[PATCH v4 02/10] dmaengine: Actions: Add support for S700 DMA engine

Vinod Koul vkoul at kernel.org
Mon Jun 29 09:21:41 EDT 2020

On 29-06-20, 12:19, André Przywara wrote:
> On 29/06/2020 10:54, Vinod Koul wrote:

> >> What newer SoCs? I don't think we should try to guess the future here.
> > 
> > In a patch for adding new SoC, quite ironical I would say!
> S700 is not a new SoC, it's just this driver didn't support it yet. What
> I meant is that I don't even know about the existence of upcoming SoCs
> (Google seems clueless), not to speak of documentation to assess which
> DMA controller they use.
> >> We can always introduce further abstractions later, once we actually
> >> *know* what we are looking at.
> > 
> > Rather if we know we are adding abstractions, why not add in a way that
> > makes it scale better rather than rework again
> I appreciate the effort, but this really tapping around in the dark,
> since we don't know which direction any new DMA controller is taking. I
> might not even be similar.
> >> Besides, I don't understand what you are after. The max frame length is
> >> 1MB in both cases, it's just a matter of where to put FCNT_VAL, either
> >> in FLEN or in CTRLB. And having an extra flag for that in driver data
> >> sounds a bit over the top at the moment.
> > 
> > Maybe, maybe not. I would rather make it support N SoC when adding
> > support for second one rather than keep adding everytime a new SoC is
> > added...
> Well, what do you suggest, specifically? At the moment we have two
> *slightly* different DMA controllers, so we differentiate between the
> two based on the model. Do you want to introduce an extra flag like
> FRAME_CNT_IN_CTRLB? That seems to be a bit over the top here, since we
> don't know if a future DMA controller is still compatible, or introduces
> completely new differences.

Fair enough, okay let us go with compatible for now


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