[alsa-devel] [PATCH v2 2/2] ASoC: rockchip: i2s: add support for grabbing output clock to codec

[Mark Brown]

On Wed, Dec 03, 2014 at 11:38:13AM -0800, Sonny Rao wrote:
> On Wed, Dec 3, 2014 at 11:20 AM, Mark Brown <broonie at kernel.org> wrote:

> > I would expect that the clock for the CODEC should be managed by the
> > CODEC if at all possible - that seems more logical than having the CPU
> > I2S controller request and manage it if it's a separate clock.  Why add
> > this to the CPU side driver?

> This output clock has a mux and can either be a fixed 12Mhz output or
> can be derived from the same fractional divider which drives the i2s
> block.   I thought it was simpler to keep them all the same, but need
> to put ownership in the i2s in anticipation of the i2s driver setting
> it's own clock rate.

> If you think this is an implementation detail and this output clock
> should just be owned by the codec driver, even though I'm guessing it
> will just have to be the same as i2s, then I think we can drop this
> and make sure simple card (or whatever other codec driver) claims this
> clock.

simple-card obviously isn't a CODEC driver...  For generality I think
the clock does need to be exposed to the CODEC driver, otherwise this
will work differently to how other systems are working and we can't
substitute in a different clock on the CODEC side so easily if it
doesn't happen to use the output from the I2S block.
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