linux-kernel - Re: [PATCH] ARM: twd: Adjust localtimer frequency withcpufreqnotifiers

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Message-ID: <alpine.LFD.2.02.1105141749510.3078@ionos>
Date:	Sat, 14 May 2011 17:51:21 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Colin Cross <ccross@...roid.com>
cc:	Linus Walleij <linus.walleij@...aro.org>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Russell King <linux@....linux.org.uk>,
	Srinidhi KASAGAR <srinidhi.kasagar@...ricsson.com>,
	Harald Gustafsson <harald.gustafsson@...csson.com>,
	Linus Walleij <linus.ml.walleij@...il.com>,
	linux-kernel@...r.kernel.org,
	Rickard ANDERSSON <rickard.andersson@...ricsson.com>,
	martin persson <martin.persson@...ricsson.com>,
	Varun Swara <Varun.Swara@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: twd: Adjust localtimer frequency
 withcpufreqnotifiers

On Fri, 13 May 2011, Colin Cross wrote:
> On Fri, May 13, 2011 at 3:02 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> >  /**
> > + * clockevents_reconfigure - Reconfigure and reprogram a clock event device.
> > + * @dev:       device to modify
> > + * @freq:      new device frequency
> > + * @secr:      guaranteed runtime conversion range in seconds
> > + *
> > + * Reconfigure and reprogram a clock event device in oneshot
> > + * mode. Must only be called from low level idle code where
> > + * interaction with hrtimers/nohz code etc. is not possible and
> > + * guaranteed not to conflict. Must be called with interrupts
> > + * disabled!
> > + * Returns 0 on success, -ETIME when the event is in the past or
> > + * -EINVAL when called with invalid parameters.
> > + */
> We need to call this from a cpufreq notifier with interrupts disabled,
> not from idle.

That works as well. Comments needs update. The important thing is that
neither a timer interrupt nor a hrtimer function should interfere on
that very cpu.

Thanks,

	tglx