drm/i915: stage modeset output changes

This is the core of the new modeset logic.

The current code which is based upon the crtc helper code first
updates all the link of the new display pipeline and then calls the
lower-level set_mode function to execute the required callbacks to get
there. The issue with this approach is that for disabling we need to
know the _current_ display pipe state, not the new one.

Hence we need to stage the new state of the display pipe and only
update it once we have disabled the current configuration and before we
start to update the hw registers with the new configuration.

This patch here just prepares the ground by switching the new output
state computation to these staging pointers. To make it clearer,
rename the old update_output_state function to stage_output_state.

A few peculiarities:
- We're also calling the set_mode function at various places to update
  properties. Hence after a successfule modeset we need to stage the
  current configuration (for otherwise we might fall back again). This
  happens automatically because as part of the (successful) modeset we
  need to copy the staged state to the real one. But for the hw
  readout code we need to make sure that this happens, too.
- Teach the new staged output state computation code the required
  smarts to handle the disabling of outputs. The current code handles
  this in a special case, but to better handle global modeset changes
  covering more than one crtc, we want to do this all in the same
  low-level modeset code.
- The actual modeset code is still a bit ugly and wants to know the new
  crtc->enabled state a bit early. Follow-on patches will clean that
  up, for now we have to apply the staged output configuration early,
  outside of the set_mode functions.
- Improve/add comments in stage_output_state.

Essentially all that is left to do now is move the disabling code into
set_mode and then move the staged state update code also into
set_mode, at the right place between disabling things and calling the
mode_set callbacks for the new configuration.

v2: Disabling a crtc works by passing in a NULL mode or fb, userspace
doesn't hand in the list of connectors. We therefore need to detect
this case manually and tear down all the output links.

v3: Properly update the output staging pointers after having read out
the hw state.

v4: Simplify the code, add more DRM_DEBUG_KMS output and check a few
assumptions with WARN_ON. Essentially all things that I've noticed
while debugging issues in other places of the code.

v4: Correctly disable the old set of connectors when enabling an
already enabled crtc on a new set of crtc. Reported by Paulo Zanoni.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -6619,6 +6619,51 @@ intel_crtc_prepare_encoders(struct drm_device *dev)
 	}
 }
 
+/**
+ * intel_modeset_update_staged_output_state
+ *
+ * Updates the staged output configuration state, e.g. after we've read out the
+ * current hw state.
+ */
+static void intel_modeset_update_staged_output_state(struct drm_device *dev)
+{
+	struct intel_encoder *encoder;
+	struct intel_connector *connector;
+
+	list_for_each_entry(connector, &dev->mode_config.connector_list,
+			    base.head) {
+		connector->new_encoder =
+			to_intel_encoder(connector->base.encoder);
+	}
+
+	list_for_each_entry(encoder, &dev->mode_config.encoder_list,
+			    base.head) {
+		encoder->new_crtc =
+			to_intel_crtc(encoder->base.crtc);
+	}
+}
+
+/**
+ * intel_modeset_commit_output_state
+ *
+ * This function copies the stage display pipe configuration to the real one.
+ */
+static void intel_modeset_commit_output_state(struct drm_device *dev)
+{
+	struct intel_encoder *encoder;
+	struct intel_connector *connector;
+
+	list_for_each_entry(connector, &dev->mode_config.connector_list,
+			    base.head) {
+		connector->base.encoder = &connector->new_encoder->base;
+	}
+
+	list_for_each_entry(encoder, &dev->mode_config.encoder_list,
+			    base.head) {
+		encoder->base.crtc = &encoder->new_crtc->base;
+	}
+}
+
 bool intel_set_mode(struct drm_crtc *crtc,
 		    struct drm_display_mode *mode,
 		    int x, int y, struct drm_framebuffer *old_fb)
@@ -6785,8 +6830,8 @@ static void intel_set_config_restore_state(struct drm_device *dev,
 					   struct intel_set_config *config)
 {
 	struct drm_crtc *crtc;
-	struct drm_encoder *encoder;
-	struct drm_connector *connector;
+	struct intel_encoder *encoder;
+	struct intel_connector *connector;
 	int count;
 
 	count = 0;
@@ -6795,13 +6840,15 @@ static void intel_set_config_restore_state(struct drm_device *dev,
 	}
 
 	count = 0;
-	list_for_each_entry(encoder, &dev->mode_config.encoder_list, head) {
-		encoder->crtc = config->save_encoder_crtcs[count++];
+	list_for_each_entry(encoder, &dev->mode_config.encoder_list, base.head) {
+		encoder->new_crtc =
+			to_intel_crtc(config->save_encoder_crtcs[count++]);
 	}
 
 	count = 0;
-	list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
-		connector->encoder = config->save_connector_encoders[count++];
+	list_for_each_entry(connector, &dev->mode_config.connector_list, base.head) {
+		connector->new_encoder =
+			to_intel_encoder(config->save_connector_encoders[count++]);
 	}
 }
 
@@ -6840,73 +6887,106 @@ intel_set_config_compute_mode_changes(struct drm_mode_set *set,
 }
 
 static int
-intel_set_config_update_output_state(struct drm_device *dev,
+intel_modeset_stage_output_state(struct drm_device *dev,
 				 struct drm_mode_set *set,
 				 struct intel_set_config *config)
 {
 	struct drm_crtc *new_crtc;
-	struct drm_encoder *new_encoder;
-	struct drm_connector *connector;
+	struct intel_connector *connector;
+	struct intel_encoder *encoder;
 	int count, ro;
 
-	/* a) traverse passed in connector list and get encoders for them */
+	/* The upper layers ensure that we either disabl a crtc or have a list
+	 * of connectors. For paranoia, double-check this. */
+	WARN_ON(!set->fb && (set->num_connectors != 0));
+	WARN_ON(set->fb && (set->num_connectors == 0));
+
 	count = 0;
-	list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
-		new_encoder = connector->encoder;
+	list_for_each_entry(connector, &dev->mode_config.connector_list,
+			    base.head) {
+		/* Otherwise traverse passed in connector list and get encoders
+		 * for them. */
 		for (ro = 0; ro < set->num_connectors; ro++) {
-			if (set->connectors[ro] == connector) {
-				new_encoder =
-					&intel_attached_encoder(connector)->base;
+			if (set->connectors[ro] == &connector->base) {
+				connector->new_encoder = connector->encoder;
 				break;
 			}
 		}
 
-		if (new_encoder != connector->encoder) {
+		/* If we disable the crtc, disable all its connectors. Also, if
+		 * the connector is on the changing crtc but not on the new
+		 * connector list, disable it. */
+		if ((!set->fb || ro == set->num_connectors) &&
+		    connector->base.encoder &&
+		    connector->base.encoder->crtc == set->crtc) {
+			connector->new_encoder = NULL;
+
+			DRM_DEBUG_KMS("[CONNECTOR:%d:%s] to [NOCRTC]\n",
+				connector->base.base.id,
+				drm_get_connector_name(&connector->base));
+		}
+
+
+		if (&connector->new_encoder->base != connector->base.encoder) {
 			DRM_DEBUG_KMS("encoder changed, full mode switch\n");
 			config->mode_changed = true;
-			/* If the encoder is reused for another connector, then
-			 * the appropriate crtc will be set later.
-			 */
-			if (connector->encoder)
-				connector->encoder->crtc = NULL;
-			connector->encoder = new_encoder;
 		}
+
+		/* Disable all disconnected encoders. */
+		if (connector->base.status == connector_status_disconnected)
+			connector->new_encoder = NULL;
 	}
+	/* connector->new_encoder is now updated for all connectors. */
 
+	/* Update crtc of enabled connectors. */
 	count = 0;
-	list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
-		if (!connector->encoder)
+	list_for_each_entry(connector, &dev->mode_config.connector_list,
+			    base.head) {
+		if (!connector->new_encoder)
 			continue;
 
-		if (connector->encoder->crtc == set->crtc)
-			new_crtc = NULL;
-		else
-			new_crtc = connector->encoder->crtc;
+		new_crtc = connector->new_encoder->base.crtc;
 
 		for (ro = 0; ro < set->num_connectors; ro++) {
-			if (set->connectors[ro] == connector)
+			if (set->connectors[ro] == &connector->base)
 				new_crtc = set->crtc;
 		}
 
 		/* Make sure the new CRTC will work with the encoder */
-		if (new_crtc &&
-		    !intel_encoder_crtc_ok(connector->encoder, new_crtc)) {
+		if (!intel_encoder_crtc_ok(&connector->new_encoder->base,
+					   new_crtc)) {
 			return -EINVAL;
 		}
-		if (new_crtc != connector->encoder->crtc) {
-			DRM_DEBUG_KMS("crtc changed, full mode switch\n");
-			config->mode_changed = true;
-			connector->encoder->crtc = new_crtc;
-		}
-		if (new_crtc) {
+		connector->encoder->new_crtc = to_intel_crtc(new_crtc);
+
 		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] to [CRTC:%d]\n",
-				connector->base.id, drm_get_connector_name(connector),
+			connector->base.base.id,
+			drm_get_connector_name(&connector->base),
 			new_crtc->base.id);
-		} else {
-			DRM_DEBUG_KMS("[CONNECTOR:%d:%s] to [NOCRTC]\n",
-				connector->base.id, drm_get_connector_name(connector));
+	}
+
+	/* Check for any encoders that needs to be disabled. */
+	list_for_each_entry(encoder, &dev->mode_config.encoder_list,
+			    base.head) {
+		list_for_each_entry(connector,
+				    &dev->mode_config.connector_list,
+				    base.head) {
+			if (connector->new_encoder == encoder) {
+				WARN_ON(!connector->new_encoder->new_crtc);
+
+				goto next_encoder;
+			}
+		}
+		encoder->new_crtc = NULL;
+next_encoder:
+		/* Only now check for crtc changes so we don't miss encoders
+		 * that will be disabled. */
+		if (&encoder->new_crtc->base != encoder->base.crtc) {
+			DRM_DEBUG_KMS("crtc changed, full mode switch\n");
+			config->mode_changed = true;
 		}
 	}
+	/* Now we've also updated encoder->new_crtc for all encoders. */
 
 	return 0;
 }
@@ -6965,11 +7045,13 @@ static int intel_crtc_set_config(struct drm_mode_set *set)
 	 * such cases. */
 	intel_set_config_compute_mode_changes(set, config);
 
-	ret = intel_set_config_update_output_state(dev, set, config);
+	ret = intel_modeset_stage_output_state(dev, set, config);
 	if (ret)
 		goto fail;
 
 	if (config->mode_changed) {
+		intel_modeset_commit_output_state(dev);
+
 		set->crtc->enabled = drm_helper_crtc_in_use(set->crtc);
 		if (set->crtc->enabled) {
 			DRM_DEBUG_KMS("attempting to set mode from"
@@ -7015,6 +7097,8 @@ static int intel_crtc_set_config(struct drm_mode_set *set)
 fail:
 	intel_set_config_restore_state(dev, config);
 
+	intel_modeset_commit_output_state(dev);
+
 	/* Try to restore the config */
 	if (config->mode_changed &&
 	    !intel_set_mode(save_set.crtc, save_set.mode,
@@ -7888,6 +7972,8 @@ void intel_modeset_setup_hw_state(struct drm_device *dev)
 		crtc = to_intel_crtc(dev_priv->pipe_to_crtc_mapping[pipe]);
 		intel_sanitize_crtc(crtc);
 	}
+
+	intel_modeset_update_staged_output_state(dev);
 }
 
 void intel_modeset_gem_init(struct drm_device *dev)

drivers/gpu/drm/i915/intel_drv.h

@@ -133,6 +133,12 @@ struct intel_fbdev {
 
 struct intel_encoder {
 	struct drm_encoder base;
+	/*
+	 * The new crtc this encoder will be driven from. Only differs from
+	 * base->crtc while a modeset is in progress.
+	 */
+	struct intel_crtc *new_crtc;
+
 	int type;
 	bool needs_tv_clock;
 	/*
@@ -153,7 +159,17 @@ struct intel_encoder {
 
 struct intel_connector {
 	struct drm_connector base;
+	/*
+	 * The fixed encoder this connector is connected to.
+	 */
 	struct intel_encoder *encoder;
+
+	/*
+	 * The new encoder this connector will be driven. Only differs from
+	 * encoder while a modeset is in progress.
+	 */
+	struct intel_encoder *new_encoder;
+
 	/* Reads out the current hw, returning true if the connector is enabled
 	 * and active (i.e. dpms ON state). */
 	bool (*get_hw_state)(struct intel_connector *);