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DMAEngine: Define interleaved transfer request api

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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 <[email protected]>
Acked-by: Barry Song <[email protected]>
[renamed dmaxfer_template to dma_interleaved_template
 did fixup after the enum dma_transfer_merge]
Signed-off-by: Vinod Koul <[email protected]>
This commit is contained in:
Jassi Brar 2011-10-13 12:33:30 +05:30 • committed by Vinod Koul
commit b14dab792d
3 changed files with 85 additions and 5 deletions
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8
Documentation/dmaengine.txt
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@ -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.