On Tue, Apr 15, 2014 at 05:13:32PM +0200, Laurent Pinchart wrote:
> Fly-by transfer mode cuts down the number of bus transactions by letting
> the slave drive or latch the memory data bus during memory transactions
?? ^^^^^^^^^^^
> instead of performing a dedicated transaction to read data from or write
/ ^^^^
> data to the slave.
>
> Support for fly-by mode by adding a new flag field to struct
> dma_slave_config.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> ---
> include/linux/dmaengine.h | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index c5c92d5..ae99153 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -304,6 +304,17 @@ enum dma_slave_buswidth {
> };
>
> /**
> + * enum dma_slave_flags - DMA slave configuration flags
> + * @DMA_SLAVE_FLAG_FLY_BY - perform DMA transfers for the slave in fly-by mode.
> + * Instead of performing a bus transaction to read (write) data from (to) the
> + * slave, let the slave drive (latch) the memory bus data signals during the
> + * memory write (read) transaction.
> + */
> +enum dma_slave_flags {
> + DMA_SLAVE_FLAG_FLY_BY = (1 << 0),
> +};
> +
> +/**
> * struct dma_slave_config - dma slave channel runtime config
> * @direction: whether the data shall go in or out on this slave
> * channel, right now. DMA_MEM_TO_DEV and DMA_DEV_TO_MEM are
> @@ -333,6 +344,7 @@ enum dma_slave_buswidth {
> * @slave_id: Slave requester id. Only valid for slave channels. The dma
> * slave peripheral will have unique id as dma requester which need to be
> * pass as slave config.
> + * @flags: DMA slave flags, a combination of enum dma_slave_flags flags.
> *
> * This struct is passed in as configuration data to a DMA engine
> * in order to set up a certain channel for DMA transport at runtime.
> @@ -361,6 +373,7 @@ struct dma_slave_config {
> u32 dst_maxburst;
> bool device_fc;
> unsigned int slave_id;
> + u32 flags;
> };
I am not sure about this. Should we have a generic flag for this or just add a
bool for fly_by mode?
Suggestions?
--
~Vinod
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