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authorJassi Brar <jaswinder.singh@linaro.org>2011-10-13 12:33:30 +0530
committerVinod Koul <vinod.koul@linux.intel.com>2011-11-18 12:16:24 +0530
commitb14dab792dee3245b628e046d80a7fad5573fea6 (patch)
treec77574d19be7c150b57bd9a9b0184580c733621b /Documentation/dmaengine.txt
parente0d23ef29ed637dc6bd739f590985746d9ad9caa (diff)
downloadlinux-linaro-stable-b14dab792dee3245b628e046d80a7fad5573fea6.tar.gz
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.txt8
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.