From 734efb467b31e56c2f9430590a9aa867ecf3eea1 Mon Sep 17 00:00:00 2001 From: john stultz Date: Mon, 26 Jun 2006 00:25:05 -0700 Subject: [PATCH] Time: Clocksource Infrastructure This introduces the clocksource management infrastructure. A clocksource is a driver-like architecture generic abstraction of a free-running counter. This code defines the clocksource structure, and provides management code for registering, selecting, accessing and scaling clocksources. Additionally, this includes the trivial jiffies clocksource, a lowest common denominator clocksource, provided mainly for use as an example. [hirofumi@mail.parknet.co.jp: Don't enable IRQ too early] Signed-off-by: John Stultz Signed-off-by: Ingo Molnar Signed-off-by: Paul Mundt Signed-off-by: John Stultz Signed-off-by: OGAWA Hirofumi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/clocksource.h | 181 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 181 insertions(+) create mode 100644 include/linux/clocksource.h (limited to 'include/linux/clocksource.h') diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h new file mode 100644 index 000000000000..c4187cda0ee4 --- /dev/null +++ b/include/linux/clocksource.h @@ -0,0 +1,181 @@ +/* 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 +#include +#include +#include +#include +#include + +/* 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. + * @interval_cycles: Used internally by timekeeping core, please ignore. + * @interval_snsecs: 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 interval_cycles; + u64 interval_snsecs; +}; + + +/** + * 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<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; +} + +/** + * calculate_clocksource_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 calculate_clocksource_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->interval_cycles = (cycle_t)tmp; + if(c->interval_cycles == 0) + c->interval_cycles = 1; + + c->interval_snsecs = (u64)c->interval_cycles * c->mult; +} + +/* used to install a new clocksource */ +int register_clocksource(struct clocksource*); +void reselect_clocksource(void); +struct clocksource* get_next_clocksource(void); + +#endif /* _LINUX_CLOCKSOURCE_H */ -- cgit v1.2.1 From 5eb6d20533d14a432df714520939a6181e28f099 Mon Sep 17 00:00:00 2001 From: john stultz Date: Mon, 26 Jun 2006 00:25:07 -0700 Subject: [PATCH] Time: Use clocksource abstraction for NTP adjustments Instead of incrementing xtime by tick_nsec + ntp adjustments, use the clocksource abstraction to increment and scale time. Using the clocksource abstraction allows other clocksources to be used consistently in the face of late or lost ticks, while preserving the existing behavior via the jiffies clocksource. This removes the need to keep time_phase adjustments as we just use the current_tick_length() function as the NTP interface and accumulate time using shifted nanoseconds. The basics of this design was by Roman Zippel, however it is my own interpretation and implementation, so the credit should go to him and the blame to me. Signed-off-by: John Stultz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/clocksource.h | 97 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 97 insertions(+) (limited to 'include/linux/clocksource.h') diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index c4187cda0ee4..c4739c4e3039 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -173,6 +173,103 @@ static inline void calculate_clocksource_interval(struct clocksource *c, c->interval_snsecs = (u64)c->interval_cycles * c->mult; } + +/** + * error_aproximation - calculates an error adjustment for a given error + * + * @error: Error value (unsigned) + * @unit: Adjustment unit + * + * For a given error value, this function takes the adjustment unit + * and uses binary approximation to return a power of two adjustment value. + * + * This function is only for use by the the make_ntp_adj() function + * and you must hold a write on the xtime_lock when calling. + */ +static inline int error_aproximation(u64 error, u64 unit) +{ + static int saved_adj = 0; + u64 adjusted_unit = unit << saved_adj; + + if (error > (adjusted_unit * 2)) { + /* large error, so increment the adjustment factor */ + saved_adj++; + } else if (error > adjusted_unit) { + /* just right, don't touch it */ + } else if (saved_adj) { + /* small error, so drop the adjustment factor */ + saved_adj--; + return 0; + } + + return saved_adj; +} + + +/** + * make_ntp_adj - Adjusts the specified clocksource for a given error + * + * @clock: Pointer to clock to be adjusted + * @cycles_delta: Current unacounted cycle delta + * @error: Pointer to current error value + * + * Returns clock shifted nanosecond adjustment to be applied against + * the accumulated time value (ie: xtime). + * + * If the error value is large enough, this function calulates the + * (power of two) adjustment value, and adjusts the clock's mult and + * interval_snsecs values accordingly. + * + * However, since there may be some unaccumulated cycles, to avoid + * time inconsistencies we must adjust the accumulation value + * accordingly. + * + * This is not very intuitive, so the following proof should help: + * The basic timeofday algorithm: base + cycle * mult + * Thus: + * new_base + cycle * new_mult = old_base + cycle * old_mult + * new_base = old_base + cycle * old_mult - cycle * new_mult + * new_base = old_base + cycle * (old_mult - new_mult) + * new_base - old_base = cycle * (old_mult - new_mult) + * base_delta = cycle * (old_mult - new_mult) + * base_delta = cycle * (mult_delta) + * + * Where mult_delta is the adjustment value made to mult + * + */ +static inline s64 make_ntp_adj(struct clocksource *clock, + cycles_t cycles_delta, s64* error) +{ + s64 ret = 0; + if (*error > ((s64)clock->interval_cycles+1)/2) { + /* calculate adjustment value */ + int adjustment = error_aproximation(*error, + clock->interval_cycles); + /* adjust clock */ + clock->mult += 1 << adjustment; + clock->interval_snsecs += clock->interval_cycles << adjustment; + + /* adjust the base and error for the adjustment */ + ret = -(cycles_delta << adjustment); + *error -= clock->interval_cycles << adjustment; + /* XXX adj error for cycle_delta offset? */ + } else if ((-(*error)) > ((s64)clock->interval_cycles+1)/2) { + /* calculate adjustment value */ + int adjustment = error_aproximation(-(*error), + clock->interval_cycles); + /* adjust clock */ + clock->mult -= 1 << adjustment; + clock->interval_snsecs -= clock->interval_cycles << adjustment; + + /* adjust the base and error for the adjustment */ + ret = cycles_delta << adjustment; + *error += clock->interval_cycles << adjustment; + /* XXX adj error for cycle_delta offset? */ + } + return ret; +} + + /* used to install a new clocksource */ int register_clocksource(struct clocksource*); void reselect_clocksource(void); -- cgit v1.2.1 From a275254975a29c51929ee175b92ac471ac2a0043 Mon Sep 17 00:00:00 2001 From: john stultz Date: Mon, 26 Jun 2006 00:25:14 -0700 Subject: [PATCH] time: rename clocksource functions As suggested by Roman Zippel, change clocksource functions to use clocksource_xyz rather then xyz_clocksource to avoid polluting the namespace. Signed-off-by: John Stultz Cc: Roman Zippel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/clocksource.h | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) (limited to 'include/linux/clocksource.h') diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index c4739c4e3039..5f4a7f72f3ee 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -118,12 +118,12 @@ static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant) } /** - * read_clocksource: - Access the clocksource's current cycle value + * 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 read_clocksource(struct clocksource *cs) +static inline cycle_t clocksource_read(struct clocksource *cs) { return cs->read(); } @@ -145,7 +145,7 @@ static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles) } /** - * calculate_clocksource_interval - Calculates a clocksource interval struct + * clocksource_calculate_interval - Calculates a clocksource interval struct * * @c: Pointer to clocksource. * @length_nsec: Desired interval length in nanoseconds. @@ -155,7 +155,7 @@ static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles) * * Unless you're the timekeeping code, you should not be using this! */ -static inline void calculate_clocksource_interval(struct clocksource *c, +static inline void clocksource_calculate_interval(struct clocksource *c, unsigned long length_nsec) { u64 tmp; @@ -271,8 +271,8 @@ static inline s64 make_ntp_adj(struct clocksource *clock, /* used to install a new clocksource */ -int register_clocksource(struct clocksource*); -void reselect_clocksource(void); -struct clocksource* get_next_clocksource(void); +int clocksource_register(struct clocksource*); +void clocksource_reselect(void); +struct clocksource* clocksource_get_next(void); #endif /* _LINUX_CLOCKSOURCE_H */ -- cgit v1.2.1 From 7f9f303aa33c7acc7b4aa9ebea25cbd990bc707b Mon Sep 17 00:00:00 2001 From: Jim Cromie Date: Mon, 26 Jun 2006 00:25:15 -0700 Subject: [PATCH] generic-time: add macro to simplify/hide mask constants Add a CLOCKSOURCE_MASK macro to simplify initializing the mask for a struct clocksource, and use it to replace literal mask constants in the various clocksource drivers. Signed-off-by: Jim Cromie Acked-by: John Stultz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/clocksource.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/clocksource.h') diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index 5f4a7f72f3ee..4bc94282c364 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -65,6 +65,8 @@ struct clocksource { u64 interval_snsecs; }; +/* simplify initialization of mask field */ +#define CLOCKSOURCE_MASK(bits) (cycle_t)(bits<64 ? ((1ULL< Date: Mon, 26 Jun 2006 00:25:18 -0700 Subject: [PATCH] fix and optimize clock source update This fixes the clock source updates in update_wall_time() to correctly track the time coming in via current_tick_length(). Optimize the fast paths to be as short as possible to keep the overhead low. Signed-off-by: Roman Zippel Acked-by: John Stultz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/clocksource.h | 113 ++++---------------------------------------- 1 file changed, 9 insertions(+), 104 deletions(-) (limited to 'include/linux/clocksource.h') diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index 4bc94282c364..d852024ed095 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -46,8 +46,8 @@ typedef u64 cycle_t; * @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. - * @interval_cycles: Used internally by timekeeping core, please ignore. - * @interval_snsecs: Used internally by timekeeping core, please ignore. + * @cycle_interval: Used internally by timekeeping core, please ignore. + * @xtime_interval: Used internally by timekeeping core, please ignore. */ struct clocksource { char *name; @@ -61,8 +61,9 @@ struct clocksource { int is_continuous; /* timekeeping specific data, ignore */ - cycle_t interval_cycles; - u64 interval_snsecs; + cycle_t cycle_last, cycle_interval; + u64 xtime_nsec, xtime_interval; + s64 error; }; /* simplify initialization of mask field */ @@ -168,107 +169,11 @@ static inline void clocksource_calculate_interval(struct clocksource *c, tmp += c->mult/2; do_div(tmp, c->mult); - c->interval_cycles = (cycle_t)tmp; - if(c->interval_cycles == 0) - c->interval_cycles = 1; + c->cycle_interval = (cycle_t)tmp; + if (c->cycle_interval == 0) + c->cycle_interval = 1; - c->interval_snsecs = (u64)c->interval_cycles * c->mult; -} - - -/** - * error_aproximation - calculates an error adjustment for a given error - * - * @error: Error value (unsigned) - * @unit: Adjustment unit - * - * For a given error value, this function takes the adjustment unit - * and uses binary approximation to return a power of two adjustment value. - * - * This function is only for use by the the make_ntp_adj() function - * and you must hold a write on the xtime_lock when calling. - */ -static inline int error_aproximation(u64 error, u64 unit) -{ - static int saved_adj = 0; - u64 adjusted_unit = unit << saved_adj; - - if (error > (adjusted_unit * 2)) { - /* large error, so increment the adjustment factor */ - saved_adj++; - } else if (error > adjusted_unit) { - /* just right, don't touch it */ - } else if (saved_adj) { - /* small error, so drop the adjustment factor */ - saved_adj--; - return 0; - } - - return saved_adj; -} - - -/** - * make_ntp_adj - Adjusts the specified clocksource for a given error - * - * @clock: Pointer to clock to be adjusted - * @cycles_delta: Current unacounted cycle delta - * @error: Pointer to current error value - * - * Returns clock shifted nanosecond adjustment to be applied against - * the accumulated time value (ie: xtime). - * - * If the error value is large enough, this function calulates the - * (power of two) adjustment value, and adjusts the clock's mult and - * interval_snsecs values accordingly. - * - * However, since there may be some unaccumulated cycles, to avoid - * time inconsistencies we must adjust the accumulation value - * accordingly. - * - * This is not very intuitive, so the following proof should help: - * The basic timeofday algorithm: base + cycle * mult - * Thus: - * new_base + cycle * new_mult = old_base + cycle * old_mult - * new_base = old_base + cycle * old_mult - cycle * new_mult - * new_base = old_base + cycle * (old_mult - new_mult) - * new_base - old_base = cycle * (old_mult - new_mult) - * base_delta = cycle * (old_mult - new_mult) - * base_delta = cycle * (mult_delta) - * - * Where mult_delta is the adjustment value made to mult - * - */ -static inline s64 make_ntp_adj(struct clocksource *clock, - cycles_t cycles_delta, s64* error) -{ - s64 ret = 0; - if (*error > ((s64)clock->interval_cycles+1)/2) { - /* calculate adjustment value */ - int adjustment = error_aproximation(*error, - clock->interval_cycles); - /* adjust clock */ - clock->mult += 1 << adjustment; - clock->interval_snsecs += clock->interval_cycles << adjustment; - - /* adjust the base and error for the adjustment */ - ret = -(cycles_delta << adjustment); - *error -= clock->interval_cycles << adjustment; - /* XXX adj error for cycle_delta offset? */ - } else if ((-(*error)) > ((s64)clock->interval_cycles+1)/2) { - /* calculate adjustment value */ - int adjustment = error_aproximation(-(*error), - clock->interval_cycles); - /* adjust clock */ - clock->mult -= 1 << adjustment; - clock->interval_snsecs -= clock->interval_cycles << adjustment; - - /* adjust the base and error for the adjustment */ - ret = cycles_delta << adjustment; - *error += clock->interval_cycles << adjustment; - /* XXX adj error for cycle_delta offset? */ - } - return ret; + c->xtime_interval = (u64)c->cycle_interval * c->mult; } -- cgit v1.2.1