On 02-07-18, 18:18, Yoshihiro Shimoda wrote:
> This patch fixes an issue that unexpected retransfering happens
> if TCR is set to 0 before rcar_dmac_sync_tcr() writes DE bit to
> the CHCR register. For example, sh-sci driver can reproduce this
> issue like below:
>
> In rx_timer_fn(): /* CHCR DE bit may be set to 1 */
> dmaengine_tx_status()
> rcar_dmac_tx_status()
> rcar_dmac_chan_get_residue()
> rcar_dmac_sync_tcr() /* TCR is possible to be set to 0 */
>
> According to the description of commit 73a47bd0da66 ("dmaengine:
> rcar-dmac: use TCRB instead of TCR for residue"), "this buffered data
> will be transferred if CHCR::DE bit was cleared". So, this patch
> doesn't need to check TCRB register.
>
> Fixes: 73a47bd0da66 ("dmaengine: rcar-dmac: use TCRB instead of TCR for
> residue")
> Signed-off-by: Yoshihiro Shimoda <[email protected]>
> ---
> This patch is based on the latest slave-dma / fixes branch.
>
> This issue can be reproduced by the following commands on r8a7795
> Salvator-XS and Windows Teraterm :) :
> # stty 921600
> (Change Teraterm baud rate)
> # cat > rx.txt
> (Send 5MiB file by Teraterm. After a few minutes later, we cannot
> input any commands by the serial console.)
Ack/tested-by ..?
>
> drivers/dma/sh/rcar-dmac.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
> index 2a2ccd9..8305a1c 100644
> --- a/drivers/dma/sh/rcar-dmac.c
> +++ b/drivers/dma/sh/rcar-dmac.c
> @@ -774,8 +774,9 @@ static void rcar_dmac_sync_tcr(struct rcar_dmac_chan
> *chan)
> /* make sure all remaining data was flushed */
> rcar_dmac_chcr_de_barrier(chan);
>
> - /* back DE */
> - rcar_dmac_chan_write(chan, RCAR_DMACHCR, chcr);
> + /* back DE if remain data exists */
> + if (rcar_dmac_chan_read(chan, RCAR_DMATCR))
> + rcar_dmac_chan_write(chan, RCAR_DMACHCR, chcr);
> }
>
> static void rcar_dmac_chan_halt(struct rcar_dmac_chan *chan)
> --
> 1.9.1
>
> --
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--
~Vinod
