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

Peter Ujfalusi peter.ujfalusi at ti.com
Fri Sep 14 03:15:05 EDT 2012

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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