Root/
1 | High Precision Event Timer Driver for Linux |
2 | |
3 | The High Precision Event Timer (HPET) hardware follows a specification |
4 | by Intel and Microsoft which can be found at |
5 | |
6 | http://www.intel.com/hardwaredesign/hpetspec_1.pdf |
7 | |
8 | Each HPET has one fixed-rate counter (at 10+ MHz, hence "High Precision") |
9 | and up to 32 comparators. Normally three or more comparators are provided, |
10 | each of which can generate oneshot interrupts and at least one of which has |
11 | additional hardware to support periodic interrupts. The comparators are |
12 | also called "timers", which can be misleading since usually timers are |
13 | independent of each other ... these share a counter, complicating resets. |
14 | |
15 | HPET devices can support two interrupt routing modes. In one mode, the |
16 | comparators are additional interrupt sources with no particular system |
17 | role. Many x86 BIOS writers don't route HPET interrupts at all, which |
18 | prevents use of that mode. They support the other "legacy replacement" |
19 | mode where the first two comparators block interrupts from 8254 timers |
20 | and from the RTC. |
21 | |
22 | The driver supports detection of HPET driver allocation and initialization |
23 | of the HPET before the driver module_init routine is called. This enables |
24 | platform code which uses timer 0 or 1 as the main timer to intercept HPET |
25 | initialization. An example of this initialization can be found in |
26 | arch/x86/kernel/hpet.c. |
27 | |
28 | The driver provides a userspace API which resembles the API found in the |
29 | RTC driver framework. An example user space program is provided in |
30 | file:Documentation/timers/hpet_example.c |
31 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9