diff options
Diffstat (limited to 'arch/i386/kernel/timers/timer_tsc.c')
| -rw-r--r-- | arch/i386/kernel/timers/timer_tsc.c | 35 |
1 files changed, 27 insertions, 8 deletions
diff --git a/arch/i386/kernel/timers/timer_tsc.c b/arch/i386/kernel/timers/timer_tsc.c index 8f4e4d5bc560..d395e3b42485 100644 --- a/arch/i386/kernel/timers/timer_tsc.c +++ b/arch/i386/kernel/timers/timer_tsc.c @@ -49,23 +49,28 @@ static seqlock_t monotonic_lock = SEQLOCK_UNLOCKED; * basic equation: * ns = cycles / (freq / ns_per_sec) * ns = cycles * (ns_per_sec / freq) - * ns = cycles * (10^9 / (cpu_mhz * 10^6)) - * ns = cycles * (10^3 / cpu_mhz) + * ns = cycles * (10^9 / (cpu_khz * 10^3)) + * ns = cycles * (10^6 / cpu_khz) * * Then we use scaling math (suggested by george@mvista.com) to get: - * ns = cycles * (10^3 * SC / cpu_mhz) / SC + * ns = cycles * (10^6 * SC / cpu_khz) / SC * ns = cycles * cyc2ns_scale / SC * * And since SC is a constant power of two, we can convert the div - * into a shift. + * into a shift. + * + * We can use khz divisor instead of mhz to keep a better percision, since + * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits. + * (mathieu.desnoyers@polymtl.ca) + * * -johnstul@us.ibm.com "math is hard, lets go shopping!" */ static unsigned long cyc2ns_scale; #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */ -static inline void set_cyc2ns_scale(unsigned long cpu_mhz) +static inline void set_cyc2ns_scale(unsigned long cpu_khz) { - cyc2ns_scale = (1000 << CYC2NS_SCALE_FACTOR)/cpu_mhz; + cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz; } static inline unsigned long long cycles_2_ns(unsigned long long cyc) @@ -286,7 +291,7 @@ time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, if (use_tsc) { if (!(freq->flags & CPUFREQ_CONST_LOOPS)) { fast_gettimeoffset_quotient = cpufreq_scale(fast_gettimeoffset_ref, freq->new, ref_freq); - set_cyc2ns_scale(cpu_khz/1000); + set_cyc2ns_scale(cpu_khz); } } #endif @@ -536,13 +541,26 @@ static int __init init_tsc(char* override) printk("Detected %u.%03u MHz processor.\n", cpu_khz / 1000, cpu_khz % 1000); } - set_cyc2ns_scale(cpu_khz/1000); + set_cyc2ns_scale(cpu_khz); return 0; } } return -ENODEV; } +static int tsc_resume(void) +{ + write_seqlock(&monotonic_lock); + /* Assume this is the last mark offset time */ + rdtsc(last_tsc_low, last_tsc_high); +#ifdef CONFIG_HPET_TIMER + if (is_hpet_enabled() && hpet_use_timer) + hpet_last = hpet_readl(HPET_COUNTER); +#endif + write_sequnlock(&monotonic_lock); + return 0; +} + #ifndef CONFIG_X86_TSC /* disable flag for tsc. Takes effect by clearing the TSC cpu flag * in cpu/common.c */ @@ -573,6 +591,7 @@ static struct timer_opts timer_tsc = { .monotonic_clock = monotonic_clock_tsc, .delay = delay_tsc, .read_timer = read_timer_tsc, + .resume = tsc_resume, }; struct init_timer_opts __initdata timer_tsc_init = { |