Re: [PATCH] ALSA: ASoC: fix PXA SSP port resume

[Daniel Mack <daniel@caiaq.de>]

On Fri, Jan 29, 2010 at 10:13:08AM +0000, Mark Brown wrote:
> On Thu, Jan 28, 2010 at 06:34:18PM +0800, Daniel Mack wrote:
> > Invalidate the cached hardware format on resume for PXA SSP ports.
> > Otherwise hw_params() will bail out early at the next stream start,
> > leaving the registers in a bogus state.
> 
> Would it not be better to write the cached state back to the hardware?
> Putting an invalid value in the cache seems like asking for trouble.

Hmm. I considered that, but the reason why the system failed to resume
in my case was that the ssp port was not active at this time. Otherwise,
the suspend/resume code would have already done the right thing.

And as the next client will indirectly call hw_params() again, the code
there will do the right thing with the invalidated cache.

Restoring the register values from priv->dai_fmt would imply adding code
to do everything what the other bit-fiddling functions do in a reverse
manner. Which is something I'd like to avoid :)

Another idea is to unconditionally save and restore the register set,
and deal with possible side-effects. Not sure what's really better.

Daniel