linux-kernel - Re: [patch 2.6.28-rc7] regulator: catch some registration errors

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Date:	Mon, 5 Jan 2009 15:45:24 -0800
From:	David Brownell <david-b@...bell.net>
To:	Mark Brown <broonie@...ena.org.uk>
Cc:	Liam Girdwood <lrg@...mlogic.co.uk>,
	lkml <linux-kernel@...r.kernel.org>, davej@...hat.com
Subject: Re: [patch 2.6.28-rc7] regulator: catch some registration errors

On Thursday 04 December 2008, Mark Brown wrote:
> [ Re Liam's comments about those non-existent cpufreq+regulator drivers ]
>
> On the bright side, looking at the situation with the clock API there
> don't seem to be any other substantial offenders here.  Most of the
> other users are part of the platform code and get to peer inside the
> clocking structure, so if cpufreq were fixed there shouldn't be much
> problem here.

Last time I looked, no cpufreq driver tried to use <linux/clk.h>
calls.  The reason was simple:  the clock framework code sits in
DRAM, so it can't be executed while changing DRAM clocks.

Those bits of cpufreq had to live in on-chip SRAM (there's usually
a few pages of it) and directly update PLL and other clock config
registers ... then wait for things to stabilize before they returned
and the CPU executed from DRAM again.

- Dave

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