media: sun6i-mipi-csi2: Require both pads to be connected for streaming

[ Upstream commit f042b08 ]

The bridge needs both its pads connected to be able to stream data.
Enforcing this is useful to produce an error when no sensor is
connected.

Fixes: af54b4f ("media: sunxi: Add support for the A31 MIPI CSI-2 controller")
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/media/platform/sunxi/sun6i-mipi-csi2/sun6i_mipi_csi2.c

@@ -519,8 +519,10 @@ static int sun6i_mipi_csi2_bridge_setup(struct sun6i_mipi_csi2_device *csi2_dev)
 
 	/* Media Pads */
 
-	pads[SUN6I_MIPI_CSI2_PAD_SINK].flags = MEDIA_PAD_FL_SINK;
-	pads[SUN6I_MIPI_CSI2_PAD_SOURCE].flags = MEDIA_PAD_FL_SOURCE;
+	pads[SUN6I_MIPI_CSI2_PAD_SINK].flags = MEDIA_PAD_FL_SINK |
+					       MEDIA_PAD_FL_MUST_CONNECT;
+	pads[SUN6I_MIPI_CSI2_PAD_SOURCE].flags = MEDIA_PAD_FL_SOURCE |
+						 MEDIA_PAD_FL_MUST_CONNECT;
 
 	ret = media_entity_pads_init(&subdev->entity, SUN6I_MIPI_CSI2_PAD_COUNT,
 				     pads);