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 <s.hauer@pengutronix.de>
Cc: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index c61d4ca..32cd84b 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -67,10 +67,11 @@
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 @@
* @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_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);