media: i2c: max9286: Configure bus width from device tree

The GMSL serial data bus width is normally selected through the BWS pin.
On some systems, the pin may not be wired to the correct value. Support
overriding the bus width by software, using the value specified in the
device tree.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/i2c/max9286.c

@@ -91,6 +91,11 @@
 /* Register 0x1b */
 #define MAX9286_SWITCHIN(n)		(1 << ((n) + 4))
 #define MAX9286_ENEQ(n)			(1 << (n))
+/* Register 0x1c */
+#define MAX9286_HIGHIMM(n)		BIT((n) + 4)
+#define MAX9286_I2CSEL			BIT(2)
+#define MAX9286_HIBW			BIT(1)
+#define MAX9286_BWS			BIT(0)
 /* Register 0x27 */
 #define MAX9286_LOCKED			BIT(7)
 /* Register 0x31 */
@@ -183,6 +188,7 @@ struct max9286_priv {
 	u32 init_rev_chan_mv;
 	u32 rev_chan_mv;
 	u8 i2c_mstbt;
+	u32 bus_width;
 
 	bool use_gpio_poc;
 	u32 gpio_poc[2];
@@ -1168,6 +1174,23 @@ static int max9286_setup(struct max9286_priv *priv)
 	max9286_set_video_format(priv, &max9286_default_format);
 	max9286_set_fsync_period(priv);
 
+	if (priv->bus_width) {
+		int val;
+
+		val = max9286_read(priv, 0x1c);
+		if (val < 0)
+			return val;
+
+		val &= ~(MAX9286_HIBW | MAX9286_BWS);
+
+		if (priv->bus_width == 27)
+			val |= MAX9286_HIBW;
+		else if (priv->bus_width == 32)
+			val |= MAX9286_BWS;
+
+		max9286_write(priv, 0x1c, val);
+	}
+
 	/*
 	 * The overlap window seems to provide additional validation by tracking
 	 * the delay between vsync and frame sync, generating an error if the
@@ -1496,6 +1519,23 @@ static int max9286_parse_dt(struct max9286_priv *priv)
 	}
 	of_node_put(node);
 
+	of_property_read_u32(dev->of_node, "maxim,bus-width", &priv->bus_width);
+	switch (priv->bus_width) {
+	case 0:
+		/*
+		 * The property isn't specified in the device tree, the driver
+		 * will keep the default value selected by the BWS pin.
+		 */
+	case 24:
+	case 27:
+	case 32:
+		break;
+	default:
+		dev_err(dev, "Invalid %s value %u\n", "maxim,bus-width",
+			priv->bus_width);
+		return -EINVAL;
+	}
+
 	of_property_read_u32(dev->of_node, "maxim,i2c-remote-bus-hz",
 			     &i2c_clk_freq);
 	for (i = 0; i < ARRAY_SIZE(max9286_i2c_speeds); ++i) {