[PATCH] timer: Added usleep[_range][_interruptable] timer

[Patrick Pannuto]

usleep[_range][_interruptable] are finer precision implmentations
of msleep[_interruptable] 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

Change-Id: I277737744ca58061323837609b121a0fc9d27f33
Change-Id: I088f14e905fc569c0a728fff5dc61ef25f49bb1e
Signed-off-by: Patrick Pannuto <ppannuto@xxxxxxxxxxxxxx>
---
 include/linux/delay.h |   12 ++++++++++++
 kernel/timer.c        |   44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+), 0 deletions(-)

diff --git a/include/linux/delay.h b/include/linux/delay.h
index fd832c6..13f5378 100644
--- a/include/linux/delay.h
+++ b/include/linux/delay.h
@@ -45,6 +45,18 @@ 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);
+unsigned long usleep_range_interruptible(unsigned long min, unsigned long max);
+
+static inline void usleep(unsigned long usecs)
+{
+	usleep_range(usecs, usecs);
+}
+
+static inline unsigned long usleep_interruptible(unsigned long usecs)
+{
+	return usleep_range_interruptible(usecs, usecs);
+}
 
 static inline void ssleep(unsigned int seconds)
 {
diff --git a/kernel/timer.c b/kernel/timer.c
index 5db5a8d..1587dad 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1684,3 +1684,47 @@ 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);
+
+/**
+ * usleep_range_interruptible - sleep waiting for signals
+ * @min: Minimum time in usecs to sleep
+ * @max: Maximum time in usecs to sleep
+ */
+unsigned long usleep_range_interruptible(unsigned long min, unsigned long max)
+{
+	int err;
+	ktime_t start;
+
+	start = ktime_get();
+
+	__set_current_state(TASK_INTERRUPTIBLE);
+	err = do_usleep_range(min, max);
+
+	if (err == -EINTR)
+		return ktime_us_delta(ktime_get(), start);
+	else
+		return 0;
+}
+EXPORT_SYMBOL(usleep_range_interruptible);
-- 
1.7.1

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