[PATCH 0/7] Posix interface for RTC (v2)

[PATCH 0/7] Posix interface for RTC (v2)

[John Stultz]

From: John Stultz <johnstul@us.ibm.com>

So I think this patch set is starting to shape up, and 
it has been functioning pretty well in my testing, so 
I wanted to send it out again for review.

The first two patches lay groundwork, pulling the timerlist
infrastructure out of hrtimers and into common code.

The next two patches rework the RTC code, so the interface is
a little more abstracted away from the hardware, allowing
us to multiplex timers from different applications ontop of
a single RTC device, and cleaning up the now redundant older
emulation layer.

This is where the patchset diverges into two paths:

The next two patches provide a posix interface layer ontop of
the RTC device. One of the patches, provided by Richard Cochran,
allows for dynamic posix clock registration and is likely to be
reworked here shortly. The other implements the posix interface.
This interface exposes the actual RTC time and allows timers
to be set against that time domain, which may not stay in sync
with the kernel's system time. It also allows wakeup timers to be
triggered in the future when the machine may be suspended.


The last patch takes a different approach. It too provides a
posix interface that can be used to trigger wakeup alarms
when the machine is suspended, but it uses a bit of a hybrid
method, basing timers off the system time clock ids (ie: 
CLOCK_REALTIME/MONOTONIC) while the system is running, and 
then setting the RTC to fire only when we go to suspend.
This hybrid approach was inspired by the Android Alarm driver,
which uses this same method, but exposes the interface to
userland via ioctl device instead of the posix interface.

I wanted to send out both of these methods to get some
feedback on which direction (or possibly both) people
would prefer to see.

Any other feedback or comments would also be appreciated!

thanks
-john


CC: Alessandro Zummo <a.zummo@towertech.it>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Richard Cochran <richardcochran@gmail.com>
CC: Arve Hjønnevåg <arve@android.com>



John Stultz (6):
  [RFC] Introduce timerlist infrastructure.
  [RFC] hrtimers: Convert hrtimers to use timerlist infrastructure
  [RFC] RTC: Rework RTC code to use timerlist for events
  [RFC] RTC: Remove UIE emulation
  [RFC] RTC: Add posix clock/timer interface
  [RFC] Introduce Alarm (hybrid) timers

Richard Cochran (1):
  [RFC] posix clocks: dynamic clock ids.

 drivers/rtc/Makefile         |    2 +-
 drivers/rtc/class.c          |   15 +
 drivers/rtc/interface.c      |  579 ++++++++++++++++++++++++++----------------
 drivers/rtc/posix.c          |  258 +++++++++++++++++++
 drivers/rtc/rtc-dev.c        |  104 --------
 drivers/rtc/rtc-lib.c        |   26 ++
 drivers/rtc/rtc-sysfs.c      |   10 +
 include/linux/alarmtimer.h   |   29 ++
 include/linux/hrtimer.h      |   32 +--
 include/linux/posix-timers.h |   11 +-
 include/linux/rtc.h          |   52 +++-
 include/linux/time.h         |    4 +
 include/linux/timerlist.h    |   37 +++
 kernel/hrtimer.c             |   86 +++----
 kernel/posix-timers.c        |   41 +++-
 kernel/time/Makefile         |    2 +-
 kernel/time/alarmtimer.c     |  522 +++++++++++++++++++++++++++++++++++++
 kernel/time/timer_list.c     |    8 +-
 lib/Makefile                 |    2 +-
 lib/timerlist.c              |  115 +++++++++
 20 files changed, 1503 insertions(+), 432 deletions(-)
 create mode 100644 drivers/rtc/posix.c
 create mode 100644 include/linux/alarmtimer.h
 create mode 100644 include/linux/timerlist.h
 create mode 100644 kernel/time/alarmtimer.c
 create mode 100644 lib/timerlist.c

-- 
1.7.3.2.146.gca209

[PATCH 1/7] [RFC] Introduce timerlist infrastructure.

[John Stultz]

The timerlist infrastructure is a thin layer over the rbtree
code that implements a simple list of timers sorted by an
expires value, and a getnext function that provides a pointer
to the earliest timer.

This infrastructure allows drivers and other kernel infrastructure
to easily implement timers without duplicating code.

Suggestions or feedback would be appreciated.

Signed-off-by: John Stultz <john.stultz@linaro.org>
CC: Alessandro Zummo <a.zummo@towertech.it>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Richard Cochran <richardcochran@gmail.com>
---
 include/linux/timerlist.h |   37 ++++++++++++++
 lib/Makefile              |    2 +-
 lib/timerlist.c           |  115 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 153 insertions(+), 1 deletions(-)
 create mode 100644 include/linux/timerlist.h
 create mode 100644 lib/timerlist.c

diff --git a/include/linux/timerlist.h b/include/linux/timerlist.h
new file mode 100644
index 0000000..c46b28a
--- /dev/null
+++ b/include/linux/timerlist.h
@@ -0,0 +1,37 @@
+#ifndef _LINUX_TIMERLIST_H
+#define _LINUX_TIMERLIST_H
+
+#include <linux/rbtree.h>
+#include <linux/ktime.h>
+
+
+struct timerlist_node {
+	struct rb_node node;
+	ktime_t expires;
+};
+
+struct timerlist_head {
+	struct rb_root head;
+	struct timerlist_node *next;
+};
+
+
+extern void timerlist_add(struct timerlist_head *head,
+				struct timerlist_node *node);
+extern void timerlist_del(struct timerlist_head *head,
+				struct timerlist_node *node);
+extern struct timerlist_node *timerlist_getnext(struct timerlist_head *head);
+extern struct timerlist_node *timerlist_iterate_next(
+						struct timerlist_node *node);
+
+static inline void timerlist_init(struct timerlist_node *node)
+{
+	RB_CLEAR_NODE(&node->node);
+}
+
+static inline void timerlist_init_head(struct timerlist_head *head)
+{
+	head->head = RB_ROOT;
+	head->next = NULL;
+}
+#endif /* _LINUX_TIMERLIST_H */
diff --git a/lib/Makefile b/lib/Makefile
index e6a3763..8b475cf 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -8,7 +8,7 @@ KBUILD_CFLAGS = $(subst -pg,,$(ORIG_CFLAGS))
 endif
 
 lib-y := ctype.o string.o vsprintf.o cmdline.o \
-	 rbtree.o radix-tree.o dump_stack.o \
+	 rbtree.o radix-tree.o dump_stack.o timerlist.o\
 	 idr.o int_sqrt.o extable.o prio_tree.o \
 	 sha1.o irq_regs.o reciprocal_div.o argv_split.o \
 	 proportions.o prio_heap.o ratelimit.o show_mem.o \
diff --git a/lib/timerlist.c b/lib/timerlist.c
new file mode 100644
index 0000000..3301b45
--- /dev/null
+++ b/lib/timerlist.c
@@ -0,0 +1,115 @@
+/*
+ *  Generic Timer-list
+ *
+ *  Manages a simple list of timers, ordered by expiration time.
+ *  Uses rbtrees for quick list adds and expiration.
+ *
+ *  NOTE: All of the following functions need to be serialized
+ *  to avoid races. No locking is done by this libary code.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <linux/timerlist.h>
+#include <linux/rbtree.h>
+
+/**
+ * timerlist_add - Adds timer to timerlist.
+ *
+ * @head: head of timerlist
+ * @node: timer node to be added
+ *
+ * Adds the timer node to the timerlist, sorted by the
+ * node's expires value.
+ */
+void timerlist_add(struct timerlist_head *head, struct timerlist_node *node)
+{
+	struct rb_node **p = &head->head.rb_node;
+	struct rb_node *parent = NULL;
+	struct timerlist_node  *ptr;
+
+	/* Make sure we don't add nodes that are already added */
+	WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node));
+
+	while (*p) {
+		parent = *p;
+		ptr = rb_entry(parent, struct timerlist_node, node);
+		if (node->expires.tv64 < ptr->expires.tv64)
+			p = &(*p)->rb_left;
+		else
+			p = &(*p)->rb_right;
+	}
+	rb_link_node(&node->node, parent, p);
+	rb_insert_color(&node->node, &head->head);
+
+	if (!head->next || node->expires.tv64 < head->next->expires.tv64)
+		head->next = node;
+}
+
+/**
+ * timerlist_del - Removes a timer from the timerlist.
+ *
+ * @head: head of timerlist
+ * @node: timer node to be removed
+ *
+ * Removes the timer node from the timerlist.
+ */
+void timerlist_del(struct timerlist_head *head, struct timerlist_node *node)
+{
+	WARN_ON_ONCE(RB_EMPTY_NODE(&node->node));
+
+	/* update next pointer */
+	if (head->next == node)
+		head->next = rb_entry(rb_next(&node->node),
+					struct timerlist_node, node);
+	rb_erase(&node->node, &head->head);
+	RB_CLEAR_NODE(&node->node);
+}
+
+
+/**
+ * timerlist_getnext - Returns the timer with the earlies expiration time
+ *
+ * @head: head of timerlist
+ *
+ * Returns a pointer to the timer node that has the
+ * earliest expiration time.
+ */
+struct timerlist_node *timerlist_getnext(struct timerlist_head *head)
+{
+	return head->next;
+}
+
+
+/**
+ * timerlist_iterate_next - Returns the timer after the provided timer
+ *
+ * @node: Pointer to a timer.
+ *
+ * Provides the timer that is after the given node. This is used, when
+ * necessary, to iterate through the list of timers in a timer list
+ * without modifying the list.
+ */
+struct timerlist_node *timerlist_iterate_next(struct timerlist_node *node)
+{
+	struct rb_node *next;
+
+	if (!node)
+		return NULL;
+	next = rb_next(&node->node);
+	if (!next)
+		return NULL;
+	return container_of(next, struct timerlist_node, node);
+}
-- 
1.7.3.2.146.gca209

[PATCH 2/7] [RFC] hrtimers: Convert hrtimers to use timerlist infrastructure

[John Stultz]

Converts the hrtimer code to use the timerlist infrastructure

Survived some light testing, but there may still be bugs.

Signed-off-by: John Stultz <john.stultz@linaro.org>
CC: Alessandro Zummo <a.zummo@towertech.it>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Richard Cochran <richardcochran@gmail.com>
CC: Arve Hjønnevåg <arve@android.com>
---
 include/linux/hrtimer.h  |   32 ++++++++---------
 kernel/hrtimer.c         |   86 ++++++++++++++++------------------------------
 kernel/time/timer_list.c |    8 ++--
 3 files changed, 49 insertions(+), 77 deletions(-)

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index fd0c1b8..019ac70 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -22,7 +22,7 @@
 #include <linux/wait.h>
 #include <linux/percpu.h>
 #include <linux/timer.h>
-
+#include <linux/timerlist.h>
 
 struct hrtimer_clock_base;
 struct hrtimer_cpu_base;
@@ -79,8 +79,8 @@ enum hrtimer_restart {
 
 /**
  * struct hrtimer - the basic hrtimer structure
- * @node:	red black tree node for time ordered insertion
- * @_expires:	the absolute expiry time in the hrtimers internal
+ * @node:	timerlist node, which also manages node.expires,
+ *		the absolute expiry time in the hrtimers internal
  *		representation. The time is related to the clock on
  *		which the timer is based. Is setup by adding
  *		slack to the _softexpires value. For non range timers
@@ -101,8 +101,7 @@ enum hrtimer_restart {
  * The hrtimer structure must be initialized by hrtimer_init()
  */
 struct hrtimer {
-	struct rb_node			node;
-	ktime_t				_expires;
+	struct timerlist_node		node;
 	ktime_t				_softexpires;
 	enum hrtimer_restart		(*function)(struct hrtimer *);
 	struct hrtimer_clock_base	*base;
@@ -141,8 +140,7 @@ struct hrtimer_sleeper {
 struct hrtimer_clock_base {
 	struct hrtimer_cpu_base	*cpu_base;
 	clockid_t		index;
-	struct rb_root		active;
-	struct rb_node		*first;
+	struct timerlist_head	active;
 	ktime_t			resolution;
 	ktime_t			(*get_time)(void);
 	ktime_t			softirq_time;
@@ -184,43 +182,43 @@ struct hrtimer_cpu_base {
 
 static inline void hrtimer_set_expires(struct hrtimer *timer, ktime_t time)
 {
-	timer->_expires = time;
+	timer->node.expires = time;
 	timer->_softexpires = time;
 }
 
 static inline void hrtimer_set_expires_range(struct hrtimer *timer, ktime_t time, ktime_t delta)
 {
 	timer->_softexpires = time;
-	timer->_expires = ktime_add_safe(time, delta);
+	timer->node.expires = ktime_add_safe(time, delta);
 }
 
 static inline void hrtimer_set_expires_range_ns(struct hrtimer *timer, ktime_t time, unsigned long delta)
 {
 	timer->_softexpires = time;
-	timer->_expires = ktime_add_safe(time, ns_to_ktime(delta));
+	timer->node.expires = ktime_add_safe(time, ns_to_ktime(delta));
 }
 
 static inline void hrtimer_set_expires_tv64(struct hrtimer *timer, s64 tv64)
 {
-	timer->_expires.tv64 = tv64;
+	timer->node.expires.tv64 = tv64;
 	timer->_softexpires.tv64 = tv64;
 }
 
 static inline void hrtimer_add_expires(struct hrtimer *timer, ktime_t time)
 {
-	timer->_expires = ktime_add_safe(timer->_expires, time);
+	timer->node.expires = ktime_add_safe(timer->node.expires, time);
 	timer->_softexpires = ktime_add_safe(timer->_softexpires, time);
 }
 
 static inline void hrtimer_add_expires_ns(struct hrtimer *timer, u64 ns)
 {
-	timer->_expires = ktime_add_ns(timer->_expires, ns);
+	timer->node.expires = ktime_add_ns(timer->node.expires, ns);
 	timer->_softexpires = ktime_add_ns(timer->_softexpires, ns);
 }
 
 static inline ktime_t hrtimer_get_expires(const struct hrtimer *timer)
 {
-	return timer->_expires;
+	return timer->node.expires;
 }
 
 static inline ktime_t hrtimer_get_softexpires(const struct hrtimer *timer)
@@ -230,7 +228,7 @@ static inline ktime_t hrtimer_get_softexpires(const struct hrtimer *timer)
 
 static inline s64 hrtimer_get_expires_tv64(const struct hrtimer *timer)
 {
-	return timer->_expires.tv64;
+	return timer->node.expires.tv64;
 }
 static inline s64 hrtimer_get_softexpires_tv64(const struct hrtimer *timer)
 {
@@ -239,12 +237,12 @@ static inline s64 hrtimer_get_softexpires_tv64(const struct hrtimer *timer)
 
 static inline s64 hrtimer_get_expires_ns(const struct hrtimer *timer)
 {
-	return ktime_to_ns(timer->_expires);
+	return ktime_to_ns(timer->node.expires);
 }
 
 static inline ktime_t hrtimer_expires_remaining(const struct hrtimer *timer)
 {
-    return ktime_sub(timer->_expires, timer->base->get_time());
+	return ktime_sub(timer->node.expires, timer->base->get_time());
 }
 
 #ifdef CONFIG_HIGH_RES_TIMERS
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 72206cf..d31ad88 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -516,10 +516,13 @@ hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
 
 	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++, base++) {
 		struct hrtimer *timer;
+		struct timerlist_node *next;
 
-		if (!base->first)
+		next = timerlist_getnext(&base->active);
+		if (!next)
 			continue;
-		timer = rb_entry(base->first, struct hrtimer, node);
+		timer = container_of(next, struct hrtimer, node);
+
 		expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
 		/*
 		 * clock_was_set() has changed base->offset so the
@@ -840,48 +843,17 @@ EXPORT_SYMBOL_GPL(hrtimer_forward);
 static int enqueue_hrtimer(struct hrtimer *timer,
 			   struct hrtimer_clock_base *base)
 {
-	struct rb_node **link = &base->active.rb_node;
-	struct rb_node *parent = NULL;
-	struct hrtimer *entry;
-	int leftmost = 1;
-
 	debug_activate(timer);
 
-	/*
-	 * Find the right place in the rbtree:
-	 */
-	while (*link) {
-		parent = *link;
-		entry = rb_entry(parent, struct hrtimer, node);
-		/*
-		 * We dont care about collisions. Nodes with
-		 * the same expiry time stay together.
-		 */
-		if (hrtimer_get_expires_tv64(timer) <
-				hrtimer_get_expires_tv64(entry)) {
-			link = &(*link)->rb_left;
-		} else {
-			link = &(*link)->rb_right;
-			leftmost = 0;
-		}
-	}
+	timerlist_add(&base->active, &timer->node);
 
 	/*
-	 * Insert the timer to the rbtree and check whether it
-	 * replaces the first pending timer
-	 */
-	if (leftmost)
-		base->first = &timer->node;
-
-	rb_link_node(&timer->node, parent, link);
-	rb_insert_color(&timer->node, &base->active);
-	/*
 	 * HRTIMER_STATE_ENQUEUED is or'ed to the current state to preserve the
 	 * state of a possibly running callback.
 	 */
 	timer->state |= HRTIMER_STATE_ENQUEUED;
 
-	return leftmost;
+	return (&timer->node == base->active.next);
 }
 
 /*
@@ -901,12 +873,7 @@ static void __remove_hrtimer(struct hrtimer *timer,
 	if (!(timer->state & HRTIMER_STATE_ENQUEUED))
 		goto out;
 
-	/*
-	 * Remove the timer from the rbtree and replace the first
-	 * entry pointer if necessary.
-	 */
-	if (base->first == &timer->node) {
-		base->first = rb_next(&timer->node);
+	if (&timer->node == timerlist_getnext(&base->active)) {
 #ifdef CONFIG_HIGH_RES_TIMERS
 		/* Reprogram the clock event device. if enabled */
 		if (reprogram && hrtimer_hres_active()) {
@@ -919,7 +886,7 @@ static void __remove_hrtimer(struct hrtimer *timer,
 		}
 #endif
 	}
-	rb_erase(&timer->node, &base->active);
+	timerlist_del(&base->active, &timer->node);
 out:
 	timer->state = newstate;
 }
@@ -1128,11 +1095,13 @@ ktime_t hrtimer_get_next_event(void)
 	if (!hrtimer_hres_active()) {
 		for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++, base++) {
 			struct hrtimer *timer;
+			struct timerlist_node *next;
 
-			if (!base->first)
+			next = timerlist_getnext(&base->active);
+			if (!next)
 				continue;
 
-			timer = rb_entry(base->first, struct hrtimer, node);
+			timer = container_of(next, struct hrtimer, node);
 			delta.tv64 = hrtimer_get_expires_tv64(timer);
 			delta = ktime_sub(delta, base->get_time());
 			if (delta.tv64 < mindelta.tv64)
@@ -1162,6 +1131,7 @@ static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
 
 	timer->base = &cpu_base->clock_base[clock_id];
 	hrtimer_init_timer_hres(timer);
+	timerlist_init(&timer->node);
 
 #ifdef CONFIG_TIMER_STATS
 	timer->start_site = NULL;
@@ -1278,14 +1248,14 @@ retry:
 
 	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
 		ktime_t basenow;
-		struct rb_node *node;
+		struct timerlist_node *node;
 
 		basenow = ktime_add(now, base->offset);
 
-		while ((node = base->first)) {
+		while ((node = timerlist_getnext(&base->active))) {
 			struct hrtimer *timer;
 
-			timer = rb_entry(node, struct hrtimer, node);
+			timer = container_of(node, struct hrtimer, node);
 
 			/*
 			 * The immediate goal for using the softexpires is
@@ -1441,7 +1411,7 @@ void hrtimer_run_pending(void)
  */
 void hrtimer_run_queues(void)
 {
-	struct rb_node *node;
+	struct timerlist_node *node;
 	struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
 	struct hrtimer_clock_base *base;
 	int index, gettime = 1;
@@ -1450,9 +1420,11 @@ void hrtimer_run_queues(void)
 		return;
 
 	for (index = 0; index < HRTIMER_MAX_CLOCK_BASES; index++) {
-		base = &cpu_base->clock_base[index];
+		struct timerlist_node *next;
 
-		if (!base->first)
+		base = &cpu_base->clock_base[index];
+		next = timerlist_getnext(&base->active);
+		if (!next)
 			continue;
 
 		if (gettime) {
@@ -1462,10 +1434,10 @@ void hrtimer_run_queues(void)
 
 		raw_spin_lock(&cpu_base->lock);
 
-		while ((node = base->first)) {
+		while ((node = next)) {
 			struct hrtimer *timer;
 
-			timer = rb_entry(node, struct hrtimer, node);
+			timer = container_of(node, struct hrtimer, node);
 			if (base->softirq_time.tv64 <=
 					hrtimer_get_expires_tv64(timer))
 				break;
@@ -1630,8 +1602,10 @@ static void __cpuinit init_hrtimers_cpu(int cpu)
 
 	raw_spin_lock_init(&cpu_base->lock);
 
-	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
+	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
 		cpu_base->clock_base[i].cpu_base = cpu_base;
+		timerlist_init_head(&cpu_base->clock_base[i].active);
+	}
 
 	hrtimer_init_hres(cpu_base);
 }
@@ -1642,10 +1616,10 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
 				struct hrtimer_clock_base *new_base)
 {
 	struct hrtimer *timer;
-	struct rb_node *node;
+	struct timerlist_node *node;
 
-	while ((node = rb_first(&old_base->active))) {
-		timer = rb_entry(node, struct hrtimer, node);
+	while ((node = timerlist_getnext(&old_base->active))) {
+		timer = container_of(node, struct hrtimer, node);
 		BUG_ON(hrtimer_callback_running(timer));
 		debug_deactivate(timer);
 
diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
index ab8f5e3..7583b8d 100644
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -79,26 +79,26 @@ print_active_timers(struct seq_file *m, struct hrtimer_clock_base *base,
 {
 	struct hrtimer *timer, tmp;
 	unsigned long next = 0, i;
-	struct rb_node *curr;
+	struct timerlist_node *curr;
 	unsigned long flags;
 
 next_one:
 	i = 0;
 	raw_spin_lock_irqsave(&base->cpu_base->lock, flags);
 
-	curr = base->first;
+	curr = timerlist_getnext(&base->active);
 	/*
 	 * Crude but we have to do this O(N*N) thing, because
 	 * we have to unlock the base when printing:
 	 */
 	while (curr && i < next) {
-		curr = rb_next(curr);
+		curr = timerlist_iterate_next(curr);
 		i++;
 	}
 
 	if (curr) {
 
-		timer = rb_entry(curr, struct hrtimer, node);
+		timer = container_of(curr, struct hrtimer, node);
 		tmp = *timer;
 		raw_spin_unlock_irqrestore(&base->cpu_base->lock, flags);
 
-- 
1.7.3.2.146.gca209

[PATCH 3/7] [RFC] RTC: Rework RTC code to use timerlist for events

[John Stultz]

This patch reworks a large portion of the generic RTC code
to in-effect virtualize the rtc interrupt code.

The current RTC interface is very much a raw hardware interface.
Via the proc, /dev/, or sysfs interfaces, applciations can set
the hardware to trigger interrupts in one of three modes:

AIE: Alarm interrupt
UIE: Update interrupt (ie: once per second)
PIE: Periodic interrupt (sub-second irqs)

The problem with this interface is that it limits the RTC hardware
so it can only be used by one application at a time.

The purpose of this patch is to extend the RTC code so that we can
multiplex multiple applications event needs onto a single RTC device.
This is done by utilizing the timerlist infrastructure to manage
a list of events, which cause the RTC hardware to be programmed
to fire an interrupt for the next event in the list.

In order to preserve the functionality of the exsting proc,/dev/ and
sysfs interfaces, we emulate the different interrupt modes as follows:

AIE: We create a rtc_timer dedicated to AIE mode interrupts. There is
only one per device, so we don't change existing interface semantics.

UIE: Again, a dedicated rtc_timer, set for periodic mode, is used
to emulate UIE interrupts. Again, only one per device.

PIE: Since PIE mode interrupts fire faster then the RTC's clock read
granularity, we emulate PIE mode interrupts using a hrtimer. Again,
one per device.

With this patch, the rtctest.c application in Documentation/rtc.txt
passes fine on x86 hardware. However, there may very well still be
bugs, so greatly I'd appreciate any feedback or testing!

Signed-off-by: John Stultz <john.stultz@linaro.org>
CC: Alessandro Zummo <a.zummo@towertech.it>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Richard Cochran <richardcochran@gmail.com>
CC: Arve Hjønnevåg <arve@android.com>
---
 drivers/rtc/class.c     |   13 +
 drivers/rtc/interface.c |  574 ++++++++++++++++++++++++++++------------------
 drivers/rtc/rtc-lib.c   |   26 +++
 include/linux/rtc.h     |   43 +++-
 4 files changed, 426 insertions(+), 230 deletions(-)

diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index e6539cb..fb59222 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -16,6 +16,7 @@
 #include <linux/kdev_t.h>
 #include <linux/idr.h>
 #include <linux/slab.h>
+#include <linux/workqueue.h>
 
 #include "rtc-core.h"
 
@@ -152,6 +153,18 @@ struct rtc_device *rtc_device_register(const char *name, struct device *dev,
 	spin_lock_init(&rtc->irq_task_lock);
 	init_waitqueue_head(&rtc->irq_queue);
 
+	/* Init timerlist */
+	timerlist_init_head(&rtc->timerlist);
+	INIT_WORK(&rtc->irqwork, rtctimer_do_work);
+	/* Init aie timer */
+	rtctimer_init(&rtc->aie_timer, rtc_aie_update_irq, (void*)rtc);
+	/* Init uie timer */
+	rtctimer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, (void*)rtc);
+	/* Init pie timer */
+	hrtimer_init(&rtc->pie_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	rtc->pie_timer.function = rtc_pie_update_irq;
+	rtc->pie_enabled = 0;
+
 	strlcpy(rtc->name, name, RTC_DEVICE_NAME_SIZE);
 	dev_set_name(&rtc->dev, "rtc%d", id);
 
diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index a0c8162..55894ee 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -14,15 +14,11 @@
 #include <linux/rtc.h>
 #include <linux/sched.h>
 #include <linux/log2.h>
+#include <linux/workqueue.h>
 
-int rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
+static int __rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
 {
 	int err;
-
-	err = mutex_lock_interruptible(&rtc->ops_lock);
-	if (err)
-		return err;
-
 	if (!rtc->ops)
 		err = -ENODEV;
 	else if (!rtc->ops->read_time)
@@ -31,7 +27,18 @@ int rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
 		memset(tm, 0, sizeof(struct rtc_time));
 		err = rtc->ops->read_time(rtc->dev.parent, tm);
 	}
+	return err;
+}
+
+int rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
+{
+	int err;
 
+	err = mutex_lock_interruptible(&rtc->ops_lock);
+	if (err)
+		return err;
+
+	err = __rtc_read_time(rtc, tm);
 	mutex_unlock(&rtc->ops_lock);
 	return err;
 }
@@ -106,188 +113,54 @@ int rtc_set_mmss(struct rtc_device *rtc, unsigned long secs)
 }
 EXPORT_SYMBOL_GPL(rtc_set_mmss);
 
-static int rtc_read_alarm_internal(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
+int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 {
 	int err;
 
 	err = mutex_lock_interruptible(&rtc->ops_lock);
 	if (err)
 		return err;
-
-	if (rtc->ops == NULL)
-		err = -ENODEV;
-	else if (!rtc->ops->read_alarm)
-		err = -EINVAL;
-	else {
-		memset(alarm, 0, sizeof(struct rtc_wkalrm));
-		err = rtc->ops->read_alarm(rtc->dev.parent, alarm);
-	}
-
+	alarm->enabled = rtc->aie_timer.enabled;
+	if (alarm->enabled)
+		alarm->time = rtc_ktime_to_tm(rtc->aie_timer.node.expires);
 	mutex_unlock(&rtc->ops_lock);
-	return err;
+
+	return 0;
 }
+EXPORT_SYMBOL_GPL(rtc_read_alarm);
 
-int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
+int __rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 {
+	struct rtc_time tm;
+	long now, scheduled;
 	int err;
-	struct rtc_time before, now;
-	int first_time = 1;
-	unsigned long t_now, t_alm;
-	enum { none, day, month, year } missing = none;
-	unsigned days;
-
-	/* The lower level RTC driver may return -1 in some fields,
-	 * creating invalid alarm->time values, for reasons like:
-	 *
-	 *   - The hardware may not be capable of filling them in;
-	 *     many alarms match only on time-of-day fields, not
-	 *     day/month/year calendar data.
-	 *
-	 *   - Some hardware uses illegal values as "wildcard" match
-	 *     values, which non-Linux firmware (like a BIOS) may try
-	 *     to set up as e.g. "alarm 15 minutes after each hour".
-	 *     Linux uses only oneshot alarms.
-	 *
-	 * When we see that here, we deal with it by using values from
-	 * a current RTC timestamp for any missing (-1) values.  The
-	 * RTC driver prevents "periodic alarm" modes.
-	 *
-	 * But this can be racey, because some fields of the RTC timestamp
-	 * may have wrapped in the interval since we read the RTC alarm,
-	 * which would lead to us inserting inconsistent values in place
-	 * of the -1 fields.
-	 *
-	 * Reading the alarm and timestamp in the reverse sequence
-	 * would have the same race condition, and not solve the issue.
-	 *
-	 * So, we must first read the RTC timestamp,
-	 * then read the RTC alarm value,
-	 * and then read a second RTC timestamp.
-	 *
-	 * If any fields of the second timestamp have changed
-	 * when compared with the first timestamp, then we know
-	 * our timestamp may be inconsistent with that used by
-	 * the low-level rtc_read_alarm_internal() function.
-	 *
-	 * So, when the two timestamps disagree, we just loop and do
-	 * the process again to get a fully consistent set of values.
-	 *
-	 * This could all instead be done in the lower level driver,
-	 * but since more than one lower level RTC implementation needs it,
-	 * then it's probably best best to do it here instead of there..
-	 */
 
-	/* Get the "before" timestamp */
-	err = rtc_read_time(rtc, &before);
-	if (err < 0)
+	err = rtc_valid_tm(&alarm->time);
+	if (err)
 		return err;
-	do {
-		if (!first_time)
-			memcpy(&before, &now, sizeof(struct rtc_time));
-		first_time = 0;
-
-		/* get the RTC alarm values, which may be incomplete */
-		err = rtc_read_alarm_internal(rtc, alarm);
-		if (err)
-			return err;
-		if (!alarm->enabled)
-			return 0;
-
-		/* full-function RTCs won't have such missing fields */
-		if (rtc_valid_tm(&alarm->time) == 0)
-			return 0;
-
-		/* get the "after" timestamp, to detect wrapped fields */
-		err = rtc_read_time(rtc, &now);
-		if (err < 0)
-			return err;
-
-		/* note that tm_sec is a "don't care" value here: */
-	} while (   before.tm_min   != now.tm_min
-		 || before.tm_hour  != now.tm_hour
-		 || before.tm_mon   != now.tm_mon
-		 || before.tm_year  != now.tm_year);
-
-	/* Fill in the missing alarm fields using the timestamp; we
-	 * know there's at least one since alarm->time is invalid.
-	 */
-	if (alarm->time.tm_sec == -1)
-		alarm->time.tm_sec = now.tm_sec;
-	if (alarm->time.tm_min == -1)
-		alarm->time.tm_min = now.tm_min;
-	if (alarm->time.tm_hour == -1)
-		alarm->time.tm_hour = now.tm_hour;
-
-	/* For simplicity, only support date rollover for now */
-	if (alarm->time.tm_mday == -1) {
-		alarm->time.tm_mday = now.tm_mday;
-		missing = day;
-	}
-	if (alarm->time.tm_mon == -1) {
-		alarm->time.tm_mon = now.tm_mon;
-		if (missing == none)
-			missing = month;
-	}
-	if (alarm->time.tm_year == -1) {
-		alarm->time.tm_year = now.tm_year;
-		if (missing == none)
-			missing = year;
-	}
-
-	/* with luck, no rollover is needed */
-	rtc_tm_to_time(&now, &t_now);
-	rtc_tm_to_time(&alarm->time, &t_alm);
-	if (t_now < t_alm)
-		goto done;
-
-	switch (missing) {
+	rtc_tm_to_time(&alarm->time, &scheduled);
 
-	/* 24 hour rollover ... if it's now 10am Monday, an alarm that
-	 * that will trigger at 5am will do so at 5am Tuesday, which
-	 * could also be in the next month or year.  This is a common
-	 * case, especially for PCs.
-	 */
-	case day:
-		dev_dbg(&rtc->dev, "alarm rollover: %s\n", "day");
-		t_alm += 24 * 60 * 60;
-		rtc_time_to_tm(t_alm, &alarm->time);
-		break;
-
-	/* Month rollover ... if it's the 31th, an alarm on the 3rd will
-	 * be next month.  An alarm matching on the 30th, 29th, or 28th
-	 * may end up in the month after that!  Many newer PCs support
-	 * this type of alarm.
+	/* Make sure we're not setting alarms in the past */
+	err = __rtc_read_time(rtc, &tm);
+	rtc_tm_to_time(&tm, &now);
+	if (scheduled <= now)
+		return -ETIME;
+	/*
+	 * XXX - We just checked to make sure the alarm time is not
+	 * in the past, but there is still a race window where if
+	 * the is alarm set for the next second and the second ticks
+	 * over right here, before we set the alarm.
 	 */
-	case month:
-		dev_dbg(&rtc->dev, "alarm rollover: %s\n", "month");
-		do {
-			if (alarm->time.tm_mon < 11)
-				alarm->time.tm_mon++;
-			else {
-				alarm->time.tm_mon = 0;
-				alarm->time.tm_year++;
-			}
-			days = rtc_month_days(alarm->time.tm_mon,
-					alarm->time.tm_year);
-		} while (days < alarm->time.tm_mday);
-		break;
-
-	/* Year rollover ... easy except for leap years! */
-	case year:
-		dev_dbg(&rtc->dev, "alarm rollover: %s\n", "year");
-		do {
-			alarm->time.tm_year++;
-		} while (rtc_valid_tm(&alarm->time) != 0);
-		break;
-
-	default:
-		dev_warn(&rtc->dev, "alarm rollover not handled\n");
-	}
 
-done:
-	return 0;
+	if (!rtc->ops)
+		err = -ENODEV;
+	else if (!rtc->ops->set_alarm)
+		err = -EINVAL;
+	else
+		err = rtc->ops->set_alarm(rtc->dev.parent, alarm);
+
+	return err;
 }
-EXPORT_SYMBOL_GPL(rtc_read_alarm);
 
 int rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 {
@@ -300,16 +173,18 @@ int rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 	err = mutex_lock_interruptible(&rtc->ops_lock);
 	if (err)
 		return err;
-
-	if (!rtc->ops)
-		err = -ENODEV;
-	else if (!rtc->ops->set_alarm)
-		err = -EINVAL;
-	else
-		err = rtc->ops->set_alarm(rtc->dev.parent, alarm);
-
+	if (rtc->aie_timer.enabled) {
+		rtctimer_remove(rtc, &rtc->aie_timer);
+		rtc->aie_timer.enabled = 0;
+	}
+	rtc->aie_timer.node.expires = rtc_tm_to_ktime(alarm->time);
+	rtc->aie_timer.period = ktime_set(0,0);
+	if (alarm->enabled) {
+		rtc->aie_timer.enabled = 1;
+		rtctimer_enqueue(rtc, &rtc->aie_timer);
+	}
 	mutex_unlock(&rtc->ops_lock);
-	return err;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(rtc_set_alarm);
 
@@ -319,6 +194,16 @@ int rtc_alarm_irq_enable(struct rtc_device *rtc, unsigned int enabled)
 	if (err)
 		return err;
 
+	if (rtc->aie_timer.enabled != enabled) {
+		if (enabled){
+			rtc->aie_timer.enabled = 1;
+			rtctimer_enqueue(rtc, &rtc->aie_timer);
+		} else {
+			rtctimer_remove(rtc, &rtc->aie_timer);
+			rtc->aie_timer.enabled = 0;
+		}
+	}
+
 	if (!rtc->ops)
 		err = -ENODEV;
 	else if (!rtc->ops->alarm_irq_enable)
@@ -337,52 +222,53 @@ int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
 	if (err)
 		return err;
 
-#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
-	if (enabled == 0 && rtc->uie_irq_active) {
-		mutex_unlock(&rtc->ops_lock);
-		return rtc_dev_update_irq_enable_emul(rtc, enabled);
+	/* make sure we're changing state */
+	if(rtc->uie_rtctimer.enabled == enabled)
+		goto out;
+
+	if (enabled) {
+		struct rtc_time tm;
+		ktime_t now, onesec;
+
+		__rtc_read_time(rtc, &tm);
+		onesec = ktime_set(1,0);
+		now = rtc_tm_to_ktime(tm);
+		rtc->uie_rtctimer.node.expires = ktime_add(now,onesec);
+		rtc->uie_rtctimer.period = ktime_set(1,0);
+		rtc->uie_rtctimer.enabled = 1;
+		rtctimer_enqueue(rtc, &rtc->uie_rtctimer);
+	} else {
+		rtctimer_remove(rtc, &rtc->uie_rtctimer);
+		rtc->uie_rtctimer.enabled = 0;
 	}
-#endif
-
-	if (!rtc->ops)
-		err = -ENODEV;
-	else if (!rtc->ops->update_irq_enable)
-		err = -EINVAL;
-	else
-		err = rtc->ops->update_irq_enable(rtc->dev.parent, enabled);
 
+out:
 	mutex_unlock(&rtc->ops_lock);
-
-#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
-	/*
-	 * Enable emulation if the driver did not provide
-	 * the update_irq_enable function pointer or if returned
-	 * -EINVAL to signal that it has been configured without
-	 * interrupts or that are not available at the moment.
-	 */
-	if (err == -EINVAL)
-		err = rtc_dev_update_irq_enable_emul(rtc, enabled);
-#endif
 	return err;
+
 }
 EXPORT_SYMBOL_GPL(rtc_update_irq_enable);
 
+
 /**
- * rtc_update_irq - report RTC periodic, alarm, and/or update irqs
- * @rtc: the rtc device
- * @num: how many irqs are being reported (usually one)
- * @events: mask of RTC_IRQF with one or more of RTC_PF, RTC_AF, RTC_UF
- * Context: any
+ * rtc_handle_legacy_irq - AIE, UIE and PIE event hook
+ * @rtc: pointer to the rtc device
+ *
+ * This function is called when an AIE, UIE or PIE mode interrupt
+ * has occured (or been emulated).
+ *
+ * Triggers the registered irq_task function callback.
  */
-void rtc_update_irq(struct rtc_device *rtc,
-		unsigned long num, unsigned long events)
+static void rtc_handle_legacy_irq(struct rtc_device* rtc, int num, int mode)
 {
 	unsigned long flags;
 
+	/* mark one irq of the appropriate mode */
 	spin_lock_irqsave(&rtc->irq_lock, flags);
-	rtc->irq_data = (rtc->irq_data + (num << 8)) | events;
+	rtc->irq_data = (rtc->irq_data + (num << 8)) | (RTC_IRQF|mode);
 	spin_unlock_irqrestore(&rtc->irq_lock, flags);
 
+	/* call the task func */
 	spin_lock_irqsave(&rtc->irq_task_lock, flags);
 	if (rtc->irq_task)
 		rtc->irq_task->func(rtc->irq_task->private_data);
@@ -391,6 +277,69 @@ void rtc_update_irq(struct rtc_device *rtc,
 	wake_up_interruptible(&rtc->irq_queue);
 	kill_fasync(&rtc->async_queue, SIGIO, POLL_IN);
 }
+
+
+/**
+ * rtc_aie_update_irq - AIE mode rtctimer hook
+ * @private: pointer to the rtc_device
+ *
+ * This functions is called when the aie_timer expires.
+ */
+void rtc_aie_update_irq(void *private)
+{
+	struct rtc_device *rtc = (struct rtc_device *)private;
+	rtc_handle_legacy_irq(rtc, 1, RTC_AF);
+}
+
+
+/**
+ * rtc_uie_update_irq - UIE mode rtctimer hook
+ * @private: pointer to the rtc_device
+ *
+ * This functions is called when the uie_timer expires.
+ */
+void rtc_uie_update_irq(void *private)
+{
+	struct rtc_device *rtc = (struct rtc_device *)private;
+	rtc_handle_legacy_irq(rtc, 1,  RTC_UF);
+}
+
+
+/**
+ * rtc_pie_update_irq - PIE mode hrtimer hook
+ * @timer: pointer to the pie mode hrtimer
+ *
+ * This function is used to emulate PIE mode interrupts
+ * using an hrtimer. This function is called when the periodic
+ * hrtimer expires.
+ */
+enum hrtimer_restart rtc_pie_update_irq(struct hrtimer *timer)
+{
+	struct rtc_device *rtc;
+	ktime_t period;
+	int count;
+	rtc = container_of(timer, struct rtc_device, pie_timer);
+
+	period = ktime_set(0,NSEC_PER_SEC/rtc->irq_freq);
+	count = hrtimer_forward_now(timer, period);
+
+	rtc_handle_legacy_irq(rtc, count, RTC_PF);
+
+	return HRTIMER_RESTART;
+}
+
+/**
+ * rtc_update_irq - Triggered when a RTC interrupt occurs.
+ * @rtc: the rtc device
+ * @num: how many irqs are being reported (usually one)
+ * @events: mask of RTC_IRQF with one or more of RTC_PF, RTC_AF, RTC_UF
+ * Context: any
+ */
+void rtc_update_irq(struct rtc_device *rtc,
+		unsigned long num, unsigned long events)
+{
+	schedule_work(&rtc->irqwork);
+}
 EXPORT_SYMBOL_GPL(rtc_update_irq);
 
 static int __rtc_match(struct device *dev, void *data)
@@ -477,18 +426,20 @@ int rtc_irq_set_state(struct rtc_device *rtc, struct rtc_task *task, int enabled
 	int err = 0;
 	unsigned long flags;
 
-	if (rtc->ops->irq_set_state == NULL)
-		return -ENXIO;
-
 	spin_lock_irqsave(&rtc->irq_task_lock, flags);
 	if (rtc->irq_task != NULL && task == NULL)
 		err = -EBUSY;
 	if (rtc->irq_task != task)
 		err = -EACCES;
-	spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
 
-	if (err == 0)
-		err = rtc->ops->irq_set_state(rtc->dev.parent, enabled);
+	if(enabled) {
+		ktime_t period = ktime_set(0, NSEC_PER_SEC/rtc->irq_freq);
+		hrtimer_start(&rtc->pie_timer, period, HRTIMER_MODE_REL);
+	} else {
+		hrtimer_cancel(&rtc->pie_timer);
+	}
+	rtc->pie_enabled = enabled;
+	spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
 
 	return err;
 }
@@ -509,21 +460,194 @@ int rtc_irq_set_freq(struct rtc_device *rtc, struct rtc_task *task, int freq)
 	int err = 0;
 	unsigned long flags;
 
-	if (rtc->ops->irq_set_freq == NULL)
-		return -ENXIO;
-
 	spin_lock_irqsave(&rtc->irq_task_lock, flags);
 	if (rtc->irq_task != NULL && task == NULL)
 		err = -EBUSY;
 	if (rtc->irq_task != task)
 		err = -EACCES;
-	spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
-
 	if (err == 0) {
-		err = rtc->ops->irq_set_freq(rtc->dev.parent, freq);
-		if (err == 0)
-			rtc->irq_freq = freq;
+		rtc->irq_freq = freq;
+		if (rtc->pie_enabled) {
+			ktime_t period;
+			hrtimer_cancel(&rtc->pie_timer);
+			period = ktime_set(0, NSEC_PER_SEC/rtc->irq_freq);
+			hrtimer_start(&rtc->pie_timer, period,
+					HRTIMER_MODE_REL);
+		}
 	}
+	spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
 	return err;
 }
 EXPORT_SYMBOL_GPL(rtc_irq_set_freq);
+
+/**
+ * rtctimer_enqueue - Adds a rtc_timer to the rtc_device timerlist
+ * @rtc rtc device
+ * @timer timer being added.
+ *
+ * Enqueues a timer onto the rtc devices timerlist and sets
+ * the next alarm event appropriately.
+ *
+ * Must hold ops_lock for proper serialization of timerlist
+ */
+void rtctimer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer)
+{
+	timerlist_add(&rtc->timerlist, &timer->node);
+	if (&timer->node == timerlist_getnext(&rtc->timerlist)) {
+		struct rtc_wkalrm alarm;
+		int err;
+		alarm.time = rtc_ktime_to_tm(timer->node.expires);
+		alarm.enabled = 1;
+		err = __rtc_set_alarm(rtc, &alarm);
+		if (err == -ETIME)
+			schedule_work(&rtc->irqwork);
+	}
+}
+
+/**
+ * rtctimer_remove - Removes a rtc_timer from the rtc_device timerlist
+ * @rtc rtc device
+ * @timer timer being removed.
+ *
+ * Removes a timer onto the rtc devices timerlist and sets
+ * the next alarm event appropriately.
+ *
+ * Must hold ops_lock for proper serialization of timerlist
+ */
+void rtctimer_remove(struct rtc_device *rtc, struct rtc_timer *timer)
+{
+	struct timerlist_node *next = timerlist_getnext(&rtc->timerlist);
+	timerlist_del(&rtc->timerlist, &timer->node);
+
+	if (next == &timer->node) {
+		struct rtc_wkalrm alarm;
+		int err;
+		next = timerlist_getnext(&rtc->timerlist);
+		if (!next)
+			return;
+		alarm.time = rtc_ktime_to_tm(next->expires);
+		alarm.enabled = 1;
+		err = __rtc_set_alarm(rtc, &alarm);
+		if (err == -ETIME)
+			schedule_work(&rtc->irqwork);
+	}
+}
+
+/**
+ * rtctimer_do_work - Expires rtc timers
+ * @rtc rtc device
+ * @timer timer being removed.
+ *
+ * Expires rtc timers. Reprograms next alarm event if needed.
+ * Called via worktask.
+ *
+ * Serializes access to timerlist via ops_lock mutex
+ */
+void rtctimer_do_work(struct work_struct *work)
+{
+	struct rtc_timer *timer;
+	struct timerlist_node *next;
+	ktime_t now;
+	struct rtc_time tm;
+
+	struct rtc_device *rtc =
+		container_of(work, struct rtc_device, irqwork);
+
+	mutex_lock(&rtc->ops_lock);
+again:
+	__rtc_read_time(rtc, &tm);
+	now = rtc_tm_to_ktime(tm);
+	while ((next = timerlist_getnext(&rtc->timerlist))) {
+		if (next->expires.tv64 > now.tv64)
+			break;
+
+		/* expire timer */
+		timer = container_of(next, struct rtc_timer, node);
+		timerlist_del(&rtc->timerlist, &timer->node);
+		timer->enabled = 0;
+		if (timer->task.func)
+			timer->task.func(timer->task.private_data);
+
+		/* Re-add/fwd periodic timers */
+		if (ktime_to_ns(timer->period)) {
+			timer->node.expires = ktime_add(timer->node.expires,
+							timer->period);
+			timer->enabled = 1;
+			timerlist_add(&rtc->timerlist, &timer->node);
+		}
+	}
+
+	/* Set next alarm */
+	if (next) {
+		struct rtc_wkalrm alarm;
+		int err;
+		alarm.time = rtc_ktime_to_tm(next->expires);
+		alarm.enabled = 1;
+		err = __rtc_set_alarm(rtc, &alarm);
+		if (err == -ETIME)
+			goto again;
+	}
+
+	mutex_unlock(&rtc->ops_lock);
+}
+
+
+/* rtctimer_init - Initializes an rtc_timer
+ * @timer: timer to be intiialized
+ * @f: function pointer to be called when timer fires
+ * @data: private data passed to function pointer
+ *
+ * Kernel interface to initializing an rtc_timer.
+ */
+void rtctimer_init(struct rtc_timer *timer, void (*f)(void* p), void* data)
+{
+	timerlist_init(&timer->node);
+	timer->enabled = 0;
+	timer->task.func = f;
+	timer->task.private_data = data;
+}
+
+/* rtctimer_start - Sets an rtc_timer to fire in the future
+ * @ rtc: rtc device to be used
+ * @ timer: timer being set
+ * @ expires: time at which to expire the timer
+ * @ period: period that the timer will recur
+ *
+ * Kernel interface to set an rtc_timer
+ */
+int rtctimer_start(struct rtc_device *rtc, struct rtc_timer* timer,
+			ktime_t expires, ktime_t period)
+{
+	int ret = 0;
+	mutex_lock(&rtc->ops_lock);
+	if (timer->enabled)
+		rtctimer_remove(rtc, timer);
+
+	timer->node.expires = expires;
+	timer->period = period;
+
+	timer->enabled = 1;
+	rtctimer_enqueue(rtc, timer);
+
+	mutex_unlock(&rtc->ops_lock);
+	return ret;
+}
+
+/* rtctimer_cancel - Stops an rtc_timer
+ * @ rtc: rtc device to be used
+ * @ timer: timer being set
+ *
+ * Kernel interface to cancel an rtc_timer
+ */
+int rtctimer_cancel(struct rtc_device *rtc, struct rtc_timer* timer)
+{
+	int ret = 0;
+	mutex_lock(&rtc->ops_lock);
+	if (timer->enabled)
+		rtctimer_remove(rtc, timer);
+	timer->enabled = 0;
+	mutex_unlock(&rtc->ops_lock);
+	return ret;
+}
+
+
diff --git a/drivers/rtc/rtc-lib.c b/drivers/rtc/rtc-lib.c
index 773851f..00df788 100644
--- a/drivers/rtc/rtc-lib.c
+++ b/drivers/rtc/rtc-lib.c
@@ -117,4 +117,30 @@ int rtc_tm_to_time(struct rtc_time *tm, unsigned long *time)
 }
 EXPORT_SYMBOL(rtc_tm_to_time);
 
+/*
+ * Convert rtc_time to ktime
+ */
+ktime_t rtc_tm_to_ktime(struct rtc_time tm)
+{
+	time_t time;
+	rtc_tm_to_time(&tm, &time);
+	return ktime_set(time, 0);
+}
+
+/*
+ * Convert ktime to rtc_time
+ */
+struct rtc_time rtc_ktime_to_tm(ktime_t kt)
+{
+	struct timespec ts;
+	struct rtc_time ret;
+
+	ts = ktime_to_timespec(kt);
+	/* Round up any ns */
+	if (ts.tv_nsec)
+		ts.tv_sec++;
+	rtc_time_to_tm(ts.tv_sec, &ret);
+	return ret;
+}
+
 MODULE_LICENSE("GPL");
diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index 14dbc83..c50fae5 100644
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -107,12 +107,17 @@ extern int rtc_year_days(unsigned int day, unsigned int month, unsigned int year
 extern int rtc_valid_tm(struct rtc_time *tm);
 extern int rtc_tm_to_time(struct rtc_time *tm, unsigned long *time);
 extern void rtc_time_to_tm(unsigned long time, struct rtc_time *tm);
+ktime_t rtc_tm_to_ktime(struct rtc_time tm);
+struct rtc_time rtc_ktime_to_tm(ktime_t kt);
+
 
 #include <linux/device.h>
 #include <linux/seq_file.h>
 #include <linux/cdev.h>
 #include <linux/poll.h>
 #include <linux/mutex.h>
+#include <linux/timerlist.h>
+#include <linux/workqueue.h>
 
 extern struct class *rtc_class;
 
@@ -151,7 +156,19 @@ struct rtc_class_ops {
 };
 
 #define RTC_DEVICE_NAME_SIZE 20
-struct rtc_task;
+typedef struct rtc_task {
+	void (*func)(void *private_data);
+	void *private_data;
+} rtc_task_t;
+
+
+struct rtc_timer {
+	struct rtc_task	task;
+	struct timerlist_node node;
+	ktime_t period;
+	int enabled;
+};
+
 
 /* flags */
 #define RTC_DEV_BUSY 0
@@ -179,6 +196,15 @@ struct rtc_device
 	spinlock_t irq_task_lock;
 	int irq_freq;
 	int max_user_freq;
+
+	struct timerlist_head timerlist;
+	struct rtc_timer aie_timer;
+	struct rtc_timer uie_rtctimer;
+	struct hrtimer pie_timer; /* sub second exp, so needs hrtimer */
+	int pie_enabled;
+	struct work_struct irqwork;
+
+
 #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
 	struct work_struct uie_task;
 	struct timer_list uie_timer;
@@ -224,15 +250,22 @@ extern int rtc_alarm_irq_enable(struct rtc_device *rtc, unsigned int enabled);
 extern int rtc_dev_update_irq_enable_emul(struct rtc_device *rtc,
 						unsigned int enabled);
 
-typedef struct rtc_task {
-	void (*func)(void *private_data);
-	void *private_data;
-} rtc_task_t;
+void rtc_aie_update_irq(void *private);
+void rtc_uie_update_irq(void *private);
+enum hrtimer_restart rtc_pie_update_irq(struct hrtimer *timer);
 
 int rtc_register(rtc_task_t *task);
 int rtc_unregister(rtc_task_t *task);
 int rtc_control(rtc_task_t *t, unsigned int cmd, unsigned long arg);
 
+void rtctimer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer);
+void rtctimer_remove(struct rtc_device *rtc, struct rtc_timer *timer);
+void rtctimer_init(struct rtc_timer *timer, void (*f)(void* p), void* data);
+int rtctimer_start(struct rtc_device *rtc, struct rtc_timer* timer,
+			ktime_t expires, ktime_t period);
+int rtctimer_cancel(struct rtc_device *rtc, struct rtc_timer* timer);
+void rtctimer_do_work(struct work_struct *work);
+
 static inline bool is_leap_year(unsigned int year)
 {
 	return (!(year % 4) && (year % 100)) || !(year % 400);
-- 
1.7.3.2.146.gca209

[PATCH 4/7] [RFC] RTC: Remove UIE emulation

[John Stultz]

Since we provide UIE interrupts via a rtc_timer, the old
emulation code can be removed.

Note: I assume this is ok, but there may be corner cases I'm missing.

Signed-off-by: John Stultz <john.stultz@linaro.org>
CC: Alessandro Zummo <a.zummo@towertech.it>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Richard Cochran <richardcochran@gmail.com>
---
 drivers/rtc/rtc-dev.c |  104 -------------------------------------------------
 include/linux/rtc.h   |   12 ------
 2 files changed, 0 insertions(+), 116 deletions(-)

diff --git a/drivers/rtc/rtc-dev.c b/drivers/rtc/rtc-dev.c
index 62227cd..212b16e 100644
--- a/drivers/rtc/rtc-dev.c
+++ b/drivers/rtc/rtc-dev.c
@@ -46,105 +46,6 @@ static int rtc_dev_open(struct inode *inode, struct file *file)
 	return err;
 }
 
-#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
-/*
- * Routine to poll RTC seconds field for change as often as possible,
- * after first RTC_UIE use timer to reduce polling
- */
-static void rtc_uie_task(struct work_struct *work)
-{
-	struct rtc_device *rtc =
-		container_of(work, struct rtc_device, uie_task);
-	struct rtc_time tm;
-	int num = 0;
-	int err;
-
-	err = rtc_read_time(rtc, &tm);
-
-	spin_lock_irq(&rtc->irq_lock);
-	if (rtc->stop_uie_polling || err) {
-		rtc->uie_task_active = 0;
-	} else if (rtc->oldsecs != tm.tm_sec) {
-		num = (tm.tm_sec + 60 - rtc->oldsecs) % 60;
-		rtc->oldsecs = tm.tm_sec;
-		rtc->uie_timer.expires = jiffies + HZ - (HZ/10);
-		rtc->uie_timer_active = 1;
-		rtc->uie_task_active = 0;
-		add_timer(&rtc->uie_timer);
-	} else if (schedule_work(&rtc->uie_task) == 0) {
-		rtc->uie_task_active = 0;
-	}
-	spin_unlock_irq(&rtc->irq_lock);
-	if (num)
-		rtc_update_irq(rtc, num, RTC_UF | RTC_IRQF);
-}
-static void rtc_uie_timer(unsigned long data)
-{
-	struct rtc_device *rtc = (struct rtc_device *)data;
-	unsigned long flags;
-
-	spin_lock_irqsave(&rtc->irq_lock, flags);
-	rtc->uie_timer_active = 0;
-	rtc->uie_task_active = 1;
-	if ((schedule_work(&rtc->uie_task) == 0))
-		rtc->uie_task_active = 0;
-	spin_unlock_irqrestore(&rtc->irq_lock, flags);
-}
-
-static int clear_uie(struct rtc_device *rtc)
-{
-	spin_lock_irq(&rtc->irq_lock);
-	if (rtc->uie_irq_active) {
-		rtc->stop_uie_polling = 1;
-		if (rtc->uie_timer_active) {
-			spin_unlock_irq(&rtc->irq_lock);
-			del_timer_sync(&rtc->uie_timer);
-			spin_lock_irq(&rtc->irq_lock);
-			rtc->uie_timer_active = 0;
-		}
-		if (rtc->uie_task_active) {
-			spin_unlock_irq(&rtc->irq_lock);
-			flush_scheduled_work();
-			spin_lock_irq(&rtc->irq_lock);
-		}
-		rtc->uie_irq_active = 0;
-	}
-	spin_unlock_irq(&rtc->irq_lock);
-	return 0;
-}
-
-static int set_uie(struct rtc_device *rtc)
-{
-	struct rtc_time tm;
-	int err;
-
-	err = rtc_read_time(rtc, &tm);
-	if (err)
-		return err;
-	spin_lock_irq(&rtc->irq_lock);
-	if (!rtc->uie_irq_active) {
-		rtc->uie_irq_active = 1;
-		rtc->stop_uie_polling = 0;
-		rtc->oldsecs = tm.tm_sec;
-		rtc->uie_task_active = 1;
-		if (schedule_work(&rtc->uie_task) == 0)
-			rtc->uie_task_active = 0;
-	}
-	rtc->irq_data = 0;
-	spin_unlock_irq(&rtc->irq_lock);
-	return 0;
-}
-
-int rtc_dev_update_irq_enable_emul(struct rtc_device *rtc, unsigned int enabled)
-{
-	if (enabled)
-		return set_uie(rtc);
-	else
-		return clear_uie(rtc);
-}
-EXPORT_SYMBOL(rtc_dev_update_irq_enable_emul);
-
-#endif /* CONFIG_RTC_INTF_DEV_UIE_EMUL */
 
 static ssize_t
 rtc_dev_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
@@ -493,11 +394,6 @@ void rtc_dev_prepare(struct rtc_device *rtc)
 
 	rtc->dev.devt = MKDEV(MAJOR(rtc_devt), rtc->id);
 
-#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
-	INIT_WORK(&rtc->uie_task, rtc_uie_task);
-	setup_timer(&rtc->uie_timer, rtc_uie_timer, (unsigned long)rtc);
-#endif
-
 	cdev_init(&rtc->char_dev, &rtc_dev_fops);
 	rtc->char_dev.owner = rtc->owner;
 }
diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index c50fae5..7af34ec 100644
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -203,18 +203,6 @@ struct rtc_device
 	struct hrtimer pie_timer; /* sub second exp, so needs hrtimer */
 	int pie_enabled;
 	struct work_struct irqwork;
-
-
-#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
-	struct work_struct uie_task;
-	struct timer_list uie_timer;
-	/* Those fields are protected by rtc->irq_lock */
-	unsigned int oldsecs;
-	unsigned int uie_irq_active:1;
-	unsigned int stop_uie_polling:1;
-	unsigned int uie_task_active:1;
-	unsigned int uie_timer_active:1;
-#endif
 };
 #define to_rtc_device(d) container_of(d, struct rtc_device, dev)
 
-- 
1.7.3.2.146.gca209

[PATCH 5/7] [RFC] posix clocks: dynamic clock ids.

[John Stultz]

From: Richard Cochran <richardcochran@gmail.com>

This patch augments the POSIX clock code to offer a dynamic clock
creation method. Instead of registering a hard coded clock ID, modules
may call create_posix_clock(), which returns a new clock ID.

Signed-off-by: Richard Cochran <richard.cochran@omicron.at>

This patch still has un-addressed lifetime issues pointed out by
Alan Cox. More work is needed here, but for now this provides the
functionality needed for the following patches.

Signed-off-by: John Stultz <john.stultz@linaro.org>
CC: Alessandro Zummo <a.zummo@towertech.it>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Richard Cochran <richardcochran@gmail.com>
CC: Arve Hjønnevåg <arve@android.com>

---
 include/linux/posix-timers.h |    7 ++++++-
 include/linux/time.h         |    2 ++
 kernel/posix-timers.c        |   41 ++++++++++++++++++++++++++++++++++-------
 3 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index 3e23844a..a9e601a 100644
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -67,6 +67,7 @@ struct k_itimer {
 };
 
 struct k_clock {
+	clockid_t id;
 	int res;		/* in nanoseconds */
 	int (*clock_getres) (const clockid_t which_clock, struct timespec *tp);
 	int (*clock_set) (const clockid_t which_clock, struct timespec * tp);
@@ -84,7 +85,11 @@ struct k_clock {
 			   struct itimerspec * cur_setting);
 };
 
-void register_posix_clock(const clockid_t clock_id, struct k_clock *new_clock);
+/* Regsiter a posix clock with a "well known" clock id. */
+int register_posix_clock(const clockid_t id, struct k_clock *clock);
+
+/* Create a new posix clock with a dynamic clock id. */
+clockid_t create_posix_clock(struct k_clock *clock);
 
 /* error handlers for timer_create, nanosleep and settime */
 int do_posix_clock_nonanosleep(const clockid_t, int flags, struct timespec *,
diff --git a/include/linux/time.h b/include/linux/time.h
index 9f15ac7..914c48d 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -299,6 +299,8 @@ struct itimerval {
 #define CLOCKS_MASK			(CLOCK_REALTIME | CLOCK_MONOTONIC)
 #define CLOCKS_MONO			CLOCK_MONOTONIC
 
+#define CLOCK_INVALID			-1
+
 /*
  * The various flags for setting POSIX.1b interval timers:
  */
diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index 9ca4973..2f88d0b 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -132,6 +132,8 @@ static DEFINE_SPINLOCK(idr_lock);
  */
 
 static struct k_clock posix_clocks[MAX_CLOCKS];
+static DECLARE_BITMAP(clocks_map, MAX_CLOCKS);
+static DEFINE_MUTEX(clocks_mux); /* protects 'posix_clocks' and 'clocks_map' */
 
 /*
  * These ones are defined below.
@@ -476,18 +478,43 @@ static struct pid *good_sigevent(sigevent_t * event)
 	return task_pid(rtn);
 }
 
-void register_posix_clock(const clockid_t clock_id, struct k_clock *new_clock)
+int register_posix_clock(const clockid_t id, struct k_clock *clock)
 {
-	if ((unsigned) clock_id >= MAX_CLOCKS) {
-		printk("POSIX clock register failed for clock_id %d\n",
-		       clock_id);
-		return;
-	}
+	struct k_clock *kc;
+	int err = 0;
 
-	posix_clocks[clock_id] = *new_clock;
+	mutex_lock(&clocks_mux);
+	if (test_bit(id, clocks_map)) {
+		pr_err("clock_id %d already registered\n", id);
+		err = -EBUSY;
+		goto out;
+	}
+	kc = &posix_clocks[id];
+	*kc = *clock;
+	kc->id = id;
+	set_bit(id, clocks_map);
+out:
+	mutex_unlock(&clocks_mux);
+	return err;
 }
 EXPORT_SYMBOL_GPL(register_posix_clock);
 
+clockid_t create_posix_clock(struct k_clock *clock)
+{
+	clockid_t id;
+
+	mutex_lock(&clocks_mux);
+	id = find_first_zero_bit(clocks_map, MAX_CLOCKS);
+	mutex_unlock(&clocks_mux);
+
+	if (id < MAX_CLOCKS) {
+		register_posix_clock(id, clock);
+		return id;
+	}
+	return CLOCK_INVALID;
+}
+EXPORT_SYMBOL_GPL(create_posix_clock);
+
 static struct k_itimer * alloc_posix_timer(void)
 {
 	struct k_itimer *tmr;
-- 
1.7.3.2.146.gca209

[PATCH 6/7] [RFC] RTC: Add posix clock/timer interface

[John Stultz]

This patch provides an initial implementation of the
posix clock/timer interface to the RTC. Since the current
/dev, proc, and sysfs interfaces don't queue events, two
applications trying to set a wakeup events in the future
might race, causing events to be missed. The posix interface
allows multiple applications to be able to set timers against
a single RTC device, letting the kernel manage the multiplexing.

One example use would be a backup job that is done at night
on a desktop system that suspends after 15 minutes of idle time.
A cron-like job manager could set a posix timer against the RTC
to ensure the system woke from suspend in order to run the backup.

However, the system might also run a DVR application to record
a favorite show. That application could also use the posix
interface to set a timer against the RTC without having to worry
if it had overwritten the timer set for the backup job.

Since there can be multiple RTCs on a system, we utilize the
dynamic posix clock registration code, and export the clockid
via /sys/class/rtc/rtcN/posix_clockid.

TODO:
   o improve clock_to_rtc() perf
   o stress test timer code
   o code comments
   o probably other stuff too

Signed-off-by: John Stultz <john.stultz@linaro.org>
CC: Alessandro Zummo <a.zummo@towertech.it>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Richard Cochran <richardcochran@gmail.com>
---
 drivers/rtc/Makefile         |    2 +-
 drivers/rtc/class.c          |    2 +
 drivers/rtc/interface.c      |    9 +-
 drivers/rtc/posix.c          |  258 ++++++++++++++++++++++++++++++++++++++++++
 drivers/rtc/rtc-sysfs.c      |   10 ++
 include/linux/posix-timers.h |    2 +
 include/linux/rtc.h          |    5 +-
 7 files changed, 283 insertions(+), 5 deletions(-)
 create mode 100644 drivers/rtc/posix.c

diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 4c2832d..05e2c90 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -9,7 +9,7 @@ endif
 obj-$(CONFIG_RTC_LIB)		+= rtc-lib.o
 obj-$(CONFIG_RTC_HCTOSYS)	+= hctosys.o
 obj-$(CONFIG_RTC_CLASS)		+= rtc-core.o
-rtc-core-y			:= class.o interface.o
+rtc-core-y			:= class.o interface.o posix.o
 
 rtc-core-$(CONFIG_RTC_INTF_DEV)	+= rtc-dev.o
 rtc-core-$(CONFIG_RTC_INTF_PROC) += rtc-proc.o
diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index fb59222..85762ea 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -165,6 +165,8 @@ struct rtc_device *rtc_device_register(const char *name, struct device *dev,
 	rtc->pie_timer.function = rtc_pie_update_irq;
 	rtc->pie_enabled = 0;
 
+	init_rtc_posix_timer(rtc);
+
 	strlcpy(rtc->name, name, RTC_DEVICE_NAME_SIZE);
 	dev_set_name(&rtc->dev, "rtc%d", id);
 
diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 55894ee..b6f1bc9 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -16,6 +16,11 @@
 #include <linux/log2.h>
 #include <linux/workqueue.h>
 
+
+static void rtctimer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer);
+static void rtctimer_remove(struct rtc_device *rtc, struct rtc_timer *timer);
+
+
 static int __rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
 {
 	int err;
@@ -490,7 +495,7 @@ EXPORT_SYMBOL_GPL(rtc_irq_set_freq);
  *
  * Must hold ops_lock for proper serialization of timerlist
  */
-void rtctimer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer)
+static void rtctimer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer)
 {
 	timerlist_add(&rtc->timerlist, &timer->node);
 	if (&timer->node == timerlist_getnext(&rtc->timerlist)) {
@@ -514,7 +519,7 @@ void rtctimer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer)
  *
  * Must hold ops_lock for proper serialization of timerlist
  */
-void rtctimer_remove(struct rtc_device *rtc, struct rtc_timer *timer)
+static void rtctimer_remove(struct rtc_device *rtc, struct rtc_timer *timer)
 {
 	struct timerlist_node *next = timerlist_getnext(&rtc->timerlist);
 	timerlist_del(&rtc->timerlist, &timer->node);
diff --git a/drivers/rtc/posix.c b/drivers/rtc/posix.c
new file mode 100644
index 0000000..911527b
--- /dev/null
+++ b/drivers/rtc/posix.c
@@ -0,0 +1,258 @@
+/*
+ * RTC posix-clock/timer interface
+ *
+ * Copyright (C) 2010 IBM Corperation
+ *
+ * Author: John Stultz <john.stultz@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/spinlock.h>
+#include <linux/posix-timers.h>
+#include <linux/rbtree.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+
+
+static void rtc_handle_irq(void *data);
+
+static int find_clockid(struct device *dev, void *clockid)
+{
+	clockid_t* id = (clockid_t*)clockid;
+
+	if (to_rtc_device(dev)->posix_id == *id)
+		return 1;
+	return 0;
+}
+
+/* XXX - This can probably be optimized better then scanning the list */
+static struct rtc_device *clock_to_rtc(clockid_t id)
+{
+	struct device *dev;
+
+	dev = class_find_device(rtc_class, NULL, &id, find_clockid);
+	if (!dev)
+		return NULL;
+	return to_rtc_device(dev);
+}
+
+
+/**
+ * rtc_clock_getres - posix getres interface
+ * @which_clock: clockid (ignored)
+ * @tp: timespec to fill.
+ *
+ * Returns the 1sec granularity of rtc interface
+ */
+static int rtc_clock_getres(const clockid_t which_clock, struct timespec *tp)
+{
+	tp->tv_sec = 1;
+	tp->tv_nsec = 0;
+	return 0;
+}
+
+
+/**
+ * rtc_clock_get - posix clock_get interface
+ * @which_clock: clockid (ignored)
+ * @tp: timespec to fill.
+ *
+ * Provides the time from the RTC
+ */
+static int rtc_clock_get(clockid_t which_clock, struct timespec *tp)
+{
+	struct rtc_device *rtc;
+	struct rtc_time tm;
+	time_t sec;
+	int ret;
+
+	rtc = clock_to_rtc(which_clock);
+	if (rtc == NULL)
+		return -ENODEV;
+
+	ret = rtc_read_time(rtc, &tm);
+	if (ret)
+		return ret;
+
+	rtc_tm_to_time(&tm, &sec);
+
+	tp->tv_sec = sec;
+	tp->tv_nsec = 0;
+	return 0;
+}
+
+
+/**
+ * rtc_clock_set - posix clock_set interface
+ * @which_clock: clockid (ignored)
+ * @tp: timespec to fill.
+ *
+ * Sets the RTC to the specified time
+ */
+static int rtc_clock_set(clockid_t clockid, struct timespec *tp)
+{
+	struct rtc_device *rtc;
+	struct rtc_time tm;
+	int ret;
+
+	rtc_time_to_tm(tp->tv_sec, &tm);
+	rtc = clock_to_rtc(clockid);
+	if (rtc == NULL)
+		return -ENODEV;
+
+	ret = rtc_set_time(rtc, &tm);
+	return ret;
+}
+
+
+/**
+ * rtc_timer_create - posix timer_create interface
+ * @new_timer: k_itimer pointer to manage
+ *
+ * Initializes the k_itimer structure.
+ */
+static int rtc_timer_create(struct k_itimer *new_timer)
+{
+	struct rtc_device *rtc;
+
+	rtc = clock_to_rtc(new_timer->it_clock);
+	if (rtc == NULL)
+		return -ENODEV;
+
+	rtctimer_init(&new_timer->it.rtctimer, rtc_handle_irq,
+			(void*)new_timer);
+	return 0;
+}
+
+
+/**
+ * rtc_timer_get - posix timer_get interface
+ * @new_timer: k_itimer pointer
+ * @cur_setting: itimerspec data to fill
+ *
+ * Copies the itimerspec data out from the k_itimer
+ */
+static void rtc_timer_get(struct k_itimer *timr, struct itimerspec *cur_setting)
+{
+	cur_setting->it_interval = ktime_to_timespec(timr->it.rtctimer.period);
+	cur_setting->it_value =
+			ktime_to_timespec(timr->it.rtctimer.node.expires);
+	return;
+}
+
+
+/**
+ * rtc_timer_del - posix timer_del interface
+ * @timr: k_itimer pointer to be deleted
+ *
+ * Cancels any programmed alarms for the given timer,
+ * then removes it from the timer list,then if needed,
+ * re-program the alarm for the next timer.
+ */
+static int rtc_timer_del(struct k_itimer *timr)
+{
+	struct rtc_device *rtc;
+
+	rtc = clock_to_rtc(timr->it_clock);
+	if (rtc == NULL)
+		return -ENODEV;
+
+	rtctimer_cancel(rtc, &timr->it.rtctimer);
+	return 0;
+}
+
+
+/**
+ * rtc_timer_set - posix timer_set interface
+ * @timr: k_itimer pointer to be deleted
+ * @flags: timer flags
+ * @new_setting: itimerspec to be used
+ * @old_setting: itimerspec being replaced
+ *
+ * Sets the timer to new_setting, adds the timer to
+ * the timer list, and if necessary sets an alarm for
+ * the new timer.
+ *
+ * If the timer was already set, it will cancel
+ * the old timer and return its value in old_settings.
+ */
+static int rtc_timer_set(struct k_itimer *timr, int flags,
+	struct itimerspec *new_setting,
+	struct itimerspec *old_setting)
+{
+	struct rtc_device *rtc;
+
+	rtc = clock_to_rtc(timr->it_clock);
+	if (rtc == NULL)
+		return -ENODEV;
+
+	/* Save old values */
+	old_setting->it_interval = ktime_to_timespec(timr->it.rtctimer.period);
+	old_setting->it_value =
+			ktime_to_timespec(timr->it.rtctimer.node.expires);
+
+	/* start the timer */
+	rtctimer_start(rtc, &timr->it.rtctimer,
+			timespec_to_ktime(new_setting->it_value),
+			timespec_to_ktime(new_setting->it_interval));
+	return 0;
+}
+
+
+/**
+ * no_nsleep - posix nsleep dummy interface
+ * @which_clock: ignored
+ * @flags: ignored
+ * @tsave: ignored
+ * @rmtp: ignored
+ *
+ * We don't implement nsleep yet, so this stub returns an error.
+ */
+static int no_nsleep(const clockid_t which_clock, int flags,
+		     struct timespec *tsave, struct timespec __user *rmtp)
+{
+	return -EOPNOTSUPP;
+}
+
+
+/**
+ * rtc_handle_irq - RTC alarm interrupt callback
+ * @data: ignored
+ *
+ * This function is called when the RTC interrupt triggers.
+ * It runs through the timer list, expiring timers,
+ * then programs the alarm to fire on the next event.
+ */
+static void rtc_handle_irq(void *data)
+{
+	struct k_itimer *ptr = (struct k_itimer *)data;
+
+	if (posix_timer_event(ptr, 0) != 0)
+		ptr->it_overrun++;
+}
+
+
+/**
+ * init_rtc_posix_timer - Registers and initializes rtc posix clockid
+ * @rtc: pointer to rtc device being initialized
+ *
+ * This function is called when an rtc device is added to the system.
+ */
+void init_rtc_posix_timer(struct rtc_device * rtc)
+{
+	struct k_clock rtc_clock = {
+		.clock_getres = rtc_clock_getres,
+		.clock_get = rtc_clock_get,
+		.clock_set = rtc_clock_set,
+		.timer_create = rtc_timer_create,
+		.timer_set = rtc_timer_set,
+		.timer_del = rtc_timer_del,
+		.timer_get = rtc_timer_get,
+		.nsleep = no_nsleep,
+	};
+
+	rtc->posix_id = create_posix_clock(&rtc_clock);
+}
diff --git a/drivers/rtc/rtc-sysfs.c b/drivers/rtc/rtc-sysfs.c
index 380083c..1e8786f 100644
--- a/drivers/rtc/rtc-sysfs.c
+++ b/drivers/rtc/rtc-sysfs.c
@@ -81,6 +81,15 @@ rtc_sysfs_show_since_epoch(struct device *dev, struct device_attribute *attr,
 }
 
 static ssize_t
+rtc_sysfs_show_posix_clockid(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	ssize_t retval;
+	retval = sprintf(buf, "%lu\n", (long)to_rtc_device(dev)->posix_id);
+	return retval;
+}
+
+static ssize_t
 rtc_sysfs_show_max_user_freq(struct device *dev, struct device_attribute *attr,
 		char *buf)
 {
@@ -121,6 +130,7 @@ static struct device_attribute rtc_attrs[] = {
 	__ATTR(date, S_IRUGO, rtc_sysfs_show_date, NULL),
 	__ATTR(time, S_IRUGO, rtc_sysfs_show_time, NULL),
 	__ATTR(since_epoch, S_IRUGO, rtc_sysfs_show_since_epoch, NULL),
+	__ATTR(posix_clockid, S_IRUGO, rtc_sysfs_show_posix_clockid, NULL),
 	__ATTR(max_user_freq, S_IRUGO | S_IWUSR, rtc_sysfs_show_max_user_freq,
 			rtc_sysfs_set_max_user_freq),
 	__ATTR(hctosys, S_IRUGO, rtc_sysfs_show_hctosys, NULL),
diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index a9e601a..e6b46b5 100644
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -4,6 +4,7 @@
 #include <linux/spinlock.h>
 #include <linux/list.h>
 #include <linux/sched.h>
+#include <linux/rtc.h>
 
 union cpu_time_count {
 	cputime_t cpu;
@@ -63,6 +64,7 @@ struct k_itimer {
 			unsigned long incr;
 			unsigned long expires;
 		} mmtimer;
+		struct rtc_timer rtctimer;
 	} it;
 };
 
diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index 7af34ec..25c96a1 100644
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -203,6 +203,8 @@ struct rtc_device
 	struct hrtimer pie_timer; /* sub second exp, so needs hrtimer */
 	int pie_enabled;
 	struct work_struct irqwork;
+
+	clockid_t posix_id;
 };
 #define to_rtc_device(d) container_of(d, struct rtc_device, dev)
 
@@ -246,8 +248,7 @@ int rtc_register(rtc_task_t *task);
 int rtc_unregister(rtc_task_t *task);
 int rtc_control(rtc_task_t *t, unsigned int cmd, unsigned long arg);
 
-void rtctimer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer);
-void rtctimer_remove(struct rtc_device *rtc, struct rtc_timer *timer);
+void init_rtc_posix_timer(struct rtc_device * rtc);
 void rtctimer_init(struct rtc_timer *timer, void (*f)(void* p), void* data);
 int rtctimer_start(struct rtc_device *rtc, struct rtc_timer* timer,
 			ktime_t expires, ktime_t period);
-- 
1.7.3.2.146.gca209

[PATCH 7/7] [RFC] Introduce Alarm (hybrid) timers

[John Stultz]

So after working on my posix interface to the RTC clocks, I came
across the Android alarm driver (by Arve Hjønnevåg) in the android
kernel tree.

See: http://android.git.kernel.org/?p=kernel/common.git;a=blob;f=drivers/rtc/alarm.c;h=1250edfbdf3302f5e4ea6194847c6ef4bb7beb1c;hb=android-2.6.36

The android alarm driver is different from the RTC posix clock
interface in that rather then directly setting timers against
the RTC device, it uses a hybrid mode, where timers are set
against hrtimers, but when the system suspends, an RTC alarm
is set to wake the system at the next timer expiration.

There are some pluses and minuses with this approach.
The good:
* No need for apps to deal with a new time domain (rtc) which
may drift or just be different from system time.

* Avoids issue of selecting which rtc to use on multi-rtc systems,
as the kernel does it for you.

The bad:
* On systems that have multiple rtc devices, we just use the first
one, which may or may not be ideal (honestly, having multiple rtcs
never made sense to me).

* For apps that actually want to deal with the RTC clock and
are interested in setting timers against it as a different
time domain, this provides no user interface to do so.

I don't really see the bad list as a problem, but please pipe
up if you do.

I had actually discussed this idea with Thomas earlier as being
a potential future interface, but seeing it already in-use
by Android verifies that it is the more interesting use mode.

The android alarm driver was built on top of direct RTC
manipulation, and also implemented its own rbtree timer
code, so instead of trying to porting it over to my
timerlist and RTC timer code, I just re-implemented the
basic functionality roughly following the android in-kernel
interface.

Another large distinction is that while the in-kernel interface
is pretty similar, the user-space interface for android alarm
timers is via ioctls. I've instead chosen to export this
functionality via the posix interface, as it seemed a little
simpler and avoids creating duplicate interfaces to things like
CLOCK_REALTIME and CLOCK_MONOTONIC under alternate names (ie:
RTC and ELAPSED_REALTIME). Instead, if one wants to use a
alarm timer, simply create a posix timer against either
CLOCK_REALTIME_ALARM or CLOCK_MONOTONIC_ALARM.

There is surely other bits of the android alarm code that
I'm sure I didn't fully understand, so some of the simplifications
that I've made may not allow Android to use this interface.
I'd be very interested if those details could be pointed out,
and hopefully we can find a good solution to get this useful
functionality upstream.

This patch is a very initial draft. I'm sure there are bugs.
I just wanted to get it out for structural comment about the
interface.

Also, this patch does not depend on the posix rtc interface
layer also included in this patchset. One or both interfaces
may be useful, so I'm including both to get a feel for what
folks actually like.

Arve: I know you're busy now, so no rush on reviewing this.
I just wanted to send this out to get some early feedback
if anyone else wants to comment. I look forward to your
input when you are a bit less swamped.

Signed-off-by: John Stultz <john.stultz@linaro.org>
CC: Arve Hjønnevåg <arve@android.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Alessandro Zummo <a.zummo@towertech.it>
---
 include/linux/alarmtimer.h   |   29 +++
 include/linux/posix-timers.h |    2 +
 include/linux/time.h         |    2 +
 kernel/time/Makefile         |    2 +-
 kernel/time/alarmtimer.c     |  522 ++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 556 insertions(+), 1 deletions(-)
 create mode 100644 include/linux/alarmtimer.h
 create mode 100644 kernel/time/alarmtimer.c

diff --git a/include/linux/alarmtimer.h b/include/linux/alarmtimer.h
new file mode 100644
index 0000000..ca3ab47
--- /dev/null
+++ b/include/linux/alarmtimer.h
@@ -0,0 +1,29 @@
+#ifndef _LINUX_ALARMTIMER_H
+#define _LINUX_ALARMTIMER_H
+
+#include <linux/time.h>
+#include <linux/hrtimer.h>
+#include <linux/timerlist.h>
+#include <linux/rtc.h>
+
+enum alarmtimer_type {
+	ALARM_REALTIME,
+	ALARM_MONOTONIC,
+
+	ALARM_NUMTYPE,
+};
+
+struct alarm {
+	struct timerlist_node node;
+	ktime_t period;
+	void (*function)(struct alarm*);
+	enum alarmtimer_type type;
+	char enabled;
+};
+
+void alarm_init(struct alarm *alarm, enum alarmtimer_type type,
+		void (*function)(struct alarm *));
+void alarm_start(struct alarm *alarm, ktime_t start, ktime_t period);
+void alarm_cancel(struct alarm *alarm);
+
+#endif
diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index e6b46b5..9d1ace6 100644
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -5,6 +5,7 @@
 #include <linux/list.h>
 #include <linux/sched.h>
 #include <linux/rtc.h>
+#include <linux/alarmtimer.h>
 
 union cpu_time_count {
 	cputime_t cpu;
@@ -65,6 +66,7 @@ struct k_itimer {
 			unsigned long expires;
 		} mmtimer;
 		struct rtc_timer rtctimer;
+		struct alarm alarmtimer;
 	} it;
 };
 
diff --git a/include/linux/time.h b/include/linux/time.h
index 914c48d..4791858 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -290,6 +290,8 @@ struct itimerval {
 #define CLOCK_MONOTONIC_RAW		4
 #define CLOCK_REALTIME_COARSE		5
 #define CLOCK_MONOTONIC_COARSE		6
+#define CLOCK_REALTIME_ALARM		7
+#define CLOCK_MONOTONIC_ALARM		8
 
 /*
  * The IDs of various hardware clocks:
diff --git a/kernel/time/Makefile b/kernel/time/Makefile
index ee26662..f85145f 100644
--- a/kernel/time/Makefile
+++ b/kernel/time/Makefile
@@ -1,4 +1,4 @@
-obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o timecompare.o timeconv.o
+obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o timecompare.o timeconv.o alarmtimer.o
 
 obj-$(CONFIG_GENERIC_CLOCKEVENTS_BUILD)		+= clockevents.o
 obj-$(CONFIG_GENERIC_CLOCKEVENTS)		+= tick-common.o
diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
new file mode 100644
index 0000000..407a6b5
--- /dev/null
+++ b/kernel/time/alarmtimer.c
@@ -0,0 +1,522 @@
+/*
+ * Alarmtimer interface
+ *
+ * This interface provides a timer which is similarto hrtimers, 
+ * but triggers a RTC alarm if the box is suspend.
+ *
+ * This interface is influenced by the Android RTC Alarm timer
+ * interface.
+ *
+ * Copyright (C) 2010 IBM Corperation
+ *
+ * Author: John Stultz <john.stultz@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/time.h>
+#include <linux/hrtimer.h>
+#include <linux/timerlist.h>
+#include <linux/rtc.h>
+#include <linux/alarmtimer.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/posix-timers.h>
+#include <linux/workqueue.h>
+
+
+static struct alarm_base {
+	struct mutex lock;
+	struct timerlist_head timerlist;
+	struct hrtimer timer;
+	ktime_t (*gettime)(void);
+	clockid_t base_clockid;
+	struct work_struct irqwork;
+} alarm_bases[ALARM_NUMTYPE];
+
+static struct rtc_timer rtctimer;
+static struct rtc_device *rtcdev;
+
+/**************************************************************************
+ * alarmtimer management code
+ */
+
+/*
+ * alarmtimer_enqueue - Adds an alarm timer to an alarm_base timerlist
+ * @base: pointer to the base where the timer is being run
+ * @alarm: pointer to alarm being enqueued.
+ *
+ * Adds alarm to a alarm_base timerlist and if necessary sets
+ * an hrtimer to run.
+ *
+ * Must hold base->lock when calling.
+ */
+static void alarmtimer_enqueue(struct alarm_base *base, struct alarm *alarm)
+{
+	timerlist_add(&base->timerlist, &alarm->node);
+	if (&alarm->node == timerlist_getnext(&base->timerlist)) {
+		hrtimer_try_to_cancel(&base->timer);
+		hrtimer_start(&base->timer, alarm->node.expires,
+				HRTIMER_MODE_ABS);
+	}
+}
+
+/*
+ * alarmtimer_remove - Removes an alarm timer from an alarm_base timerlist
+ * @base: pointer to the base where the timer is running
+ * @alarm: pointer to alarm being removed
+ *
+ * Removes alarm to a alarm_base timerlist and if necessary sets
+ * a new timer to run.
+ *
+ * Must hold base->lock when calling.
+ */
+static void alarmtimer_remove(struct alarm_base *base, struct alarm *alarm)
+{
+	struct timerlist_node *next = timerlist_getnext(&base->timerlist);
+
+	timerlist_del(&base->timerlist, &alarm->node);
+	if (next == &alarm->node) {
+		hrtimer_try_to_cancel(&base->timer);
+		next = timerlist_getnext(&base->timerlist);
+		if (!next)
+			return;
+		hrtimer_start(&base->timer, next->expires, HRTIMER_MODE_ABS);
+	}
+}
+
+/*
+ * alarmtimer_do_work - Handles alarm being fired.
+ * @work: pointer to workqueue being run
+ *
+ * When a timer fires, this runs through the timerlist to see
+ * which alarm timers, and run those that expired. If there are
+ * more alarm timers queued, we set the hrtimer to fire in the 
+ * future.
+ */
+void alarmtimer_do_work(struct work_struct *work)
+{
+	struct alarm_base *base = container_of(work, struct alarm_base,
+						irqwork);
+	struct timerlist_node *next;
+	ktime_t now;
+
+	mutex_lock(&base->lock);
+	now = base->gettime();
+	while((next = timerlist_getnext(&base->timerlist))) {
+		struct alarm *alarm;
+		ktime_t expired = next->expires;
+
+		if (expired.tv64 >= now.tv64)
+			break;
+
+		alarm = container_of(next, struct alarm, node);
+
+		timerlist_del(&base->timerlist, &alarm->node);
+		alarm->enabled = 0;
+		/* Re-add periodic timers */
+		if (alarm->period.tv64) {
+			alarm->node.expires = ktime_add(expired, alarm->period);
+			timerlist_add(&base->timerlist, &alarm->node);
+			alarm->enabled = 1;
+		}
+		mutex_unlock(&base->lock);
+		if (alarm->function)
+			alarm->function(alarm);
+		mutex_lock(&base->lock);
+	}
+
+	if (next) {
+		hrtimer_start(&base->timer, next->expires,
+				HRTIMER_MODE_ABS);
+	}
+	mutex_unlock(&base->lock);
+}
+
+
+/*
+ * alarmtimer_fired - Handles alarm hrtimer being fired.
+ * @timer: pointer to hrtimer being run
+ *
+ * When a timer fires, this schedules the do_work function to
+ * be run.
+ */
+static enum hrtimer_restart alarmtimer_fired(struct hrtimer *timer)
+{
+	struct alarm_base *base = container_of(timer, struct alarm_base, timer);
+	schedule_work(&base->irqwork);
+	return HRTIMER_NORESTART;
+}
+
+/*
+ * alarmtimer_suspend - Suspend time callback
+ * @dev: unused
+ * @state: unused
+ *
+ * When we are going into suspend, we look through the bases
+ * to see which is the soonest timer to expire. We then
+ * set an rtc timer to fire that far into the future, which 
+ * will wake us from suspend.
+ */
+static int alarmtimer_suspend(struct device *dev)
+{
+	struct rtc_time tm;
+	ktime_t min = ktime_set(0,0);
+	ktime_t now;
+	int i;
+
+	/* If we have no rtcdev, just return */
+	if(!rtcdev)
+		return 0;
+
+	/* Find the soonest timer to expire*/
+	for (i=0;i < ALARM_NUMTYPE; i++) {
+		struct alarm_base *base = &alarm_bases[i];
+		struct timerlist_node *next;
+		ktime_t delta;
+
+		mutex_lock(&base->lock);
+		next = timerlist_getnext(&base->timerlist);
+		mutex_unlock(&base->lock);
+		if (!next)
+			continue;
+		delta = ktime_sub(next->expires, base->gettime());
+		if (!min.tv64 || (delta.tv64 < min.tv64))
+			min = delta;
+	}
+
+	/* Setup an rtc timer to fire that far in the future */
+	rtctimer_cancel(rtcdev, &rtctimer);
+	rtc_read_time(rtcdev, &tm);
+	now = rtc_tm_to_ktime(tm);
+	now = ktime_add(now, min);
+	rtctimer_start(rtcdev, &rtctimer, now, ktime_set(0,0));
+
+	return 0;
+}
+
+/**************************************************************************
+ * alarm kernel interface code
+ */
+ 
+/*
+ * alarm_init - Initialize an alarm structure
+ * @alarm: ptr to alarm to be initialized
+ * @type: the type of the alarm
+ * @function: callback that is run when the alarm fires
+ *
+ * In-kernel interface to initializes the alarm structure.
+ */
+void alarm_init(struct alarm *alarm, enum alarmtimer_type type,
+		void (*function)(struct alarm *))
+{
+	timerlist_init(&alarm->node);
+	alarm->period = ktime_set(0,0);
+	alarm->function = function;
+	alarm->type = type;
+	alarm->enabled = 0;
+}
+
+/*
+ * alarm_start - Sets an alarm to fire
+ * @alarm: ptr to alarm to set
+ * @start: time to run the alarm
+ * @period: period at which the alarm will recur
+ *
+ * In-kernel interface set an alarm timer.
+ */
+void alarm_start(struct alarm *alarm, ktime_t start, ktime_t period)
+{
+	struct alarm_base *base = &alarm_bases[alarm->type];
+
+	mutex_lock(&base->lock);
+	if (alarm->enabled)
+		alarmtimer_remove(base, alarm);
+	alarm->node.expires = start;
+	alarm->period = period;
+	alarmtimer_enqueue(base, alarm);
+	alarm->enabled = 1;
+	mutex_unlock(&base->lock);
+}
+
+/*
+ * alarm_cancel - Tries to cancel an alarm timer
+ * @alarm: ptr to alarm to be canceled
+ *
+ * In-kernel interface to cancel an alarm timer.
+ */
+void alarm_cancel(struct alarm *alarm)
+{
+	struct alarm_base *base = &alarm_bases[alarm->type];
+
+	mutex_lock(&base->lock);
+	if (alarm->enabled)
+		alarmtimer_remove(base, alarm);
+	alarm->enabled = 0;
+	mutex_unlock(&base->lock);
+}
+
+
+/**************************************************************************
+ * alarm posix interface code 
+ */
+
+/*
+ * clock2alarm - helper that converts from clockid to alarmtypes
+ * @clockid: clockid.
+ *
+ * Helper function that converts from clockids to alarmtypes
+ */
+static enum alarmtimer_type clock2alarm(clockid_t clockid)
+{
+	if (clockid == CLOCK_REALTIME_ALARM)
+		return ALARM_REALTIME;
+	if (clockid == CLOCK_MONOTONIC_ALARM)
+		return ALARM_MONOTONIC;
+	return -1;
+}
+
+/*
+ * alarm_handle_timer - Callback for posix timers
+ * @alarm: alarm that fired
+ *
+ * Posix timer callback for expired alarm timers.
+ */
+static void alarm_handle_timer(struct alarm* alarm)
+{
+	struct k_itimer *ptr = container_of(alarm, struct k_itimer,
+						it.alarmtimer);
+	if (posix_timer_event(ptr, 0) != 0)
+		ptr->it_overrun++;
+}
+
+/*
+ * alarm_clock_getres - posix getres interface
+ * @which_clock: clockid
+ * @tp: timespec to fill
+ *
+ * Returns the granularity of underlying alarm base clock
+ */
+static int alarm_clock_getres(const clockid_t which_clock, struct timespec *tp)
+{
+	clockid_t baseid = alarm_bases[clock2alarm(which_clock)].base_clockid;
+
+	return hrtimer_get_res(baseid, tp);
+}
+
+/**
+ * alarm_clock_get - posix clock_get interface
+ * @which_clock: clockid
+ * @tp: timespec to fill.
+ *
+ * Provides the underlying alarm base time.
+ */
+static int alarm_clock_get(clockid_t which_clock, struct timespec *tp)
+{
+	clockid_t baseid = alarm_bases[clock2alarm(which_clock)].base_clockid;
+
+	if (baseid == CLOCK_REALTIME)
+		ktime_get_real_ts(tp);
+	else if (baseid == CLOCK_MONOTONIC)
+		ktime_get_ts(tp);
+	else
+		return -1;
+	return 0;
+}
+
+/**
+ * alarm_timer_create - posix timer_create interface
+ * @new_timer: k_itimer pointer to manage
+ *
+ * Initializes the k_itimer structure.
+ */
+static int alarm_timer_create(struct k_itimer *new_timer)
+{
+	struct alarm_base *base;
+
+	base = &alarm_bases[clock2alarm(new_timer->it_clock)];
+	alarm_init(&new_timer->it.alarmtimer, clock2alarm(new_timer->it_clock),
+			alarm_handle_timer);
+	return 0;
+}
+
+/**
+ * alarm_timer_get - posix timer_get interface
+ * @new_timer: k_itimer pointer
+ * @cur_setting: itimerspec data to fill
+ *
+ * Copies the itimerspec data out from the k_itimer
+ */
+static void alarm_timer_get(struct k_itimer *timr,
+				struct itimerspec *cur_setting)
+{
+	cur_setting->it_interval =
+			ktime_to_timespec(timr->it.alarmtimer.period);
+	cur_setting->it_value =
+			ktime_to_timespec(timr->it.alarmtimer.node.expires);
+	return;
+}
+
+/**
+ * alarm_timer_del - posix timer_del interface
+ * @timr: k_itimer pointer to be deleted
+ *
+ * Cancels any programmed alarms for the given timer.
+ */
+ static int alarm_timer_del(struct k_itimer *timr)
+{
+	alarm_cancel(&timr->it.alarmtimer);
+	return 0;
+}
+
+/**
+ * alarm_timer_set - posix timer_set interface
+ * @timr: k_itimer pointer to be deleted
+ * @flags: timer flags
+ * @new_setting: itimerspec to be used
+ * @old_setting: itimerspec being replaced
+ *
+ * Sets the timer to new_setting, and starts the timer.
+ */
+ static int alarm_timer_set(struct k_itimer *timr, int flags,
+				struct itimerspec *new_setting,
+				struct itimerspec *old_setting)
+{
+	/* Save old values */
+	old_setting->it_interval =
+			ktime_to_timespec(timr->it.alarmtimer.period);
+	old_setting->it_value =
+			ktime_to_timespec(timr->it.alarmtimer.node.expires);
+
+	/* If the timer was already set, cancel it */
+	alarm_cancel(&timr->it.alarmtimer);
+
+	/* start the timer */
+	alarm_start(&timr->it.alarmtimer,
+			timespec_to_ktime(new_setting->it_value),
+			timespec_to_ktime(new_setting->it_interval));
+	return 0;
+}
+
+/**
+ * no_nsleep - posix nsleep dummy interface
+ * @which_clock: ignored
+ * @flags: ignored
+ * @tsave: ignored
+ * @rmtp: ignored
+ *
+ * We don't implement nsleep yet, so this stub returns an error.
+ */
+static int no_nsleep(const clockid_t which_clock, int flags,
+		     struct timespec *tsave, struct timespec __user *rmtp)
+{
+	return -EOPNOTSUPP;
+}
+
+/**************************************************************************
+ * alarmtimer initialization code
+ */
+
+/* Suspend hook structures */
+static const struct dev_pm_ops alarmtimer_pm_ops = {
+	.suspend = alarmtimer_suspend,
+};
+
+static struct platform_driver alarmtimer_driver = {
+	.driver = {
+		.name = "alarmtimer",
+		.pm = &alarmtimer_pm_ops,
+	}
+};
+
+/**
+ * alarmtimer_init - Initialize alarm timer code
+ *
+ * This function initializes the alarm bases and registers
+ * the posix clock ids.
+ */
+static int __init alarmtimer_init(void)
+{
+	int error = 0;
+	int i;
+	struct k_clock alarm_clock = {
+		.clock_getres = alarm_clock_getres,
+		.clock_get = alarm_clock_get,
+		.clock_set = do_posix_clock_nosettime,
+		.timer_create = alarm_timer_create,
+		.timer_set = alarm_timer_set,
+		.timer_del = alarm_timer_del,
+		.timer_get = alarm_timer_get,
+		.nsleep = no_nsleep,
+	};
+
+	register_posix_clock(CLOCK_REALTIME_ALARM, &alarm_clock);
+	register_posix_clock(CLOCK_MONOTONIC_ALARM, &alarm_clock);
+
+	/* Initialize alarm bases */
+	alarm_bases[ALARM_REALTIME].base_clockid = CLOCK_REALTIME;
+	alarm_bases[ALARM_REALTIME].gettime = &ktime_get_real;
+	alarm_bases[ALARM_MONOTONIC].base_clockid = CLOCK_MONOTONIC;
+	alarm_bases[ALARM_MONOTONIC].gettime = &ktime_get;
+	for (i=0; i< ALARM_NUMTYPE; i++) {
+		timerlist_init_head(&alarm_bases[i].timerlist);
+		mutex_init(&alarm_bases[i].lock);
+		hrtimer_init(&alarm_bases[i].timer,
+				alarm_bases[i].base_clockid,
+				HRTIMER_MODE_ABS);
+		alarm_bases[i].timer.function = alarmtimer_fired;
+		INIT_WORK(&alarm_bases[i].irqwork, alarmtimer_do_work);
+	}
+	error = platform_driver_register(&alarmtimer_driver);
+	platform_device_register_simple("alarmtimer", -1, NULL, 0);
+
+	return error;
+}
+device_initcall(alarmtimer_init);
+
+/**
+ * has_wakealarm - check rtc device has wakealarm ability
+ * @dev: current device 
+ * @name_ptr: name to be returned
+ *
+ * This helper function checks to see if the rtc device can wake
+ * from suspend.
+ */
+static int __init has_wakealarm(struct device *dev, void *name_ptr)
+{
+	struct rtc_device *candidate = to_rtc_device(dev);
+
+	if (!candidate->ops->set_alarm)
+		return 0;
+	if (!device_may_wakeup(candidate->dev.parent))
+		return 0;
+
+	*(const char **)name_ptr = dev_name(dev);
+	return 1;
+}
+
+/**
+ * alarmtimer_init_late - Late initializing of alarmtimer code
+ *
+ * This function locates a rtc device to use for wakealarms.
+ * Run as late_initcall to make sure rtc devices have been
+ * registered.
+ */
+static int __init alarmtimer_init_late(void)
+{
+	char* str;
+
+	/* Find an rtc device and init the rtctimer */
+	class_find_device(rtc_class, NULL, &str, has_wakealarm);
+	if (str)
+		rtcdev = rtc_class_open(str);
+	if (!rtcdev) {
+		printk("No RTC device found, ALARM timers will not wake"
+			" from suspend");
+	}
+	rtctimer_init(&rtctimer, NULL, NULL);
+
+	return 0;
+}
+late_initcall(alarmtimer_init_late);
-- 
1.7.3.2.146.gca209

Re: [PATCH 7/7] [RFC] Introduce Alarm (hybrid) timers

[Richard Cochran]

On Wed, Nov 03, 2010 at 11:31:19AM -0700, John Stultz wrote:

> Another large distinction is that while the in-kernel interface
> is pretty similar, the user-space interface for android alarm
> timers is via ioctls. I've instead chosen to export this
> functionality via the posix interface, as it seemed a little
> simpler and avoids creating duplicate interfaces to things like
> CLOCK_REALTIME and CLOCK_MONOTONIC under alternate names (ie:
> RTC and ELAPSED_REALTIME). Instead, if one wants to use a
> alarm timer, simply create a posix timer against either
> CLOCK_REALTIME_ALARM or CLOCK_MONOTONIC_ALARM.

I have a comment on this, below ...

> diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
> index e6b46b5..9d1ace6 100644
> --- a/include/linux/posix-timers.h
> +++ b/include/linux/posix-timers.h
> @@ -5,6 +5,7 @@
>  #include <linux/list.h>
>  #include <linux/sched.h>
>  #include <linux/rtc.h>
> +#include <linux/alarmtimer.h>
>  
>  union cpu_time_count {
>  	cputime_t cpu;
> @@ -65,6 +66,7 @@ struct k_itimer {
>  			unsigned long expires;
>  		} mmtimer;
>  		struct rtc_timer rtctimer;
> +		struct alarm alarmtimer;
>  	} it;
>  };

I have an initial dynamic clock patch set ready for review and will
post it later today if I can. In implementing the timer_ calls, I
began to wonder about this 'it' union. If we really allow and
implement many kinds of dynamic clocks, then it would seem ugly to me
to simply add yet another union member for each new clock. Wouldn't it
be better to provide a private void pointer for the underlying
driver's use?

> diff --git a/include/linux/time.h b/include/linux/time.h
> index 914c48d..4791858 100644
> --- a/include/linux/time.h
> +++ b/include/linux/time.h
> @@ -290,6 +290,8 @@ struct itimerval {
>  #define CLOCK_MONOTONIC_RAW		4
>  #define CLOCK_REALTIME_COARSE		5
>  #define CLOCK_MONOTONIC_COARSE		6
> +#define CLOCK_REALTIME_ALARM		7
> +#define CLOCK_MONOTONIC_ALARM		8

I have thought about and have taken Alan Cox's anti-SYS5.4/SuS/POSIX
enumeration arguments to heart. If you need a really good example of
the weaknesses of that way, take a look at clock_getcpuclockid,
pthread_getcpuclockid, and their implementation in posix-cpu-timers.c

If we are serious about dynamic clocks, then we will never again touch
the CLOCK_ list. I hope that, after reviewing the coming patch set,
you will also agree ;)

Richard

Re: [PATCH 7/7] [RFC] Introduce Alarm (hybrid) timers

[John Stultz]

On Thu, 2010-11-04 at 08:52 +0100, Richard Cochran wrote:
> On Wed, Nov 03, 2010 at 11:31:19AM -0700, John Stultz wrote:
> 
> > Another large distinction is that while the in-kernel interface
> > is pretty similar, the user-space interface for android alarm
> > timers is via ioctls. I've instead chosen to export this
> > functionality via the posix interface, as it seemed a little
> > simpler and avoids creating duplicate interfaces to things like
> > CLOCK_REALTIME and CLOCK_MONOTONIC under alternate names (ie:
> > RTC and ELAPSED_REALTIME). Instead, if one wants to use a
> > alarm timer, simply create a posix timer against either
> > CLOCK_REALTIME_ALARM or CLOCK_MONOTONIC_ALARM.
> 
> I have a comment on this, below ...
> 
> > diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
> > index e6b46b5..9d1ace6 100644
> > --- a/include/linux/posix-timers.h
> > +++ b/include/linux/posix-timers.h
> > @@ -5,6 +5,7 @@
> >  #include <linux/list.h>
> >  #include <linux/sched.h>
> >  #include <linux/rtc.h>
> > +#include <linux/alarmtimer.h>
> >  
> >  union cpu_time_count {
> >  	cputime_t cpu;
> > @@ -65,6 +66,7 @@ struct k_itimer {
> >  			unsigned long expires;
> >  		} mmtimer;
> >  		struct rtc_timer rtctimer;
> > +		struct alarm alarmtimer;
> >  	} it;
> >  };
> 
> I have an initial dynamic clock patch set ready for review and will
> post it later today if I can. In implementing the timer_ calls, I
> began to wonder about this 'it' union. If we really allow and
> implement many kinds of dynamic clocks, then it would seem ugly to me
> to simply add yet another union member for each new clock. Wouldn't it
> be better to provide a private void pointer for the underlying
> driver's use?

Yea. That union is getting a bit ugly, but it lets us avoid having to
manage allocating and freeing a parallel timer structure that points
back to the k_itimer. Its not a huge issue, but the code in this case is
much simpler, but at the cost of making the k_itimer it union a little
gross. So yea, I'm fine changing it if there's a real desire for it to
be done.


> > diff --git a/include/linux/time.h b/include/linux/time.h
> > index 914c48d..4791858 100644
> > --- a/include/linux/time.h
> > +++ b/include/linux/time.h
> > @@ -290,6 +290,8 @@ struct itimerval {
> >  #define CLOCK_MONOTONIC_RAW		4
> >  #define CLOCK_REALTIME_COARSE		5
> >  #define CLOCK_MONOTONIC_COARSE		6
> > +#define CLOCK_REALTIME_ALARM		7
> > +#define CLOCK_MONOTONIC_ALARM		8
> 
> I have thought about and have taken Alan Cox's anti-SYS5.4/SuS/POSIX
> enumeration arguments to heart. If you need a really good example of
> the weaknesses of that way, take a look at clock_getcpuclockid,
> pthread_getcpuclockid, and their implementation in posix-cpu-timers.c
> 
> If we are serious about dynamic clocks, then we will never again touch
> the CLOCK_ list. I hope that, after reviewing the coming patch set,
> you will also agree ;)

Well, I'm eager to see you patch, and I do think dynamic clockids are a
very useful concept that we need.

However, I suspect there will still be a need for static clockids for
those cases where its a conceptual api that doesn't deal with specific
hardware that has lifetime issues, such as the MONOTONIC/REALTIME_ALARM
cases above.

I look forward to your patches!

thanks
-john