linux-kernel - Re: [PATCH v2 4/8] usb: dwc3: implement stream transfer timeout

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Message-ID: <30102591E157244384E984126FC3CB4F544AB8CD@us01wembx1.internal.synopsys.com>
Date:   Wed, 5 Sep 2018 06:01:55 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Anurag Kumar Vulisha <anurag.kumar.vulisha@...inx.com>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     "v.anuragkumar@...il.com" <v.anuragkumar@...il.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/8] usb: dwc3: implement stream transfer timeout

On 8/17/2018 5:25 AM, Anurag Kumar Vulisha wrote:
> According to dwc3 databook when streams are used, it may be possible
> for the host and device become out of sync, where device may wait for
> host to issue prime transcation and host may wait for device to issue
> erdy. To avoid such deadlock, timeout needs to be implemented. After
> timeout occurs, device will first stop transfer and restart the transfer
> again. This patch does the same.
>
> Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@...inx.com>
> ---
>  Changes in v2:
> 	1. Changed STREAM_TIMEOUT to STREAM_TIMEOUT_MS as suggested by
> 	   Andy Shevchenko
> ---
>  drivers/usb/dwc3/core.h   |  7 +++++++
>  drivers/usb/dwc3/gadget.c | 39 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 46 insertions(+)
>
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index 285ce0e..f58640f 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -619,6 +619,11 @@ struct dwc3_event_buffer {
>  
>  #define DWC3_TRB_NUM		256
>  
> +/*
> + * Timeout value in msecs used by stream_timeout_timer when streams are enabled
> + */
> +#define STREAM_TIMEOUT_MS	50
> +
>  /**
>   * struct dwc3_ep - device side endpoint representation
>   * @endpoint: usb endpoint
> @@ -642,6 +647,7 @@ struct dwc3_event_buffer {
>   * @name: a human readable name e.g. ep1out-bulk
>   * @direction: true for TX, false for RX
>   * @stream_capable: true when streams are enabled
> + * @stream_timeout_timer: timer used to aviod deadlock when streams are used
>   */
>  struct dwc3_ep {
>  	struct usb_ep		endpoint;
> @@ -691,6 +697,7 @@ struct dwc3_ep {
>  
>  	unsigned		direction:1;
>  	unsigned		stream_capable:1;
> +	struct timer_list	stream_timeout_timer;
>  };
>  
>  enum dwc3_phy {
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index b3e9e7f..8cef488 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -254,6 +254,7 @@ int dwc3_send_gadget_generic_command(struct dwc3 *dwc, unsigned cmd, u32 param)
>  }
>  
>  static int __dwc3_gadget_wakeup(struct dwc3 *dwc);
> +static void stream_timeout_function(struct timer_list *arg);
>  
>  /**
>   * dwc3_send_gadget_ep_cmd - issue an endpoint command
> @@ -574,6 +575,8 @@ static int dwc3_gadget_set_ep_config(struct dwc3_ep *dep, unsigned int action)
>  			| DWC3_DEPCFG_STREAM_EVENT_EN
>  			| DWC3_DEPCFG_XFER_COMPLETE_EN;
>  		dep->stream_capable = true;
> +		timer_setup(&dep->stream_timeout_timer,
> +			    stream_timeout_function, 0);
>  	}
>  
>  	if (!usb_endpoint_xfer_control(desc))
> @@ -730,6 +733,9 @@ static int __dwc3_gadget_ep_disable(struct dwc3_ep *dep)
>  
>  	trace_dwc3_gadget_ep_disable(dep);
>  
> +	if (dep->stream_capable)
> +		del_timer(&dep->stream_timeout_timer);
> +
>  	dwc3_remove_requests(dwc, dep);
>  
>  	/* make sure HW endpoint isn't stalled */
> @@ -1257,6 +1263,12 @@ static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
>  		return ret;
>  	}
>  
> +	if (starting && dep->stream_capable) {
> +		dep->stream_timeout_timer.expires = jiffies +
> +					msecs_to_jiffies(STREAM_TIMEOUT_MS);
> +		add_timer(&dep->stream_timeout_timer);
> +	}
> +
>  	return 0;
>  }
>  
> @@ -2403,6 +2415,13 @@ static void dwc3_gadget_endpoint_transfer_in_progress(struct dwc3_ep *dep,
>  			stop = true;
>  	}
>  
> +	/*
> +	 * Delete the timer that was started in __dwc3_gadget_kick_transfer()
> +	 * for stream capable endpoints.
> +	 */
> +	if (dep->stream_capable)
> +		del_timer(&dep->stream_timeout_timer);
> +
>  	dwc3_gadget_ep_cleanup_completed_requests(dep, event, status);
>  
>  	if (stop) {
> @@ -2486,6 +2505,14 @@ static void dwc3_endpoint_interrupt(struct dwc3 *dwc,
>  		}
>  		break;
>  	case DWC3_DEPEVT_STREAMEVT:
> +		switch (event->status) {
> +		case DEPEVT_STREAMEVT_FOUND:
> +			del_timer(&dep->stream_timeout_timer);
> +			break;
> +		case DEPEVT_STREAMEVT_NOTFOUND:
> +		default:
> +			dev_err(dwc->dev, "unable to find suitable stream");
> +		}
Add break after this. Also, it's probably easier to read if we use
if-else case here.

>  	case DWC3_DEPEVT_RXTXFIFOEVT:
>  		break;
>  	}
> @@ -2587,6 +2614,18 @@ static void dwc3_stop_active_transfer(struct dwc3_ep *dep, bool force)
>  	}
>  }
>  
> +static void stream_timeout_function(struct timer_list *arg)
> +{
> +	struct dwc3_ep *dep = from_timer(dep, arg, stream_timeout_timer);
> +	struct dwc3		*dwc = dep->dwc;
> +	unsigned long		flags;
> +
> +	spin_lock_irqsave(&dwc->lock, flags);
> +	dwc3_stop_active_transfer(dep, true);
> +	__dwc3_gadget_kick_transfer(dep);
> +	spin_unlock_irqrestore(&dwc->lock, flags);
> +}
> +
>  static void dwc3_clear_stall_all_ep(struct dwc3 *dwc)
>  {
>  	u32 epnum;

Thinh