usb: xhci: add the suspend/resume functionality

Adds power management support to xHCI platform driver.

This patch facilitates the transition of xHCI host controller
between S0 and S3/S4 power states, during suspend/resume cycles.

Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
Signed-off-by: Vikas C Sajjan <vikas.sajjan@linaro.org>
CC: Doug Anderson <dianders@chromium.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

drivers/usb/host/xhci-plat.c

@@ -186,11 +186,37 @@ static int xhci_plat_remove(struct platform_device *dev)
 	return 0;
 }
 
+#ifdef CONFIG_PM
+static int xhci_plat_suspend(struct device *dev)
+{
+	struct usb_hcd	*hcd = dev_get_drvdata(dev);
+	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
+
+	return xhci_suspend(xhci);
+}
+
+static int xhci_plat_resume(struct device *dev)
+{
+	struct usb_hcd	*hcd = dev_get_drvdata(dev);
+	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
+
+	return xhci_resume(xhci, 0);
+}
+
+static const struct dev_pm_ops xhci_plat_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(xhci_plat_suspend, xhci_plat_resume)
+};
+#define DEV_PM_OPS	(&xhci_plat_pm_ops)
+#else
+#define DEV_PM_OPS	NULL
+#endif /* CONFIG_PM */
+
 static struct platform_driver usb_xhci_driver = {
 	.probe	= xhci_plat_probe,
 	.remove	= xhci_plat_remove,
 	.driver	= {
 		.name = "xhci-hcd",
+		.pm = DEV_PM_OPS,
 	},
 };
 MODULE_ALIAS("platform:xhci-hcd");