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SubjectRe: [PATCH 3/3] dmaengine: at_xdmac: only monitor overflow errors for peripheral xfer
On Tue, Feb 05, 2019 at 12:03:43PM +0100, Nicolas Ferre wrote:
> The overflow error flag (ROI: Request Overflow Error) is only relevant
> for the case when the channel handles a peripheral synchronized transfer.
> Not in the case of memory to memory transfer where there is no hardware
> request signal.
>
> Remove the use of this interrupt source in such a case. It's based on
> the first descriptor which holds the configuration for the whole
> linked list transfer.
>
> Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>

> ---
> drivers/dma/at_xdmac.c | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
> index ec7a29d8e448..b558a23ffbc2 100644
> --- a/drivers/dma/at_xdmac.c
> +++ b/drivers/dma/at_xdmac.c
> @@ -308,6 +308,11 @@ static inline int at_xdmac_csize(u32 maxburst)
> return csize;
> };
>
> +static inline bool at_xdmac_chan_is_peripheral_xfer(u32 cfg)
> +{
> + return cfg & AT_XDMAC_CC_TYPE_PER_TRAN;
> +}
> +
> static inline u8 at_xdmac_get_dwidth(u32 cfg)
> {
> return (cfg & AT_XDMAC_CC_DWIDTH_MASK) >> AT_XDMAC_CC_DWIDTH_OFFSET;
> @@ -389,7 +394,13 @@ static void at_xdmac_start_xfer(struct at_xdmac_chan *atchan,
> at_xdmac_chan_read(atchan, AT_XDMAC_CUBC));
>
> at_xdmac_chan_write(atchan, AT_XDMAC_CID, 0xffffffff);
> - reg = AT_XDMAC_CIE_RBEIE | AT_XDMAC_CIE_WBEIE | AT_XDMAC_CIE_ROIE;
> + reg = AT_XDMAC_CIE_RBEIE | AT_XDMAC_CIE_WBEIE;
> + /*
> + * Request Overflow Error is only for peripheral synchronized transfers
> + */
> + if (at_xdmac_chan_is_peripheral_xfer(first->lld.mbr_cfg))
> + reg |= AT_XDMAC_CIE_ROIE;
> +
> /*
> * There is no end of list when doing cyclic dma, we need to get
> * an interrupt after each periods.
> --
> 2.17.1
>

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