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

From: Vinod Koul
Date: Thu Sep 13 2012 - 23:33:38 EST

On Thu, 2012-09-13 at 16:38 +0100, 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
Looks like I have repeated the correct action!
> 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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