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author | Srikant Patnaik | 2015-01-11 12:28:04 +0530 |
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committer | Srikant Patnaik | 2015-01-11 12:28:04 +0530 |
commit | 871480933a1c28f8a9fed4c4d34d06c439a7a422 (patch) | |
tree | 8718f573808810c2a1e8cb8fb6ac469093ca2784 /Documentation/timers/hpet.txt | |
parent | 9d40ac5867b9aefe0722bc1f110b965ff294d30d (diff) | |
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Moved, renamed, and deleted files
The original directory structure was scattered and unorganized.
Changes are basically to make it look like kernel structure.
Diffstat (limited to 'Documentation/timers/hpet.txt')
-rw-r--r-- | Documentation/timers/hpet.txt | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/Documentation/timers/hpet.txt b/Documentation/timers/hpet.txt new file mode 100644 index 00000000..767392ff --- /dev/null +++ b/Documentation/timers/hpet.txt @@ -0,0 +1,30 @@ + High Precision Event Timer Driver for Linux + +The High Precision Event Timer (HPET) hardware follows a specification +by Intel and Microsoft which can be found at + + http://www.intel.com/hardwaredesign/hpetspec_1.pdf + +Each HPET has one fixed-rate counter (at 10+ MHz, hence "High Precision") +and up to 32 comparators. Normally three or more comparators are provided, +each of which can generate oneshot interrupts and at least one of which has +additional hardware to support periodic interrupts. The comparators are +also called "timers", which can be misleading since usually timers are +independent of each other ... these share a counter, complicating resets. + +HPET devices can support two interrupt routing modes. In one mode, the +comparators are additional interrupt sources with no particular system +role. Many x86 BIOS writers don't route HPET interrupts at all, which +prevents use of that mode. They support the other "legacy replacement" +mode where the first two comparators block interrupts from 8254 timers +and from the RTC. + +The driver supports detection of HPET driver allocation and initialization +of the HPET before the driver module_init routine is called. This enables +platform code which uses timer 0 or 1 as the main timer to intercept HPET +initialization. An example of this initialization can be found in +arch/x86/kernel/hpet.c. + +The driver provides a userspace API which resembles the API found in the +RTC driver framework. An example user space program is provided in +file:Documentation/timers/hpet_example.c |