Re: DMA

[mahdi hamzeh]

Paul,

Thanks for your help. You were right. There was a version mismatch
between my header files and I got it fixed. I could compile all
related dma modules including async modules. However, I cannot use dma
engine because I receive following error when I run my code,
"__dma_request_channel: fail ((null))". Even I tried
Documentation/crypto/async-tx-api.txt but it turns out that when I
issue a transaction such that "async_memcpy" and I wait for
transaction to be completed by "wait_for_completion", it is never
completed. Is this problem related to my machine or my code?

Here is my code:

struct async_submit_ctl submit;
struct completion cmp;
init_completion(&cmp);
init_async_submit(&submit, flag, NULL, NULL, &cmp,  addr_conv);
desc=async_memcpy(dest, src, 0, 0, 10,  &submit);
async_tx_issue_pending_all();
wait_for_completion(&cmp);

My other code:

dma_cap_mask_t myMask;
dma_cap_zero(myMask);
dma_cap_set(DMA_PRIVATE, myMask); //I tried different combination of
flags like DMA_MEMCPY ,....
myDMAChannel = dma_request_channel(myMask, NULL, filter_param);

myDMAChannel is always NULL.


Thanks

On Tue, Jan 25, 2011 at 12:15 AM, Paul Mundt <lethal@xxxxxxxxxxxx> wrote:
> On Mon, Jan 24, 2011 at 04:04:57PM -0700, mahdi hamzeh wrote:
>> I am working on a research project for which I should be able to
>> transfer data from memory to memory using DMA. I am working on a x86
>> machine but I want my code to be architecture independent as much as
>> possible. Please?accept?my?apology?if my question is too basic to be
>> asked from this mailing list. Here is my problem:
>> I?used "struct dma_chan" to define a channel structure but when I use
>> "dma_request_channel" function to get a DMA channel, with all
>> different possible masks including?DMA_MEMCPY,?DMA_PRIVATE,....
>> anything, the function returns always NULL. This function is defined
>> in "dmaengine.h".?I also tried a low level function to see dma channel
>> availability?and "request_dma" function defined in "dma.h" works
>> perfect.
>> Any comment, help, document, program, reference anything that helps me
>> to create a simple DMA transaction would really be appreciated.
>> PS: There is a test program called dmatest.c is provided in the linux
>> kernel files. I tried to get it compiled but I could not since the
>> functions and structures used in this file has been changed in the
>> kernel header files.
>>
> I'm not sure how you selected the sh list as the best forum for this
> inquiry (I assume it's because Guennadi has been doing a lot of dmaengine
> driver work recently), but this is really something that's better suited
> for l-k directly, with Dan CC'ed (as I've done here).
>
> If you're looking for preliminary getting started information, then your
> best bet is Documentation/crypto/async-tx-api.txt, as referenced in the
> top-level MAINTAINERS.
>
> The dmatest driver of course also provides you with some examples of how
> to plug in to the API. In any event, I'm able to compile dmatest without
> any difficulty, so I'm not sure what bitrot you are seeing, perhaps it's
> something related to the driver you are using? You'll have to provide the
> relevant bits from your .config or the errors you're seeing before anyone
> will be able to point you in the right direction here.
>



-- 
---Mahdi Hamzeh
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