On Tue, Sep 29, 2015 at 10:44:43PM +0200, hamzahfrq.sub@xxxxxxxxx wrote:
> From: Muhammad Hamza Farooq <mfarooq@xxxxxxxxxxx>
>
> DMA engine does not stop instantaneously when transaction is going on
> (see datasheet). Wait has been added
Hmmm, why is threading broken in this series?
Also why is this PATCH 1/6 whereas the rest of series is v3!
Right way is to let git do this for you and use git format-patch
--subject-prefix="PATCH v3"...
You don't do these things manually, that would be terrible waste of time
Also use git send-email to keep threading
> Signed-off-by: Muhammad Hamza Farooq <mfarooq@xxxxxxxxxxx>
> ---
> drivers/dma/sh/rcar-dmac.c | 28 ++++++++++++++++++++++++++--
> 1 file changed, 26 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
> index 7820d07..2b28291 100644
> --- a/drivers/dma/sh/rcar-dmac.c
> +++ b/drivers/dma/sh/rcar-dmac.c
> @@ -716,14 +716,38 @@ static int rcar_dmac_fill_hwdesc(struct rcar_dmac_chan *chan,
> /* -----------------------------------------------------------------------------
> * Stop and reset
> */
> +#define NR_READS_TO_WAIT 5 /* number of times to check if 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;
> + cpu_relax();
> + dev_dbg(chan->chan.device->dev, "DMA xfer couldn't be stopped");
And user has no way of knowing this on production system
> + } while (++i < NR_READS_TO_WAIT);
>
> -static void rcar_dmac_chan_halt(struct rcar_dmac_chan *chan)
> + return -EBUSY;
> +}
> +
> +/* Called with chan lock held */
> +static int rcar_dmac_chan_halt(struct rcar_dmac_chan *chan)
> {
> - u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
> + u32 chcr;
> + int ret;
>
> + chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
> chcr &= ~(RCAR_DMACHCR_DSE | RCAR_DMACHCR_DSIE | RCAR_DMACHCR_IE |
> RCAR_DMACHCR_TE | RCAR_DMACHCR_DE);
> rcar_dmac_chan_write(chan, RCAR_DMACHCR, chcr);
> + ret = rcar_dmac_wait_stop(chan);
> +
> + WARN_ON(ret < 0);
What if we have broken board and will see dmesg storm for this, perhaps
WARN_ON_ONCE and also would be helpful to use the verbose version and print
some meaningful message
--
~Vinod
--
To unsubscribe from this list: send the line "unsubscribe dmaengine" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
