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

[Ravi Kumar V]

On 1/25/2012 6:41 PM, Ravi Kumar V wrote:
> 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.
>
> Thanks,
> Ravi Kumar

Please can you suggest best way.

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