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rapidio/tsi721_dma: rework scatter-gather list handling

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Rework Tsi721 RapidIO DMA engine support to allow handling data
scatter/gather lists longer than number of hardware buffer descriptors in
the DMA channel's descriptor list.

The current implementation of Tsi721 DMA transfers requires that number of
entries in a scatter/gather list provided by a caller of
dmaengine_prep_rio_sg() should not exceed number of allocated hardware
buffer descriptors.

This patch removes the limitation by processing long scatter/gather lists
by sections that can be transferred using hardware descriptor ring of
configured size.  It also introduces a module parameter
"dma_desc_per_channel" to allow run-time configuration of Tsi721 hardware
buffer descriptor rings.

Signed-off-by: Alexandre Bounine <[email protected]>
Cc: Matt Porter <[email protected]>
Cc: Andre van Herk <[email protected]>
Cc: Stef van Os <[email protected]>
Cc: Vinod Koul <[email protected]>
Cc: Dan Williams <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Alexandre Bounine 2014-08-08 14:22:12 -07:00 • committed by Linus Torvalds
commit 50835e977b
3 changed files with 394 additions and 355 deletions
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19
Documentation/rapidio/tsi721.txt
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@ -20,13 +20,26 @@ II. Known problems
None.
III. To do
III. DMA Engine Support
Add DMA data transfers (non-messaging).
Add inbound region (SRIO-to-PCIe) mapping.
Tsi721 mport driver supports DMA data transfers between local system memory and
remote RapidIO devices. This functionality is implemented according to SLAVE
mode API defined by common Linux kernel DMA Engine framework.
Depending on system requirements RapidIO DMA operations can be included/excluded
by setting CONFIG_RAPIDIO_DMA_ENGINE option. Tsi721 miniport driver uses seven
out of eight available BDMA channels to support DMA data transfers.
One BDMA channel is reserved for generation of maintenance read/write requests.
If Tsi721 mport driver have been built with RAPIDIO_DMA_ENGINE support included,
this driver will accept DMA-specific module parameter:
"dma_desc_per_channel" - defines number of hardware buffer descriptors used by
each BDMA channel of Tsi721 (by default - 128).
IV. Version History
1.1.0 - DMA operations re-worked to support data scatter/gather lists larger
than hardware buffer descriptors ring.
1.0.0 - Initial driver release.
V. License