Re: [PATCH v4 3/6] clk: introduce the common clock framework

[Saravana Kannan]

On 12/17/2011 03:04 AM, Russell King - ARM Linux wrote:
> On Fri, Dec 16, 2011 at 04:45:48PM -0800, Turquette, Mike wrote:
> > On Wed, Dec 14, 2011 at 5:18 AM, Thomas Gleixner<tglx@xxxxxxxxxxxxx>  wrote:
> > > On Tue, 13 Dec 2011, Mike Turquette wrote:
> > > > +void __clk_unprepare(struct clk *clk)
> > > > +{
> > > > +     if (!clk)
> > > > +             return;
> > > > +
> > > > +     if (WARN_ON(clk->prepare_count == 0))
> > > > +             return;
> > > > +
> > > > +     if (--clk->prepare_count>  0)
> > > > +             return;
> > > > +
> > > > +     WARN_ON(clk->enable_count>  0);
> > >
> > > So this leaves the clock enable count set. I'm a bit wary about
> > > that. Shouldn't it either return (including bumping the prepare_count
> > > again) or call clk_disable() ?
>
> No it should not.
>
> > I've hit this in my port of OMAP.  It comes from this simple situation:
> >
> > driver 1 (adapted for clk_prepare/clk_unprepare):
> > clk_prepare(clk);
> > clk_enable(clk);
> >
> > ...
> >
> > driver2 (not adapted for clk_prepare/clk_unprepare):
> > clk_enable(clk);
>
> So this is basically buggy.  Look, it's quite simple.  Convert _all_
> your drivers to clk_prepare/clk_unprepare _before_ you start switching
> your platform to use these new functions.  You can do that _today_
> without exception.
>
> We must refuse to merge _any_ user which does this the old way - and
> we should have been doing this since my commit was merged into mainline
> to allow drivers to be converted.
>
> And stop trying to think of ways around this inside clk_prepare/
> clk_unprepare/clk_enable/clk_disable.  You can't do it.  Just fix _all_
> the drivers.  Now.  Before you start implementing clk_prepare/clk_unprepare.

I agree with Russell's suggestion. This is what I'm trying to do with 
the MSM platform. Not sure if I'm too optimistic, but as of today, I'm 
still optimistic I can push the MSM driver devs to get this done before 
we enable real prepare/unprepare support.

Thanks,
Saravana

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