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author | Mauro Carvalho Chehab <mchehab+samsung@kernel.org> | 2019-06-12 20:53:00 +0300 |
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committer | Jonathan Corbet <corbet@lwn.net> | 2019-06-14 23:31:48 +0300 |
commit | 458f69ef36656dc74679667380422dd8063eabfb (patch) | |
tree | c44aafca54ae7d01160fe8ef09e7999594145a67 /Documentation/timers/hpet.rst | |
parent | 4ca9bc225e46eb7bc040dd948be7cb68975d80d3 (diff) | |
download | linux-458f69ef36656dc74679667380422dd8063eabfb.tar.xz |
docs: timers: convert docs to ReST and rename to *.rst
The conversion here is really trivial: just a bunch of title
markups and very few puntual changes is enough to make it to
be parsed by Sphinx and generate a nice html.
The conversion is actually:
- add blank lines and identation in order to identify paragraphs;
- fix tables markups;
- add some lists markups;
- mark literal blocks;
- adjust title markups.
At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/timers/hpet.rst')
-rw-r--r-- | Documentation/timers/hpet.rst | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/Documentation/timers/hpet.rst b/Documentation/timers/hpet.rst new file mode 100644 index 000000000000..c9d05d3caaca --- /dev/null +++ b/Documentation/timers/hpet.rst @@ -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, revision 1. + +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:samples/timers/hpet_example.c |