From mboxrd@z Thu Jan 1 00:00:00 1970 From: Magnus Damm Date: Mon, 01 Dec 2008 10:33:47 +0000 Subject: [PATCH 09/10] clocksource: add enable() and disable() callbacks Message-Id: <20081201103347.26620.3670.sendpatchset@rx1.opensource.se> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-sh@vger.kernel.org From: Magnus Damm 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 --- include/linux/clocksource.h | 31 +++++++++++++++++++++++++++++++ kernel/time/timekeeping.c | 12 +++++++++--- 2 files changed, 40 insertions(+), 3 deletions(-) --- 0009/include/linux/clocksource.h +++ work/include/linux/clocksource.h 2008-12-01 14:19:43.000000000 +0900 @@ -44,6 +44,8 @@ struct clocksource; * available. * @read: returns a cycle value * @read2: 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) @@ -64,6 +66,8 @@ struct clocksource { int rating; cycle_t (*read)(void); cycle_t (*read2)(struct clocksource *cs); + int (*enable)(struct clocksource *cs); + void (*disable)(struct clocksource *cs); cycle_t mask; u32 mult; u32 mult_orig; @@ -176,6 +180,33 @@ 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 --- 0001/kernel/time/timekeeping.c +++ work/kernel/time/timekeeping.c 2008-12-01 14:20:32.000000000 +0900 @@ -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);