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Message-Id: <20081211114909.17624.85712.sendpatchset@rx1.opensource.se>
Date: Thu, 11 Dec 2008 20:49:09 +0900
From: Magnus Damm <magnus.damm@...il.com>
To: linux-kernel@...r.kernel.org
Cc: akpm@...ux-foundation.org, johnstul@...ibm.com,
lethal@...ux-sh.org, tglx@...utronix.de,
Magnus Damm <magnus.damm@...il.com>, mingo@...hat.com
Subject: [PATCH] clocksource: add enable() and disable() callbacks
From: Magnus Damm <damm@...l.co.jp>
Add enable() and disable() callbacks for clocksources. This allows
us to put unused clocksources in power save mode. The functions
clocksource_enable() and clocksource_disable() wrap the callbacks
and are inserted in the timekeeping code to enable before use and
disable after switching to a new clocksource.
Signed-off-by: Magnus Damm <damm@...l.co.jp>
Acked-by: John Stultz <johnstul@...ibm.com>
---
Same as before, but applies on top of the new read() patch.
include/linux/clocksource.h | 31 +++++++++++++++++++++++++++++++
kernel/time/timekeeping.c | 12 +++++++++---
2 files changed, 40 insertions(+), 3 deletions(-)
--- 0005/include/linux/clocksource.h
+++ work/include/linux/clocksource.h 2008-12-11 19:52:25.000000000 +0900
@@ -43,6 +43,8 @@ struct clocksource;
* The ideal clocksource. A must-use where
* available.
* @read: returns a cycle value, passes clocksource as argument
+ * @enable: optional function to enable the clocksource
+ * @disable: optional function to disable the clocksource
* @mask: bitmask for two's complement
* subtraction of non 64 bit counters
* @mult: cycle to nanosecond multiplier (adjusted by NTP)
@@ -62,6 +64,8 @@ struct clocksource {
struct list_head list;
int rating;
cycle_t (*read)(struct clocksource *cs);
+ int (*enable)(struct clocksource *cs);
+ void (*disable)(struct clocksource *cs);
cycle_t mask;
u32 mult;
u32 mult_orig;
@@ -174,6 +178,33 @@ static inline cycle_t clocksource_read(s
}
/**
+ * clocksource_enable: - enable clocksource
+ * @cs: pointer to clocksource
+ *
+ * Enables the specified clocksource. The clocksource callback
+ * function should start up the hardware and setup mult and field
+ * members of struct clocksource to reflect hardware capabilities.
+ */
+static inline int clocksource_enable(struct clocksource *cs)
+{
+ return cs->enable ? cs->enable(cs) : 0;
+}
+
+/**
+ * clocksource_disable: - disable clocksource
+ * @cs: pointer to clocksource
+ *
+ * Disables the specified clocksource. The clocksource callback
+ * function should power down the now unused hardware block to
+ * save power.
+ */
+static inline void clocksource_disable(struct clocksource *cs)
+{
+ if (cs->disable)
+ cs->disable(cs);
+}
+
+/**
* cyc2ns - converts clocksource cycles to nanoseconds
* @cs: Pointer to clocksource
* @cycles: Cycles
--- 0004/kernel/time/timekeeping.c
+++ work/kernel/time/timekeeping.c 2008-12-11 19:51:16.000000000 +0900
@@ -184,7 +184,7 @@ EXPORT_SYMBOL(do_settimeofday);
*/
static void change_clocksource(void)
{
- struct clocksource *new;
+ struct clocksource *new, *old;
new = clocksource_get_next();
@@ -193,11 +193,16 @@ static void change_clocksource(void)
clocksource_forward_now();
- new->raw_time = clock->raw_time;
+ if (clocksource_enable(new))
+ return;
+ new->raw_time = clock->raw_time;
+ old = clock;
clock = new;
+ clocksource_disable(old);
+
clock->cycle_last = 0;
- clock->cycle_last = clocksource_read(new);
+ clock->cycle_last = clocksource_read(clock);
clock->error = 0;
clock->xtime_nsec = 0;
clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
@@ -293,6 +298,7 @@ void __init timekeeping_init(void)
ntp_init();
clock = clocksource_get_next();
+ clocksource_enable(clock);
clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
clock->cycle_last = clocksource_read(clock);
--
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