linux-kernel - Re: [PATCH v2 08/22] usb: chipidea: Remove locking in ci_udc

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Date:	Fri, 8 Jul 2016 17:45:28 +0800
From:	Peter Chen <hzpeterchen@...il.com>
To:	Stephen Boyd <stephen.boyd@...aro.org>
Cc:	linux-usb@...r.kernel.org, Felipe Balbi <balbi@...nel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Neil Armstrong <narmstrong@...libre.com>,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Bjorn Andersson <bjorn.andersson@...aro.org>,
	Peter Chen <peter.chen@....com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andy Gross <andy.gross@...aro.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 08/22] usb: chipidea: Remove locking in ci_udc_start()

On Thu, Jul 07, 2016 at 03:20:59PM -0700, Stephen Boyd wrote:
> We don't call hw_device_reset() with the ci->lock held, so it
> doesn't seem like this lock here is protecting anything. Let's
> just remove it. This allows us to call sleeping functions like
> phy_init() from within the CI_HDRC_CONTROLLER_RESET_EVENT hook.
> 
> Cc: Peter Chen <peter.chen@....com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Signed-off-by: Stephen Boyd <stephen.boyd@...aro.org>
> ---
>  drivers/usb/chipidea/udc.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/usb/chipidea/udc.c b/drivers/usb/chipidea/udc.c
> index 065f5d97aa67..f16be4710cdb 100644
> --- a/drivers/usb/chipidea/udc.c
> +++ b/drivers/usb/chipidea/udc.c
> @@ -1719,7 +1719,6 @@ static int ci_udc_start(struct usb_gadget *gadget,
>  			 struct usb_gadget_driver *driver)
>  {
>  	struct ci_hdrc *ci = container_of(gadget, struct ci_hdrc, gadget);
> -	unsigned long flags;
>  	int retval = -ENOMEM;
>  
>  	if (driver->disconnect == NULL)
> @@ -1746,7 +1745,6 @@ static int ci_udc_start(struct usb_gadget *gadget,
>  
>  	pm_runtime_get_sync(&ci->gadget.dev);
>  	if (ci->vbus_active) {
> -		spin_lock_irqsave(&ci->lock, flags);
>  		hw_device_reset(ci);
>  	} else {
>  		usb_udc_vbus_handler(&ci->gadget, false);
> @@ -1755,7 +1753,6 @@ static int ci_udc_start(struct usb_gadget *gadget,
>  	}
>  
>  	retval = hw_device_state(ci, ci->ep0out->qh.dma);
> -	spin_unlock_irqrestore(&ci->lock, flags);
>  	if (retval)
>  		pm_runtime_put_sync(&ci->gadget.dev);
>  

The main purpose for this is disabling interrupt when reset controller,
in case the unexpected interrupts occur.

You can move this between hw_device_state.

-- 

Best Regards,
Peter Chen