Re: [PATCH v2 0/2] Add Qualcomm MSM ADM DMAEngine driver

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On 1/23/2012 7:21 PM, Vinod Koul wrote:
On Mon, 2012-01-23 at 16:41 +0530, Ravi Kumar V wrote:

If some changes are made in interleave API then it can support our BOX
mode. Here in interleaved template he is assuming destination pattern as
can be contiguous or same as source pattern, but in our case destination
pattern is different from source pattern.
So if a new parameter destination data chunk is added in "struct
dma_interleaved_template" structure then it can support different
destination pattern.
do you mean you have cases where you are doing a "memcpy" from one
interleaved memory to another?
Can you provide me with a scenario where this maybe helpful?

Presently we are transferring data from interleaved memory tho contagious memory and vice-verse. We can use the interleaved API for present scenario, but it will restrict the HW capability of transferring data from one interleaved pattern to other interleaved pattern.

The reason why the API was designed like this was to give ability to
take these kind of interleaved memory and copy them to peripheral
(constant addr) or memory (typically contagious).

In case it is just a pattern I wonder why it cannot be described in
standard scatter gather definitions as you can split the block further
down to copy from one respective block to somewhere else in memory.

We can use scatter gather but it will be extra burden on software to create those many SG list unlike in box mode just a single command serves the purpose.

Also it will good if you can provide another parameter for passing
private data to dma driver.
1. what does this parameter do?

Private parameter in our case will be command configuration parameter where we are passing information to HW like endianness, synchronization & acknowledge mechanism between DMA HW and peripherals running with different clock than DMA.

2. is this parameter static for a channel or it changes per transfer?

This parameter changes per each transfer.

We can see these possibilities to implement our DMA driver but still have to add new parameter in "scatterlist" & "interleaved template" for supporting per transfer private data like our command configuration parameter.

1.We have to add new parameter "struct data_chunk" in "interleaved_template" for supporting different destination pattern.
It helps a lot for implementing our total HW capability.

2.We have to use present API's for box mode.
--scatter gather API for different interleaved source & destination patterns. --interleaved API for interleaved source pattern to destination contiguous pattern/vice-verse.
It causes some extra burden on our software to create sglist.

3.Implement New API for BOX mode.

I feel if we can go with first option then it helps a lot.

Please can you suggest a better way to solve our problem.

Ravi Kumar

Sent by a consultant of the Qualcomm Innovation Center, Inc.
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