[PATCH RFC] clk: add support for automatic parent handling

[Tony Lindgren]

* Mark Brown <broonie at opensource.wolfsonmicro.com> [110421 03:29]:
> On Thu, Apr 21, 2011 at 11:12:36AM +0200, Thomas Gleixner wrote:
> > On Thu, 21 Apr 2011, Uwe Kleine-K?nig wrote:
> 
> > > If there were a pointer tracking the parent you still needed to program
> > > out the get_parent function anyhow to set the pointer initially. But I
> > > agree that in other situations having a pointer is more comfortable and
> > > saves ugly error handling e.g. in set_parent.
> 
> > That's nonsense. Why do you want a get_parent() function at all?
> > parent is set up when the clock is established in the clock tree. And
> > that's not done by some random driver. That's a property of the clock.
> 
> That's not universal - right now the drivers can and do know about this
> on some platforms.  In some cases there will be requirements beyond the
> clock rate which mean that the driver will need to be able to tell the
> framework that, for example, it needs one clock to be in the same clock
> domain as another.

Also there can be multiple parent clocks. An example are the timers on
omaps where the parent clock can be either the 32KiHz clock or external
source clock. Τhis may need to be reprogrammed dynamically in some cases
for advanced idle modes as one of the parent clocks may be shut down.

Tony