Commit 2a926e46 authored Mar 06, 2012 by Russell King - ARM Linux Committed by Vinod Koul Mar 13, 2012

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>

parent d3ee98cd

drivers/dma/iop-adma.c

+2 −10

Original line number	Diff line number	Diff line
		@@ -1622,16 +1622,12 @@ static void iop_chan_start_null_memcpy(struct iop_adma_chan *iop_chan)
		iop_desc_set_dest_addr(grp_start, iop_chan, 0);
		iop_desc_set_memcpy_src_addr(grp_start, 0);

		cookie = iop_chan->common.cookie;
		cookie++;
		if (cookie <= 1)
		cookie = 2;
		cookie = dma_cookie_assign(&sw_desc->async_tx);

		/* initialize the completed cookie to be less than
		* the most recently used cookie
		*/
		iop_chan->common.completed_cookie = cookie - 1;
		iop_chan->common.cookie = sw_desc->async_tx.cookie = cookie;

		/* channel should not be busy */
		BUG_ON(iop_chan_is_busy(iop_chan));
		@@ -1679,16 +1675,12 @@ static void iop_chan_start_null_xor(struct iop_adma_chan *iop_chan)
		iop_desc_set_xor_src_addr(grp_start, 0, 0);
		iop_desc_set_xor_src_addr(grp_start, 1, 0);

		cookie = iop_chan->common.cookie;
		cookie++;
		if (cookie <= 1)
		cookie = 2;
		cookie = dma_cookie_assign(&sw_desc->async_tx);

		/* initialize the completed cookie to be less than
		* the most recently used cookie
		*/
		iop_chan->common.completed_cookie = cookie - 1;
		iop_chan->common.cookie = sw_desc->async_tx.cookie = cookie;

		/* channel should not be busy */
		BUG_ON(iop_chan_is_busy(iop_chan));

drivers/dma/ppc4xx/adma.c

+1 −5

Original line number	Diff line number	Diff line
		@@ -4022,16 +4022,12 @@ static void ppc440spe_chan_start_null_xor(struct ppc440spe_adma_chan *chan)
		async_tx_ack(&sw_desc->async_tx);
		ppc440spe_desc_init_null_xor(group_start);

		cookie = chan->common.cookie;
		cookie++;
		if (cookie <= 1)
		cookie = 2;
		cookie = dma_cookie_assign(&sw_desc->async_tx);

		/* 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;

		/* channel should not be busy */
		BUG_ON(ppc440spe_chan_is_busy(chan));