diff options
Diffstat (limited to 'arch/x86/kernel/tsc.c')
| -rw-r--r-- | arch/x86/kernel/tsc.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 346cae5ac423..aa11413e7c1d 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -122,6 +122,10 @@ static u64 tsc_read_refs(u64 *pm, u64 *hpet) return ULLONG_MAX; } +#define CAL_MS 50 +#define CAL_LATCH (CLOCK_TICK_RATE / (1000 / CAL_MS)) +#define CAL_PIT_LOOPS 5000 + /* * Try to calibrate the TSC against the Programmable * Interrupt Timer and return the frequency of the TSC @@ -144,8 +148,8 @@ static unsigned long pit_calibrate_tsc(void) * (LSB then MSB) to begin countdown. */ outb(0xb0, 0x43); - outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42); - outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42); + outb(CAL_LATCH & 0xff, 0x42); + outb(CAL_LATCH >> 8, 0x42); tsc = t1 = t2 = get_cycles(); @@ -166,18 +170,18 @@ static unsigned long pit_calibrate_tsc(void) /* * Sanity checks: * - * If we were not able to read the PIT more than 5000 + * If we were not able to read the PIT more than PIT_MIN_LOOPS * times, then we have been hit by a massive SMI * * If the maximum is 10 times larger than the minimum, * then we got hit by an SMI as well. */ - if (pitcnt < 5000 || tscmax > 10 * tscmin) + if (pitcnt < CAL_PIT_LOOPS || tscmax > 10 * tscmin) return ULONG_MAX; /* Calculate the PIT value */ delta = t2 - t1; - do_div(delta, 50); + do_div(delta, CAL_MS); return delta; } |