media: adv748x: Store the source subdevice in TX

The power_up_tx() procedure needs to set a few registers conditionally to
the selected video source, but it currently checks for the provided tx to
be either TXA or TXB.

With the introduction of dynamic routing between HDMI and AFE entities to
TXA, checking which TX the function is operating on is not meaningful anymore.

To fix this, store the subdevice of the source providing video data to the
CSI-2 TX in the 'struct adv748x_csi2' representing the TX and check on it.
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/i2c/adv748x/adv748x-core.c

@@ -254,7 +254,7 @@ static int adv748x_power_up_tx(struct adv748x_csi2 *tx)
 	adv748x_write_check(state, page, 0x00, 0xa0 | tx->num_lanes, &ret);
 
 	/* ADI Required Write */
-	if (is_txa(tx)) {
+	if (tx->src == &state->hdmi.sd) {
 		adv748x_write_check(state, page, 0xdb, 0x10, &ret);
 		adv748x_write_check(state, page, 0xd6, 0x07, &ret);
 	} else {

drivers/media/i2c/adv748x/adv748x-csi2.c

@@ -46,9 +46,16 @@ static int adv748x_csi2_register_link(struct adv748x_csi2 *tx,
 			return ret;
 	}
 
-	return media_create_pad_link(&src->entity, src_pad,
+	ret = media_create_pad_link(&src->entity, src_pad,
 				    &tx->sd.entity, ADV748X_CSI2_SINK,
 				    enable ? MEDIA_LNK_FL_ENABLED : 0);
+	if (ret)
+		return ret;
+
+	if (enable)
+		tx->src = src;
+
+	return 0;
 }
 
 /* -----------------------------------------------------------------------------

drivers/media/i2c/adv748x/adv748x.h

@@ -84,6 +84,7 @@ struct adv748x_csi2 {
 	struct media_pad pads[ADV748X_CSI2_NR_PADS];
 	struct v4l2_ctrl_handler ctrl_hdl;
 	struct v4l2_ctrl *pixel_rate;
+	struct v4l2_subdev *src;
 	struct v4l2_subdev sd;
 };