dmaengine: sh: rcar-dmac: Fix glitch in dmaengine_tx_status
The tx_status poll in the rcar_dmac driver reads the status register which indicates which chunk is busy (DMACHCRB). Afterwards the point inside the chunk is read from DMATCRB. It is possible that the chunk has changed between the two reads. The result is a non-monotonous increase of the residue. Fix this by introducing a 'safe read' logic. Fixes: 73a47bd0 ("dmaengine: rcar-dmac: use TCRB instead of TCR for residue") Signed-off-by: Achim Dahlhoff <Achim.Dahlhoff@de.bosch.com> Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com> Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com> Cc: <stable@vger.kernel.org> # v4.16+ Signed-off-by: Vinod Koul <vkoul@kernel.org>
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