media: i2c: max9286: Configure reverse channel amplitude

Adjust the initial reverse channel amplitude parsing from
firmware interface the 'maxim,reverse-channel-microvolt'
property.

This change is required for both rdacm20 and rdacm21 camera
modules to be correctly probed when used in combination with
the max9286 deserializer.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
index 4d7587dfb5aa5ec4028966201400200425a47b69..6fd4d59fcc7234619614f59ffe4ab83d4cc19a0a 100644 (file)
--- a/drivers/media/i2c/max9286.c
+++ b/drivers/media/i2c/max9286.c
@@ -163,6 +163,8 @@ struct max9286_priv {
        unsigned int mux_channel;
        bool mux_open;
 
+       u32 reverse_channel_mv;
+
        struct v4l2_ctrl_handler ctrls;
        struct v4l2_ctrl *pixelrate;
 
@@ -556,10 +558,14 @@ static int max9286_notify_bound(struct v4l2_async_notifier *notifier,
         * All enabled sources have probed and enabled their reverse control
         * channels:
         *
+        * - Increase the reverse channel amplitude to compensate for the
+        *   remote ends high threshold, if not done already
         * - Verify all configuration links are properly detected
         * - Disable auto-ack as communication on the control channel are now
         *   stable.
         */
+       if (priv->reverse_channel_mv < 170)
+               max9286_reverse_channel_setup(priv, 170);
        max9286_check_config_link(priv, priv->source_mask);
 
        /*
@@ -966,7 +972,7 @@ static int max9286_setup(struct max9286_priv *priv)
         * only. This should be disabled after the mux is initialised.
         */
        max9286_configure_i2c(priv, true);
-       max9286_reverse_channel_setup(priv, 170);
+       max9286_reverse_channel_setup(priv, priv->reverse_channel_mv);
 
        /*
         * Enable GMSL links, mask unused ones and autodetect link
@@ -1130,6 +1136,7 @@ static int max9286_parse_dt(struct max9286_priv *priv)
        struct device_node *i2c_mux;
        struct device_node *node = NULL;
        unsigned int i2c_mux_mask = 0;
+       u32 reverse_channel_microvolt;
 
        /* Balance the of_node_put() performed by of_find_node_by_name(). */
        of_node_get(dev->of_node);
@@ -1220,6 +1227,20 @@ static int max9286_parse_dt(struct max9286_priv *priv)
        }
        of_node_put(node);
 
+       /*
+        * Parse the initial value of the reverse channel amplitude from
+        * the firmware interface and convert it to millivolts.
+        *
+        * Default it to 170mV for backward compatibility with DTBs that do not
+        * provide the property.
+        */
+       if (of_property_read_u32(dev->of_node,
+                                "maxim,reverse-channel-microvolt",
+                                &reverse_channel_microvolt))
+               priv->reverse_channel_mv = 170;
+       else
+               priv->reverse_channel_mv = reverse_channel_microvolt / 1000U;
+
        priv->route_mask = priv->source_mask;
 
        return 0;