Patch "usb: dwc3: gadget: Don't modify GEVNTCOUNT in pullup()" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     usb-dwc3-gadget-don-t-modify-gevntcount-in-pullup.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 14604b0553494d9f3a6241c6778310bf88111675
Author: Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx>
Date:   Thu Apr 21 19:22:44 2022 -0700

    usb: dwc3: gadget: Don't modify GEVNTCOUNT in pullup()
    
    [ Upstream commit 8f8034f493b5eb1ad21ff392fd30c0cf9e71f73f ]
    
    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@xxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/ea306ec93c41ccafbdb5d16404ff3b6eca299613.1650593829.git.Thinh.Nguyen@xxxxxxxxxxxx
    Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
    Stable-dep-of: 040f2dbd2010 ("usb: dwc3: gadget: Avoid duplicate requests to enable Run/Stop")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index cdc03ee439f8..484b5e1d921a 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2437,8 +2437,9 @@ 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;
 
 	/*
@@ -2450,29 +2451,21 @@ 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;
@@ -2516,14 +2509,6 @@ 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 {
@@ -2533,16 +2518,12 @@ 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);