4 Time interpolators are a base of time calculation between timer ticks and
5 allow an accurate determination of time down to the accuracy of the time
8 The architecture specific code typically provides gettimeofday and
9 settimeofday under Linux. The time interpolator provides both if an arch
10 defines CONFIG_TIME_INTERPOLATION. The arch still must set up timer tick
11 operations and call the necessary functions to advance the clock.
12 With the time interpolator a standardized interface exists for time
13 interpolation between ticks which also allows the determination
14 of time in a hardware independent way. The provided logic is highly scalable
15 and has been tested in SMP situations of up to 512 CPUs.
17 If CONFIG_TIME_INTERPOLATION is defined then the architecture specific code
18 (or the device drivers - like HPET) must register time interpolators.
19 These are typically defined in the following way:
21 static struct time_interpolator my_interpolator;
26 /* Initialization of the timer *.
27 my_interpolator.frequency = MY_FREQUENCY;
28 my_interpolator.source = TIME_SOURCE_MMIO32;
29 my_interpolator.address = &my_timer;
30 my_interpolator.shift = 32; /* increase accuracy of scaling */
31 my_interpolator.drift = -1; /* Unknown */
32 my_interpolator.jitter = 0; /* A stable time source */
33 register_time_interpolator(&my_interpolator);
37 For more details see include/linux/timex.h.
39 Christoph Lameter <christoph@lameter.com>, September 8, 2004