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author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/time_interpolators.txt | |
download | kernel_samsung_espresso10-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.zip kernel_samsung_espresso10-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz kernel_samsung_espresso10-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.bz2 |
Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'Documentation/time_interpolators.txt')
-rw-r--r-- | Documentation/time_interpolators.txt | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/Documentation/time_interpolators.txt b/Documentation/time_interpolators.txt new file mode 100644 index 0000000..e3b6085 --- /dev/null +++ b/Documentation/time_interpolators.txt @@ -0,0 +1,41 @@ +Time Interpolators +------------------ + +Time interpolators are a base of time calculation between timer ticks and +allow an accurate determination of time down to the accuracy of the time +source in nanoseconds. + +The architecture specific code typically provides gettimeofday and +settimeofday under Linux. The time interpolator provides both if an arch +defines CONFIG_TIME_INTERPOLATION. The arch still must set up timer tick +operations and call the necessary functions to advance the clock. + +With the time interpolator a standardized interface exists for time +interpolation between ticks. The provided logic is highly scalable +and has been tested in SMP situations of up to 512 CPUs. + +If CONFIG_TIME_INTERPOLATION is defined then the architecture specific code +(or the device drivers - like HPET) may register time interpolators. +These are typically defined in the following way: + +static struct time_interpolator my_interpolator { + .frequency = MY_FREQUENCY, + .source = TIME_SOURCE_MMIO32, + .shift = 8, /* scaling for higher accuracy */ + .drift = -1, /* Unknown drift */ + .jitter = 0 /* time source is stable */ +}; + +void time_init(void) +{ + .... + /* Initialization of the timer *. + my_interpolator.address = &my_timer; + register_time_interpolator(&my_interpolator); + .... +} + +For more details see include/linux/timex.h and kernel/timer.c. + +Christoph Lameter <christoph@lameter.com>, October 31, 2004 + |