media: imx7: csi: Fix pad link validation

We can not make the assumption that the bound subdev is always a CSI
mux, in i.MX6UL/i.MX6ULL that is not the case. So, just get the entity
selected by source directly upstream from the CSI.

Fixes: 86e02d07 ("media: imx5/6/7: csi: Mark a bound video mux as a CSI mux")
Reported-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Rui Miguel Silva <rmfrfs@gmail.com>
Tested-by: Fabio Estevam <festevam@gmail.com>
Tested-by: Sébastien Szymanski <sebastien.szymanski@armadeus.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/staging/media/imx/imx7-media-csi.c

@@ -499,6 +499,7 @@ static int imx7_csi_pad_link_validate(struct v4l2_subdev *sd,
 				      struct v4l2_subdev_format *sink_fmt)
 {
 	struct imx7_csi *csi = v4l2_get_subdevdata(sd);
+	struct media_entity *src;
 	struct media_pad *pad;
 	int ret;
 
@@ -509,11 +510,21 @@ static int imx7_csi_pad_link_validate(struct v4l2_subdev *sd,
 	if (!csi->src_sd)
 		return -EPIPE;
 
+	src = &csi->src_sd->entity;
+
+	/*
+	 * if the source is neither a CSI MUX or CSI-2 get the one directly
+	 * upstream from this CSI
+	 */
+	if (src->function != MEDIA_ENT_F_VID_IF_BRIDGE &&
+	    src->function != MEDIA_ENT_F_VID_MUX)
+		src = &csi->sd.entity;
+
 	/*
-	 * find the entity that is selected by the CSI mux. This is needed
+	 * find the entity that is selected by the source. This is needed
 	 * to distinguish between a parallel or CSI-2 pipeline.
 	 */
-	pad = imx_media_pipeline_pad(&csi->src_sd->entity, 0, 0, true);
+	pad = imx_media_pipeline_pad(src, 0, 0, true);
 	if (!pad)
 		return -ENODEV;