From: Russell King - ARM Linux <linux@arm.linux.org.uk>
Date: Tue, 6 Mar 2012 22:36:07 +0000 (+0000)
Subject: dmaengine: fix cookie handling in iop-adma.c and ppc4xx/adma.c
X-Git-Tag: v3.4-rc1~39^2~20^2~3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2a926e46022ad7a03e0ac167d8c2b0d88c12c5a8;p=pandora-kernel.git

dmaengine: fix cookie handling in iop-adma.c and ppc4xx/adma.c

Dan Williams said:
> > Russell King wrote:
> > Firstly, we have DMA_MIN_COOKIE which has value 1 - so any cookies below
> > that aren't valid.  That seems sane.
> >
> > We seem to have different behaviours:
> >
> > -       cookie = c->cookie;
> > -       cookie++;
> > -       if (cookie < 0)
> > -               cookie = 1;
> > -       c->cookie = cookie;
> > -       tx->cookie = cookie;
> >
> > c->cookie here is initialized to zero, so the first cookie given out will
> > be 1.  This is how most DMA engine drivers implement this.
> >
> > Then we have this:
> >
> >                cookie = chan->common.cookie;
> >                cookie++;
> >                if (cookie <= 1)
> >                        cookie = 2;
> >
> >                /* initialize the completed cookie to be less than
> >                 * the most recently used cookie
> >                 */
> >                chan->common.completed_cookie = cookie - 1;
> >                chan->common.cookie = sw_desc->async_tx.cookie = cookie;
> >
> > Again, chan->common.cookie starts off at 0.  The first cookie given out
> > will be 2, and 1 will never be used.  There are three drivers which
> > implement it this way.
> >
> > Why is there this difference, and can these three be corrected to behave
> > the same way as the first (and therefore the assignment of cookies
> > consolidated?)
>
> Yes, they should be consolidated, and I believe they have drifted only
> because there were no good common helpers and murphy's law took over.

So lets fix this up to use the common dma_cookie_assign() helper.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Jassi Brar <jassisinghbrar@gmail.com>
[imx-sdma.c & mxs-dma.c]
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
---

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