usb: common: add support to get maximum speed from dt

Add support to get maximum speed from dt so that usb drivers
makes use of it for DT parsing.

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
(rebase and fix errors)
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/usb/common/common.c

@@ -9,6 +9,7 @@
 #include <common.h>
 #include <linux/libfdt.h>
 #include <linux/usb/otg.h>
+#include <linux/usb/ch9.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -37,3 +38,31 @@ enum usb_dr_mode usb_get_dr_mode(int node)
 
 	return USB_DR_MODE_UNKNOWN;
 }
+
+static const char *const speed_names[] = {
+	[USB_SPEED_UNKNOWN] = "UNKNOWN",
+	[USB_SPEED_LOW] = "low-speed",
+	[USB_SPEED_FULL] = "full-speed",
+	[USB_SPEED_HIGH] = "high-speed",
+	[USB_SPEED_WIRELESS] = "wireless",
+	[USB_SPEED_SUPER] = "super-speed",
+};
+
+enum usb_device_speed usb_get_maximum_speed(int node)
+{
+	const void *fdt = gd->fdt_blob;
+	const char *max_speed;
+	int i;
+
+	max_speed = fdt_getprop(fdt, node, "maximum-speed", NULL);
+	if (!max_speed) {
+		pr_err("usb maximum-speed not found\n");
+		return USB_SPEED_UNKNOWN;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(speed_names); i++)
+		if (!strcmp(max_speed, speed_names[i]))
+			return i;
+
+	return USB_SPEED_UNKNOWN;
+}

include/linux/usb/otg.h

@@ -25,4 +25,13 @@ enum usb_dr_mode {
  */
 enum usb_dr_mode usb_get_dr_mode(int node);
 
+/**
+ * usb_get_maximum_speed() - Get maximum speed for given device
+ * @node: Node offset to the given device
+ *
+ * The function gets phy interface string from property 'maximum-speed',
+ * and returns the correspondig enum usb_device_speed
+ */
+enum usb_device_speed usb_get_maximum_speed(int node);
+
 #endif /* __LINUX_USB_OTG_H */