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-rw-r--r--include/linux/clocksource.h31
-rw-r--r--kernel/time/timekeeping.c12
2 files changed, 40 insertions, 3 deletions
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 0d96cde9ee5d..5a40d14daa9f 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -144,6 +144,8 @@ extern u64 timecounter_cyc2time(struct timecounter *tc,
144 * The ideal clocksource. A must-use where 144 * The ideal clocksource. A must-use where
145 * available. 145 * available.
146 * @read: returns a cycle value, passes clocksource as argument 146 * @read: returns a cycle value, passes clocksource as argument
147 * @enable: optional function to enable the clocksource
148 * @disable: optional function to disable the clocksource
147 * @mask: bitmask for two's complement 149 * @mask: bitmask for two's complement
148 * subtraction of non 64 bit counters 150 * subtraction of non 64 bit counters
149 * @mult: cycle to nanosecond multiplier (adjusted by NTP) 151 * @mult: cycle to nanosecond multiplier (adjusted by NTP)
@@ -163,6 +165,8 @@ struct clocksource {
163 struct list_head list; 165 struct list_head list;
164 int rating; 166 int rating;
165 cycle_t (*read)(struct clocksource *cs); 167 cycle_t (*read)(struct clocksource *cs);
168 int (*enable)(struct clocksource *cs);
169 void (*disable)(struct clocksource *cs);
166 cycle_t mask; 170 cycle_t mask;
167 u32 mult; 171 u32 mult;
168 u32 mult_orig; 172 u32 mult_orig;
@@ -275,6 +279,33 @@ static inline cycle_t clocksource_read(struct clocksource *cs)
275} 279}
276 280
277/** 281/**
282 * clocksource_enable: - enable clocksource
283 * @cs: pointer to clocksource
284 *
285 * Enables the specified clocksource. The clocksource callback
286 * function should start up the hardware and setup mult and field
287 * members of struct clocksource to reflect hardware capabilities.
288 */
289static inline int clocksource_enable(struct clocksource *cs)
290{
291 return cs->enable ? cs->enable(cs) : 0;
292}
293
294/**
295 * clocksource_disable: - disable clocksource
296 * @cs: pointer to clocksource
297 *
298 * Disables the specified clocksource. The clocksource callback
299 * function should power down the now unused hardware block to
300 * save power.
301 */
302static inline void clocksource_disable(struct clocksource *cs)
303{
304 if (cs->disable)
305 cs->disable(cs);
306}
307
308/**
278 * cyc2ns - converts clocksource cycles to nanoseconds 309 * cyc2ns - converts clocksource cycles to nanoseconds
279 * @cs: Pointer to clocksource 310 * @cs: Pointer to clocksource
280 * @cycles: Cycles 311 * @cycles: Cycles
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 900f1b6598d1..687dff49f6e7 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -182,7 +182,7 @@ EXPORT_SYMBOL(do_settimeofday);
182 */ 182 */
183static void change_clocksource(void) 183static void change_clocksource(void)
184{ 184{
185 struct clocksource *new; 185 struct clocksource *new, *old;
186 186
187 new = clocksource_get_next(); 187 new = clocksource_get_next();
188 188
@@ -191,11 +191,16 @@ static void change_clocksource(void)
191 191
192 clocksource_forward_now(); 192 clocksource_forward_now();
193 193
194 new->raw_time = clock->raw_time; 194 if (clocksource_enable(new))
195 return;
195 196
197 new->raw_time = clock->raw_time;
198 old = clock;
196 clock = new; 199 clock = new;
200 clocksource_disable(old);
201
197 clock->cycle_last = 0; 202 clock->cycle_last = 0;
198 clock->cycle_last = clocksource_read(new); 203 clock->cycle_last = clocksource_read(clock);
199 clock->error = 0; 204 clock->error = 0;
200 clock->xtime_nsec = 0; 205 clock->xtime_nsec = 0;
201 clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH); 206 clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
@@ -292,6 +297,7 @@ void __init timekeeping_init(void)
292 ntp_init(); 297 ntp_init();
293 298
294 clock = clocksource_get_next(); 299 clock = clocksource_get_next();
300 clocksource_enable(clock);
295 clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH); 301 clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
296 clock->cycle_last = clocksource_read(clock); 302 clock->cycle_last = clocksource_read(clock);
297 303