struct clocksource;
/**
+ * struct cyclecounter - hardware abstraction for a free running counter
+ * Provides completely state-free accessors to the underlying hardware.
+ * Depending on which hardware it reads, the cycle counter may wrap
+ * around quickly. Locking rules (if necessary) have to be defined
+ * by the implementor and user of specific instances of this API.
+ *
+ * @read: returns the current cycle value
+ * @mask: bitmask for two's complement
+ * subtraction of non 64 bit counters,
+ * see CLOCKSOURCE_MASK() helper macro
+ * @mult: cycle to nanosecond multiplier
+ * @shift: cycle to nanosecond divisor (power of two)
+ */
+struct cyclecounter {
+ cycle_t (*read)(const struct cyclecounter *cc);
+ cycle_t mask;
+ u32 mult;
+ u32 shift;
+};
+
+/**
+ * struct timecounter - layer above a %struct cyclecounter which counts nanoseconds
+ * Contains the state needed by timecounter_read() to detect
+ * cycle counter wrap around. Initialize with
+ * timecounter_init(). Also used to convert cycle counts into the
+ * corresponding nanosecond counts with timecounter_cyc2time(). Users
+ * of this code are responsible for initializing the underlying
+ * cycle counter hardware, locking issues and reading the time
+ * more often than the cycle counter wraps around. The nanosecond
+ * counter will only wrap around after ~585 years.
+ *
+ * @cc: the cycle counter used by this instance
+ * @cycle_last: most recent cycle counter value seen by
+ * timecounter_read()
+ * @nsec: continuously increasing count
+ */
+struct timecounter {
+ const struct cyclecounter *cc;
+ cycle_t cycle_last;
+ u64 nsec;
+};
+
+/**
+ * cyclecounter_cyc2ns - converts cycle counter cycles to nanoseconds
+ * @tc: Pointer to cycle counter.
+ * @cycles: Cycles
+ *
+ * XXX - This could use some mult_lxl_ll() asm optimization. Same code
+ * as in cyc2ns, but with unsigned result.
+ */
+static inline u64 cyclecounter_cyc2ns(const struct cyclecounter *cc,
+ cycle_t cycles)
+{
+ u64 ret = (u64)cycles;
+ ret = (ret * cc->mult) >> cc->shift;
+ return ret;
+}
+
+/**
+ * timecounter_init - initialize a time counter
+ * @tc: Pointer to time counter which is to be initialized/reset
+ * @cc: A cycle counter, ready to be used.
+ * @start_tstamp: Arbitrary initial time stamp.
+ *
+ * After this call the current cycle register (roughly) corresponds to
+ * the initial time stamp. Every call to timecounter_read() increments
+ * the time stamp counter by the number of elapsed nanoseconds.
+ */
+extern void timecounter_init(struct timecounter *tc,
+ const struct cyclecounter *cc,
+ u64 start_tstamp);
+
+/**
+ * timecounter_read - return nanoseconds elapsed since timecounter_init()
+ * plus the initial time stamp
+ * @tc: Pointer to time counter.
+ *
+ * In other words, keeps track of time since the same epoch as
+ * the function which generated the initial time stamp.
+ */
+extern u64 timecounter_read(struct timecounter *tc);
+
+/**
+ * timecounter_cyc2time - convert a cycle counter to same
+ * time base as values returned by
+ * timecounter_read()
+ * @tc: Pointer to time counter.
+ * @cycle: a value returned by tc->cc->read()
+ *
+ * Cycle counts that are converted correctly as long as they
+ * fall into the interval [-1/2 max cycle count, +1/2 max cycle count],
+ * with "max cycle count" == cs->mask+1.
+ *
+ * This allows conversion of cycle counter values which were generated
+ * in the past.
+ */
+extern u64 timecounter_cyc2time(struct timecounter *tc,
+ cycle_t cycle_tstamp);
+
+/**
* struct clocksource - hardware abstraction for a free running counter
* Provides mostly state-free accessors to the underlying hardware.
+ * This is the structure used for system time.
*
* @name: ptr to clocksource name
* @list: list head for registration
* 400-499: Perfect
* The ideal clocksource. A must-use where
* available.
- * @read: returns a cycle value
+ * @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
+ * @mult: cycle to nanosecond multiplier (adjusted by NTP)
+ * @mult_orig: cycle to nanosecond multiplier (unadjusted by NTP)
* @shift: cycle to nanosecond divisor (power of two)
* @flags: flags describing special properties
* @vread: vsyscall based read
char *name;
struct list_head list;
int rating;
- cycle_t (*read)(void);
+ cycle_t (*read)(struct clocksource *cs);
+ int (*enable)(struct clocksource *cs);
+ void (*disable)(struct clocksource *cs);
cycle_t mask;
u32 mult;
+ u32 mult_orig;
u32 shift;
unsigned long flags;
cycle_t (*vread)(void);
/* timekeeping specific data, ignore */
cycle_t cycle_interval;
u64 xtime_interval;
+ u32 raw_interval;
/*
* Second part is written at each timer interrupt
* Keep it in a different cache line to dirty no
cycle_t cycle_last ____cacheline_aligned_in_smp;
u64 xtime_nsec;
s64 error;
+ struct timespec raw_time;
#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
/* Watchdog related data, used by the framework */
#endif
};
+extern struct clocksource *clock; /* current clocksource */
+
/*
* Clock source flags bits::
*/
*/
static inline cycle_t clocksource_read(struct clocksource *cs)
{
- return cs->read();
+ return cs->read(cs);
+}
+
+/**
+ * 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)
+{
+ int ret = 0;
+
+ if (cs->enable)
+ ret = cs->enable(cs);
+
+ /*
+ * The frequency may have changed while the clocksource
+ * was disabled. If so the code in ->enable() must update
+ * the mult value to reflect the new frequency. Make sure
+ * mult_orig follows this change.
+ */
+ cs->mult_orig = cs->mult;
+
+ return ret;
+}
+
+/**
+ * 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)
+{
+ /*
+ * Save mult_orig in mult so clocksource_enable() can
+ * restore the value regardless if ->enable() updates
+ * the value of mult or not.
+ */
+ cs->mult = cs->mult_orig;
+
+ if (cs->disable)
+ cs->disable(cs);
}
/**
{
u64 tmp;
- /* XXX - All of this could use a whole lot of optimization */
+ /* Do the ns -> cycle conversion first, using original mult */
tmp = length_nsec;
tmp <<= c->shift;
- tmp += c->mult/2;
- do_div(tmp, c->mult);
+ tmp += c->mult_orig/2;
+ do_div(tmp, c->mult_orig);
c->cycle_interval = (cycle_t)tmp;
if (c->cycle_interval == 0)
c->cycle_interval = 1;
+ /* Go back from cycles -> shifted ns, this time use ntp adjused mult */
c->xtime_interval = (u64)c->cycle_interval * c->mult;
+ c->raw_interval = ((u64)c->cycle_interval * c->mult_orig) >> c->shift;
}
/* used to install a new clocksource */
extern int clocksource_register(struct clocksource*);
extern void clocksource_unregister(struct clocksource*);
+extern void clocksource_touch_watchdog(void);
extern struct clocksource* clocksource_get_next(void);
extern void clocksource_change_rating(struct clocksource *cs, int rating);
extern void clocksource_resume(void);
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff