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

Mark Brown broonie at kernel.org
Mon Jan 27 11:55:08 CET 2014

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
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