[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 <johnstul@us.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Paul Mundt <lethal@linux-sh.org> Signed-off-by: John Stultz <johnstul@us.ibm.com> Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
john stultz
Linus Torvalds
parent
ade1a29e16
commit
734efb467b
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@ -61,6 +61,7 @@ parameter is applicable:
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MTD MTD support is enabled.
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NET Appropriate network support is enabled.
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NUMA NUMA support is enabled.
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GENERIC_TIME The generic timeofday code is enabled.
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NFS Appropriate NFS support is enabled.
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OSS OSS sound support is enabled.
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PARIDE The ParIDE subsystem is enabled.
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@ -341,10 +342,11 @@ running once the system is up.
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Value can be changed at runtime via
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/selinux/checkreqprot.
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clock= [BUGS=IA-32,HW] gettimeofday timesource override.
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Forces specified timesource (if avaliable) to be used
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when calculating gettimeofday(). If specicified
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timesource is not avalible, it defaults to PIT.
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clock= [BUGS=IA-32, HW] gettimeofday clocksource override.
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[Deprecated]
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Forces specified clocksource (if avaliable) to be used
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when calculating gettimeofday(). If specified
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clocksource is not avalible, it defaults to PIT.
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Format: { pit | tsc | cyclone | pmtmr }
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disable_8254_timer
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@ -1617,6 +1619,10 @@ running once the system is up.
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time Show timing data prefixed to each printk message line
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clocksource= [GENERIC_TIME] Override the default clocksource
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Override the default clocksource and use the clocksource
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with the name specified.
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tipar.timeout= [HW,PPT]
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Set communications timeout in tenths of a second
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(default 15).
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@ -0,0 +1,181 @@
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/* linux/include/linux/clocksource.h
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*
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* This file contains the structure definitions for clocksources.
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*
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* If you are not a clocksource, or timekeeping code, you should
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* not be including this file!
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*/
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#ifndef _LINUX_CLOCKSOURCE_H
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#define _LINUX_CLOCKSOURCE_H
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#include <linux/types.h>
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#include <linux/timex.h>
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#include <linux/time.h>
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#include <linux/list.h>
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#include <asm/div64.h>
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#include <asm/io.h>
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/* clocksource cycle base type */
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typedef u64 cycle_t;
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/**
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* struct clocksource - hardware abstraction for a free running counter
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* Provides mostly state-free accessors to the underlying hardware.
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*
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* @name: ptr to clocksource name
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* @list: list head for registration
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* @rating: rating value for selection (higher is better)
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* To avoid rating inflation the following
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* list should give you a guide as to how
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* to assign your clocksource a rating
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* 1-99: Unfit for real use
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* Only available for bootup and testing purposes.
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* 100-199: Base level usability.
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* Functional for real use, but not desired.
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* 200-299: Good.
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* A correct and usable clocksource.
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* 300-399: Desired.
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* A reasonably fast and accurate clocksource.
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* 400-499: Perfect
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* The ideal clocksource. A must-use where
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* available.
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* @read: returns a cycle value
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* @mask: bitmask for two's complement
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* subtraction of non 64 bit counters
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* @mult: cycle to nanosecond multiplier
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* @shift: cycle to nanosecond divisor (power of two)
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* @update_callback: called when safe to alter clocksource values
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* @is_continuous: defines if clocksource is free-running.
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* @interval_cycles: Used internally by timekeeping core, please ignore.
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* @interval_snsecs: Used internally by timekeeping core, please ignore.
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*/
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struct clocksource {
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char *name;
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struct list_head list;
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int rating;
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cycle_t (*read)(void);
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cycle_t mask;
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u32 mult;
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u32 shift;
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int (*update_callback)(void);
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int is_continuous;
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/* timekeeping specific data, ignore */
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cycle_t interval_cycles;
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u64 interval_snsecs;
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};
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/**
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* clocksource_khz2mult - calculates mult from khz and shift
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* @khz: Clocksource frequency in KHz
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* @shift_constant: Clocksource shift factor
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*
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* Helper functions that converts a khz counter frequency to a timsource
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* multiplier, given the clocksource shift value
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*/
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static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
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{
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/* khz = cyc/(Million ns)
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* mult/2^shift = ns/cyc
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* mult = ns/cyc * 2^shift
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* mult = 1Million/khz * 2^shift
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* mult = 1000000 * 2^shift / khz
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* mult = (1000000<<shift) / khz
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*/
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u64 tmp = ((u64)1000000) << shift_constant;
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tmp += khz/2; /* round for do_div */
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do_div(tmp, khz);
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return (u32)tmp;
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}
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/**
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* clocksource_hz2mult - calculates mult from hz and shift
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* @hz: Clocksource frequency in Hz
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* @shift_constant: Clocksource shift factor
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*
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* Helper functions that converts a hz counter
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* frequency to a timsource multiplier, given the
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* clocksource shift value
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*/
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static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
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{
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/* hz = cyc/(Billion ns)
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* mult/2^shift = ns/cyc
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* mult = ns/cyc * 2^shift
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* mult = 1Billion/hz * 2^shift
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* mult = 1000000000 * 2^shift / hz
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* mult = (1000000000<<shift) / hz
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*/
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u64 tmp = ((u64)1000000000) << shift_constant;
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tmp += hz/2; /* round for do_div */
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do_div(tmp, hz);
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return (u32)tmp;
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}
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/**
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* read_clocksource: - Access the clocksource's current cycle value
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* @cs: pointer to clocksource being read
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*
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* Uses the clocksource to return the current cycle_t value
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*/
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static inline cycle_t read_clocksource(struct clocksource *cs)
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{
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return cs->read();
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}
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/**
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* cyc2ns - converts clocksource cycles to nanoseconds
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* @cs: Pointer to clocksource
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* @cycles: Cycles
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*
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* Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds.
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*
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* XXX - This could use some mult_lxl_ll() asm optimization
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*/
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static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles)
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{
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u64 ret = (u64)cycles;
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ret = (ret * cs->mult) >> cs->shift;
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return ret;
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}
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/**
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* calculate_clocksource_interval - Calculates a clocksource interval struct
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*
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* @c: Pointer to clocksource.
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* @length_nsec: Desired interval length in nanoseconds.
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*
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* Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
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* pair and interval request.
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*
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* Unless you're the timekeeping code, you should not be using this!
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*/
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static inline void calculate_clocksource_interval(struct clocksource *c,
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unsigned long length_nsec)
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{
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u64 tmp;
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/* XXX - All of this could use a whole lot of optimization */
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tmp = length_nsec;
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tmp <<= c->shift;
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tmp += c->mult/2;
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do_div(tmp, c->mult);
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c->interval_cycles = (cycle_t)tmp;
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if(c->interval_cycles == 0)
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c->interval_cycles = 1;
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c->interval_snsecs = (u64)c->interval_cycles * c->mult;
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}
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/* used to install a new clocksource */
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int register_clocksource(struct clocksource*);
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void reselect_clocksource(void);
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struct clocksource* get_next_clocksource(void);
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#endif /* _LINUX_CLOCKSOURCE_H */
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@ -0,0 +1 @@
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obj-y += clocksource.o jiffies.o
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@ -0,0 +1,344 @@
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/*
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* linux/kernel/time/clocksource.c
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*
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* This file contains the functions which manage clocksource drivers.
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*
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* Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* TODO WishList:
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* o Allow clocksource drivers to be unregistered
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* o get rid of clocksource_jiffies extern
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*/
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#include <linux/clocksource.h>
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#include <linux/sysdev.h>
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#include <linux/init.h>
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#include <linux/module.h>
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/* XXX - Would like a better way for initializing curr_clocksource */
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extern struct clocksource clocksource_jiffies;
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/*[Clocksource internal variables]---------
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* curr_clocksource:
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* currently selected clocksource. Initialized to clocksource_jiffies.
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* next_clocksource:
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* pending next selected clocksource.
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* clocksource_list:
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* linked list with the registered clocksources
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* clocksource_lock:
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* protects manipulations to curr_clocksource and next_clocksource
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* and the clocksource_list
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* override_name:
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* Name of the user-specified clocksource.
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*/
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static struct clocksource *curr_clocksource = &clocksource_jiffies;
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static struct clocksource *next_clocksource;
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static LIST_HEAD(clocksource_list);
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static DEFINE_SPINLOCK(clocksource_lock);
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static char override_name[32];
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static int finished_booting;
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/* clocksource_done_booting - Called near the end of bootup
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*
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* Hack to avoid lots of clocksource churn at boot time
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*/
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static int clocksource_done_booting(void)
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{
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finished_booting = 1;
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return 0;
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}
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late_initcall(clocksource_done_booting);
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/**
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* get_next_clocksource - Returns the selected clocksource
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*
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*/
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struct clocksource *get_next_clocksource(void)
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{
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unsigned long flags;
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spin_lock_irqsave(&clocksource_lock, flags);
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if (next_clocksource && finished_booting) {
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curr_clocksource = next_clocksource;
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next_clocksource = NULL;
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}
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spin_unlock_irqrestore(&clocksource_lock, flags);
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return curr_clocksource;
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}
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/**
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* select_clocksource - Finds the best registered clocksource.
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*
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* Private function. Must hold clocksource_lock when called.
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*
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* Looks through the list of registered clocksources, returning
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* the one with the highest rating value. If there is a clocksource
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* name that matches the override string, it returns that clocksource.
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*/
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static struct clocksource *select_clocksource(void)
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{
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struct clocksource *best = NULL;
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struct list_head *tmp;
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list_for_each(tmp, &clocksource_list) {
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struct clocksource *src;
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src = list_entry(tmp, struct clocksource, list);
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if (!best)
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best = src;
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/* check for override: */
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if (strlen(src->name) == strlen(override_name) &&
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!strcmp(src->name, override_name)) {
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best = src;
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break;
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}
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/* pick the highest rating: */
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if (src->rating > best->rating)
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best = src;
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}
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return best;
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}
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/**
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* is_registered_source - Checks if clocksource is registered
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* @c: pointer to a clocksource
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*
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* Private helper function. Must hold clocksource_lock when called.
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*
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* Returns one if the clocksource is already registered, zero otherwise.
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*/
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static int is_registered_source(struct clocksource *c)
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{
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int len = strlen(c->name);
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struct list_head *tmp;
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list_for_each(tmp, &clocksource_list) {
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struct clocksource *src;
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src = list_entry(tmp, struct clocksource, list);
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if (strlen(src->name) == len && !strcmp(src->name, c->name))
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return 1;
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}
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return 0;
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}
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/**
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* register_clocksource - Used to install new clocksources
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* @t: clocksource to be registered
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*
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* Returns -EBUSY if registration fails, zero otherwise.
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*/
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int register_clocksource(struct clocksource *c)
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{
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int ret = 0;
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unsigned long flags;
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spin_lock_irqsave(&clocksource_lock, flags);
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/* check if clocksource is already registered */
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if (is_registered_source(c)) {
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printk("register_clocksource: Cannot register %s. "
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"Already registered!", c->name);
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ret = -EBUSY;
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} else {
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/* register it */
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list_add(&c->list, &clocksource_list);
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/* scan the registered clocksources, and pick the best one */
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next_clocksource = select_clocksource();
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}
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spin_unlock_irqrestore(&clocksource_lock, flags);
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return ret;
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}
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EXPORT_SYMBOL(register_clocksource);
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/**
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* reselect_clocksource - Rescan list for next clocksource
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*
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* A quick helper function to be used if a clocksource changes its
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* rating. Forces the clocksource list to be re-scaned for the best
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* clocksource.
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*/
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void reselect_clocksource(void)
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{
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unsigned long flags;
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spin_lock_irqsave(&clocksource_lock, flags);
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next_clocksource = select_clocksource();
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spin_unlock_irqrestore(&clocksource_lock, flags);
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}
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/**
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* sysfs_show_current_clocksources - sysfs interface for current clocksource
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* @dev: unused
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* @buf: char buffer to be filled with clocksource list
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*
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* Provides sysfs interface for listing current clocksource.
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*/
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static ssize_t
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sysfs_show_current_clocksources(struct sys_device *dev, char *buf)
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{
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char *curr = buf;
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spin_lock_irq(&clocksource_lock);
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curr += sprintf(curr, "%s ", curr_clocksource->name);
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spin_unlock_irq(&clocksource_lock);
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curr += sprintf(curr, "\n");
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return curr - buf;
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}
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/**
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* sysfs_override_clocksource - interface for manually overriding clocksource
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* @dev: unused
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* @buf: name of override clocksource
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* @count: length of buffer
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*
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* Takes input from sysfs interface for manually overriding the default
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* clocksource selction.
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*/
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static ssize_t sysfs_override_clocksource(struct sys_device *dev,
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const char *buf, size_t count)
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{
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size_t ret = count;
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/* strings from sysfs write are not 0 terminated! */
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if (count >= sizeof(override_name))
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return -EINVAL;
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/* strip of \n: */
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if (buf[count-1] == '\n')
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count--;
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if (count < 1)
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return -EINVAL;
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spin_lock_irq(&clocksource_lock);
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/* copy the name given: */
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memcpy(override_name, buf, count);
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override_name[count] = 0;
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/* try to select it: */
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next_clocksource = select_clocksource();
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spin_unlock_irq(&clocksource_lock);
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return ret;
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}
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/**
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* sysfs_show_available_clocksources - sysfs interface for listing clocksource
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* @dev: unused
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* @buf: char buffer to be filled with clocksource list
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*
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* Provides sysfs interface for listing registered clocksources
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*/
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static ssize_t
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sysfs_show_available_clocksources(struct sys_device *dev, char *buf)
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{
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struct list_head *tmp;
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char *curr = buf;
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spin_lock_irq(&clocksource_lock);
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list_for_each(tmp, &clocksource_list) {
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struct clocksource *src;
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||||
src = list_entry(tmp, struct clocksource, list);
|
||||
curr += sprintf(curr, "%s ", src->name);
|
||||
}
|
||||
spin_unlock_irq(&clocksource_lock);
|
||||
|
||||
curr += sprintf(curr, "\n");
|
||||
|
||||
return curr - buf;
|
||||
}
|
||||
|
||||
/*
|
||||
* Sysfs setup bits:
|
||||
*/
|
||||
static SYSDEV_ATTR(current_clocksource, 0600, sysfs_show_current_clocksources,
|
||||
sysfs_override_clocksource);
|
||||
|
||||
static SYSDEV_ATTR(available_clocksource, 0600,
|
||||
sysfs_show_available_clocksources, NULL);
|
||||
|
||||
static struct sysdev_class clocksource_sysclass = {
|
||||
set_kset_name("clocksource"),
|
||||
};
|
||||
|
||||
static struct sys_device device_clocksource = {
|
||||
.id = 0,
|
||||
.cls = &clocksource_sysclass,
|
||||
};
|
||||
|
||||
static int init_clocksource_sysfs(void)
|
||||
{
|
||||
int error = sysdev_class_register(&clocksource_sysclass);
|
||||
|
||||
if (!error)
|
||||
error = sysdev_register(&device_clocksource);
|
||||
if (!error)
|
||||
error = sysdev_create_file(
|
||||
&device_clocksource,
|
||||
&attr_current_clocksource);
|
||||
if (!error)
|
||||
error = sysdev_create_file(
|
||||
&device_clocksource,
|
||||
&attr_available_clocksource);
|
||||
return error;
|
||||
}
|
||||
|
||||
device_initcall(init_clocksource_sysfs);
|
||||
|
||||
/**
|
||||
* boot_override_clocksource - boot clock override
|
||||
* @str: override name
|
||||
*
|
||||
* Takes a clocksource= boot argument and uses it
|
||||
* as the clocksource override name.
|
||||
*/
|
||||
static int __init boot_override_clocksource(char* str)
|
||||
{
|
||||
unsigned long flags;
|
||||
spin_lock_irqsave(&clocksource_lock, flags);
|
||||
if (str)
|
||||
strlcpy(override_name, str, sizeof(override_name));
|
||||
spin_unlock_irqrestore(&clocksource_lock, flags);
|
||||
return 1;
|
||||
}
|
||||
|
||||
__setup("clocksource=", boot_override_clocksource);
|
||||
|
||||
/**
|
||||
* boot_override_clock - Compatibility layer for deprecated boot option
|
||||
* @str: override name
|
||||
*
|
||||
* DEPRECATED! Takes a clock= boot argument and uses it
|
||||
* as the clocksource override name
|
||||
*/
|
||||
static int __init boot_override_clock(char* str)
|
||||
{
|
||||
printk("Warning! clock= boot option is deprecated.\n");
|
||||
|
||||
return boot_override_clocksource(str);
|
||||
}
|
||||
|
||||
__setup("clock=", boot_override_clock);
|
||||
|
|
@ -0,0 +1,73 @@
|
|||
/***********************************************************************
|
||||
* linux/kernel/time/jiffies.c
|
||||
*
|
||||
* This file contains the jiffies based clocksource.
|
||||
*
|
||||
* Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
|
||||
*
|
||||
* This program is free software; you can redistribute it and/or modify
|
||||
* it under the terms of the GNU General Public License as published by
|
||||
* the Free Software Foundation; either version 2 of the License, or
|
||||
* (at your option) any later version.
|
||||
*
|
||||
* This program is distributed in the hope that it will be useful,
|
||||
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||||
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||||
* GNU General Public License for more details.
|
||||
*
|
||||
* You should have received a copy of the GNU General Public License
|
||||
* along with this program; if not, write to the Free Software
|
||||
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
|
||||
*
|
||||
************************************************************************/
|
||||
#include <linux/clocksource.h>
|
||||
#include <linux/jiffies.h>
|
||||
#include <linux/init.h>
|
||||
|
||||
/* The Jiffies based clocksource is the lowest common
|
||||
* denominator clock source which should function on
|
||||
* all systems. It has the same coarse resolution as
|
||||
* the timer interrupt frequency HZ and it suffers
|
||||
* inaccuracies caused by missed or lost timer
|
||||
* interrupts and the inability for the timer
|
||||
* interrupt hardware to accuratly tick at the
|
||||
* requested HZ value. It is also not reccomended
|
||||
* for "tick-less" systems.
|
||||
*/
|
||||
#define NSEC_PER_JIFFY ((u32)((((u64)NSEC_PER_SEC)<<8)/ACTHZ))
|
||||
|
||||
/* Since jiffies uses a simple NSEC_PER_JIFFY multiplier
|
||||
* conversion, the .shift value could be zero. However
|
||||
* this would make NTP adjustments impossible as they are
|
||||
* in units of 1/2^.shift. Thus we use JIFFIES_SHIFT to
|
||||
* shift both the nominator and denominator the same
|
||||
* amount, and give ntp adjustments in units of 1/2^8
|
||||
*
|
||||
* The value 8 is somewhat carefully chosen, as anything
|
||||
* larger can result in overflows. NSEC_PER_JIFFY grows as
|
||||
* HZ shrinks, so values greater then 8 overflow 32bits when
|
||||
* HZ=100.
|
||||
*/
|
||||
#define JIFFIES_SHIFT 8
|
||||
|
||||
static cycle_t jiffies_read(void)
|
||||
{
|
||||
return (cycle_t) jiffies;
|
||||
}
|
||||
|
||||
struct clocksource clocksource_jiffies = {
|
||||
.name = "jiffies",
|
||||
.rating = 0, /* lowest rating*/
|
||||
.read = jiffies_read,
|
||||
.mask = 0xffffffff, /*32bits*/
|
||||
.mult = NSEC_PER_JIFFY << JIFFIES_SHIFT, /* details above */
|
||||
.shift = JIFFIES_SHIFT,
|
||||
.is_continuous = 0, /* tick based, not free running */
|
||||
};
|
||||
|
||||
static int __init init_jiffies_clocksource(void)
|
||||
{
|
||||
return register_clocksource(&clocksource_jiffies);
|
||||
}
|
||||
|
||||
module_init(init_jiffies_clocksource);
|
||||
Loading…
Reference in New Issue