usb: dwc2: Add hibernation entering flow by system suspend

Adds a new flow of entering hibernation when PC is
hibernated or suspended.
Acked-by: NMinas Harutyunyan <Minas.Harutyunyan@synopsys.com>
Signed-off-by: NArtur Petrosyan <Arthur.Petrosyan@synopsys.com>
Link: https://lore.kernel.org/r/20210416124811.BBFDBA005C@mailhost.synopsys.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc2/hcd.c

@@ -4387,6 +4387,16 @@ static int _dwc2_hcd_suspend(struct usb_hcd *hcd)
 		clear_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
 		break;
 	case DWC2_POWER_DOWN_PARAM_HIBERNATION:
+		/* Enter hibernation */
+		spin_unlock_irqrestore(&hsotg->lock, flags);
+		ret = dwc2_enter_hibernation(hsotg, 1);
+		if (ret)
+			dev_err(hsotg->dev, "enter hibernation failed\n");
+		spin_lock_irqsave(&hsotg->lock, flags);
+
+		/* After entering suspend, hardware is not accessible */
+		clear_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
+		break;
 	case DWC2_POWER_DOWN_PARAM_NONE:
 		/*
 		 * If not hibernation nor partial power down are supported,