Power down sink before disabling the port, otherwise we end
@@ -2303,12 +2311,19 @@ static void intel_ddi_post_disable(struct intel_encoder *encoder,
 				   const struct drm_connector_state *old_conn_state)
 {
 	/*
-	 * old_crtc_state and old_conn_state are NULL when called from
-	 * DP_MST. The main connector associated with this port is never
-	 * bound to a crtc for MST.
+	 * When called from DP MST code:
+	 * - old_conn_state will be NULL
+	 * - encoder will be the main encoder (ie. mst->primary)
+	 * - the main connector associated with this port
+	 *   won't be active or linked to a crtc
+	 * - old_crtc_state will be the state of the last stream to
+	 *   be deactivated on this port, and it may not be the same
+	 *   stream that was activated last, but each stream
+	 *   should have a state that is identical when it comes to
+	 *   the DP link parameteres
 	 */
-	if (old_crtc_state &&
-	    intel_crtc_has_type(old_crtc_state, INTEL_OUTPUT_HDMI))
+
+	if (intel_crtc_has_type(old_crtc_state, INTEL_OUTPUT_HDMI))
 		intel_ddi_post_disable_hdmi(encoder,
 					    old_crtc_state, old_conn_state);
 	else

drivers/gpu/drm/i915/intel_dp_mst.c

@@ -179,10 +179,10 @@ static void intel_mst_post_disable_dp(struct intel_encoder *encoder,
 	intel_dp->active_mst_links--;
 
 	intel_mst->connector = NULL;
-	if (intel_dp->active_mst_links == 0) {
+	if (intel_dp->active_mst_links == 0)
 		intel_dig_port->base.post_disable(&intel_dig_port->base,
-						  NULL, NULL);
-	}
+						  old_crtc_state, NULL);
+
 	DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);
 }