[PATCH] drm/fbdev: Fallback to non tiled mode if all tiles not present

[Manasi Navare]

In case of tiled displays, if we hotplug just one connector,
fbcon currently just selects the preferred mode and if it is
tiled mode then that becomes a problem if rest of the tiles are
not present.
So in the fbdev driver on hotplug when we probe the client modeset,
we we dont find all the connectors for all tiles, then on a connector
with one tile, just fallback to the first available non tiled mode
to display over a single connector.

Suggested-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
Suggested-by: Dave Airlie <airlied at redhat.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Dave Airlie <airlied at redhat.com>
Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
---
 drivers/gpu/drm/drm_client_modeset.c | 29 ++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/drm_client_modeset.c b/drivers/gpu/drm/drm_client_modeset.c
index 895b73f23079..e28a723587db 100644
--- a/drivers/gpu/drm/drm_client_modeset.c
+++ b/drivers/gpu/drm/drm_client_modeset.c
@@ -114,6 +114,20 @@ drm_client_find_modeset(struct drm_client_dev *client, struct drm_crtc *crtc)
 	return NULL;
 }
 
+static struct drm_display_mode *
+drm_connector_fallback_non_tiled_mode(struct drm_connector *connector)
+{
+	struct drm_display_mode *mode;
+
+	list_for_each_entry(mode, &connector->modes, head) {
+		if (mode->hdisplay == connector->tile_h_size &&
+		    mode->vdisplay == connector->tile_v_size)
+			continue;
+		return mode;
+	}
+	return NULL;
+}
+
 static struct drm_display_mode *
 drm_connector_has_preferred_mode(struct drm_connector *connector, int width, int height)
 {
@@ -348,8 +362,17 @@ static bool drm_client_target_preferred(struct drm_connector **connectors,
 	struct drm_connector *connector;
 	u64 conn_configured = 0;
 	int tile_pass = 0;
+	int num_tiled_conns = 0;
 	int i;
 
+	for (i = 0; i < connector_count; i++) {
+		connector = connectors[i];
+		if (!connector->has_tile)
+			continue;
+
+		num_tiled_conns ++;
+	}
+
 retry:
 	for (i = 0; i < connector_count; i++) {
 		connector = connectors[i];
@@ -394,6 +417,12 @@ static bool drm_client_target_preferred(struct drm_connector **connectors,
 				      connector->base.id, connector->tile_group ? connector->tile_group->id : 0);
 			modes[i] = drm_connector_has_preferred_mode(connector, width, height);
 		}
+		if (connector->has_tile &&
+		    num_tiled_conns < connector->num_h_tile * connector->num_v_tile) {
+			DRM_DEBUG_KMS("Falling back to non tiled mode on Connector %d\n",
+				      connector->base.id);
+			modes[i] = drm_connector_fallback_non_tiled_mode(connector);
+		}
 		/* No preferred modes, pick one off the list */
 		if (!modes[i] && !list_empty(&connector->modes)) {
 			list_for_each_entry(modes[i], &connector->modes, head)
-- 
2.19.1