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

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Message-ID: <BANLkTimxkY4MvQ+-qiOwdwbo7jPUAQ1vxw@mail.gmail.com>
Date:	Fri, 13 May 2011 14:24:10 -0700
From:	Colin Cross <ccross@...roid.com>
To:	Thomas Gleixner <tglx@...utronix.de>
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, May 13, 2011 at 3:02 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> Does the following work for you ?
Not if the comments are accurate.

> Thanks,
>
>        tglx
>
> ---------->
> Subject: clock-ev-reconf.patch
> From: Thomas Gleixner <tglx@...utronix.de>
> Date: Fri, 13 May 2011 10:53:13 +0200
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  include/linux/clockchips.h |    2 ++
>  kernel/time/clockevents.c  |   24 ++++++++++++++++++++++++
>  2 files changed, 26 insertions(+)
>
> Index: linux-2.6/include/linux/clockchips.h
> ===================================================================
> --- linux-2.6.orig/include/linux/clockchips.h
> +++ linux-2.6/include/linux/clockchips.h
> @@ -132,6 +132,8 @@ extern int clockevents_program_event(str
>
>  extern void clockevents_handle_noop(struct clock_event_device *dev);
>
> +extern int clockevents_reconfigure(struct clock_event_device *ce, u32 freq, u32 minsec);
> +
>  static inline void
>  clockevents_calc_mult_shift(struct clock_event_device *ce, u32 freq, u32 minsec)
>  {
> Index: linux-2.6/kernel/time/clockevents.c
> ===================================================================
> --- linux-2.6.orig/kernel/time/clockevents.c
> +++ linux-2.6/kernel/time/clockevents.c
> @@ -133,6 +133,30 @@ int clockevents_program_event(struct clo
>  }
>
>  /**
> + * 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.

> +int clockevents_reconfigure(struct clock_event_device *dev, u32 freq, u32 secr)
> +{
> +       if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
> +               return -EINVAL;
> +
> +       clockevents_calc_mult_shift(dev, freq, secr ? secr : 1);
> +
> +       return clockevents_program_event(dev, dev->next_event, ktime_get());
> +}
> +
> +/**
>  * clockevents_register_notifier - register a clock events change listener
>  */
>  int clockevents_register_notifier(struct notifier_block *nb)
>
--
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