From 74d23cc704d19732e70ef1579a669f7d5f09dd9a Mon Sep 17 00:00:00 2001 From: Richard Cochran Date: Sun, 21 Dec 2014 19:46:56 +0100 Subject: time: move the timecounter/cyclecounter code into its own file. The timecounter code has almost nothing to do with the clocksource code. Let it live in its own file. This will help isolate the timecounter users from the clocksource users in the source tree. Signed-off-by: Richard Cochran Acked-by: Jeff Kirsher Signed-off-by: David S. Miller --- include/linux/clocksource.h | 102 ------------------------------------ include/linux/mlx4/device.h | 2 +- include/linux/timecounter.h | 122 ++++++++++++++++++++++++++++++++++++++++++++ include/linux/types.h | 3 ++ 4 files changed, 126 insertions(+), 103 deletions(-) create mode 100644 include/linux/timecounter.h (limited to 'include/linux') diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index abcafaa20b86..9c78d15d33e4 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -18,8 +18,6 @@ #include #include -/* clocksource cycle base type */ -typedef u64 cycle_t; struct clocksource; struct module; @@ -27,106 +25,6 @@ struct module; #include #endif -/** - * 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 - * @cc: 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_tstamp: 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. diff --git a/include/linux/mlx4/device.h b/include/linux/mlx4/device.h index 25c791e295fd..f1e41b33462f 100644 --- a/include/linux/mlx4/device.h +++ b/include/linux/mlx4/device.h @@ -42,7 +42,7 @@ #include -#include +#include #define MAX_MSIX_P_PORT 17 #define MAX_MSIX 64 diff --git a/include/linux/timecounter.h b/include/linux/timecounter.h new file mode 100644 index 000000000000..146f07a6651b --- /dev/null +++ b/include/linux/timecounter.h @@ -0,0 +1,122 @@ +/* + * linux/include/linux/timecounter.h + * + * based on code that migrated away from + * linux/include/linux/clocksource.h + * + * 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. + */ +#ifndef _LINUX_TIMECOUNTER_H +#define _LINUX_TIMECOUNTER_H + +#include + +/** + * 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 + * @cc: 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_tstamp: 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); + +#endif diff --git a/include/linux/types.h b/include/linux/types.h index a0bb7048687f..62323825cff9 100644 --- a/include/linux/types.h +++ b/include/linux/types.h @@ -213,5 +213,8 @@ struct callback_head { }; #define rcu_head callback_head +/* clocksource cycle base type */ +typedef u64 cycle_t; + #endif /* __ASSEMBLY__ */ #endif /* _LINUX_TYPES_H */ -- cgit v1.2.3 From 796c1efd6fa0ed696d550b68f4410ab1a1749d01 Mon Sep 17 00:00:00 2001 From: Richard Cochran Date: Sun, 21 Dec 2014 19:46:57 +0100 Subject: timecounter: provide a helper function to shift the time. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Some PTP Hardware Clock drivers use a struct timecounter to represent their clock. To adjust the time by a given offset, these drivers all perform a two step read/write of their timecounter. However, it is better and simpler just to adjust the offset in one step. This patch introduces a little routine to help drivers implement the adjtime method. Suggested-by: Janusz Użycki Signed-off-by: Richard Cochran Signed-off-by: David S. Miller --- include/linux/timecounter.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/linux') diff --git a/include/linux/timecounter.h b/include/linux/timecounter.h index 146f07a6651b..af3dfa4e90f0 100644 --- a/include/linux/timecounter.h +++ b/include/linux/timecounter.h @@ -78,6 +78,15 @@ static inline u64 cyclecounter_cyc2ns(const struct cyclecounter *cc, return ret; } +/** + * timecounter_adjtime - Shifts the time of the clock. + * @delta: Desired change in nanoseconds. + */ +static inline void timecounter_adjtime(struct timecounter *tc, s64 delta) +{ + tc->nsec += delta; +} + /** * timecounter_init - initialize a time counter * @tc: Pointer to time counter which is to be initialized/reset -- cgit v1.2.3 From 2eebdde6528a722fbf8e2cffcf7aa52cbb4c2de0 Mon Sep 17 00:00:00 2001 From: Richard Cochran Date: Sun, 21 Dec 2014 19:47:06 +0100 Subject: timecounter: keep track of accumulated fractional nanoseconds MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The current timecounter implementation will drop a variable amount of resolution, depending on the magnitude of the time delta. In other words, reading the clock too often or too close to a time stamp conversion will introduce errors into the time values. This patch fixes the issue by introducing a fractional nanosecond field that accumulates the low order bits. Reported-by: Janusz Użycki Signed-off-by: Richard Cochran Signed-off-by: David S. Miller --- include/linux/timecounter.h | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) (limited to 'include/linux') diff --git a/include/linux/timecounter.h b/include/linux/timecounter.h index af3dfa4e90f0..74f45496e6d1 100644 --- a/include/linux/timecounter.h +++ b/include/linux/timecounter.h @@ -55,27 +55,32 @@ struct cyclecounter { * @cycle_last: most recent cycle counter value seen by * timecounter_read() * @nsec: continuously increasing count + * @mask: bit mask for maintaining the 'frac' field + * @frac: accumulated fractional nanoseconds */ struct timecounter { const struct cyclecounter *cc; cycle_t cycle_last; u64 nsec; + u64 mask; + u64 frac; }; /** * cyclecounter_cyc2ns - converts cycle counter cycles to nanoseconds * @cc: 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. + * @mask: bit mask for maintaining the 'frac' field + * @frac: pointer to storage for the fractional nanoseconds. */ static inline u64 cyclecounter_cyc2ns(const struct cyclecounter *cc, - cycle_t cycles) + cycle_t cycles, u64 mask, u64 *frac) { - u64 ret = (u64)cycles; - ret = (ret * cc->mult) >> cc->shift; - return ret; + u64 ns = (u64) cycles; + + ns = (ns * cc->mult) + *frac; + *frac = ns & mask; + return ns >> cc->shift; } /** -- cgit v1.2.3