linux-kernel - Re: [PATCH 2/6] pinctrl: Update clock handling for the pinctrl-nomadik GPIO driver

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Date:	Thu, 25 Oct 2012 16:51:43 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	arnd@...db.de, linus.walleij@...ricsson.com,
	Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH 2/6] pinctrl: Update clock handling for the
 pinctrl-nomadik GPIO driver

On Thu, 25 Oct 2012, Linus Walleij wrote:

> On Thu, Oct 25, 2012 at 2:41 PM, Linus Walleij <linus.walleij@...aro.org> wrote:
> > On Wed, Oct 24, 2012 at 4:45 PM, Lee Jones <lee.jones@...aro.org> wrote:
> >
> >> The clock framework has changed somewhat and it's now better to
> >> invoke clock_prepare_enable() and clk_disable_unprepare() rather
> >> than the legacy clk_enable() and clk_disable() calls. This patch
> >> converts the Nomadik Pin Control driver to the new framework.
> >>
> >> Signed-off-by: Lee Jones <lee.jones@...aro.org>
> >
> > I was convinced that this is a good change but no regression,
> > so applied to the devel branch for 3.8.
> >
> > I also removed the initial clk_prepare() so the reference count
> > may actually go down to 0 for the GPIO block and the peripheral
> > cluster eventually gets relaxed.
> 
> Famous last words!
> 
> The good news is that this actually works, and the refcount
> *does* go down to zero and gate off entire peripheral
> clusters.
> 
> However that was not good because something vital in
> some peripheral cluster died and killed the system :-D
> 
> Lee, could to to track down the reason and fix it so the patch
> can be applied?
> 
> The only thing you need to do is to remove the superfluous
> clk_prepare() right after the devm_clk_get() that hogs each
> peripheral cluster.
> 
> Probably some driver is needing a clk_get() or a clk_get_sys() is
> needs to be added somewhere to bring up some vital cluster,
> or there may be some out-of-tree driver needed to bring up the
> cluster properly I have no clue... Maybe some cluster just
> cannot be declocked like that.

I leave work in 10 mins and won't be coding again for ~2.5 weeks.
So if this is something you could squeeze in and fix-up, I'd be
very grateful.

Kind regards,
Lee

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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