usb: dwc3: gadget: Don't modify GEVNTCOUNT in pullup()

If the GEVNTCOUNT indicates events in the event buffer, the driver needs
to acknowledge them before the controller can halt. Simply let the
interrupt handler acknowledges the remaining event generated by the
controller while polling for DSTS.DEVCTLHLT. This avoids disabling irq
and taking care of race condition between the interrupt handlers and
pullup().

Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/ea306ec93c41ccafbdb5d16404ff3b6eca299613.1650593829.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc3/gadget.c

@@ -2509,8 +2509,9 @@ static int __dwc3_gadget_start(struct dwc3 *dwc);
 
 static int dwc3_gadget_soft_disconnect(struct dwc3 *dwc)
 {
-	u32 count;
+	unsigned long flags;
 
+	spin_lock_irqsave(&dwc->lock, flags);
 	dwc->connected = false;
 
 	/*
@@ -2522,29 +2523,21 @@ static int dwc3_gadget_soft_disconnect(struct dwc3 *dwc)
 	 */
 	dwc3_stop_active_transfers(dwc);
 	__dwc3_gadget_stop(dwc);
+	spin_unlock_irqrestore(&dwc->lock, flags);
 
 	/*
-	 * In the Synopsys DesignWare Cores USB3 Databook Rev. 3.30a
-	 * Section 1.3.4, it mentions that for the DEVCTRLHLT bit, the
-	 * "software needs to acknowledge the events that are generated
-	 * (by writing to GEVNTCOUNTn) while it is waiting for this bit
-	 * to be set to '1'."
+	 * Note: if the GEVNTCOUNT indicates events in the event buffer, the
+	 * driver needs to acknowledge them before the controller can halt.
+	 * Simply let the interrupt handler acknowledges and handle the
+	 * remaining event generated by the controller while polling for
+	 * DSTS.DEVCTLHLT.
 	 */
-	count = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
-	count &= DWC3_GEVNTCOUNT_MASK;
-	if (count > 0) {
-		dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), count);
-		dwc->ev_buf->lpos = (dwc->ev_buf->lpos + count) %
-			dwc->ev_buf->length;
-	}
-
 	return dwc3_gadget_run_stop(dwc, false, false);
 }
 
 static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 {
 	struct dwc3		*dwc = gadget_to_dwc(g);
-	unsigned long		flags;
 	int			ret;
 
 	is_on = !!is_on;
@@ -2588,14 +2581,6 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 		return 0;
 	}
 
-	/*
-	 * Synchronize and disable any further event handling while controller
-	 * is being enabled/disabled.
-	 */
-	disable_irq(dwc->irq_gadget);
-
-	spin_lock_irqsave(&dwc->lock, flags);
-
 	if (!is_on) {
 		ret = dwc3_gadget_soft_disconnect(dwc);
 	} else {
@@ -2605,16 +2590,12 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 		 * device-initiated disconnect requires a core soft reset
 		 * (DCTL.CSftRst) before enabling the run/stop bit.
 		 */
-		spin_unlock_irqrestore(&dwc->lock, flags);
 		dwc3_core_soft_reset(dwc);
-		spin_lock_irqsave(&dwc->lock, flags);
 
 		dwc3_event_buffers_setup(dwc);
 		__dwc3_gadget_start(dwc);
 		ret = dwc3_gadget_run_stop(dwc, true, false);
 	}
-	spin_unlock_irqrestore(&dwc->lock, flags);
-	enable_irq(dwc->irq_gadget);
 
 	pm_runtime_put(dwc->dev);