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>

1 files changed, 2 insertions, 0 deletions

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);