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    Subject[tip:timers/core] timer: Added usleep[_range] timer
    Commit-ID:  22b8f15c2f7130bb0386f548428df2ffd4e81903
    Gitweb: http://git.kernel.org/tip/22b8f15c2f7130bb0386f548428df2ffd4e81903
    Author: Patrick Pannuto <ppannuto@codeaurora.org>
    AuthorDate: Mon, 19 Jul 2010 15:09:26 -0700
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Fri, 23 Jul 2010 15:08:12 +0200

    timer: Added usleep[_range] timer

    usleep[_range] are finer precision implementations of msleep
    and are designed to be drop-in replacements for udelay where
    a precise sleep / busy-wait is unnecessary. They also allow
    an easy interface to specify slack when a precise (ish)
    wakeup is unnecessary to help minimize wakeups

    Signed-off-by: Patrick Pannuto <ppannuto@codeaurora.org>
    Cc: akinobu.mita@gmail.com
    Cc: sboyd@codeaurora.org
    Acked-by: Arjan van de Ven <arjan@linux.intel.com>
    LKML-Reference: <4C44CDD2.1070708@codeaurora.org>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    include/linux/delay.h | 6 ++++++
    kernel/timer.c | 22 ++++++++++++++++++++++
    2 files changed, 28 insertions(+), 0 deletions(-)

    diff --git a/include/linux/delay.h b/include/linux/delay.h
    index fd832c6..0e303d1 100644
    --- a/include/linux/delay.h
    +++ b/include/linux/delay.h
    @@ -45,6 +45,12 @@ extern unsigned long lpj_fine;
    void calibrate_delay(void);
    void msleep(unsigned int msecs);
    unsigned long msleep_interruptible(unsigned int msecs);
    +void usleep_range(unsigned long min, unsigned long max);
    +
    +static inline void usleep(unsigned long usecs)
    +{
    + usleep_range(usecs, usecs);
    +}

    static inline void ssleep(unsigned int seconds)
    {
    diff --git a/kernel/timer.c b/kernel/timer.c
    index ce98685..f110f24 100644
    --- a/kernel/timer.c
    +++ b/kernel/timer.c
    @@ -1755,3 +1755,25 @@ unsigned long msleep_interruptible(unsigned int msecs)
    }

    EXPORT_SYMBOL(msleep_interruptible);
    +
    +static int __sched do_usleep_range(unsigned long min, unsigned long max)
    +{
    + ktime_t kmin;
    + unsigned long delta;
    +
    + kmin = ktime_set(0, min * NSEC_PER_USEC);
    + delta = max - min;
    + return schedule_hrtimeout_range(&kmin, delta, HRTIMER_MODE_REL);
    +}
    +
    +/**
    + * usleep_range - Drop in replacement for udelay where wakeup is flexible
    + * @min: Minimum time in usecs to sleep
    + * @max: Maximum time in usecs to sleep
    + */
    +void usleep_range(unsigned long min, unsigned long max)
    +{
    + __set_current_state(TASK_UNINTERRUPTIBLE);
    + do_usleep_range(min, max);
    +}
    +EXPORT_SYMBOL(usleep_range);

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