Define a new api that could be used for doing fancy data transfers
like interleaved to contiguous copy and vice-versa.
Traditional SG_list based transfers tend to be very inefficient in
such cases as where the interleave and chunk are only a few bytes,
which call for a very condensed api to convey pattern of the transfer.
This api supports all 4 variants of scatter-gather and contiguous transfer.
Of course, neither can this api help transfers that don't lend to DMA by
nature, i.e, scattered tiny read/writes with no periodic pattern.
Also since now we support SLAVE channels that might not provide
device_prep_slave_sg callback but device_prep_interleaved_dma,
remove the BUG_ON check.
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
Acked-by: Barry Song <Baohua.Song@csr.com>
[renamed dmaxfer_template to dma_interleaved_template
did fixup after the enum dma_transfer_merge]
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
Improve the documentation for the slave and cyclic DMA engine support
reformatting it for easier reading, adding further APIs, splitting it
into five steps, and including references to the documentation in
dmaengine.h.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
[Fixed the index title to reflect new changes]
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
"Wouldn't it be better if the dmaengine layer made sure it didn't pass
the same channel several times to a client?
I mean, you seem concerned that the memcpy() API should be transparent
and easy to use, but the whole registration interface is just
ridiculously complicated..."
- Haavard
The dmaengine and async_tx registration/allocation interface is indeed
needlessly complicated. This redesign has the following goals:
1/ Simplify reference counting: dma channels are not something one would
expect to be hotplugged, it should be an exceptional event handled by
drivers not something clients should be mandated to handle in a
callback. The common case channel removal event is 'rmmod <dma driver>',
which for simplicity should be disallowed if the channel is in use.
2/ Add an interface for requesting exclusive access to a channel
suitable to device-to-memory users.
3/ Convert all memory-to-memory users over to a common allocator, the goal
here is to not have competing channel allocation schemes. The only
competition should be between device-to-memory exclusive allocations and
the memory-to-memory usage case where channels are shared between
multiple "clients".
Cc: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Jeff Garzik <jeff@garzik.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
