diff options
| author | Suresh Siddha <suresh.b.siddha@intel.com> | 2012-10-22 14:37:58 -0700 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2012-11-02 11:23:37 +0100 |
| commit | 279f1461432ccdec0b98c0bcbe0a8e2c0f6fdda5 (patch) | |
| tree | 1adaa912a846b6d45cff5c8b03db8f97d30ac779 /Documentation/kernel-parameters.txt | |
| parent | 1e207eb1c3f0e8b690401f02fe08e7b53903f010 (diff) | |
x86: apic: Use tsc deadline for oneshot when available
If the TSC deadline mode is supported, LAPIC timer one-shot mode can be
implemented using IA32_TSC_DEADLINE MSR. An interrupt will be generated
when the TSC value equals or exceeds the value in the IA32_TSC_DEADLINE
MSR.
This enables us to skip the APIC calibration during boot. Also, in
xapic mode, this enables us to skip the uncached apic access to re-arm
the APIC timer.
As this timer ticks at the high frequency TSC rate, we use the
TSC_DIVISOR (32) to work with the 32-bit restrictions in the
clockevent API's to avoid 64-bit divides etc (frequency is u32 and
"unsigned long" in the set_next_event(), max_delta limits the next
event to 32-bit for 32-bit kernel).
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: venki@google.com
Cc: len.brown@intel.com
Link: http://lkml.kernel.org/r/1350941878.6017.31.camel@sbsiddha-desk.sc.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'Documentation/kernel-parameters.txt')
| -rw-r--r-- | Documentation/kernel-parameters.txt | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 9776f068306..4aa9ca0de63 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1304,6 +1304,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted. lapic [X86-32,APIC] Enable the local APIC even if BIOS disabled it. + lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline + value for LAPIC timer one-shot implementation. Default + back to the programmable timer unit in the LAPIC. + lapic_timer_c2_ok [X86,APIC] trust the local apic timer in C2 power state. |