Commit 782bc950 authored by Sascha Hauer's avatar Sascha Hauer Committed by Dan Williams
Browse files

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: default avatarSascha Hauer <s.hauer@pengutronix.de>
Cc: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent b30a3f62

drivers/dma/dmaengine.c

+2 −0
Original line number Diff line number Diff line
@@ -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);

include/linux/dmaengine.h

+8 −1
Original line number Diff line number Diff line
@@ -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);

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