linux-kernel - Re: [PATCH v6 3/8] ARM: sunxi: Move the clock protection to machine hooks

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Date:	Wed, 23 Apr 2014 15:31:06 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	devicetree@...r.kernel.org, Mike Turquette <mturquette@...aro.org>,
	andriy.shevchenko@...el.com, Emilio Lopez <emilio@...pez.com.ar>,
	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
	zhuzhenhua@...winnertech.com, Vinod Koul <vinod.koul@...el.com>,
	linux-sunxi@...glegroups.com, kevin.z.m.zh@...il.com,
	sunny@...winnertech.com, shuge@...winnertech.com,
	Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH v6 3/8] ARM: sunxi: Move the clock protection to machine hooks

On Wednesday 23 April 2014 15:17:20 Maxime Ripard wrote:
> > > +#include <linux/clk.h>
> > >  #include <linux/init.h>
> > >  #include <linux/of_platform.h>
> > >  
> > > @@ -19,9 +20,17 @@
> > >  
> > >  static void __init sun4i_dt_init(void)
> > >  {
> > > +       struct clk *clk;
> > > +
> > >         sunxi_setup_restart();
> > >  
> > >         of_platform_populate(NULL, of_default_bus_match_table, NULL, NULL);
> > > +
> > > +       /* Make sure the clocks we absolutely need are enabled */
> > > +       /* DDR clock */
> > > +       clk = clk_get(NULL, "pll5_ddr");
> > > +       if (!IS_ERR(clk))
> > > +               clk_prepare_enable(clk);
> > >  }
> > 
> > Isn't there already DT syntax to do the same? If not, should there be?
> 
> I don't think there is, and I gave some thought about it too. But
> something a la regulator-always-on wouldn't work with clocks with
> multiple outputs (like pll5), because you might need to leave only one
> of the output enabled, but not the others, and I couldn't think of a
> nice way to do so.
> 
> If you have one, I'd be happy to implement it.

We had a discussion a while ago about encoding default settings for clock
providers in the clock provider nodes. I don't remember the details
unfortunately.

Mike, can you explain how this should be done?

	Arnd
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