usb: dwc2: Add reset control to dwc2

Allow for platforms that have a reset controller driver in place to bring
the USB IP out of reset.

Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Acked-by: John Youn <johnyoun@synopsys.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc2/core.h

@@ -868,6 +868,7 @@ struct dwc2_hsotg {
 	void *priv;
 	int     irq;
 	struct clk *clk;
+	struct reset_control *reset;
 
 	unsigned int queuing_high_bandwidth:1;
 	unsigned int srp_success:1;

drivers/usb/dwc2/platform.c

@@ -45,6 +45,7 @@
 #include <linux/platform_device.h>
 #include <linux/phy/phy.h>
 #include <linux/platform_data/s3c-hsotg.h>
+#include <linux/reset.h>
 
 #include <linux/usb/of.h>
 
@@ -337,6 +338,24 @@ static int dwc2_lowlevel_hw_init(struct dwc2_hsotg *hsotg)
 {
 	int i, ret;
 
+	hsotg->reset = devm_reset_control_get_optional(hsotg->dev, "dwc2");
+	if (IS_ERR(hsotg->reset)) {
+		ret = PTR_ERR(hsotg->reset);
+		switch (ret) {
+		case -ENOENT:
+		case -ENOTSUPP:
+			hsotg->reset = NULL;
+			break;
+		default:
+			dev_err(hsotg->dev, "error getting reset control %d\n",
+				ret);
+			return ret;
+		}
+	}
+
+	if (hsotg->reset)
+		reset_control_deassert(hsotg->reset);
+
 	/* Set default UTMI width */
 	hsotg->phyif = GUSBCFG_PHYIF16;
 
@@ -434,6 +453,9 @@ static int dwc2_driver_remove(struct platform_device *dev)
 	if (hsotg->ll_hw_enabled)
 		dwc2_lowlevel_hw_disable(hsotg);
 
+	if (hsotg->reset)
+		reset_control_assert(hsotg->reset);
+
 	return 0;
 }