From mboxrd@z Thu Jan  1 00:00:00 1970
From: Kuninori Morimoto <kuninori.morimoto.gx@gmail.com>
Subject: Re: About snd_dmaengine_pcm_trigger()
Date: Tue, 11 Mar 2014 17:28:07 -0700 (PDT)
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To: Mark Brown <broonie@kernel.org>
Cc: Linux-ALSA <alsa-devel@alsa-project.org>, Lars-Peter Clausen <lars@metafoo.de>, Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>, Simon <horms@verge.net.au>, Liam Girdwood <lgirdwood@gmail.com>
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Hi Lars, Mark

> > The reason why we factored out the dmaengine DMA stuff is because
> > there is a standard API that hides the implementation details and is
> > supposed to behave the same for each system. For PIO you do not have
> > such a abstraction layer that hides the details, so I'm not sure how
> > similar PIO between different platforms will actually be.
> 
> I keep thinking that there ought to be *some* commonality between the
> platforms that use FIQs if only in the timer stuff at least.  Part of
> the reason that doesn't get factored out is that it's normally just a
> temporary bodge until DMA is working of course, though Qualcomm do it
> because their DMA for the DSP doesn't fit well with dmaengine and the
> i.MX AC'97 needs it since the hardware doesn't fully understand AC'97.

Yes, there is no pioengine (never created :)
I'm not sure detail of non-Renesas platform driver whether it is supporting PIO.
But at least my driver (= FSI/rcar) has PIO support,
and I think these can share same method/function.
So, I create pcm_pio.c under ${LINUX}/sound/soc/sh for Renesas chip
with pcm_dmaengine similar style (as much as possible).
And, use common ${LINUX}/sound/core/pcm_dmaengine.c for DMA.
How about this ?