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dmaengine: add helper function to request a slave DMA channel 

Currently slave DMA channels are requested by calling dma_request_channel()
and requires DMA clients to pass various filter parameters to obtain the
appropriate channel.

With device-tree being used by architectures such as arm and the addition of
device-tree helper functions to extract the relevant DMA client information
from device-tree, add a new function to request a slave DMA channel using
device-tree. This function is currently a simple wrapper that calls the
device-tree of_dma_request_slave_channel() function.

Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>

Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
This commit is contained in:
Jon Hunter 2012-09-14 17:41:57 -05:00 committed by Vinod Koul
parent d1c3ed669a
commit 9a6cecc846
2 changed files with 22 additions and 0 deletions
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16
drivers/dma/dmaengine.c
View File

@ -62,6 +62,7 @@
#include <linux/rculist.h>
#include <linux/idr.h>
#include <linux/slab.h>
#include <linux/of_dma.h>
static DEFINE_MUTEX(dma_list_mutex);
static DEFINE_IDR(dma_idr);
@ -546,6 +547,21 @@ struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, v
}
EXPORT_SYMBOL_GPL(__dma_request_channel);
/**
* dma_request_slave_channel - try to allocate an exclusive slave channel
* @dev: pointer to client device structure
* @name: slave channel name
*/
struct dma_chan *dma_request_slave_channel(struct device *dev, char *name)
{
/* If device-tree is present get slave info from here */
if (dev->of_node)
return of_dma_request_slave_channel(dev->of_node, name);
return NULL;
}
EXPORT_SYMBOL_GPL(dma_request_slave_channel);
void dma_release_channel(struct dma_chan *chan)
{
mutex_lock(&dma_list_mutex);

6
include/linux/dmaengine.h
View File

@ -974,6 +974,7 @@ enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie);
enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx);
void dma_issue_pending_all(void);
struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param);
struct dma_chan *dma_request_slave_channel(struct device *dev, char *name);
void dma_release_channel(struct dma_chan *chan);
#else
static inline enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx)
@ -988,6 +989,11 @@ static inline struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask,
{
return NULL;
}
static inline struct dma_chan *dma_request_slave_channel(struct device *dev,
char *name)
{
return NULL
}
static inline void dma_release_channel(struct dma_chan *chan)
{
}