usb: dwc2: Update enter clock gating when port is suspended

Updates the implementation of entering clock gating mode
when core receives port suspend.
Instead of setting the required bit fields of the registers
inline, called the "dwc2_host_enter_clock_gating()" function.

Signed-off-by: Artur Petrosyan <Arthur.Petrosyan@synopsys.com>
Link: https://lore.kernel.org/r/20210413073653.9F493A0094@mailhost.synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc2/hcd.c

@@ -3298,7 +3298,6 @@ static int dwc2_host_is_b_hnp_enabled(struct dwc2_hsotg *hsotg)
 int dwc2_port_suspend(struct dwc2_hsotg *hsotg, u16 windex)
 {
 	unsigned long flags;
-	u32 hprt0;
 	u32 pcgctl;
 	u32 gotgctl;
 	int ret = 0;
@@ -3323,22 +3322,12 @@ int dwc2_port_suspend(struct dwc2_hsotg *hsotg, u16 windex)
 		break;
 	case DWC2_POWER_DOWN_PARAM_HIBERNATION:
 	case DWC2_POWER_DOWN_PARAM_NONE:
-	default:
-		hprt0 = dwc2_read_hprt0(hsotg);
-		hprt0 |= HPRT0_SUSP;
-		dwc2_writel(hsotg, hprt0, HPRT0);
-		hsotg->bus_suspended = true;
 		/*
-		 * If power_down is supported, Phy clock will be suspended
-		 * after registers are backuped.
+		 * If not hibernation nor partial power down are supported,
+		 * clock gating is used to save power.
 		 */
-		if (!hsotg->params.power_down) {
-			/* Suspend the Phy Clock */
-			pcgctl = dwc2_readl(hsotg, PCGCTL);
-			pcgctl |= PCGCTL_STOPPCLK;
-			dwc2_writel(hsotg, pcgctl, PCGCTL);
-			udelay(10);
-		}
+		dwc2_host_enter_clock_gating(hsotg);
+		break;
 	}
 
 	/* For HNP the bus must be suspended for at least 200ms */