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    Subject[PATCH 1/3] dmaengine: add possibility for cyclic transfers
    Date
    Cyclic transfers are useful for audio where a single buffer divided
    in periods has to be transfered endlessly until stopped. After being
    prepared the transfer is started using the dma_async_descriptor->tx_submit
    function. dma_async_descriptor->callback is called after each period.
    The transfer is stopped using the DMA_TERMINATE_ALL callback.
    While being used for cyclic transfers the channel cannot be used
    for other transfer types.

    Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
    Cc: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
    ---
    drivers/dma/dmaengine.c | 2 ++
    include/linux/dmaengine.h | 6 +++++-
    2 files changed, 7 insertions(+), 1 deletions(-)

    diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
    index 9d31d5e..e5e79ce 100644
    --- a/drivers/dma/dmaengine.c
    +++ b/drivers/dma/dmaengine.c
    @@ -692,6 +692,8 @@ int dma_async_device_register(struct dma_device *device)
    !device->device_prep_dma_interrupt);
    BUG_ON(dma_has_cap(DMA_SLAVE, device->cap_mask) &&
    !device->device_prep_slave_sg);
    + BUG_ON(dma_has_cap(DMA_CYCLIC, device->cap_mask) &&
    + !device->device_prep_dma_cyclic);
    BUG_ON(dma_has_cap(DMA_SLAVE, device->cap_mask) &&
    !device->device_control);

    diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
    index c61d4ca..0df7864 100644
    --- a/include/linux/dmaengine.h
    +++ b/include/linux/dmaengine.h
    @@ -67,10 +67,11 @@ enum dma_transaction_type {
    DMA_PRIVATE,
    DMA_ASYNC_TX,
    DMA_SLAVE,
    + DMA_CYCLIC,
    };

    /* last transaction type for creation of the capabilities mask */
    -#define DMA_TX_TYPE_END (DMA_SLAVE + 1)
    +#define DMA_TX_TYPE_END (DMA_CYCLIC + 1)


    /**
    @@ -478,6 +479,9 @@ struct dma_device {
    struct dma_chan *chan, struct scatterlist *sgl,
    unsigned int sg_len, enum dma_data_direction direction,
    unsigned long flags);
    + struct dma_async_tx_descriptor *(*device_prep_dma_cyclic)(
    + struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
    + size_t period_len, enum dma_data_direction direction);
    int (*device_control)(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
    unsigned long arg);

    --
    1.7.1


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