2010-02-22 17:40:50

by Steven J. Magnani

Subject: [async_tx-next PATCH 2/2] fsldma: Fix cookie issues

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 <[email protected]>
---
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 2147483647

#define dma_submit_error(cookie) ((cookie) < 0 ? 1 : 0)

2010-02-22 20:26:25

by Guennadi Liakhovetski

Subject: Re: [async_tx-next PATCH 2/2] fsldma: Fix cookie issues

On Mon, 22 Feb 2010, Steven J. Magnani wrote:

> 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 2147483647

Taking into account, that dma_cookie_t is 32 bits:

+#define DMA_MAX_COOKIE ((1 << 31) - 1)

Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/

2010-02-25 19:25:42

by Ira W. Snyder

Subject: Re: [async_tx-next PATCH 2/2] fsldma: Fix cookie issues

On Mon, Feb 22, 2010 at 09:26:13PM +0100, Guennadi Liakhovetski wrote:
> On Mon, 22 Feb 2010, Steven J. Magnani wrote:
>
> > 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 2147483647
>
> Taking into account, that dma_cookie_t is 32 bits:
>
> +#define DMA_MAX_COOKIE ((1 << 31) - 1)
>

Steven,

After you take Guennadi's comment into acount, the rest of the patch
looks good. I'm sure I've never rolled the cookie around during testing.

Ira