The patch titled
clocksource: add enable() and disable() callbacks
has been added to the -mm tree. Its filename is
clocksource-add-enable-and-disable-callbacks.patch
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Subject: clocksource: add enable() and disable() callbacks
From: Magnus Damm <damm@xxxxxxxxxx>
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@xxxxxxxxxx>
Acked-by: John Stultz <johnstul@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/clocksource.h | 31 +++++++++++++++++++++++++++++++
kernel/time/timekeeping.c | 12 +++++++++---
2 files changed, 40 insertions(+), 3 deletions(-)
diff -puN include/linux/clocksource.h~clocksource-add-enable-and-disable-callbacks include/linux/clocksource.h
--- a/include/linux/clocksource.h~clocksource-add-enable-and-disable-callbacks
+++ a/include/linux/clocksource.h
@@ -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
diff -puN kernel/time/timekeeping.c~clocksource-add-enable-and-disable-callbacks kernel/time/timekeeping.c
--- a/kernel/time/timekeeping.c~clocksource-add-enable-and-disable-callbacks
+++ a/kernel/time/timekeeping.c
@@ -177,7 +177,7 @@ EXPORT_SYMBOL(do_settimeofday);
*/
static void change_clocksource(void)
{
- struct clocksource *new;
+ struct clocksource *new, *old;
new = clocksource_get_next();
@@ -186,11 +186,16 @@ 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);
@@ -287,6 +292,7 @@ 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);
_
Patches currently in -mm which might be from damm@xxxxxxxxxx are
linux-next.patch
clocksource-pass-clocksource-to-read-callback.patch
clocksource-add-enable-and-disable-callbacks.patch
irq-free-setup_irq-interrupt-using-free_irq.patch
spi_gpio-driver.patch
spi_gpio-driver-cleanups.patch
vmcore-remove-saved_max_pfn-check.patch
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