linux-kernel - Re: Locking in the clk API

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Date:	Thu, 20 Jan 2011 17:02:55 +0000
From:	Ben Dooks <ben-linux@...ff.org>
To:	Richard Zhao <linuxzsc@...il.com>
CC:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-sh <linux-sh@...r.kernel.org>,
	Ben Herrenschmidt <benh@...nel.crashing.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Jeremy Kerr <jeremy.kerr@...onical.com>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: Locking in the clk API

On 11/01/11 11:15, Richard Zhao wrote:
> 2011/1/11 Uwe Kleine-König <u.kleine-koenig@...gutronix.de>:

[snip]

> A well running board will not enable/disable PLLs frequently. It don't
> make sense. PLLs are normally disabled on request to enter low power
> mode, rather not because all their child clocks are disabled.   So we
> don't have to consider the time here.

I'd rather see that if all child clocks are disabled the PLL is
powered down then. It means PLLs _could_ be left running even
when power-down mode is selected because the system still thinks
that a peripheral is using them.

If you want to make it so that each low-power mode has to work
out what PLLs need to be disabled and then re-enabled makes me
want to be sick. Hiding this stuff behind specific implementations
is a recipe for disaster.
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