[alsa-devel] [PATCH] ASoC: arizona: Check clocking during hw_params rather than startup

Charles Keepax ckeepax at opensource.wolfsonmicro.com
Mon Jan 27 12:25:26 CET 2014

On Mon, Jan 27, 2014 at 10:55:08AM +0000, Mark Brown wrote:
> On Mon, Jan 27, 2014 at 08:17:18AM +0100, Lars-Peter Clausen wrote:
> > On 01/24/2014 06:37 PM, Mark Brown wrote:
> > > Thanks, that's about what I was going to write.  The current theory is
> > > that setting the sysclk to zero is the equivalent of a dynamic SYSCLK
> > > flag - with the extensive use of charge pumps and so on in modern
> > > devices on the fly reclocking is normally difficult to do safely so the
> > > idea is that if the machine driver is in a position to reclock it should
> > > set the clock to zero.
> > It's a bit ugly though to set the clock to 0 in the startup callback of the
> > machine driver and then set it to the actual sysclk in the hw_params callback.
> If something is doing this I'd expect it to set the clock to zero when
> it is idled rather than during startup() - set_bias_level() is usually a
> good place to do this, or possibly a DAPM widget supplying the clocks in
> the device if the clocks are visible in DAPM.  That's a bit nicer and
> doing it on startup runs into issues with things like bypass paths
> anyway.

Yeah I think the existing support is actually likely sufficent
looks likely this was actually an issue with the machine driver
in question, apologies for the noise.


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