diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2009-03-26 15:54:36 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-03-26 15:54:36 -0700 |
commit | 13220a94d35708d5378114e96ffcc88d0a74fe99 (patch) | |
tree | be6530677d5f9536c7211e05ba012923e4c0b307 /include/linux/clocksource.h | |
parent | 8690d8a9f6c2d5728a9c9f68231f1bb4de109e3a (diff) | |
parent | 08abe18af1f78ee80c3c3a5ac47c3e0ae0beadf6 (diff) |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6: (1750 commits)
ixgbe: Allow Priority Flow Control settings to survive a device reset
net: core: remove unneeded include in net/core/utils.c.
e1000e: update version number
e1000e: fix close interrupt race
e1000e: fix loss of multicast packets
e1000e: commonize tx cleanup routine to match e1000 & igb
netfilter: fix nf_logger name in ebt_ulog.
netfilter: fix warning in ebt_ulog init function.
netfilter: fix warning about invalid const usage
e1000: fix close race with interrupt
e1000: cleanup clean_tx_irq routine so that it completely cleans ring
e1000: fix tx hang detect logic and address dma mapping issues
bridge: bad error handling when adding invalid ether address
bonding: select current active slave when enslaving device for mode tlb and alb
gianfar: reallocate skb when headroom is not enough for fcb
Bump release date to 25Mar2009 and version to 0.22
r6040: Fix second PHY address
qeth: fix wait_event_timeout handling
qeth: check for completion of a running recovery
qeth: unregister MAC addresses during recovery.
...
Manually fixed up conflicts in:
drivers/infiniband/hw/cxgb3/cxio_hal.h
drivers/infiniband/hw/nes/nes_nic.c
Diffstat (limited to 'include/linux/clocksource.h')
-rw-r--r-- | include/linux/clocksource.h | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index f88d32f8ff7..573819ef4cc 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -22,8 +22,109 @@ typedef u64 cycle_t; 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 |