[v3,1/2] time: Don't bother to run rtc_resume() for the nonstop clocksource

From: Xunlei Pang <pang.xunlei@linaro.org>

If a system does not provide a persistent_clock(), the time
will be updated on resume by rtc_resume(). With the addition
of the non-stop clocksources for suspend timing, those systems
set the time on resume in timekeeping_resume(), but may not
provide a valid persistent_clock().

This results in the rtc_resume() logic thinking no one has set
the time and it then will over-write the suspend time again,
which is not necessary and only increases clock error.

So, fix this for rtc_resume().

Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
---
v2->v3:
Refine according to John's comments using internal variable.

 drivers/rtc/class.c         |  2 +-
 include/linux/timekeeping.h |  1 +
 kernel/time/timekeeping.c   | 32 ++++++++++++++++++++------------
 3 files changed, 22 insertions(+), 13 deletions(-)

Ping ...

On 29 January 2015 at 23:59, Xunlei Pang <xlpang@126.com> wrote:
> From: Xunlei Pang <pang.xunlei@linaro.org>
>
> If a system does not provide a persistent_clock(), the time
> will be updated on resume by rtc_resume(). With the addition
> of the non-stop clocksources for suspend timing, those systems
> set the time on resume in timekeeping_resume(), but may not
> provide a valid persistent_clock().
>
> This results in the rtc_resume() logic thinking no one has set
> the time and it then will over-write the suspend time again,
> which is not necessary and only increases clock error.
>
> So, fix this for rtc_resume().
>
> Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
> ---
> v2->v3:
> Refine according to John's comments using internal variable.
>
>  drivers/rtc/class.c         |  2 +-
>  include/linux/timekeeping.h |  1 +
>  kernel/time/timekeeping.c   | 32 ++++++++++++++++++++------------
>  3 files changed, 22 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
> index 472a5ad..6100af5 100644
> --- a/drivers/rtc/class.c
> +++ b/drivers/rtc/class.c
> @@ -102,7 +102,7 @@ static int rtc_resume(struct device *dev)
>         struct timespec64       sleep_time;
>         int err;
>
> -       if (has_persistent_clock())
> +       if (timekeeping_sleeptime_injected())
>                 return 0;
>
>         rtc_hctosys_ret = -ENODEV;
> diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
> index 9b63d13..17a460d 100644
> --- a/include/linux/timekeeping.h
> +++ b/include/linux/timekeeping.h
> @@ -225,6 +225,7 @@ static inline void timekeeping_clocktai(struct timespec *ts)
>  /*
>   * RTC specific
>   */
> +extern bool timekeeping_sleeptime_injected(void);
>  extern void timekeeping_inject_sleeptime64(struct timespec64 *delta);
>
>  /*
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index 6a93185..b02133e 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -1125,12 +1125,26 @@ static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
>         tk_debug_account_sleep_time(delta);
>  }
>
> +static bool sleeptime_inject;
> +
> +#if defined(CONFIG_RTC_CLASS) && \
> +       defined(CONFIG_PM_SLEEP) && \
> +       defined(CONFIG_RTC_HCTOSYS_DEVICE)
> +/**
> + * Used by rtc_resume().
> + */
> +bool timekeeping_sleeptime_injected(void)
> +{
> +       return sleeptime_inject;
> +}
> +
>  /**
>   * timekeeping_inject_sleeptime64 - Adds suspend interval to timeekeeping values
>   * @delta: pointer to a timespec64 delta value
>   *
>   * This hook is for architectures that cannot support read_persistent_clock
> - * because their RTC/persistent clock is only accessible when irqs are enabled.
> + * because their RTC/persistent clock is only accessible when irqs are enabled,
> + * and also don't have an effective nonstop clocksource.
>   *
>   * This function should only be called by rtc_resume(), and allows
>   * a suspend offset to be injected into the timekeeping values.
> @@ -1140,13 +1154,6 @@ void timekeeping_inject_sleeptime64(struct timespec64 *delta)
>         struct timekeeper *tk = &tk_core.timekeeper;
>         unsigned long flags;
>
> -       /*
> -        * Make sure we don't set the clock twice, as timekeeping_resume()
> -        * already did it
> -        */
> -       if (has_persistent_clock())
> -               return;
> -
>         raw_spin_lock_irqsave(&timekeeper_lock, flags);
>         write_seqcount_begin(&tk_core.seq);
>
> @@ -1162,6 +1169,7 @@ void timekeeping_inject_sleeptime64(struct timespec64 *delta)
>         /* signal hrtimers about time change */
>         clock_was_set();
>  }
> +#endif
>
>  /**
>   * timekeeping_resume - Resumes the generic timekeeping subsystem.
> @@ -1178,8 +1186,8 @@ static void timekeeping_resume(void)
>         struct timespec64 ts_new, ts_delta;
>         struct timespec tmp;
>         cycle_t cycle_now, cycle_delta;
> -       bool suspendtime_found = false;
>
> +       sleeptime_inject = false;
>         read_persistent_clock(&tmp);
>         ts_new = timespec_to_timespec64(tmp);
>
> @@ -1226,13 +1234,13 @@ static void timekeeping_resume(void)
>                 nsec += ((u64) cycle_delta * mult) >> shift;
>
>                 ts_delta = ns_to_timespec64(nsec);
> -               suspendtime_found = true;
> +               sleeptime_inject = true;
>         } else if (timespec64_compare(&ts_new, &timekeeping_suspend_time) > 0) {
>                 ts_delta = timespec64_sub(ts_new, timekeeping_suspend_time);
> -               suspendtime_found = true;
> +               sleeptime_inject = true;
>         }
>
> -       if (suspendtime_found)
> +       if (sleeptime_inject)
>                 __timekeeping_inject_sleeptime(tk, &ts_delta);
>
>         /* Re-base the last cycle value */
> --
> 1.9.1
>
>
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On Thu, Jan 29, 2015 at 11:59 PM, Xunlei Pang <xlpang@126.com> wrote:
> From: Xunlei Pang <pang.xunlei@linaro.org>
>
> If a system does not provide a persistent_clock(), the time
> will be updated on resume by rtc_resume(). With the addition
> of the non-stop clocksources for suspend timing, those systems
> set the time on resume in timekeeping_resume(), but may not
> provide a valid persistent_clock().
>
> This results in the rtc_resume() logic thinking no one has set
> the time and it then will over-write the suspend time again,
> which is not necessary and only increases clock error.
>
> So, fix this for rtc_resume().
>
> Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
> ---
> v2->v3:
> Refine according to John's comments using internal variable.
>
>  drivers/rtc/class.c         |  2 +-
>  include/linux/timekeeping.h |  1 +
>  kernel/time/timekeeping.c   | 32 ++++++++++++++++++++------------
>  3 files changed, 22 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
> index 472a5ad..6100af5 100644
> --- a/drivers/rtc/class.c
> +++ b/drivers/rtc/class.c
> @@ -102,7 +102,7 @@ static int rtc_resume(struct device *dev)
>         struct timespec64       sleep_time;
>         int err;
>
> -       if (has_persistent_clock())
> +       if (timekeeping_sleeptime_injected())
>                 return 0;

Took a closer look here.. So you're replacing has_persistent_clock()
in the resume side, but not the suspend... Can we not cleanup
has_persistent_clock and consolidate to one accessor for both sides of
the suspend?

>
>         rtc_hctosys_ret = -ENODEV;
> diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
> index 9b63d13..17a460d 100644
> --- a/include/linux/timekeeping.h
> +++ b/include/linux/timekeeping.h
> @@ -225,6 +225,7 @@ static inline void timekeeping_clocktai(struct timespec *ts)
>  /*
>   * RTC specific
>   */
> +extern bool timekeeping_sleeptime_injected(void);
>  extern void timekeeping_inject_sleeptime64(struct timespec64 *delta);
>
>  /*
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index 6a93185..b02133e 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -1125,12 +1125,26 @@ static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
>         tk_debug_account_sleep_time(delta);
>  }
>
> +static bool sleeptime_inject;
> +
> +#if defined(CONFIG_RTC_CLASS) && \
> +       defined(CONFIG_PM_SLEEP) && \
> +       defined(CONFIG_RTC_HCTOSYS_DEVICE)

This change wasn't explained in the commit message. Its fine as a
small optimization, but probably should be split into its own patch.

thanks
-john
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Hi John,

On 11 February 2015 at 08:01, John Stultz <john.stultz@linaro.org> wrote:
> On Thu, Jan 29, 2015 at 11:59 PM, Xunlei Pang <xlpang@126.com> wrote:
>> From: Xunlei Pang <pang.xunlei@linaro.org>
>>
>> If a system does not provide a persistent_clock(), the time
>> will be updated on resume by rtc_resume(). With the addition
>> of the non-stop clocksources for suspend timing, those systems
>> set the time on resume in timekeeping_resume(), but may not
>> provide a valid persistent_clock().
>>
>> This results in the rtc_resume() logic thinking no one has set
>> the time and it then will over-write the suspend time again,
>> which is not necessary and only increases clock error.
>>
>> So, fix this for rtc_resume().
>>
>> Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
>> ---
>> v2->v3:
>> Refine according to John's comments using internal variable.
>>
>>  drivers/rtc/class.c         |  2 +-
>>  include/linux/timekeeping.h |  1 +
>>  kernel/time/timekeeping.c   | 32 ++++++++++++++++++++------------
>>  3 files changed, 22 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
>> index 472a5ad..6100af5 100644
>> --- a/drivers/rtc/class.c
>> +++ b/drivers/rtc/class.c
>> @@ -102,7 +102,7 @@ static int rtc_resume(struct device *dev)
>>         struct timespec64       sleep_time;
>>         int err;
>>
>> -       if (has_persistent_clock())
>> +       if (timekeeping_sleeptime_injected())
>>                 return 0;
>
> Took a closer look here.. So you're replacing has_persistent_clock()
> in the resume side, but not the suspend... Can we not cleanup
> has_persistent_clock and consolidate to one accessor for both sides of
> the suspend?

The sequential calls when the system is suspended are:
rtc_suspend(), then timekeeping_suspend().

The sequential calls when the system is resumed are:
timekeeping_resume(), then rtc_resume().

Obviously, timekeeping_sleeptime_injected() used by rtc_resume()
can be easily determined at timekeeping_resume().

And for nonstop clocksources, currently we have code below:
timekeeping_resume():
cycle_now = tk->tkr.read(clock);
    if ((clock->flags & CLOCK_SOURCE_SUSPEND_NONSTOP) &&
        cycle_now > tk->tkr.cycle_last) {

Here comes the confusing thing: "cycle_now > tk->tkr.cycle_last".
I can't quite catch what's the purpose by judging cycle_now and cycle_last here,
May Nonstop clocksource get wrapped or still can get disfunctional during
system suspend? If so, I think it would be hard to judge exactly whether
rtc_suspend() is needed for nonstop clocksource cases.

If we can get rid of this judgement, I think it would be easy to
consolidate this just
using read_persistent_clock() and CLOCK_SOURCE_SUSPEND_NONSTOP flag.

Any suggestion for this?

Thanks,
Xunlei

>
>>
>>         rtc_hctosys_ret = -ENODEV;
>> diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
>> index 9b63d13..17a460d 100644
>> --- a/include/linux/timekeeping.h
>> +++ b/include/linux/timekeeping.h
>> @@ -225,6 +225,7 @@ static inline void timekeeping_clocktai(struct timespec *ts)
>>  /*
>>   * RTC specific
>>   */
>> +extern bool timekeeping_sleeptime_injected(void);
>>  extern void timekeeping_inject_sleeptime64(struct timespec64 *delta);
>>
>>  /*
>> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
>> index 6a93185..b02133e 100644
>> --- a/kernel/time/timekeeping.c
>> +++ b/kernel/time/timekeeping.c
>> @@ -1125,12 +1125,26 @@ static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
>>         tk_debug_account_sleep_time(delta);
>>  }
>>
>> +static bool sleeptime_inject;
>> +
>> +#if defined(CONFIG_RTC_CLASS) && \
>> +       defined(CONFIG_PM_SLEEP) && \
>> +       defined(CONFIG_RTC_HCTOSYS_DEVICE)
>
> This change wasn't explained in the commit message. Its fine as a
> small optimization, but probably should be split into its own patch.
>
> thanks
> -john
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