usb: dwc3: core: add power management support

Add support for basic power management on
the dwc3 driver. While there is still lots
to improve for full PM support, this minimal
patch will already make sure that we survive
suspend-to-ram and suspend-to-disk without
major issues.

Cc: Vikas C Sajjan <vikas.sajjan@linaro.org>
Tested-by: Vivek Gautam <gautam.vivek@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 35e4d3c..52e48e2 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -626,6 +626,8 @@
  * @mode: mode of operation
  * @usb2_phy: pointer to USB2 PHY
  * @usb3_phy: pointer to USB3 PHY
+ * @dcfg: saved contents of DCFG register
+ * @gctl: saved contents of GCTL register
  * @is_selfpowered: true when we are selfpowered
  * @three_stage_setup: set if we perform a three phase setup
  * @ep0_bounced: true when we used bounce buffer
@@ -675,6 +677,10 @@
 	void __iomem		*regs;
 	size_t			regs_size;
 
+	/* used for suspend/resume */
+	u32			dcfg;
+	u32			gctl;
+
 	u32			num_event_buffers;
 	u32			u1u2;
 	u32			maximum_speed;
@@ -885,4 +891,31 @@
 { }
 #endif
 
+/* power management interface */
+#if !IS_ENABLED(CONFIG_USB_DWC3_HOST)
+int dwc3_gadget_prepare(struct dwc3 *dwc);
+void dwc3_gadget_complete(struct dwc3 *dwc);
+int dwc3_gadget_suspend(struct dwc3 *dwc);
+int dwc3_gadget_resume(struct dwc3 *dwc);
+#else
+static inline int dwc3_gadget_prepare(struct dwc3 *dwc)
+{
+	return 0;
+}
+
+static inline void dwc3_gadget_complete(struct dwc3 *dwc)
+{
+}
+
+static inline int dwc3_gadget_suspend(struct dwc3 *dwc)
+{
+	return 0;
+}
+
+static inline int dwc3_gadget_resume(struct dwc3 *dwc)
+{
+	return 0;
+}
+#endif /* !IS_ENABLED(CONFIG_USB_DWC3_HOST) */
+
 #endif /* __DRIVERS_USB_DWC3_CORE_H */