Re: [alsa-devel] [PATCH] ASoC: rsnd: Protect register accesses with a spinlock instead of a mutex

[Kuninori Morimoto <kuninori.morimoto.gx@gmail.com>]

Hi Laurent

> > The hardware registers are accessed from atomic contexts (the
> > rsnd_soc_dai_trigger function, for instance, is called with the PCM
> > substream spinlock held). They thus can't be protected by a mutex.
> > 
> > Protect regmap register accesses with a spinlock instead of a mutex by
> > setting the fast_io flag.
> > 
> > Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> > ---
> >  sound/soc/sh/rcar/gen.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > An even better solution might be to use regmap-mmio instead of a custom bus.
> > Morimoto-san, is there anything that would prevent the driver from switching
> > to regmap-mmio ?
> 
> I guess it is possilbe to use regmap-mmio.
> I check it.

Hmm... rsnd driver is using "regmap_field".
regmap-mmio  requests "offset"  on "reg"
regmap-filed requests "address" on "reg"

So, if rsnd driver uses regmap-mmio,
then, it needs tricky initialize like...

      regmap_init_mmio(dev, 0, config)

Best regards
---
Kuninori Morimoto