Re: [PATCH v2 03/15] dmaengine: Add no_wakeup parameter to dmaengine_prep_dma_cyclic()

From: Peter Ujfalusi
Date: Fri Sep 14 2012 - 03:14:18 EST

On 09/13/2012 06:38 PM, Russell King - ARM Linux wrote:
> On Thu, Sep 13, 2012 at 05:27:09PM +0200, Lars-Peter Clausen wrote:
>> Hm... Do you think it would work as well if we implement this by setting the
>> callback for the descriptor to NULL? If the callback is NULL there is
>> nothing to at the end of a transfer/period and the dma engine driver may
>> choose to disable interrupts. This would also benefit non cyclic transfers
>> where the callback is NULL and we do not need add the new parameter to
>> dmaengine_prep_dma_cyclic.
> Actually, there's a way to do that already. DMA_PREP_INTERRUPT.
> Unfortunately, most DMA engine slave API users don't set it when they
> setup their transfer:
> * @DMA_PREP_INTERRUPT - trigger an interrupt (callback) upon completion of
> * this transaction

As I mentioned already to Vinod: the description of this flag is close enough
for our needs (other than the notion of 'this transaction' is not really
correct for cyclic mode).
I will resend the series to add the flags as new parameter instead of the

> if we fixed that, then we could use the lack of it to avoid the interrupt.
> However, cyclic transfers don't have the flags parameter used to pass this
> bit. Yet another bit of yucky inconsistent design in DMA engine land...

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