drm: try harder to avoid regression when merging mode bits

For QXL hw we really want the bits to be replaced as we change
the preferred mode on the fly, and the same goes for virgl when
I get to it, however the original fix for this seems to have caused
a wierd regression on Intel G33 that in a stunning display of failure
at opposition to his normal self, Daniel failed to diagnose.

So we are left doing this, ugly ugly ugly ugly, Daniel you fixed
that G33 yet?, ugly, ugly.

Tested-by: Marc-André Lureau <[e-mail]>
Signed-off-by: Dave Airlie <[e-mail]>

drivers/gpu/drm/drm_modes.c

···
 /**
  * drm_mode_connector_list_update - update the mode list for the connector
  * @connector: the connector to update
+ * @merge_type_bits: whether to merge or overright type bits.
  *
  * This moves the modes from the @connector probed_modes list
  * to the actual mode list. It compares the probed mode against the current
···
  * This is just a helper functions doesn't validate any modes itself and also
  * doesn't prune any invalid modes. Callers need to do that themselves.
  */
-void drm_mode_connector_list_update(struct drm_connector *connector)
+void drm_mode_connector_list_update(struct drm_connector *connector,
+				    bool merge_type_bits)
 {
 	struct drm_display_mode *mode;
 	struct drm_display_mode *pmode, *pt;
···
 				/* if equal delete the probed mode */
 				mode->status = pmode->status;
 				/* Merge type bits together */
-				mode->type |= pmode->type;
+				if (merge_type_bits)
+					mode->type |= pmode->type;
+				else
+					mode->type = pmode->type;
 				list_del(&pmode->head);
 				drm_mode_destroy(connector->dev, pmode);
 				break;

drivers/gpu/drm/drm_probe_helper.c

···
 	return;
 }
 
-/**
- * drm_helper_probe_single_connector_modes - get complete set of display modes
- * @connector: connector to probe
- * @maxX: max width for modes
- * @maxY: max height for modes
- *
- * Based on the helper callbacks implemented by @connector try to detect all
- * valid modes.  Modes will first be added to the connector's probed_modes list,
- * then culled (based on validity and the @maxX, @maxY parameters) and put into
- * the normal modes list.
- *
- * Intended to be use as a generic implementation of the ->fill_modes()
- * @connector vfunc for drivers that use the crtc helpers for output mode
- * filtering and detection.
- *
- * Returns:
- * The number of modes found on @connector.
- */
-int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
-					    uint32_t maxX, uint32_t maxY)
+static int drm_helper_probe_single_connector_modes_merge_bits(struct drm_connector *connector,
+							      uint32_t maxX, uint32_t maxY, bool merge_type_bits)
 {
 	struct drm_device *dev = connector->dev;
 	struct drm_display_mode *mode;
···
 	if (count == 0)
 		goto prune;
 
-	drm_mode_connector_list_update(connector);
+	drm_mode_connector_list_update(connector, merge_type_bits);
 
 	if (maxX && maxY)
 		drm_mode_validate_size(dev, &connector->modes, maxX, maxY);
···
 
 	return count;
 }
+
+/**
+ * drm_helper_probe_single_connector_modes - get complete set of display modes
+ * @connector: connector to probe
+ * @maxX: max width for modes
+ * @maxY: max height for modes
+ *
+ * Based on the helper callbacks implemented by @connector try to detect all
+ * valid modes.  Modes will first be added to the connector's probed_modes list,
+ * then culled (based on validity and the @maxX, @maxY parameters) and put into
+ * the normal modes list.
+ *
+ * Intended to be use as a generic implementation of the ->fill_modes()
+ * @connector vfunc for drivers that use the crtc helpers for output mode
+ * filtering and detection.
+ *
+ * Returns:
+ * The number of modes found on @connector.
+ */
+int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
+					    uint32_t maxX, uint32_t maxY)
+{
+	return drm_helper_probe_single_connector_modes_merge_bits(connector, maxX, maxY, true);
+}
 EXPORT_SYMBOL(drm_helper_probe_single_connector_modes);
+
+/**
+ * drm_helper_probe_single_connector_modes_nomerge - get complete set of display modes
+ * @connector: connector to probe
+ * @maxX: max width for modes
+ * @maxY: max height for modes
+ *
+ * This operates like drm_hehlper_probe_single_connector_modes except it
+ * replaces the mode bits instead of merging them for preferred modes.
+ */
+int drm_helper_probe_single_connector_modes_nomerge(struct drm_connector *connector,
+					    uint32_t maxX, uint32_t maxY)
+{
+	return drm_helper_probe_single_connector_modes_merge_bits(connector, maxX, maxY, false);
+}
+EXPORT_SYMBOL(drm_helper_probe_single_connector_modes_nomerge);
 
 /**
  * drm_kms_helper_hotplug_event - fire off KMS hotplug events

drivers/gpu/drm/qxl/qxl_display.c

···
 	.save = qxl_conn_save,
 	.restore = qxl_conn_restore,
 	.detect = qxl_conn_detect,
-	.fill_modes = drm_helper_probe_single_connector_modes,
+	.fill_modes = drm_helper_probe_single_connector_modes_nomerge,
 	.set_property = qxl_conn_set_property,
 	.destroy = qxl_conn_destroy,
 };

drivers/gpu/drm/vmwgfx/vmwgfx_kms.c

···
 	if (du->pref_mode)
 		list_move(&du->pref_mode->head, &connector->probed_modes);
 
-	drm_mode_connector_list_update(connector);
+	drm_mode_connector_list_update(connector, true);
 
 	return 1;
 }

include/drm/drm_crtc_helper.h

···
 extern int drm_helper_probe_single_connector_modes(struct drm_connector
 						   *connector, uint32_t maxX,
 						   uint32_t maxY);
+extern int drm_helper_probe_single_connector_modes_nomerge(struct drm_connector
+							   *connector,
+							   uint32_t maxX,
+							   uint32_t maxY);
 extern void drm_kms_helper_poll_init(struct drm_device *dev);
 extern void drm_kms_helper_poll_fini(struct drm_device *dev);
 extern bool drm_helper_hpd_irq_event(struct drm_device *dev);

include/drm/drm_modes.h

···
 void drm_mode_prune_invalid(struct drm_device *dev,
 			    struct list_head *mode_list, bool verbose);
 void drm_mode_sort(struct list_head *mode_list);
-void drm_mode_connector_list_update(struct drm_connector *connector);
+void drm_mode_connector_list_update(struct drm_connector *connector, bool merge_type_bits);
 
 /* parsing cmdline modes */
 bool