2 files changed, 73 insertions, 4 deletions

diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index 733028b4d45e..1c3a8c557140 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -452,6 +452,59 @@ static void drm_setup_crtcs(struct drm_device *dev)
         kfree(modes);
         kfree(enabled);
 }
+
+/**
+ * drm_encoder_crtc_ok - can a given crtc drive a given encoder?
+ * @encoder: encoder to test
+ * @crtc: crtc to test
+ *
+ * Return false if @encoder can't be driven by @crtc, true otherwise.
+ */
+static bool drm_encoder_crtc_ok(struct drm_encoder *encoder,
+                                struct drm_crtc *crtc)
+{
+        struct drm_device *dev;
+        struct drm_crtc *tmp;
+        int crtc_mask = 1;
+
+        WARN(!crtc, "checking null crtc?");
+
+        dev = crtc->dev;
+
+        list_for_each_entry(tmp, &dev->mode_config.crtc_list, head) {
+                if (tmp == crtc)
+                        break;
+                crtc_mask <<= 1;
+        }
+
+        if (encoder->possible_crtcs & crtc_mask)
+                return true;
+        return false;
+}
+
+/*
+ * Check the CRTC we're going to map each output to vs. its current
+ * CRTC.  If they don't match, we have to disable the output and the CRTC
+ * since the driver will have to re-route things.
+ */
+static void
+drm_crtc_prepare_encoders(struct drm_device *dev)
+{
+        struct drm_encoder_helper_funcs *encoder_funcs;
+        struct drm_encoder *encoder;
+
+        list_for_each_entry(encoder, &dev->mode_config.encoder_list, head) {
+                encoder_funcs = encoder->helper_private;
+                /* Disable unused encoders */
+                if (encoder->crtc == NULL)
+                        (*encoder_funcs->dpms)(encoder, DRM_MODE_DPMS_OFF);
+                /* Disable encoders whose CRTC is about to change */
+                if (encoder_funcs->get_crtc &&
+                    encoder->crtc != (*encoder_funcs->get_crtc)(encoder))
+                        (*encoder_funcs->dpms)(encoder, DRM_MODE_DPMS_OFF);
+        }
+}
+
 /**
  * drm_crtc_set_mode - set a mode
  * @crtc: CRTC to program
@@ -547,6 +600,8 @@ bool drm_crtc_helper_set_mode(struct drm_crtc *crtc,
                 encoder_funcs->prepare(encoder);
         }
 
+        drm_crtc_prepare_encoders(dev);
+
         crtc_funcs->prepare(crtc);
 
         /* Set up the DPLL and any encoders state that needs to adjust or depend
@@ -617,7 +672,7 @@ int drm_crtc_helper_set_config(struct drm_mode_set *set)
         struct drm_device *dev;
         struct drm_crtc **save_crtcs, *new_crtc;
         struct drm_encoder **save_encoders, *new_encoder;
-        struct drm_framebuffer *old_fb;
+        struct drm_framebuffer *old_fb = NULL;
         bool save_enabled;
         bool mode_changed = false;
         bool fb_changed = false;
@@ -668,9 +723,10 @@ int drm_crtc_helper_set_config(struct drm_mode_set *set)
          * and then just flip_or_move it */
         if (set->crtc->fb != set->fb) {
                 /* If we have no fb then treat it as a full mode set */
-                if (set->crtc->fb == NULL)
+                if (set->crtc->fb == NULL) {
+                        DRM_DEBUG("crtc has no fb, full mode set\n");
                         mode_changed = true;
-                else if ((set->fb->bits_per_pixel !=
+                } else if ((set->fb->bits_per_pixel !=
                          set->crtc->fb->bits_per_pixel) ||
                          set->fb->depth != set->crtc->fb->depth)
                         fb_changed = true;
@@ -682,7 +738,7 @@ int drm_crtc_helper_set_config(struct drm_mode_set *set)
                 fb_changed = true;
 
         if (set->mode && !drm_mode_equal(set->mode, &set->crtc->mode)) {
-                DRM_DEBUG("modes are different\n");
+                DRM_DEBUG("modes are different, full mode set\n");
                 drm_mode_debug_printmodeline(&set->crtc->mode);
                 drm_mode_debug_printmodeline(set->mode);
                 mode_changed = true;
@@ -708,6 +764,7 @@ int drm_crtc_helper_set_config(struct drm_mode_set *set)
                 }
 
                 if (new_encoder != connector->encoder) {
+                        DRM_DEBUG("encoder changed, full mode switch\n");
                         mode_changed = true;
                         connector->encoder = new_encoder;
                 }
@@ -734,10 +791,20 @@ int drm_crtc_helper_set_config(struct drm_mode_set *set)
                         if (set->connectors[ro] == connector)
                                 new_crtc = set->crtc;
                 }
+
+                /* Make sure the new CRTC will work with the encoder */
+                if (new_crtc &&
+                    !drm_encoder_crtc_ok(connector->encoder, new_crtc)) {
+                        ret = -EINVAL;
+                        goto fail_set_mode;
+                }
                 if (new_crtc != connector->encoder->crtc) {
+                        DRM_DEBUG("crtc changed, full mode switch\n");
                         mode_changed = true;
                         connector->encoder->crtc = new_crtc;
                 }
+                DRM_DEBUG("setting connector %d crtc to %p\n",
+                          connector->base.id, new_crtc);
         }
 
         /* mode_set_base is not a required function */
@@ -781,6 +848,7 @@ int drm_crtc_helper_set_config(struct drm_mode_set *set)
 
 fail_set_mode:
         set->crtc->enabled = save_enabled;
+        set->crtc->fb = old_fb;
         count = 0;
         list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
                 if (!connector->encoder)
diff --git a/include/drm/drm_crtc_helper.h b/include/drm/drm_crtc_helper.h
index 0b0d236c2154..c7d4b2e606a5 100644
--- a/include/drm/drm_crtc_helper.h
+++ b/include/drm/drm_crtc_helper.h
@@ -76,6 +76,7 @@ struct drm_encoder_helper_funcs {
         void (*mode_set)(struct drm_encoder *encoder,
                          struct drm_display_mode *mode,
                          struct drm_display_mode *adjusted_mode);
+        struct drm_crtc *(*get_crtc)(struct drm_encoder *encoder);
         /* detect for DAC style encoders */
         enum drm_connector_status (*detect)(struct drm_encoder *encoder,
                                             struct drm_connector *connector);