usb: dwc2: Update partial power down entering by system suspend

With current implementation the port power is being disabled,
which is not required by the programming guide. Also, if there
is a system which works only in "DWC2_POWER_DOWN_PARAM_NONE"
(clock gating) mode the current implementation does not set
Gate hclk bit in pcgctl register.

Rearranges and updates the implementation of entering to partial
power down power saving mode when PC is suspended to get
rid of many "if" statements and removes disabling of port power.

NOTE: Switch case statement is used for hibernation partial
power down and clock gating mode determination. In this patch
only Partial Power Down is implemented the Hibernation and
clock gating implementations are planned to be added.
Acked-by: Minas Harutyunyan <Minas.Harutyunyan@synopsys.com>
Signed-off-by: Artur Petrosyan <Arthur.Petrosyan@synopsys.com>
Link: https://lore.kernel.org/r/20210408094559.33541A022E@mailhost.synopsys.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc2/hcd.c

@@ -4367,8 +4367,6 @@ static int _dwc2_hcd_suspend(struct usb_hcd *hcd)
 	struct dwc2_hsotg *hsotg = dwc2_hcd_to_hsotg(hcd);
 	unsigned long flags;
 	int ret = 0;
-	u32 hprt0;
-	u32 pcgctl;
 
 	spin_lock_irqsave(&hsotg->lock, flags);
 
@@ -4384,47 +4382,32 @@ static int _dwc2_hcd_suspend(struct usb_hcd *hcd)
 	if (hsotg->op_state == OTG_STATE_B_PERIPHERAL)
 		goto unlock;
 
-	if (hsotg->params.power_down != DWC2_POWER_DOWN_PARAM_PARTIAL ||
-	    hsotg->flags.b.port_connect_status == 0)
+	if (hsotg->bus_suspended)
 		goto skip_power_saving;
 
-	/*
-	 * Drive USB suspend and disable port Power
-	 * if usb bus is not suspended.
-	 */
-	if (!hsotg->bus_suspended) {
-		hprt0 = dwc2_read_hprt0(hsotg);
-		if (hprt0 & HPRT0_CONNSTS) {
-			hprt0 |= HPRT0_SUSP;
-			if (hsotg->params.power_down == DWC2_POWER_DOWN_PARAM_PARTIAL)
-				hprt0 &= ~HPRT0_PWR;
-			dwc2_writel(hsotg, hprt0, HPRT0);
-		}
-		if (hsotg->params.power_down == DWC2_POWER_DOWN_PARAM_PARTIAL) {
-			spin_unlock_irqrestore(&hsotg->lock, flags);
-			dwc2_vbus_supply_exit(hsotg);
-			spin_lock_irqsave(&hsotg->lock, flags);
-		} else {
-			pcgctl = readl(hsotg->regs + PCGCTL);
-			pcgctl |= PCGCTL_STOPPCLK;
-			writel(pcgctl, hsotg->regs + PCGCTL);
-		}
-	}
+	if (hsotg->flags.b.port_connect_status == 0)
+		goto skip_power_saving;
 
-	if (hsotg->params.power_down == DWC2_POWER_DOWN_PARAM_PARTIAL) {
+	switch (hsotg->params.power_down) {
+	case DWC2_POWER_DOWN_PARAM_PARTIAL:
 		/* Enter partial_power_down */
 		ret = dwc2_enter_partial_power_down(hsotg);
-		if (ret) {
-			if (ret != -ENOTSUPP)
-				dev_err(hsotg->dev,
-					"enter partial_power_down failed\n");
-			goto skip_power_saving;
-		}
-
-		/* After entering partial_power_down, hardware is no more accessible */
+		if (ret)
+			dev_err(hsotg->dev,
+				"enter partial_power_down failed\n");
+		/* After entering suspend, hardware is not accessible */
 		clear_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
+		break;
+	case DWC2_POWER_DOWN_PARAM_HIBERNATION:
+	case DWC2_POWER_DOWN_PARAM_NONE:
+	default:
+		goto skip_power_saving;
 	}
 
+	spin_unlock_irqrestore(&hsotg->lock, flags);
+	dwc2_vbus_supply_exit(hsotg);
+	spin_lock_irqsave(&hsotg->lock, flags);
+
 	/* Ask phy to be suspended */
 	if (!IS_ERR_OR_NULL(hsotg->uphy)) {
 		spin_unlock_irqrestore(&hsotg->lock, flags);