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

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Message-ID: <83dfad53-b38e-54c9-0f90-8fe834a1bca6@kernel.org>
Date:   Fri, 28 Apr 2023 15:04:57 +0300
From:   Roger Quadros <rogerq@...nel.org>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc:     "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 28/04/2023 01:13, Thinh Nguyen wrote:
> 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);

return dwc3_gadget_run_stop(dwc, true, false);

> +}> +
>  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)

We need to check for dwc->softconnect here. If it is not set that means
controller has already stopped so we can simply exit.

>  		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)

Everything else looks ok. I will send a patch soon.

--
cheers,
-roger