linux-kernel - Re: [PATCH] fsl_usb2_udc: Add a wmb before priming endpoint.

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Message-ID: <20080603172415.GB29125@kedavra.cpe.vivax.com.br>
Date:	Tue, 3 Jun 2008 20:24:15 +0300
From:	Felipe Balbi <me@...ipebalbi.com>
To:	Will Newton <will.newton@...il.com>
Cc:	linux-usb@...r.kernel.org,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	leoli@...escale.com
Subject: Re: [PATCH] fsl_usb2_udc: Add a wmb before priming endpoint.

On Tue, Jun 03, 2008 at 04:20:25PM +0100, Will Newton wrote:
> Add a wmb to fsl_queue_td before priming the endpoint. This ensures that the
> modifications to the QH are seen by the hardware.
> 
> Signed-off-by: Will Newton <will.newton@...il.com>
> ---
>  drivers/usb/gadget/fsl_usb2_udc.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/usb/gadget/fsl_usb2_udc.c
> b/drivers/usb/gadget/fsl_usb2_udc.c
> index 1868754..dd06a5b 100644
> --- a/drivers/usb/gadget/fsl_usb2_udc.c
> +++ b/drivers/usb/gadget/fsl_usb2_udc.c
> @@ -653,6 +653,8 @@ static int fsl_queue_td(struct fsl_ep *ep, struct
> fsl_req *req)
>  			| EP_QUEUE_HEAD_STATUS_HALT));
>  	dQH->size_ioc_int_sts &= temp;
> 
> +	wmb();

checkpatch.pl will complain that there's not comment above the memory
barrier. Could you just add it and in one line summarize why wmb()??

> +
>  	/* Prime endpoint by writing 1 to ENDPTPRIME */
>  	temp = ep_is_in(ep)
>  		? (1 << (ep_index(ep) + 16))
> -- 
> 1.5.5.2



-- 
Best Regards,

Felipe Balbi
me@...ipebalbi.com
http://blog.felipebalbi.com
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