[alsa-devel] [PATCH v2] ASoC: Intel: Add Cherrytrail & Braswell machine driver cht_bsw_rt5672

[Lin, Mengdong]

> -----Original Message-----
> From: Mark Brown [mailto:broonie at kernel.org]
> Sent: Friday, October 31, 2014 8:54 PM
 
> On Fri, Oct 31, 2014 at 12:48:26PM +0000, Lin, Mengdong wrote:
> 
> > Now we're working with Realtek to enable runtime PM on RT5672 codec
> driver.
> > With help of ACPI,
> > - the codec will be in suspended to D3 when idle , switch to its
> > internal clock,  and BIOS will turn off the platform clock output (MCLK) to
> save power.
> > - And when the codec resumes to D0, BIOS will turn on the clock at
> > first. And  hw_params will make the codec use PLL and lock to MCLK again.
> 
> > Thus the machine driver does not need to explicitly turn on/off the
> > platform codec by itself.
> 
> If the machine driver has asked for the PLL to be on I'd expect the CODEC
> driver to be respecting that...

The codec driver rt5670 defines a supply widget to control the power of PLL.
So the PLL will be power on when there is active audio streaming and power
off when Idle. 
The machine driver need not explicitly turn on/off the PLL, but only need to 
select PLL source to MCLK in hw_params and configure the in/out frequency.

And we've verified to enable runtime PM on the codec driver and trigger ACPI
method to dynamically control the MCLK output from SOC to the codec:
- When codec is active (D0), BIOS will turn on MCLK at first
- When codec is suspended on idle (D3), codec will switch to its internal clock,
 and BIOS will turn off MCLK

I'll post V3 machine driver based on your comments on v2.
After an internal sync, this machine driver will be moved to sound/soc/intel
directory, with other existing Intel machines.

Thanks
Mengdong