usb: dwc2: Fix partial power down exiting by system resume

Fixes the implementation of exiting from partial power down
power saving mode when PC is resumed.

Added port connection status checking which prevents exiting from
Partial Power Down mode from _dwc2_hcd_resume() if not in Partial
Power Down mode.

Rearranged the implementation to get rid of many "if"
statements.

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.

Fixes: 6f6d705 ("usb: dwc2: bus suspend/resume for hosts with DWC2_POWER_DOWN_PARAM_NONE")
Cc: <stable@vger.kernel.org>
Acked-by: Minas Harutyunyan <Minas.Harutyunyan@synopsys.com>
Signed-off-by: Artur Petrosyan <Arthur.Petrosyan@synopsys.com>
Link: https://lore.kernel.org/r/20210408094607.1A9BAA0094@mailhost.synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Artur Petrosyan

drivers/usb/dwc2/hcd.c

@@ -4427,7 +4427,7 @@ static int _dwc2_hcd_resume(struct usb_hcd *hcd)
 {
 	struct dwc2_hsotg *hsotg = dwc2_hcd_to_hsotg(hcd);
 	unsigned long flags;
-	u32 pcgctl;
+	u32 hprt0;
 	int ret = 0;
 
 	spin_lock_irqsave(&hsotg->lock, flags);
@@ -4438,11 +4438,40 @@ static int _dwc2_hcd_resume(struct usb_hcd *hcd)
 	if (hsotg->lx_state != DWC2_L2)
 		goto unlock;
 
-	if (hsotg->params.power_down > DWC2_POWER_DOWN_PARAM_PARTIAL) {
+	hprt0 = dwc2_read_hprt0(hsotg);
+
+	/*
+	 * Added port connection status checking which prevents exiting from
+	 * Partial Power Down mode from _dwc2_hcd_resume() if not in Partial
+	 * Power Down mode.
+	 */
+	if (hprt0 & HPRT0_CONNSTS) {
+		hsotg->lx_state = DWC2_L0;
+		goto unlock;
+	}
+
+	switch (hsotg->params.power_down) {
+	case DWC2_POWER_DOWN_PARAM_PARTIAL:
+		ret = dwc2_exit_partial_power_down(hsotg, 0, true);
+		if (ret)
+			dev_err(hsotg->dev,
+				"exit partial_power_down failed\n");
+		/*
+		 * Set HW accessible bit before powering on the controller
+		 * since an interrupt may rise.
+		 */
+		set_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
+		break;
+	case DWC2_POWER_DOWN_PARAM_HIBERNATION:
+	case DWC2_POWER_DOWN_PARAM_NONE:
+	default:
 		hsotg->lx_state = DWC2_L0;
 		goto unlock;
 	}
 
+	/* Change Root port status, as port status change occurred after resume.*/
+	hsotg->flags.b.port_suspend_change = 1;
+
 	/*
 	 * Enable power if not already done.
 	 * This must not be spinlocked since duration
@@ -4454,52 +4483,25 @@ static int _dwc2_hcd_resume(struct usb_hcd *hcd)
 		spin_lock_irqsave(&hsotg->lock, flags);
 	}
 
-	if (hsotg->params.power_down == DWC2_POWER_DOWN_PARAM_PARTIAL) {
-		/*
-		 * Set HW accessible bit before powering on the controller
-		 * since an interrupt may rise.
-		 */
-		set_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
-
-
-		/* Exit partial_power_down */
-		ret = dwc2_exit_partial_power_down(hsotg, 0, true);
-		if (ret && (ret != -ENOTSUPP))
-			dev_err(hsotg->dev, "exit partial_power_down failed\n");
-	} else {
-		pcgctl = readl(hsotg->regs + PCGCTL);
-		pcgctl &= ~PCGCTL_STOPPCLK;
-		writel(pcgctl, hsotg->regs + PCGCTL);
-	}
-
-	hsotg->lx_state = DWC2_L0;
-
+	/* Enable external vbus supply after resuming the port. */
 	spin_unlock_irqrestore(&hsotg->lock, flags);
+	dwc2_vbus_supply_init(hsotg);
 
-	if (hsotg->bus_suspended) {
-		spin_lock_irqsave(&hsotg->lock, flags);
-		hsotg->flags.b.port_suspend_change = 1;
-		spin_unlock_irqrestore(&hsotg->lock, flags);
-		dwc2_port_resume(hsotg);
-	} else {
-		if (hsotg->params.power_down == DWC2_POWER_DOWN_PARAM_PARTIAL) {
-			dwc2_vbus_supply_init(hsotg);
-
-			/* Wait for controller to correctly update D+/D- level */
-			usleep_range(3000, 5000);
-		}
+	/* Wait for controller to correctly update D+/D- level */
+	usleep_range(3000, 5000);
+	spin_lock_irqsave(&hsotg->lock, flags);
 
-		/*
-		 * Clear Port Enable and Port Status changes.
-		 * Enable Port Power.
-		 */
-		dwc2_writel(hsotg, HPRT0_PWR | HPRT0_CONNDET |
-				HPRT0_ENACHG, HPRT0);
-		/* Wait for controller to detect Port Connect */
-		usleep_range(5000, 7000);
-	}
+	/*
+	 * Clear Port Enable and Port Status changes.
+	 * Enable Port Power.
+	 */
+	dwc2_writel(hsotg, HPRT0_PWR | HPRT0_CONNDET |
+			HPRT0_ENACHG, HPRT0);
 
-	return ret;
+	/* Wait for controller to detect Port Connect */
+	spin_unlock_irqrestore(&hsotg->lock, flags);
+	usleep_range(5000, 7000);
+	spin_lock_irqsave(&hsotg->lock, flags);
 unlock:
 	spin_unlock_irqrestore(&hsotg->lock, flags);