lkml.org 
[lkml]   [2010]   [Aug]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
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


\
 
 \ /
  Last update: 2010-08-16 13:11    [from the cache]
©2003-2011 Jasper Spaans