linux-kernel - Re: [PATCH 3/3] dmaengine: at_xdmac: only monitor overflow errors for peripheral xfer

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Date:   Tue, 5 Feb 2019 13:35:10 +0100
From:   Ludovic Desroches <ludovic.desroches@...rochip.com>
To:     Nicolas Ferre <nicolas.ferre@...rochip.com>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <dmaengine@...r.kernel.org>, "Vinod Koul" <vkoul@...nel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [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@...rochip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@...rochip.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
>