When expires is set to KTIME_MAX in tick_program_event(), we are sure that there are no events enqueued for a very long time and so there is no point keeping event device running. We will get interrupted without any work to do many a times, for example when timer's counter overflows.
So, its better to SHUTDOWN the event device then and restart it ones we get a request for next event. For implementing this a new field 'last_mode' is added to 'struct clock_event_device' to keep track of last mode used. Signed-off-by: Viresh Kumar <[email protected]> --- include/linux/clockchips.h | 1 + kernel/time/tick-oneshot.c | 14 +++++++++++++- 2 files changed, 14 insertions(+), 1 deletion(-) diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h index 2e4cb67..36a4ca6 100644 --- a/include/linux/clockchips.h +++ b/include/linux/clockchips.h @@ -105,6 +105,7 @@ struct clock_event_device { u32 mult; u32 shift; enum clock_event_mode mode; + enum clock_event_mode last_mode; unsigned int features; unsigned long retries; diff --git a/kernel/time/tick-oneshot.c b/kernel/time/tick-oneshot.c index 8241090..9543815 100644 --- a/kernel/time/tick-oneshot.c +++ b/kernel/time/tick-oneshot.c @@ -27,8 +27,20 @@ int tick_program_event(ktime_t expires, int force) { struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); + int ret = 0; - return clockevents_program_event(dev, expires, force); + /* Shut down event device if it is not required for long */ + if (unlikely(expires.tv64 == KTIME_MAX)) { + dev->last_mode = dev->mode; + clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN); + } else { + /* restore mode when restarting event dev */ + if (unlikely(dev->mode == CLOCK_EVT_MODE_SHUTDOWN)) + clockevents_set_mode(dev, dev->last_mode); + ret = clockevents_program_event(dev, expires, force); + } + + return ret; } /** -- 2.0.0.rc2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
