linux-kernel - Re: [PATCH v3 6/8] usb: dwc3: Increase DWC3 controller halt timeout

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Date:   Wed, 17 Aug 2022 00:34:20 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Wesley Cheng <quic_wcheng@...cinc.com>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Subject: Re: [PATCH v3 6/8] usb: dwc3: Increase DWC3 controller halt timeout

On 8/15/2022, Wesley Cheng wrote:
> Since EP0 transactions need to be completed before the controller halt
> sequence is finished, this may take some time depending on the host and the
> enabled functions.  Increase the controller halt timeout, so that we give
> the controller sufficient time to handle EP0 transfers.  Remove the need
> for making dwc3_gadget_suspend() and dwc3_gadget_resume() to be called in
> a spinlock.

Sounds like the removal of the spin_lock and the increase of halt
timeout are 2 separate change. It would be nice to separate this patch
since the $subject only indicates 1 of them.

> 
> Suggested-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
> Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.com>
> ---
>  drivers/usb/dwc3/core.c   | 4 ----
>  drivers/usb/dwc3/gadget.c | 8 +++++++-
>  2 files changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index c5c238ab3083..23e123a1ab5f 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1976,9 +1976,7 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
>  	case DWC3_GCTL_PRTCAP_DEVICE:
>  		if (pm_runtime_suspended(dwc->dev))
>  			break;
> -		spin_lock_irqsave(&dwc->lock, flags);
>  		dwc3_gadget_suspend(dwc);
> -		spin_unlock_irqrestore(&dwc->lock, flags);
>  		synchronize_irq(dwc->irq_gadget);
>  		dwc3_core_exit(dwc);
>  		break;
> @@ -2039,9 +2037,7 @@ static int dwc3_resume_common(struct dwc3 *dwc, pm_message_t msg)
>  			return ret;
>  
>  		dwc3_set_prtcap(dwc, DWC3_GCTL_PRTCAP_DEVICE);
> -		spin_lock_irqsave(&dwc->lock, flags);
>  		dwc3_gadget_resume(dwc);
> -		spin_unlock_irqrestore(&dwc->lock, flags);
>  		break;
>  	case DWC3_GCTL_PRTCAP_HOST:
>  		if (!PMSG_IS_AUTO(msg) && !device_can_wakeup(dwc->dev)) {
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 7b66a54250a0..b2668a83cc29 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -2444,7 +2444,7 @@ static void __dwc3_gadget_set_speed(struct dwc3 *dwc)
>  static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on, int suspend)
>  {
>  	u32			reg;
> -	u32			timeout = 500;
> +	u32			timeout = 100;
>  
>  	if (pm_runtime_suspended(dwc->dev))
>  		return 0;
> @@ -2477,6 +2477,7 @@ static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on, int suspend)
>  	dwc3_gadget_dctl_write_safe(dwc, reg);
>  
>  	do {
> +		msleep(20);

Polling interval of 20ms seems a bit much. Can we use usleep_range()
between 1-2ms?

Thanks,
Thinh

>  		reg = dwc3_readl(dwc->regs, DWC3_DSTS);
>  		reg &= DWC3_DSTS_DEVCTRLHLT;
>  	} while (--timeout && !(!is_on ^ !reg));
> @@ -4520,12 +4521,17 @@ void dwc3_gadget_exit(struct dwc3 *dwc)
>  
>  int dwc3_gadget_suspend(struct dwc3 *dwc)
>  {
> +	unsigned long flags;
> +
>  	if (!dwc->gadget_driver)
>  		return 0;
>  
>  	dwc3_gadget_run_stop(dwc, false, false);
> +
> +	spin_lock_irqsave(&dwc->lock, flags);
>  	dwc3_disconnect_gadget(dwc);
>  	__dwc3_gadget_stop(dwc);
> +	spin_unlock_irqrestore(&dwc->lock, flags);
>  
>  	return 0;
>  }