Date:	Mon, 30 Jan 2012 13:23:50 +0530
From:	Ravi Kumar V <kumarrav@...eaurora.org>
To:	Vinod Koul <vinod.koul@...el.com>
CC:	linux-arch@...r.kernel.org, tsoni@...eaurora.org,
	linux@....linux.org.uk, arnd@...db.de,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	bryanh@...eaurora.org, johlstei@...eaurora.org,
	Daniel Walker <dwalker@...o99.com>, dan.j.williams@...el.com,
	davidb@...eaurora.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 0/2] Add Qualcomm MSM ADM DMAEngine driver

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.

-- 
Sent by a consultant of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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