drm: add fallback override/firmware EDID modes workaround

From Jani Nikula
04757d0e37897cdfa59050157b9083d661bd099e in linux 4.19.y/4.19.53
48eaeb7664c76139438724d520a1ea4a84a3ed92 in mainline linux

3 files changed, 38 insertions, 0 deletions

diff --git a/sys/dev/pci/drm/drm_edid.c b/sys/dev/pci/drm/drm_edid.c
index e969161f7b0..35892e859f6 100644
--- a/sys/dev/pci/drm/drm_edid.c
+++ b/sys/dev/pci/drm/drm_edid.c
@@ -1595,6 +1595,36 @@ static struct edid *drm_get_override_edid(struct drm_connector *connector)
 }
 
 /**
+ * drm_add_override_edid_modes - add modes from override/firmware EDID
+ * @connector: connector we're probing
+ *
+ * Add modes from the override/firmware EDID, if available. Only to be used from
+ * drm_helper_probe_single_connector_modes() as a fallback for when DDC probe
+ * failed during drm_get_edid() and caused the override/firmware EDID to be
+ * skipped.
+ *
+ * Return: The number of modes added or 0 if we couldn't find any.
+ */
+int drm_add_override_edid_modes(struct drm_connector *connector)
+{
+	struct edid *override;
+	int num_modes = 0;
+
+	override = drm_get_override_edid(connector);
+	if (override) {
+		drm_connector_update_edid_property(connector, override);
+		num_modes = drm_add_edid_modes(connector, override);
+		kfree(override);
+
+		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] adding %d modes via fallback override/firmware EDID\n",
+			      connector->base.id, connector->name, num_modes);
+	}
+
+	return num_modes;
+}
+EXPORT_SYMBOL(drm_add_override_edid_modes);
+
+/**
  * drm_do_get_edid - get EDID data using a custom EDID block read function
  * @connector: connector we're probing
  * @get_edid_block: EDID block read function
diff --git a/sys/dev/pci/drm/drm_probe_helper.c b/sys/dev/pci/drm/drm_probe_helper.c
index 32312615c3a..5cbd1f54d71 100644
--- a/sys/dev/pci/drm/drm_probe_helper.c
+++ b/sys/dev/pci/drm/drm_probe_helper.c
@@ -481,6 +481,13 @@ retry:
 
 	count = (*connector_funcs->get_modes)(connector);
 
+	/*
+	 * Fallback for when DDC probe failed in drm_get_edid() and thus skipped
+	 * override/firmware EDID.
+	 */
+	if (count == 0 && connector->status == connector_status_connected)
+		count = drm_add_override_edid_modes(connector);
+
 	if (count == 0 && connector->status == connector_status_connected)
 		count = drm_add_modes_noedid(connector, 1024, 768);
 	count += drm_helper_probe_add_cmdline_mode(connector);
diff --git a/sys/dev/pci/drm/include/drm/drm_edid.h b/sys/dev/pci/drm/include/drm/drm_edid.h
index 9eda6bd4cd3..269249b7f09 100644
--- a/sys/dev/pci/drm/include/drm/drm_edid.h
+++ b/sys/dev/pci/drm/include/drm/drm_edid.h
@@ -463,6 +463,7 @@ struct edid *drm_get_edid_switcheroo(struct drm_connector *connector,
 				     struct i2c_adapter *adapter);
 struct edid *drm_edid_duplicate(const struct edid *edid);
 int drm_add_edid_modes(struct drm_connector *connector, struct edid *edid);
+int drm_add_override_edid_modes(struct drm_connector *connector);
 
 u8 drm_match_cea_mode(const struct drm_display_mode *to_match);
 enum hdmi_picture_aspect drm_get_cea_aspect_ratio(const u8 video_code);