From 782bc950d84e404422ba21008fd51ee894c8d231 Mon Sep 17 00:00:00 2001 From: Sascha Hauer Date: Thu, 30 Sep 2010 13:56:32 +0000 Subject: [PATCH] dmaengine: add possibility for cyclic transfers 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 Cc: Haavard Skinnemoen Signed-off-by: Dan Williams --- drivers/dma/dmaengine.c | 2 ++ include/linux/dmaengine.h | 9 ++++++++- 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index 9d31d5eb95c1..e5e79ced4f4b 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 c61d4ca27bcc..32cd84b47478 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) /** @@ -422,6 +423,9 @@ struct dma_tx_state { * @device_prep_dma_memset: prepares a memset operation * @device_prep_dma_interrupt: prepares an end of chain interrupt operation * @device_prep_slave_sg: prepares a slave dma operation + * @device_prep_dma_cyclic: prepare a cyclic dma operation suitable for audio. + * The function takes a buffer of size buf_len. The callback function will + * be called after period_len bytes have been transferred. * @device_control: manipulate all pending operations on a channel, returns * zero or error code * @device_tx_status: poll for transaction completion, the optional @@ -478,6 +482,9 @@ 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); -- 2.20.1