linux-kernel - Re: [PATCH] update clocksource raw_time in timekeeping

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Date:	Wed, 9 Sep 2009 22:25:52 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	ye janboe <janboe.ye@...il.com>
Cc:	johnstul@...ibm.com, zippel@...ux-m68k.org,
	akpm@...ux-foundation.org, mingo@...e.hu,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] update clocksource raw_time in timekeeping_suspend

On Wed, Sep 9, 2009 at 3:35 PM, ye janboe<janboe.ye@...il.com> wrote:
> after resume from suspend, raw_time is not updated in
> timekeeping_suspend. CLOCK_MONOTONIC_RAW could not get the real hw
> time.

It seems that this is not a bug. The design of CLOCK_MONOTONIC_RAW doesn't
say it will reflect the real hw time. It's just monotonic time which
is unpoisoned by
ntp.

Cheers,
Yong

> This patch fix this issue.
>
> Signed-off-by: janboe <janboe.ye@...il.com>
> ---
>  kernel/time/timekeeping.c |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index e8c77d9..8420b85 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -331,6 +331,8 @@ static unsigned long timekeeping_suspend_time;
>  static int timekeeping_resume(struct sys_device *dev)
>  {
>        unsigned long flags;
> +       s64 nsec;
> +       cycle_t last_cycle, cycle_delta;
>        unsigned long now = read_persistent_clock();
>
>        clocksource_resume();
> @@ -346,8 +348,12 @@ static int timekeeping_resume(struct sys_device *dev)
>        }
>        update_xtime_cache(0);
>        /* re-base the last cycle value */
> +       last_cycle = clock->cycle_last;
>        clock->cycle_last = 0;
>        clock->cycle_last = clocksource_read(clock);
> +       cycle_delta = clock->cycle_last - last_cycle;
> +       nsec = cyc2ns(clock, cycle_delta);
> +       timespec_add_ns(&clock->raw_time, nsec);
>        clock->error = 0;
>        timekeeping_suspended = 0;
>        write_sequnlock_irqrestore(&xtime_lock, flags);
> --
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