media: imx: csi: Allow unknown nearest upstream entities

On i.MX6, the nearest upstream entity to the CSI can only be the
CSI video muxes or the Synopsys DW MIPI CSI-2 receiver.

However the i.MX53 has no CSI video muxes or a MIPI CSI-2 receiver.
So allow for the nearest upstream entity to the CSI to be something
other than those.

Fixes: bf3cfaa7 ("media: staging/imx: get CSI bus type from nearest
upstream entity")
Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/staging/media/imx/imx-media-csi.c

@@ -154,9 +154,10 @@ static inline bool requires_passthrough(struct v4l2_fwnode_endpoint *ep,
 /*
  * Parses the fwnode endpoint from the source pad of the entity
  * connected to this CSI. This will either be the entity directly
- * upstream from the CSI-2 receiver, or directly upstream from the
- * video mux. The endpoint is needed to determine the bus type and
- * bus config coming into the CSI.
+ * upstream from the CSI-2 receiver, directly upstream from the
+ * video mux, or directly upstream from the CSI itself. The endpoint
+ * is needed to determine the bus type and bus config coming into
+ * the CSI.
  */
 static int csi_get_upstream_endpoint(struct csi_priv *priv,
 				     struct v4l2_fwnode_endpoint *ep)
@@ -172,7 +173,8 @@ static int csi_get_upstream_endpoint(struct csi_priv *priv,
 	if (!priv->src_sd)
 		return -EPIPE;
 
-	src = &priv->src_sd->entity;
+	sd = priv->src_sd;
+	src = &sd->entity;
 
 	if (src->function == MEDIA_ENT_F_VID_MUX) {
 		/*
@@ -186,6 +188,14 @@ static int csi_get_upstream_endpoint(struct csi_priv *priv,
 			src = &sd->entity;
 	}
 
+	/*
+	 * If the source is neither the video mux nor the CSI-2 receiver,
+	 * get the source pad directly upstream from CSI itself.
+	 */
+	if (src->function != MEDIA_ENT_F_VID_MUX &&
+	    sd->grp_id != IMX_MEDIA_GRP_ID_CSI2)
+		src = &priv->sd.entity;
+
 	/* get source pad of entity directly upstream from src */
 	pad = imx_media_find_upstream_pad(priv->md, src, 0);
 	if (IS_ERR(pad))