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| author | Jassi Brar <jaswinder.singh@linaro.org> | 2011-10-13 12:33:30 +0530 |
|---|---|---|
| committer | Vinod Koul <vinod.koul@linux.intel.com> | 2011-11-18 12:16:24 +0530 |
| commit | b14dab792dee3245b628e046d80a7fad5573fea6 (patch) | |
| tree | c77574d19be7c150b57bd9a9b0184580c733621b /Documentation/dmaengine.txt | |
| parent | e0d23ef29ed637dc6bd739f590985746d9ad9caa (diff) | |
| download | lwn-b14dab792dee3245b628e046d80a7fad5573fea6.tar.gz lwn-b14dab792dee3245b628e046d80a7fad5573fea6.zip | |
DMAEngine: Define interleaved transfer request api
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>
Diffstat (limited to 'Documentation/dmaengine.txt')
| -rw-r--r-- | Documentation/dmaengine.txt | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/Documentation/dmaengine.txt b/Documentation/dmaengine.txt index 94b7e0f96b38..bbe6cb3d1856 100644 --- a/Documentation/dmaengine.txt +++ b/Documentation/dmaengine.txt @@ -75,6 +75,10 @@ The slave DMA usage consists of following steps: slave_sg - DMA a list of scatter gather buffers from/to a peripheral dma_cyclic - Perform a cyclic DMA operation from/to a peripheral till the operation is explicitly stopped. + interleaved_dma - This is common to Slave as well as M2M clients. For slave + address of devices' fifo could be already known to the driver. + Various types of operations could be expressed by setting + appropriate values to the 'dma_interleaved_template' members. A non-NULL return of this transfer API represents a "descriptor" for the given transaction. @@ -89,6 +93,10 @@ The slave DMA usage consists of following steps: struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len, size_t period_len, enum dma_data_direction direction); + struct dma_async_tx_descriptor *(*device_prep_interleaved_dma)( + struct dma_chan *chan, struct dma_interleaved_template *xt, + unsigned long flags); + The peripheral driver is expected to have mapped the scatterlist for the DMA operation prior to calling device_prep_slave_sg, and must keep the scatterlist mapped until the DMA operation has completed. |