--- /dev/null
+/* linux/include/linux/clocksource.h
+ *
+ * This file contains the structure definitions for clocksources.
+ *
+ * If you are not a clocksource, or timekeeping code, you should
+ * not be including this file!
+ */
+#ifndef _LINUX_CLOCKSOURCE_H
+#define _LINUX_CLOCKSOURCE_H
+
+#include <linux/types.h>
+#include <linux/timex.h>
+#include <linux/time.h>
+#include <linux/list.h>
+#include <asm/div64.h>
+#include <asm/io.h>
+
+/* clocksource cycle base type */
+typedef u64 cycle_t;
+
+/**
+ * struct clocksource - hardware abstraction for a free running counter
+ * Provides mostly state-free accessors to the underlying hardware.
+ *
+ * @name: ptr to clocksource name
+ * @list: list head for registration
+ * @rating: rating value for selection (higher is better)
+ * To avoid rating inflation the following
+ * list should give you a guide as to how
+ * to assign your clocksource a rating
+ * 1-99: Unfit for real use
+ * Only available for bootup and testing purposes.
+ * 100-199: Base level usability.
+ * Functional for real use, but not desired.
+ * 200-299: Good.
+ * A correct and usable clocksource.
+ * 300-399: Desired.
+ * A reasonably fast and accurate clocksource.
+ * 400-499: Perfect
+ * The ideal clocksource. A must-use where
+ * available.
+ * @read: returns a cycle value
+ * @mask: bitmask for two's complement
+ * subtraction of non 64 bit counters
+ * @mult: cycle to nanosecond multiplier
+ * @shift: cycle to nanosecond divisor (power of two)
+ * @update_callback: called when safe to alter clocksource values
+ * @is_continuous: defines if clocksource is free-running.
+ * @cycle_interval: Used internally by timekeeping core, please ignore.
+ * @xtime_interval: Used internally by timekeeping core, please ignore.
+ */
+struct clocksource {
+ char *name;
+ struct list_head list;
+ int rating;
+ cycle_t (*read)(void);
+ cycle_t mask;
+ u32 mult;
+ u32 shift;
+ int (*update_callback)(void);
+ int is_continuous;
+
+ /* timekeeping specific data, ignore */
+ cycle_t cycle_last, cycle_interval;
+ u64 xtime_nsec, xtime_interval;
+ s64 error;
+};
+
+/* simplify initialization of mask field */
+#define CLOCKSOURCE_MASK(bits) (cycle_t)(bits<64 ? ((1ULL<<bits)-1) : -1)
+
+/**
+ * clocksource_khz2mult - calculates mult from khz and shift
+ * @khz: Clocksource frequency in KHz
+ * @shift_constant: Clocksource shift factor
+ *
+ * Helper functions that converts a khz counter frequency to a timsource
+ * multiplier, given the clocksource shift value
+ */
+static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
+{
+ /* khz = cyc/(Million ns)
+ * mult/2^shift = ns/cyc
+ * mult = ns/cyc * 2^shift
+ * mult = 1Million/khz * 2^shift
+ * mult = 1000000 * 2^shift / khz
+ * mult = (1000000<<shift) / khz
+ */
+ u64 tmp = ((u64)1000000) << shift_constant;
+
+ tmp += khz/2; /* round for do_div */
+ do_div(tmp, khz);
+
+ return (u32)tmp;
+}
+
+/**
+ * clocksource_hz2mult - calculates mult from hz and shift
+ * @hz: Clocksource frequency in Hz
+ * @shift_constant: Clocksource shift factor
+ *
+ * Helper functions that converts a hz counter
+ * frequency to a timsource multiplier, given the
+ * clocksource shift value
+ */
+static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
+{
+ /* hz = cyc/(Billion ns)
+ * mult/2^shift = ns/cyc
+ * mult = ns/cyc * 2^shift
+ * mult = 1Billion/hz * 2^shift
+ * mult = 1000000000 * 2^shift / hz
+ * mult = (1000000000<<shift) / hz
+ */
+ u64 tmp = ((u64)1000000000) << shift_constant;
+
+ tmp += hz/2; /* round for do_div */
+ do_div(tmp, hz);
+
+ return (u32)tmp;
+}
+
+/**
+ * clocksource_read: - Access the clocksource's current cycle value
+ * @cs: pointer to clocksource being read
+ *
+ * Uses the clocksource to return the current cycle_t value
+ */
+static inline cycle_t clocksource_read(struct clocksource *cs)
+{
+ return cs->read();
+}
+
+/**
+ * cyc2ns - converts clocksource cycles to nanoseconds
+ * @cs: Pointer to clocksource
+ * @cycles: Cycles
+ *
+ * Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds.
+ *
+ * XXX - This could use some mult_lxl_ll() asm optimization
+ */
+static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles)
+{
+ u64 ret = (u64)cycles;
+ ret = (ret * cs->mult) >> cs->shift;
+ return ret;
+}
+
+/**
+ * clocksource_calculate_interval - Calculates a clocksource interval struct
+ *
+ * @c: Pointer to clocksource.
+ * @length_nsec: Desired interval length in nanoseconds.
+ *
+ * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
+ * pair and interval request.
+ *
+ * Unless you're the timekeeping code, you should not be using this!
+ */
+static inline void clocksource_calculate_interval(struct clocksource *c,
+ unsigned long length_nsec)
+{
+ u64 tmp;
+
+ /* XXX - All of this could use a whole lot of optimization */
+ tmp = length_nsec;
+ tmp <<= c->shift;
+ tmp += c->mult/2;
+ do_div(tmp, c->mult);
+
+ c->cycle_interval = (cycle_t)tmp;
+ if (c->cycle_interval == 0)
+ c->cycle_interval = 1;
+
+ c->xtime_interval = (u64)c->cycle_interval * c->mult;
+}
+
+
+/* used to install a new clocksource */
+int clocksource_register(struct clocksource*);
+void clocksource_reselect(void);
+struct clocksource* clocksource_get_next(void);
+
+#endif /* _LINUX_CLOCKSOURCE_H */
git://git.onelab.eu / linux-2.6.git / blobdiff