Hi Hamza,
On Mon, Sep 14, 2015 at 2:02 PM, <hamzahfrq.sub@xxxxxxxxx> wrote:
> DMA engine does not stop instantaneously when transaction is going on
> (see datasheet). Wait has been added
>
> Signed-off-by: Muhammad Hamza Farooq <mfarooq@xxxxxxxxxxx>
Thanks for your patch!
> diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
> index 7820d07..920f977 100644
> --- a/drivers/dma/sh/rcar-dmac.c
> +++ b/drivers/dma/sh/rcar-dmac.c
> @@ -716,14 +716,37 @@ static int rcar_dmac_fill_hwdesc(struct rcar_dmac_chan *chan,
> /* -----------------------------------------------------------------------------
> * Stop and reset
> */
> +#define NR_READS_TO_WAIT (5) /* number of reads to perform to check DE = 0 */
> +static inline int rcar_dmac_wait_stop(struct rcar_dmac_chan *chan)
> +{
> + unsigned int i = 0;
> + do {
> + u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
> +
> + if(!(chcr & RCAR_DMACHCR_DE))
> + return 0;
> + dev_dbg(chan->chan.device->dev, "DMA transfer couldn't be stopped");
I would add a cpu_relax() to the loop.
> + }
> + while(++i < NR_READS_TO_WAIT);
BTW, please run scripts/checkpatch.pl on your patches before submission.
Thanks!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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