media: i2c: max9286: Define high channel amplitude

Provide a macro to define the reverse channel amplitude to
be used to compensate the remote serializer noise immunity.

While at it, update a comment.
Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/i2c/max9286.c

@@ -113,6 +113,7 @@
 #define MAX9286_REV_TRF(n)		((n) << 4)
 #define MAX9286_REV_AMP(n)		((((n) - 30) / 10) << 1) /* in mV */
 #define MAX9286_REV_AMP_X		BIT(0)
+#define MAX9286_REV_AMP_HIGH		170
 /* Register 0x3f */
 #define MAX9286_EN_REV_CFG		BIT(6)
 #define MAX9286_REV_FLEN(n)		((n) - 20)
@@ -567,12 +568,12 @@ static int max9286_notify_bound(struct v4l2_async_notifier *notifier,
 	 * channels:
 	 *
 	 * - Increase the reverse channel amplitude to compensate for the
-	 *   remote ends high threshold, if not done already
+	 *   remote ends high threshold
 	 * - Verify all configuration links are properly detected
 	 * - Disable auto-ack as communication on the control channel are now
 	 *   stable.
 	 */
-	max9286_reverse_channel_setup(priv, 170);
+	max9286_reverse_channel_setup(priv, MAX9286_REV_AMP_HIGH);
 	max9286_check_config_link(priv, priv->source_mask);
 
 	/*