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authorLinus Torvalds <torvalds@linux-foundation.org>2008-10-13 09:54:35 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-10-13 09:54:45 -0700
commite7f2f9918c0e97aa98ba147ca387e2c7238f0711 (patch)
treedd85d6d2907bffeda76b42ce55a445e3142fe738 /Documentation
parent11a96d1820113fde0d55c3487b7da7a9031326b8 (diff)
parentc00193f9f09f9b852249a66391985f585d066084 (diff)
Merge phase #5 (misc) of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
Merges oprofile, timers/hpet, x86/traps, x86/time, and x86/core misc items. * 'x86-core-v4-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (132 commits) x86: change early_ioremap to use slots instead of nesting x86: adjust dependencies for CONFIG_X86_CMOV dumpstack: x86: various small unification steps, fix x86: remove additional_cpus x86: remove additional_cpus configurability x86: improve UP kernel when CPU-hotplug and SMP is enabled dumpstack: x86: various small unification steps dumpstack: i386: make kstack= an early boot-param and add oops=panic dumpstack: x86: use log_lvl and unify trace formatting dumptrace: x86: consistently include loglevel, print stack switch dumpstack: x86: add "end" parameter to valid_stack_ptr and print_context_stack dumpstack: x86: make printk_address equal dumpstack: x86: move die_nmi to dumpstack_32.c traps: x86: finalize unification of traps.c traps: x86: make traps_32.c and traps_64.c equal traps: x86: various noop-changes preparing for unification of traps_xx.c traps: x86_64: use task_pid_nr(tsk) instead of tsk->pid in do_general_protection traps: i386: expand clear_mem_error and remove from mach_traps.h traps: x86_64: make io_check_error equal to the one on i386 traps: i386: use preempt_conditional_sti/cli in do_int3 ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/00-INDEX2
-rw-r--r--Documentation/timers/00-INDEX10
-rw-r--r--Documentation/timers/hpet.txt (renamed from Documentation/hpet.txt)43
3 files changed, 31 insertions, 24 deletions
diff --git a/Documentation/00-INDEX b/Documentation/00-INDEX
index 73060819ed9..43827780010 100644
--- a/Documentation/00-INDEX
+++ b/Documentation/00-INDEX
@@ -159,8 +159,6 @@ hayes-esp.txt
- info on using the Hayes ESP serial driver.
highuid.txt
- notes on the change from 16 bit to 32 bit user/group IDs.
-hpet.txt
- - High Precision Event Timer Driver for Linux.
timers/
- info on the timer related topics
hw_random.txt
diff --git a/Documentation/timers/00-INDEX b/Documentation/timers/00-INDEX
new file mode 100644
index 00000000000..397dc35e132
--- /dev/null
+++ b/Documentation/timers/00-INDEX
@@ -0,0 +1,10 @@
+00-INDEX
+ - this file
+highres.txt
+ - High resolution timers and dynamic ticks design notes
+hpet.txt
+ - High Precision Event Timer Driver for Linux
+hrtimers.txt
+ - subsystem for high-resolution kernel timers
+timer_stats.txt
+ - timer usage statistics
diff --git a/Documentation/hpet.txt b/Documentation/timers/hpet.txt
index 6ad52d9dad6..e7c09abcfab 100644
--- a/Documentation/hpet.txt
+++ b/Documentation/timers/hpet.txt
@@ -1,21 +1,32 @@
High Precision Event Timer Driver for Linux
-The High Precision Event Timer (HPET) hardware is the future replacement
-for the 8254 and Real Time Clock (RTC) periodic timer functionality.
-Each HPET can have up to 32 timers. It is possible to configure the
-first two timers as legacy replacements for 8254 and RTC periodic timers.
-A specification done by Intel and Microsoft can be found at
-<http://www.intel.com/technology/architecture/hpetspec.htm>.
+The High Precision Event Timer (HPET) hardware follows a specification
+by Intel and Microsoft which can be found at
+
+ http://www.intel.com/technology/architecture/hpetspec.htm
+
+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 interupts 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/i386/kernel/time_hpet.c.
+arch/x86/kernel/hpet.c.
-The driver provides two APIs which are very similar to the API found in
-the rtc.c driver. There is a user space API and a kernel space API.
-An example user space program is provided below.
+The driver provides a userspace API which resembles the API found in the
+RTC driver framework. An example user space program is provided below.
#include <stdio.h>
#include <stdlib.h>
@@ -286,15 +297,3 @@ out:
return;
}
-
-The kernel API has three interfaces exported from the driver:
-
- hpet_register(struct hpet_task *tp, int periodic)
- hpet_unregister(struct hpet_task *tp)
- hpet_control(struct hpet_task *tp, unsigned int cmd, unsigned long arg)
-
-The kernel module using this interface fills in the ht_func and ht_data
-members of the hpet_task structure before calling hpet_register.
-hpet_control simply vectors to the hpet_ioctl routine and has the same
-commands and respective arguments as the user API. hpet_unregister
-is used to terminate usage of the HPET timer reserved by hpet_register.