RE: [PATCH] clk: Add functions to get optional clocks

[Phil Edworthy <phil.edworthy@renesas.com>]

Hi Russell,

On 18 July 2018 14:19, Geert Uytterhoeven wrote:
> On Wed, Jul 18, 2018 at 3:02 PM Russell King - ARM Linux  wrote:
> > On Wed, Jul 18, 2018 at 01:57:38PM +0100, Phil Edworthy wrote:
> > > Behaves the same as (devm_)clk_get except where there is no clock
> > > producer. In this case, instead of returning -ENOENT, the function
> > > returns NULL. This makes error checking simpler and allows
> > > clk_prepare_enable, etc to be called on the returned reference
> > > without additional checks.
> >
> > How does this work with non-DT systems, where looking a clock up which
> > isn't yet registered with clkdev returns -ENOENT ?
> >
> > (clkdev doesn't know when all clocks are registered with it.)
> 
> Good question.
> 
> I guess all drivers trying to handle optional clocks this way are already broken
> on non-DT systems where clocks may be registered late...

So how do non-DT systems that look a clock up which isn't yet
registered with clkdev, determine that an optional clock is there
or not?

Thanks
Phil