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path: root/drivers/dma/sh/rcar-dmac.c
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Diffstat (limited to 'drivers/dma/sh/rcar-dmac.c')
-rw-r--r--drivers/dma/sh/rcar-dmac.c26
1 files changed, 23 insertions, 3 deletions
diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index 54810ffd95e2..e2a5398f89b5 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -1282,6 +1282,9 @@ static unsigned int rcar_dmac_chan_get_residue(struct rcar_dmac_chan *chan,
enum dma_status status;
unsigned int residue = 0;
unsigned int dptr = 0;
+ unsigned int chcrb;
+ unsigned int tcrb;
+ unsigned int i;
if (!desc)
return 0;
@@ -1330,14 +1333,31 @@ static unsigned int rcar_dmac_chan_get_residue(struct rcar_dmac_chan *chan,
}
/*
+ * We need to read two registers.
+ * Make sure the control register does not skip to next chunk
+ * while reading the counter.
+ * Trying it 3 times should be enough: Initial read, retry, retry
+ * for the paranoid.
+ */
+ for (i = 0; i < 3; i++) {
+ chcrb = rcar_dmac_chan_read(chan, RCAR_DMACHCRB) &
+ RCAR_DMACHCRB_DPTR_MASK;
+ tcrb = rcar_dmac_chan_read(chan, RCAR_DMATCRB);
+ /* Still the same? */
+ if (chcrb == (rcar_dmac_chan_read(chan, RCAR_DMACHCRB) &
+ RCAR_DMACHCRB_DPTR_MASK))
+ break;
+ }
+ WARN_ONCE(i >= 3, "residue might be not continuous!");
+
+ /*
* In descriptor mode the descriptor running pointer is not maintained
* by the interrupt handler, find the running descriptor from the
* descriptor pointer field in the CHCRB register. In non-descriptor
* mode just use the running descriptor pointer.
*/
if (desc->hwdescs.use) {
- dptr = (rcar_dmac_chan_read(chan, RCAR_DMACHCRB) &
- RCAR_DMACHCRB_DPTR_MASK) >> RCAR_DMACHCRB_DPTR_SHIFT;
+ dptr = chcrb >> RCAR_DMACHCRB_DPTR_SHIFT;
if (dptr == 0)
dptr = desc->nchunks;
dptr--;
@@ -1355,7 +1375,7 @@ static unsigned int rcar_dmac_chan_get_residue(struct rcar_dmac_chan *chan,
}
/* Add the residue for the current chunk. */
- residue += rcar_dmac_chan_read(chan, RCAR_DMATCRB) << desc->xfer_shift;
+ residue += tcrb << desc->xfer_shift;
return residue;
}