From: Muhammad Hamza Farooq <mfarooq@xxxxxxxxxxx>
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>
---
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");
+ } 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);
+
+ return ret;
}
static void rcar_dmac_chan_reinit(struct rcar_dmac_chan *chan)
--
1.9.1
--
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