linux-kernel - Re: dwc3 gadget: controller stop times out on system sleep

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Message-ID: <20230427221315.nmvy32j6lfxlsmdk@synopsys.com>
Date:   Thu, 27 Apr 2023 22:13:25 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Roger Quadros <rogerq@...nel.org>
CC:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: dwc3 gadget: controller stop times out on system sleep

On Thu, Apr 27, 2023, Roger Quadros wrote:
> Hi,
> 
> On 26/04/2023 23:01, Thinh Nguyen wrote:
> > Hi,
> > 
> > On Wed, Apr 26, 2023, Roger Quadros wrote:
> >> Hi Thinh,
> >>
> >> On Linux kernel v6.3
> >> Test procedure: 
> >>
> >> - modprobe g_zero
> >> - Connect to PC host
> >> - systemctl suspend
> >>
> >> A large delay of 3 seconds is observed. The delay comes from dwc3_gadget_suspend()->dwc3_gadget_run_stop() waiting for DWC3_DSTS_DEVCTRLHLT to be set.
> >> It returns -ETIMEDOUT.
> >>
> >> Are we missing something to do a clean stop during suspend?
> >>
> >> FYI. Unloading g_zero does not show this delay on stop.
> >>
> >> cheers,
> >> -roger
> > 
> > When clearing run_stop bit and the controller doesn't halt, that usually
> > means there are active transfers/endpoints that aren't ended yet.
> > 
> > The dwc3_gadget_suspend() doesn't properly do all the cleanup before
> > clearing the run_stop bit. I think you just need to call
> > dwc3_gadget_soft_disconnect() in dwc3_gadget_suspend() to fix this.
> 
> That seems to do the trick.
> How does this look?
> 
> -------------------------- drivers/usb/dwc3/gadget.c --------------------------
> @@ -4674,11 +4676,18 @@ void dwc3_gadget_exit(struct dwc3 *dwc)
>  int dwc3_gadget_suspend(struct dwc3 *dwc)
>  {
>  	unsigned long flags;
> +	int ret;
>  
> -	if (!dwc->gadget_driver)
> +	if (!dwc->gadget_driver || !dwc->softconnect)
>  		return 0;
>  
> -	dwc3_gadget_run_stop(dwc, false, false);
> +	ret = dwc3_gadget_soft_disconnect(dwc);
> +	if (ret)
> +		goto err0;
> +
> +	ret = dwc3_gadget_run_stop(dwc, false, false);
> +	if (ret)
> +		goto err1;
>  

We already clear run_stop in dwc3_gadget_soft_disconnect().

Can you try the following change (not tested):

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index c0ca4d12f95d..2996bcb4d53d 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2699,6 +2699,21 @@ static int dwc3_gadget_soft_disconnect(struct dwc3 *dwc)
 	return ret;
 }
 
+static int dwc3_gadget_soft_connect(struct dwc3 *dwc)
+{
+	/*
+	 * In the Synopsys DWC_usb31 1.90a programming guide section
+	 * 4.1.9, it specifies that for a reconnect after a
+	 * device-initiated disconnect requires a core soft reset
+	 * (DCTL.CSftRst) before enabling the run/stop bit.
+	 */
+	dwc3_core_soft_reset(dwc);
+
+	dwc3_event_buffers_setup(dwc);
+	__dwc3_gadget_start(dwc);
+	return dwc3_gadget_run_stop(dwc, true);
+}
+
 static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 {
 	struct dwc3		*dwc = gadget_to_dwc(g);
@@ -2737,21 +2752,10 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 
 	synchronize_irq(dwc->irq_gadget);
 
-	if (!is_on) {
+	if (!is_on)
 		ret = dwc3_gadget_soft_disconnect(dwc);
-	} else {
-		/*
-		 * In the Synopsys DWC_usb31 1.90a programming guide section
-		 * 4.1.9, it specifies that for a reconnect after a
-		 * device-initiated disconnect requires a core soft reset
-		 * (DCTL.CSftRst) before enabling the run/stop bit.
-		 */
-		dwc3_core_soft_reset(dwc);
-
-		dwc3_event_buffers_setup(dwc);
-		__dwc3_gadget_start(dwc);
-		ret = dwc3_gadget_run_stop(dwc, true);
-	}
+	else
+		ret = dwc3_gadget_soft_connect(dwc);
 
 	pm_runtime_put(dwc->dev);
 
@@ -4655,42 +4659,39 @@ void dwc3_gadget_exit(struct dwc3 *dwc)
 int dwc3_gadget_suspend(struct dwc3 *dwc)
 {
 	unsigned long flags;
+	int ret;
 
 	if (!dwc->gadget_driver)
 		return 0;
 
-	dwc3_gadget_run_stop(dwc, false);
+	ret = dwc3_gadget_soft_disconnect(dwc);
+	if (ret)
+		goto err;
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	dwc3_disconnect_gadget(dwc);
-	__dwc3_gadget_stop(dwc);
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
 	return 0;
+
+err:
+	/*
+	 * Attempt to reset the controller's state. Likely no
+	 * communication can be established until the host
+	 * performs a port reset.
+	 */
+	if (dwc->softconnect)
+		dwc3_gadget_soft_connect(dwc);
+
+	return ret;
 }
 
 int dwc3_gadget_resume(struct dwc3 *dwc)
 {
-	int			ret;
-
 	if (!dwc->gadget_driver || !dwc->softconnect)
 		return 0;
 
-	ret = __dwc3_gadget_start(dwc);
-	if (ret < 0)
-		goto err0;
-
-	ret = dwc3_gadget_run_stop(dwc, true);
-	if (ret < 0)
-		goto err1;
-
-	return 0;
-
-err1:
-	__dwc3_gadget_stop(dwc);
-
-err0:
-	return ret;
+	return dwc3_gadget_soft_connect(dwc);
 }
 
 void dwc3_gadget_process_pending_events(struct dwc3 *dwc)



--

Thanks,
Thinh