Re: [PATCH v2] spi: qup: Add DMA capabilities

[Andy Gross <agross@codeaurora.org>]

On Tue, Feb 24, 2015 at 06:08:54PM +0200, Stanimir Varbanov wrote:

<snip>

> 
> yes, there is a potential race between atomic_inc and dma callback. I
> reordered these calls to save few checks, and now it returns to me.
> 
> I imagine few options here:
> 
>  - reorder the dmaengine calls and atomic operations, i.e.
> call atomic_inc for rx and tx channels before corresponding
> dmaengine_submit and dmaengine_issue_pending.
> 
>  - have two different dma callbacks and two completions and waiting for
> the two.

This is probably the better solution.  The only thing you'll have to take into
consideration is that you may not have a RX DMA transactions.

> 
>  - manage to receive only one dma callback, i.e. the last transfer in
> case of presence of the rx_buf and tx_buf at the same time.

You use separate channels for the RX and TX, so as long as you have separate
callbacks, it shouldnt be a problem.


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