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;
 }