usb: dwc2: fix a race with external vbus supply

There's a race with root hub resume, when using external vbus supply.
Root hub gets resumed, but runtime pm autosuspend runs as external vbus
supply isn't enabled. So, host never exit from power down properly.
Initialize vbus external supply before, rater that after hub resume.

Fixes: 531ef5eb ("usb: dwc2: add support for host mode external
vbus supply")
Tested-by: Artur Petrosyan <arturp@synopsys.com>
Acked-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc2/hcd.c

@@ -4384,6 +4384,7 @@ static int _dwc2_hcd_start(struct usb_hcd *hcd)
 	struct dwc2_hsotg *hsotg = dwc2_hcd_to_hsotg(hcd);
 	struct usb_bus *bus = hcd_to_bus(hcd);
 	unsigned long flags;
+	int ret;
 
 	dev_dbg(hsotg->dev, "DWC OTG HCD START\n");
 
@@ -4399,6 +4400,13 @@ static int _dwc2_hcd_start(struct usb_hcd *hcd)
 
 	dwc2_hcd_reinit(hsotg);
 
+	/* enable external vbus supply before resuming root hub */
+	spin_unlock_irqrestore(&hsotg->lock, flags);
+	ret = dwc2_vbus_supply_init(hsotg);
+	if (ret)
+		return ret;
+	spin_lock_irqsave(&hsotg->lock, flags);
+
 	/* Initialize and connect root hub if one is not already attached */
 	if (bus->root_hub) {
 		dev_dbg(hsotg->dev, "DWC OTG HCD Has Root Hub\n");
@@ -4408,7 +4416,7 @@ static int _dwc2_hcd_start(struct usb_hcd *hcd)
 
 	spin_unlock_irqrestore(&hsotg->lock, flags);
 
-	return dwc2_vbus_supply_init(hsotg);
+	return 0;
 }
 
 /*