diff options
| author | David P. Reed <dpreed@reed.com> | 2007-05-02 21:27:20 +0400 |
|---|---|---|
| committer | Andi Kleen <andi@basil.nowhere.org> | 2007-05-02 21:27:20 +0400 |
| commit | 4637a74cf2ac3a3696d385c8624d84de789d1bbe (patch) | |
| tree | 358cd844b60771697d8cff6b85c5ab7db4b96deb /arch | |
| parent | 9d016dd43b8df0228f1022f483f582eeb52d256e (diff) | |
| download | linux-4637a74cf2ac3a3696d385c8624d84de789d1bbe.tar.xz | |
[PATCH] x86-64: Avoid overflows during apic timer calibration
- Use 64bit TSC calculations to avoid handling overflow
- Use 32bit unsigned arithmetic for the APIC timer. This
way overflows are handled correctly.
- Fix exit check of loop to account for apic timer counting down
Signed-off-by: dpreed@reed.com
Signed-off-by: Andi Kleen <ak@suse.de>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86_64/kernel/apic.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/arch/x86_64/kernel/apic.c b/arch/x86_64/kernel/apic.c index 943ec4d1bd8e..d198f7d82e5a 100644 --- a/arch/x86_64/kernel/apic.c +++ b/arch/x86_64/kernel/apic.c @@ -839,14 +839,15 @@ static void setup_APIC_timer(unsigned int clocks) static int __init calibrate_APIC_clock(void) { - int apic, apic_start, tsc, tsc_start; + unsigned apic, apic_start; + unsigned long tsc, tsc_start; int result; /* * Put whatever arbitrary (but long enough) timeout * value into the APIC clock, we just want to get the * counter running for calibration. */ - __setup_APIC_LVTT(1000000000); + __setup_APIC_LVTT(4000000000); apic_start = apic_read(APIC_TMCCT); #ifdef CONFIG_X86_PM_TIMER @@ -857,13 +858,13 @@ static int __init calibrate_APIC_clock(void) } else #endif { - rdtscl(tsc_start); + rdtscll(tsc_start); do { apic = apic_read(APIC_TMCCT); - rdtscl(tsc); + rdtscll(tsc); } while ((tsc - tsc_start) < TICK_COUNT && - (apic - apic_start) < TICK_COUNT); + (apic_start - apic) < TICK_COUNT); result = (apic_start - apic) * 1000L * tsc_khz / (tsc - tsc_start); |