linux-kernel - Re: [PATCH] usb: dwc3: gadget: fix burst size corruption

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Message-ID: <20140430200353.GC3839@saruman.home>
Date:	Wed, 30 Apr 2014 15:03:53 -0500
From:	Felipe Balbi <balbi@...com>
To:	Zhuang Jin Can <jin.can.zhuang@...el.com>
CC:	Felipe Balbi <balbi@...com>, <linux-usb@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: gadget: fix burst size corruption

On Thu, May 01, 2014 at 03:16:04AM -0400, Zhuang Jin Can wrote:
> endpoint.maxburst may be 0 if a gadget doesn't call config_ep_by_speed()
> to update it from the companion descriptor.
> And endpoint.maxburst - 1 returns 11111b which wrongly sets bit
> 26 of endpoint parameter 0.
> This sets a wrong endpoint state and will cause "Get Endpoint State"
> command can't get the corret endpoint state and "Set Endpoint Config"
> command can't restore the correct endpoint state during hibernation
> resume flow.
> Thus, when endpoint.maxburst is 0, we should set burst as 0 directly.
> 
> Signed-off-by: Zhuang Jin Can <jin.can.zhuang@...el.com>
> ---
>  drivers/usb/dwc3/gadget.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 70715ee..44eca95 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -440,7 +440,8 @@ static int dwc3_gadget_set_ep_config(struct dwc3 *dwc, struct dwc3_ep *dep,
>  
>  	/* Burst size is only needed in SuperSpeed mode */
>  	if (dwc->gadget.speed == USB_SPEED_SUPER) {
> -		u32 burst = dep->endpoint.maxburst - 1;
> +		u32 burst = dep->endpoint.maxburst ?
> +				dep->endpoint.maxburst - 1 : 0;

again, you found a bug on the gadget driver. Fix that. composite.c
guarantees that for those functions which don't pass bMaxBurst,
gadget->maxburst will be set to *at least* 1.

-- 
balbi

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