dmaengine: rcar-dmac: Fix residue reporting for pending descriptors

Cookies corresponding to pending transfers have a residue value equal to
the full size of the corresponding descriptor. The driver miscomputes
that and uses the size of the active descriptor instead. Fix it.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
[geert: Also check desc.active list]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

1 files changed, 29 insertions, 2 deletions

diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index 561476c1e741..0dd953884d1d 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -1145,6 +1145,7 @@ static unsigned int rcar_dmac_chan_get_residue(struct rcar_dmac_chan *chan,
         struct rcar_dmac_desc *desc = chan->desc.running;
         struct rcar_dmac_xfer_chunk *running = NULL;
         struct rcar_dmac_xfer_chunk *chunk;
+        enum dma_status status;
         unsigned int residue = 0;
         unsigned int dptr = 0;
 
@@ -1152,12 +1153,38 @@ static unsigned int rcar_dmac_chan_get_residue(struct rcar_dmac_chan *chan,
                 return 0;
 
         /*
+         * If the cookie corresponds to a descriptor that has been completed
+         * there is no residue. The same check has already been performed by the
+         * caller but without holding the channel lock, so the descriptor could
+         * now be complete.
+         */
+        status = dma_cookie_status(&chan->chan, cookie, NULL);
+        if (status == DMA_COMPLETE)
+                return 0;
+
+        /*
          * If the cookie doesn't correspond to the currently running transfer
          * then the descriptor hasn't been processed yet, and the residue is
          * equal to the full descriptor size.
          */
-        if (cookie != desc->async_tx.cookie)
-                return desc->size;
+        if (cookie != desc->async_tx.cookie) {
+                list_for_each_entry(desc, &chan->desc.pending, node) {
+                        if (cookie == desc->async_tx.cookie)
+                                return desc->size;
+                }
+                list_for_each_entry(desc, &chan->desc.active, node) {
+                        if (cookie == desc->async_tx.cookie)
+                                return desc->size;
+                }
+
+                /*
+                 * No descriptor found for the cookie, there's thus no residue.
+                 * This shouldn't happen if the calling driver passes a correct
+                 * cookie value.
+                 */
+                WARN(1, "No descriptor for cookie!");
+                return 0;
+        }
 
         /*
          * In descriptor mode the descriptor running pointer is not maintained