From 9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 Mon Sep 17 00:00:00 2001 From: Yunhong Jiang Date: Tue, 4 Aug 2015 12:17:53 -0700 Subject: Add the rt linux 4.1.3-rt3 as base Import the rt linux 4.1.3-rt3 as OPNFV kvm base. It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and the base is: commit 0917f823c59692d751951bf5ea699a2d1e2f26a2 Author: Sebastian Andrzej Siewior Date: Sat Jul 25 12:13:34 2015 +0200 Prepare v4.1.3-rt3 Signed-off-by: Sebastian Andrzej Siewior We lose all the git history this way and it's not good. We should apply another opnfv project repo in future. Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423 Signed-off-by: Yunhong Jiang --- kernel/Documentation/timers/hpet.txt | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) create mode 100644 kernel/Documentation/timers/hpet.txt (limited to 'kernel/Documentation/timers/hpet.txt') diff --git a/kernel/Documentation/timers/hpet.txt b/kernel/Documentation/timers/hpet.txt new file mode 100644 index 000000000..767392ffd --- /dev/null +++ b/kernel/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 -- cgit 1.2.3-korg