linux-kernel - Re: [PATCH v4 4/8] usb: dwc3: implement stream transfer timeout

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Message-ID: <30102591E157244384E984126FC3CB4F544AECB6@us01wembx1.internal.synopsys.com>
Date:   Thu, 13 Sep 2018 21:24:00 +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:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Thinh.Nguyen@...opsys.com" <Thinh.Nguyen@...opsys.com>,
        "v.anuragkumar@...il.com" <v.anuragkumar@...il.com>
Subject: Re: [PATCH v4 4/8] usb: dwc3: implement stream transfer timeout

Hi Anurag,

On 9/8/2018 8:03 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>
> Reviewed-by: Thinh Nguyen <thinhn@...opsys.com>
> ---
>  Chnages in v4:
> 	1. Added description for stream timeout timer as suggested by
> 	   "Thinh Nguyen"
>
>  Changes in v3:
> 	1. Added the changes suggested by "Thinh Nguyen"
>
>  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 | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 52 insertions(+)
>
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index 5bfb625..f62e8c4 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -633,6 +633,11 @@ 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
> @@ -656,6 +661,7 @@ 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: timeout timer used by bulk streams
>   */
>  struct dwc3_ep {
>  	struct usb_ep		endpoint;
> @@ -705,6 +711,7 @@ 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 13ea282..306d4c5 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 +575,17 @@ 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;
> +
> +		/*
> +		 * When BULK streams are enabled 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.
> +		 */
> +		timer_setup(&dep->stream_timeout_timer,
> +			    stream_timeout_function, 0);
>  	}
>  
>  	if (!usb_endpoint_xfer_control(desc))
> @@ -730,6 +742,9 @@ 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 +1272,12 @@ 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 +2424,13 @@ 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) {
> @@ -2487,6 +2515,11 @@ static void dwc3_endpoint_interrupt(struct dwc3 *dwc,
>  		}
>  		break;
>  	case DWC3_DEPEVT_STREAMEVT:
> +		if (event->status == DEPEVT_STREAMEVT_FOUND)
> +			del_timer(&dep->stream_timeout_timer);
> +		else
> +			dev_dbg(dwc->dev, "unable to find suitable stream");

This debug message is already printed in the driver tracepoint. There's
no need to print it here. Also, I don't think Felipe will accept adding
new dev_dbg() after removing all of them and converting them to tracepoints.

Thinh