linux-kernel - Re: [async_tx-next PATCH v2 2/2] fsldma: Fix cookie issues

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Date:	Sun, 28 Feb 2010 22:14:27 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	"Steven J. Magnani" <steve@...idescorp.com>
Cc:	Li Yang <leoli@...escale.com>, Zhang Wei <zw@...kernel.org>,
	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	"Ira W. Snyder" <iws@...o.caltech.edu>
Subject: Re: [async_tx-next PATCH v2 2/2] fsldma: Fix cookie issues

On Thu, Feb 25, 2010 at 12:39 PM, Steven J. Magnani
<steve@...idescorp.com> wrote:
> fsl_dma_update_completed_cookie() appears to calculate the last completed
> cookie incorrectly in the corner case where DMA on cookie 1 is in progress
> just following a cookie wrap.
>
> Signed-off-by: Steven J. Magnani <steve@...idescorp.com>
> ---
> diff -uprN a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c
> --- a/drivers/dma/fsldma.c      2010-02-22 11:16:36.000000000 -0600
> +++ b/drivers/dma/fsldma.c      2010-02-22 11:08:41.000000000 -0600
> @@ -819,8 +819,11 @@ static void fsl_dma_update_completed_coo
>        desc = to_fsl_desc(chan->ld_running.prev);
>        if (dma_is_idle(chan))
>                cookie = desc->async_tx.cookie;
> -       else
> +       else {
>                cookie = desc->async_tx.cookie - 1;
> +               if (unlikely(cookie < DMA_MIN_COOKIE))
> +                       cookie = DMA_MAX_COOKIE;
> +       }
>
>        chan->completed_cookie = cookie;
>
> diff -uprN a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> --- a/include/linux/dmaengine.h 2010-02-22 11:18:11.000000000 -0600
> +++ b/include/linux/dmaengine.h 2010-02-22 11:18:30.000000000 -0600
> @@ -31,6 +31,8 @@
>  * if dma_cookie_t is >0 it's a DMA request cookie, <0 it's an error code
>  */
>  typedef s32 dma_cookie_t;
> +#define DMA_MIN_COOKIE 1
> +#define DMA_MAX_COOKIE ((1 << 31) - 1)
>

This patch introduces a new warning::

drivers/dma/fsldma.c:825: warning: integer overflow in expression

I'll fix this up to use INT_MAX instead.

--
Dan

powerpc-linux-gnu-gcc --version
powerpc-linux-gnu-gcc (Sourcery G++ Lite 4.2-50) 4.2.1
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