Re: [PATCH 1/2] dma: axi-dmac: Only use hardware cyclic mode for single segment transfers

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I screwed up, the subject prefix should of course be "dmaengine" and not
"dma". Vinod can you fix this up, or should I resend?

On 09/05/2017 10:16 AM, Lars-Peter Clausen wrote:
> In hardware cyclic mode the submitted segment is repeated. This means
> hardware cyclic mode can only be used if the transfer has a single segment.
> 
> Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
> ---
>  drivers/dma/dma-axi-dmac.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/dma-axi-dmac.c b/drivers/dma/dma-axi-dmac.c
> index 7f0b9aa15867..eb289aa187dd 100644
> --- a/drivers/dma/dma-axi-dmac.c
> +++ b/drivers/dma/dma-axi-dmac.c
> @@ -220,9 +220,11 @@ static void axi_dmac_start_transfer(struct axi_dmac_chan *chan)
>  
>  	/*
>  	 * If the hardware supports cyclic transfers and there is no callback to
> -	 * call, enable hw cyclic mode to avoid unnecessary interrupts.
> +	 * call and only a single segment, enable hw cyclic mode to avoid
> +	 * unnecessary interrupts.
>  	 */
> -	if (chan->hw_cyclic && desc->cyclic && !desc->vdesc.tx.callback)
> +	if (chan->hw_cyclic && desc->cyclic && !desc->vdesc.tx.callback &&
> +		desc->num_sgs == 1)
>  		flags |= AXI_DMAC_FLAG_CYCLIC;
>  
>  	axi_dmac_write(dmac, AXI_DMAC_REG_X_LENGTH, sg->x_len - 1);
> 

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