coreboot: introduce monotonic timer API

The notion of a monotonic timer is introduced. Along with it
are helper functions and other types for comparing times. This
is just the framework where it is the responsibility of the
chipset/board to provide the implementation of timer_monotonic_get().

The reason structs are used instead of native types is to allow
for future changes to the data structure without chaning all the
call sites.

Change-Id: Ie56b9ab9dedb0da69dea86ef87ca744004eb1ae3
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/3152
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/Kconfig

@@ -313,6 +313,11 @@ config HAVE_INIT_TIMER
 	default n if UDELAY_IO
 	default y
 
+config HAVE_MONOTONIC_TIMER
+	def_bool n
+	help
+	 The board/chipset provides a monotonic timer.
+
 config HIGH_SCRATCH_MEMORY_SIZE
 	hex
 	default 0x0

src/include/timer.h

@@ -0,0 +1,140 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2013 Google, Inc.
+ *
+ * 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; version 2 of the License.
+ *
+ * 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+#ifndef TIMER_H
+#define TIMER_H
+
+#define USECS_PER_SEC 1000000
+#define MSECS_PER_SEC 1000
+#define USECS_PER_MSEC (USECS_PER_SEC / MSECS_PER_SEC)
+
+/* The time structures are defined to be a representation of the time since
+ * coreboot started executing one of its stages. The reason for using structures
+ * is to allow for changes in the future. The structures' details are exposed
+ * so that the compiler can allocate space on the stack and use in other
+ * structures. In other words, accessing any field within this structure
+ * outside of the core timer code is not supported. */
+
+struct mono_time {
+	long microseconds;
+};
+
+struct rela_time {
+	long microseconds;
+};
+
+/* Obtain the current monotonic time. The assumption is that the time counts
+ * up from the value 0 with value 0 being the point when the timer was
+ * initialized.  Additionally, the timer is assumed to only be valid for the
+ * duration of the boot.
+ *
+ * Note that any implementations of timer_monotonic_get()
+ * need to ensure its timesource does not roll over within 10 secs. The reason
+ * is that the time between calls to timer_monotonic_get() may be on order
+ * of 10 seconds. */
+void timer_monotonic_get(struct mono_time *mt);
+
+/* Add microseconds to an absoute time. */
+static inline void mono_time_add_usecs(struct mono_time *mt, long us)
+{
+	mt->microseconds += us;
+}
+
+/* Add milliseconds to an absoute time. */
+static inline void mono_time_add_msecs(struct mono_time *mt, long ms)
+{
+	mono_time_add_usecs(mt, ms * USECS_PER_MSEC);
+}
+
+static inline void mono_time_add_rela_time(struct mono_time *mt,
+                                           const struct rela_time *t)
+{
+	mono_time_add_usecs(mt, t->microseconds);
+}
+
+/* Compare two absoluted times: Return -1, 0, or 1 if t1 is <, =, or > t2,
+ * respectively. */
+static inline int mono_time_cmp(const struct mono_time *t1,
+                                const struct mono_time *t2)
+{
+	if (t1->microseconds == t2->microseconds)
+		return 0;
+
+	if (t1->microseconds < t2->microseconds)
+		return -1;
+
+	return 1;
+}
+
+static inline int rela_time_cmp(const struct rela_time *t1,
+                                const struct rela_time *t2)
+{
+	if (t1->microseconds == t2->microseconds)
+		return 0;
+
+	if (t1->microseconds < t2->microseconds)
+		return -1;
+
+	return 1;
+}
+
+/* Iniitalize a rela_time structure. */
+static inline struct rela_time rela_time_init_usecs(long us)
+{
+	struct rela_time t;
+	t.microseconds = us;
+	return t;
+}
+
+/* Return time difference between t1 and t2. i.e. t2 - t1. */
+static struct rela_time mono_time_diff(const struct mono_time *t1,
+                                       const struct mono_time *t2)
+{
+	return rela_time_init_usecs(t2->microseconds - t1->microseconds);
+}
+
+/* Return true if t1 after t2  */
+static inline int mono_time_after(const struct mono_time *t1,
+                                  const struct mono_time *t2)
+{
+	return mono_time_cmp(t1, t2) > 0;
+}
+
+/* Return true if t1 before t2. */
+static inline int mono_time_before(const struct mono_time *t1,
+                                   const struct mono_time *t2)
+{
+	return mono_time_cmp(t1, t2) < 0;
+}
+
+/* Return the difference between now and t. */
+static inline struct rela_time current_time_from(const struct mono_time *t)
+{
+	struct mono_time now;
+
+	timer_monotonic_get(&now);
+	return mono_time_diff(t, &now);
+
+}
+
+static inline long rela_time_in_microseconds(const struct rela_time *rt)
+{
+	return rt->microseconds;
+}
+
+#endif /* TIMER_H */