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SubjectRe: [PATCH] alarmtimer: implement minimum alarm interval for allowing suspend
Date
On Thursday, August 09, 2012, Todd Poynor wrote:
> alarmtimer suspend return -EBUSY if the next alarm will fire in less
> than 2 seconds. This allows one RTC seconds tick to occur subsequent
> to this check before the alarm wakeup time is set, ensuring the wakeup
> time is still in the future (assuming the RTC does not tick one more
> second prior to setting the alarm).
>
> If suspend is rejected due to an imminent alarm, hold a wakeup source
> for 2 seconds to process the alarm prior to reattempting suspend.
>
> If setting the alarm incurs an -ETIME for an alarm set in the past,
> or any other problem setting the alarm, abort suspend and hold a
> wakelock for 1 second while the alarm is allowed to be serviced or
> other hopefully transient conditions preventing the alarm clear up.
>
> Signed-off-by: Todd Poynor <toddpoynor@google.com>
> ---
> kernel/time/alarmtimer.c | 18 +++++++++++++-----
> 1 files changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
> index aa27d39..f979d85 100644
> --- a/kernel/time/alarmtimer.c
> +++ b/kernel/time/alarmtimer.c
> @@ -46,6 +46,8 @@ static struct alarm_base {
> static ktime_t freezer_delta;
> static DEFINE_SPINLOCK(freezer_delta_lock);
>
> +static struct wakeup_source *ws;
> +
> #ifdef CONFIG_RTC_CLASS
> /* rtc timer and device for setting alarm wakeups at suspend */
> static struct rtc_timer rtctimer;
> @@ -250,6 +252,7 @@ static int alarmtimer_suspend(struct device *dev)
> unsigned long flags;
> struct rtc_device *rtc;
> int i;
> + int ret;
>
> spin_lock_irqsave(&freezer_delta_lock, flags);
> min = freezer_delta;
> @@ -279,8 +282,10 @@ static int alarmtimer_suspend(struct device *dev)
> if (min.tv64 == 0)
> return 0;
>
> - /* XXX - Should we enforce a minimum sleep time? */
> - WARN_ON(min.tv64 < NSEC_PER_SEC);
> + if (ktime_to_ns(min) < 2 * NSEC_PER_SEC) {
> + __pm_wakeup_event(ws, 2 * MSEC_PER_SEC);
> + return -EBUSY;
> + }
>
> /* Setup an rtc timer to fire that far in the future */
> rtc_timer_cancel(rtc, &rtctimer);
> @@ -288,9 +293,11 @@ static int alarmtimer_suspend(struct device *dev)
> now = rtc_tm_to_ktime(tm);
> now = ktime_add(now, min);
>
> - rtc_timer_start(rtc, &rtctimer, now, ktime_set(0, 0));
> -
> - return 0;
> + /* Set alarm, if in the past reject suspend briefly to handle */
> + ret = rtc_timer_start(rtc, &rtctimer, now, ktime_set(0, 0));
> + if (ret < 0)
> + __pm_wakeup_event(ws, 1 * MSEC_PER_SEC);

Why not just MSEC_PER_SEC?

> + return ret;
> }
> #else
> static int alarmtimer_suspend(struct device *dev)
> @@ -821,6 +828,7 @@ static int __init alarmtimer_init(void)
> error = PTR_ERR(pdev);
> goto out_drv;
> }
> + ws = wakeup_source_register("alarmtimer");
> return 0;
>
> out_drv:
>



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