phy: tegra: xusb: Parse dual-role mode property

The device tree bindings document the "mode" property of "ports"
subnodes, but the driver was not parsing the property. In preparation
for adding role switching, parse the property at probe time.

Based on work by JC Kuo <jckuo@nvidia.com>.
Reviewed-by: JC Kuo <jckuo@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>

drivers/phy/tegra/xusb.c

@@ -546,13 +546,34 @@ static void tegra_xusb_port_unregister(struct tegra_xusb_port *port)
 	device_unregister(&port->dev);
 }
 
+static const char *const modes[] = {
+	[USB_DR_MODE_UNKNOWN] = "",
+	[USB_DR_MODE_HOST] = "host",
+	[USB_DR_MODE_PERIPHERAL] = "peripheral",
+	[USB_DR_MODE_OTG] = "otg",
+};
+
 static int tegra_xusb_usb2_port_parse_dt(struct tegra_xusb_usb2_port *usb2)
 {
 	struct tegra_xusb_port *port = &usb2->base;
 	struct device_node *np = port->dev.of_node;
+	const char *mode;
 
 	usb2->internal = of_property_read_bool(np, "nvidia,internal");
 
+	if (!of_property_read_string(np, "mode", &mode)) {
+		int err = match_string(modes, ARRAY_SIZE(modes), mode);
+		if (err < 0) {
+			dev_err(&port->dev, "invalid value %s for \"mode\"\n",
+				mode);
+			usb2->mode = USB_DR_MODE_UNKNOWN;
+		} else {
+			usb2->mode = err;
+		}
+	} else {
+		usb2->mode = USB_DR_MODE_HOST;
+	}
+
 	usb2->supply = devm_regulator_get(&port->dev, "vbus");
 	return PTR_ERR_OR_ZERO(usb2->supply);
 }

drivers/phy/tegra/xusb.h

@@ -19,6 +19,8 @@
 #include <linux/mutex.h>
 #include <linux/workqueue.h>
 
+#include <linux/usb/otg.h>
+
 /* legacy entry points for backwards-compatibility */
 int tegra_xusb_padctl_legacy_probe(struct platform_device *pdev);
 int tegra_xusb_padctl_legacy_remove(struct platform_device *pdev);
@@ -271,6 +273,7 @@ struct tegra_xusb_usb2_port {
 	struct tegra_xusb_port base;
 
 	struct regulator *supply;
+	enum usb_dr_mode mode;
 	bool internal;
 };