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authorLinus Torvalds <torvalds@linux-foundation.org>2009-03-26 15:54:36 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-03-26 15:54:36 -0700
commit13220a94d35708d5378114e96ffcc88d0a74fe99 (patch)
treebe6530677d5f9536c7211e05ba012923e4c0b307 /include/linux/clocksource.h
parent8690d8a9f6c2d5728a9c9f68231f1bb4de109e3a (diff)
parent08abe18af1f78ee80c3c3a5ac47c3e0ae0beadf6 (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.h101
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