#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include unsigned int __read_mostly cpu_khz; /* TSC clocks / usec, not used here */ EXPORT_SYMBOL(cpu_khz); unsigned int __read_mostly tsc_khz; EXPORT_SYMBOL(tsc_khz); /* * TSC can be unstable due to cpufreq or due to unsynced TSCs */ static int __read_mostly tsc_unstable; /* native_sched_clock() is called before tsc_init(), so we must start with the TSC soft disabled to prevent erroneous rdtsc usage on !cpu_has_tsc processors */ static int __read_mostly tsc_disabled = -1; int tsc_clocksource_reliable; /* * Use a ring-buffer like data structure, where a writer advances the head by * writing a new data entry and a reader advances the tail when it observes a * new entry. * * Writers are made to wait on readers until there's space to write a new * entry. * * This means that we can always use an {offset, mul} pair to compute a ns * value that is 'roughly' in the right direction, even if we're writing a new * {offset, mul} pair during the clock read. * * The down-side is that we can no longer guarantee strict monotonicity anymore * (assuming the TSC was that to begin with), because while we compute the * intersection point of the two clock slopes and make sure the time is * continuous at the point of switching; we can no longer guarantee a reader is * strictly before or after the switch point. * * It does mean a reader no longer needs to disable IRQs in order to avoid * CPU-Freq updates messing with his times, and similarly an NMI reader will * no longer run the risk of hitting half-written state. */ struct cyc2ns { struct cyc2ns_data data[2]; /* 0 + 2*24 = 48 */ struct cyc2ns_data *head; /* 48 + 8 = 56 */ struct cyc2ns_data *tail; /* 56 + 8 = 64 */ }; /* exactly fits one cacheline */ static DEFINE_PER_CPU_ALIGNED(struct cyc2ns, cyc2ns); struct cyc2ns_data *cyc2ns_read_begin(void) { struct cyc2ns_data *head; preempt_disable(); head = this_cpu_read(cyc2ns.head); /* * Ensure we observe the entry when we observe the pointer to it. * matches the wmb from cyc2ns_write_end(). */ smp_read_barrier_depends(); head->__count++; barrier(); return head; } void cyc2ns_read_end(struct cyc2ns_data *head) { barrier(); /* * If we're the outer most nested read; update the tail pointer * when we're done. This notifies possible pending writers * that we've observed the head pointer and that the other * entry is now free. */ if (!--head->__count) { /* * x86-TSO does not reorder writes with older reads; * therefore once this write becomes visible to another * cpu, we must be finished reading the cyc2ns_data. * * matches with cyc2ns_write_begin(). */ this_cpu_write(cyc2ns.tail, head); } preempt_enable(); } /* * Begin writing a new @data entry for @cpu. * * Assumes some sort of write side lock; currently 'provided' by the assumption * that cpufreq will call its notifiers sequentially. */ static struct cyc2ns_data *cyc2ns_write_begin(int cpu) { struct cyc2ns *c2n = &per_cpu(cyc2ns, cpu); struct cyc2ns_data *data = c2n->data; if (data == c2n->head) data++; /* XXX send an IPI to @cpu in order to guarantee a read? */ /* * When we observe the tail write from cyc2ns_read_end(), * the cpu must be done with that entry and its safe * to start writing to it. */ while (c2n->tail == data) cpu_relax(); return data; } static void cyc2ns_write_end(int cpu, struct cyc2ns_data *data) { struct cyc2ns *c2n = &per_cpu(cyc2ns, cpu); /* * Ensure the @data writes are visible before we publish the * entry. Matches the data-depencency in cyc2ns_read_begin(). */ smp_wmb(); ACCESS_ONCE(c2n->head) = data; } /* * Accelerators for sched_clock() * convert from cycles(64bits) => nanoseconds (64bits) * basic equation: * ns = cycles / (freq / ns_per_sec) * ns = cycles * (ns_per_sec / freq) * 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 * (10^6 * 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. * * We can use khz divisor instead of mhz to keep a better precision, 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!" */ #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */ static void cyc2ns_data_init(struct cyc2ns_data *data) { data->cyc2ns_mul = 1U << CYC2NS_SCALE_FACTOR; data->cyc2ns_shift = CYC2NS_SCALE_FACTOR; data->cyc2ns_offset = 0; data->__count = 0; } static void cyc2ns_init(int cpu) { struct cyc2ns *c2n = &per_cpu(cyc2ns, cpu); cyc2ns_data_init(&c2n->data[0]); cyc2ns_data_init(&c2n->data[1]); c2n->head = c2n->data; c2n->tail = c2n->data; } static inline unsigned long long cycles_2_ns(unsigned long long cyc) { struct cyc2ns_data *data, *tail; unsigned long long ns; /* * See cyc2ns_read_*() for details; replicated in order to avoid * an extra few instructions that came with the abstraction. * Notable, it allows us to only do the __count and tail update * dance when its actually needed. */ preempt_disable(); data = this_cpu_read(cyc2ns.head); tail = this_cpu_read(cyc2ns.tail); if (likely(data == tail)) { ns = data->cyc2ns_offset; ns += mul_u64_u32_shr(cyc, data->cyc2ns_mul, CYC2NS_SCALE_FACTOR); } else { data->__count++; barrier(); ns = data->cyc2ns_offset; ns += mul_u64_u32_shr(cyc, data->cyc2ns_mul, CYC2NS_SCALE_FACTOR); barrier(); if (!--data->__count) this_cpu_write(cyc2ns.tail, data); } preempt_enable(); return ns; } /* XXX surely we already have this someplace in the kernel?! */ #define DIV_ROUND(n, d) (((n) + ((d) / 2)) / (d)) static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu) { unsigned long long tsc_now, ns_now; struct cyc2ns_data *data; unsigned long flags; local_irq_save(flags); sched_clock_idle_sleep_event(); if (!cpu_khz) goto done; data = cyc2ns_write_begin(cpu); rdtscll(tsc_now); ns_now = cycles_2_ns(tsc_now); /* * Compute a new multiplier as per the above comment and ensure our * time function is continuous; see the comment near struct * cyc2ns_data. */ data->cyc2ns_mul = DIV_ROUND(NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR, cpu_khz); data->cyc2ns_shift = CYC2NS_SCALE_FACTOR; data->cyc2ns_offset = ns_now - mul_u64_u32_shr(tsc_now, data->cyc2ns_mul, CYC2NS_SCALE_FACTOR); cyc2ns_write_end(cpu, data); done: sched_clock_idle_wakeup_event(0); local_irq_restore(flags); } /* * Scheduler clock - returns current time in nanosec units. */ u64 native_sched_clock(void) { u64 tsc_now; /* * Fall back to jiffies if there's no TSC available: * ( But note that we still use it if the TSC is marked * unstable. We do this because unlike Time Of Day, * the scheduler clock tolerates small errors and it's * very important for it to be as fast as the platform * can achieve it. ) */ if (unlikely(tsc_disabled)) { /* No locking but a rare wrong value is not a big deal: */ return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ); } /* read the Time Stamp Counter: */ rdtscll(tsc_now); /* return the value in ns */ return cycles_2_ns(tsc_now); } /* We need to define a real function for sched_clock, to override the weak default version */ #ifdef CONFIG_PARAVIRT unsigned long long sched_clock(void) { return paravirt_sched_clock(); } #else unsigned long long sched_clock(void) __attribute__((alias("native_sched_clock"))); #endif unsigned long long native_read_tsc(void) { return __native_read_tsc(); } EXPORT_SYMBOL(native_read_tsc); int check_tsc_unstable(void) { return tsc_unstable; } EXPORT_SYMBOL_GPL(check_tsc_unstable); int check_tsc_disabled(void) { return tsc_disabled; } EXPORT_SYMBOL_GPL(check_tsc_disabled); #ifdef CONFIG_X86_TSC int __init notsc_setup(char *str) { pr_warn("Kernel compiled with CONFIG_X86_TSC, cannot disable TSC completely\n"); tsc_disabled = 1; return 1; } #else /* * disable flag for tsc. Takes effect by clearing the TSC cpu flag * in cpu/common.c */ int __init notsc_setup(char *str) { setup_clear_cpu_cap(X86_FEATURE_TSC); return 1; } #endif __setup("notsc", notsc_setup); static int no_sched_irq_time; static int __init tsc_setup(char *str) { if (!strcmp(str, "reliable")) tsc_clocksource_reliable = 1; if (!strncmp(str, "noirqtime", 9)) no_sched_irq_time = 1; return 1; } __setup("tsc=", tsc_setup); #define MAX_RETRIES 5 #define SMI_TRESHOLD 50000 /* * Read TSC and the reference counters. Take care of SMI disturbance */ static u64 tsc_read_refs(u64 *p, int hpet) { u64 t1, t2; int i; for (i = 0; i < MAX_RETRIES; i++) { t1 = get_cycles(); if (hpet) *p = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF; else *p = acpi_pm_read_early(); t2 = get_cycles(); if ((t2 - t1) < SMI_TRESHOLD) return t2; } return ULLONG_MAX; } /* * Calculate the TSC frequency from HPET reference */ static unsigned long calc_hpet_ref(u64 deltatsc, u64 hpet1, u64 hpet2) { u64 tmp; if (hpet2 < hpet1) hpet2 += 0x100000000ULL; hpet2 -= hpet1; tmp = ((u64)hpet2 * hpet_readl(HPET_PERIOD)); do_div(tmp, 1000000); do_div(deltatsc, tmp); return (unsigned long) deltatsc; } /* * Calculate the TSC frequency from PMTimer reference */ static unsigned long calc_pmtimer_ref(u64 deltatsc, u64 pm1, u64 pm2) { u64 tmp; if (!pm1 && !pm2) return ULONG_MAX; if (pm2 < pm1) pm2 += (u64)ACPI_PM_OVRRUN; pm2 -= pm1; tmp = pm2 * 1000000000LL; do_div(tmp, PMTMR_TICKS_PER_SEC); do_div(deltatsc, tmp); return (unsigned long) deltatsc; } #define CAL_MS 10 #define CAL_LATCH (PIT_TICK_RATE / (1000 / CAL_MS)) #define CAL_PIT_LOOPS 1000 #define CAL2_MS 50 #define CAL2_LATCH (PIT_TICK_RATE / (1000 / CAL2_MS)) #define CAL2_PIT_LOOPS 5000 /* * Try to calibrate the TSC against the Programmable * Interrupt Timer and return the frequency of the TSC * in kHz. * * Return ULONG_MAX on failure to calibrate. */ static unsigned long pit_calibrate_tsc(u32 latch, unsigned long ms, int loopmin) { u64 tsc, t1, t2, delta; unsigned long tscmin, tscmax; int pitcnt; /* Set the Gate high, disable speaker */ outb((inb(0x61) & ~0x02) | 0x01, 0x61); /* * Setup CTC channel 2* for mode 0, (interrupt on terminal * count mode), binary count. Set the latch register to 50ms * (LSB then MSB) to begin countdown. */ outb(0xb0, 0x43); outb(latch & 0xff, 0x42); outb(latch >> 8, 0x42); tsc = t1 = t2 = get_cycles(); pitcnt = 0; tscmax = 0; tscmin = ULONG_MAX; while ((inb(0x61) & 0x20) == 0) { t2 = get_cycles(); delta = t2 - tsc; tsc = t2; if ((unsigned long) delta < tscmin) tscmin = (unsigned int) delta; if ((unsigned long) delta > tscmax) tscmax = (unsigned int) delta; pitcnt++; } /* * Sanity checks: * * If we were not able to read the PIT more than loopmin * 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 < loopmin || tscmax > 10 * tscmin) return ULONG_MAX; /* Calculate the PIT value */ delta = t2 - t1; do_div(delta, ms); return delta; } /* * This reads the current MSB of the PIT counter, and * checks if we are running on sufficiently fast and * non-virtualized hardware. * * Our expectations are: * * - the PIT is running at roughly 1.19MHz * * - each IO is going to take about 1us on real hardware, * but we allow it to be much faster (by a factor of 10) or * _slightly_ slower (ie we allow up to a 2us read+counter * update - anything else implies a unacceptably slow CPU * or PIT for the fast calibration to work. * * - with 256 PIT ticks to read the value, we have 214us to * see the same MSB (and overhead like doing a single TSC * read per MSB value etc). * * - We're doing 2 reads per loop (LSB, MSB), and we expect * them each to take about a microsecond on real hardware. * So we expect a count value of around 100. But we'll be * generous, and accept anything over 50. * * - if the PIT is stuck, and we see *many* more reads, we * return early (and the next caller of pit_expect_msb() * then consider it a failure when they don't see the * next expected value). * * These expectations mean that we know that we have seen the * transition from one expected value to another with a fairly * high accuracy, and we didn't miss any events. We can thus * use the TSC value at the transitions to calculate a pretty * good value for the TSC frequencty. */ static inline int pit_verify_msb(unsigned char val) { /* Ignore LSB */ inb(0x42); return inb(0x42) == val; } static inline int pit_expect_msb(unsigned char val, u64 *tscp, unsigned long *deltap) { int count; u64 tsc = 0, prev_tsc = 0; for (count = 0; count < 50000; count++) { if (!pit_verify_msb(val)) break; prev_tsc = tsc; tsc = get_cycles(); } *deltap = get_cycles() - prev_tsc; *tscp = tsc; /* * We require _some_ success, but the quality control * will be based on the error terms on the TSC values. */ return count > 5; } /* * How many MSB values do we want to see? We aim for * a maximum error rate of 500ppm (in practice the * real error is much smaller), but refuse to spend * more than 50ms on it. */ #define MAX_QUICK_PIT_MS 50 #define MAX_QUICK_PIT_ITERATIONS (MAX_QUICK_PIT_MS * PIT_TICK_RATE / 1000 / 256) static unsigned long quick_pit_calibrate(void) { int i; u64 tsc, delta; unsigned long d1, d2; /* Set the Gate high, disable speaker */ outb((inb(0x61) & ~0x02) | 0x01, 0x61); /* * Counter 2, mode 0 (one-shot), binary count * * NOTE! Mode 2 decrements by two (and then the * output is flipped each time, giving the same * final output frequency as a decrement-by-one), * so mode 0 is much better when looking at the * individual counts. */ outb(0xb0, 0x43); /* Start at 0xffff */ outb(0xff, 0x42); outb(0xff, 0x42); /* * The PIT starts counting at the next edge, so we * need to delay for a microsecond. The easiest way * to do that is to just read back the 16-bit counter * once from the PIT. */ pit_verify_msb(0); if (pit_expect_msb(0xff, &tsc, &d1)) { for (i = 1; i <= MAX_QUICK_PIT_ITERATIONS; i++) { if (!pit_expect_msb(0xff-i, &delta, &d2)) break; /* * Iterate until the error is less than 500 ppm */ delta -= tsc; if (d1+d2 >= delta >> 11) continue; /* * Check the PIT one more time to verify that * all TSC reads were stable wrt the PIT. * * This also guarantees serialization of the * last cycle read ('d2') in pit_expect_msb. */ if (!pit_verify_msb(0xfe - i)) break; goto success; } } pr_err("Fast TSC calibration failed\n"); return 0; success: /* * Ok, if we get here, then we've seen the * MSB of the PIT decrement 'i' times, and the * error has shrunk to less than 500 ppm. * * As a result, we can depend on there not being * any odd delays anywhere, and the TSC reads are * reliable (within the error). * * kHz = ticks / time-in-seconds / 1000; * kHz = (t2 - t1) / (I * 256 / PIT_TICK_RATE) / 1000 * kHz = ((t2 - t1) * PIT_TICK_RATE) / (I * 256 * 1000) */ delta *= PIT_TICK_RATE; do_div(delta, i*256*1000); pr_info("Fast TSC calibration using PIT\n"); return delta; } /** * native_calibrate_tsc - calibrate the tsc on boot */ unsigned long native_calibrate_tsc(void) { u64 tsc1, tsc2, delta, ref1, ref2; unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX; unsigned long flags, latch, ms, fast_calibrate; int hpet = is_hpet_enabled(), i, loopmin; local_irq_save(flags); fast_calibrate = quick_pit_calibrate(); local_irq_restore(flags); if (fast_calibrate) return fast_calibrate; /* * Run 5 calibration loops to get the lowest frequency value * (the best estimate). We use two different calibration modes * here: * * 1) PIT loop. We set the PIT Channel 2 to oneshot mode and * load a timeout of 50ms. We read the time right after we * started the timer and wait until the PIT count down reaches * zero. In each wait loop iteration we read the TSC and check * the delta to the previous read. We keep track of the min * and max values of that delta. The delta is mostly defined * by the IO time of the PIT access, so we can detect when a * SMI/SMM disturbance happened between the two reads. If the * maximum time is significantly larger than the minimum time, * then we discard the result and have another try. * * 2) Reference counter. If available we use the HPET or the * PMTIMER as a reference to check the sanity of that value. * We use separate TSC readouts and check inside of the * reference read for a SMI/SMM disturbance. We dicard * disturbed values here as well. We do that around the PIT * calibration delay loop as we have to wait for a certain * amount of time anyway. */ /* Preset PIT loop values */ latch = CAL_LATCH; ms = CAL_MS; loopmin = CAL_PIT_LOOPS; for (i = 0; i < 3; i++) { unsigned long tsc_pit_khz; /* * Read the start value and the reference count of * hpet/pmtimer when available. Then do the PIT * calibration, which will take at least 50ms, and * read the end value. */ local_irq_save(flags); tsc1 = tsc_read_refs(&ref1, hpet); tsc_pit_khz = pit_calibrate_tsc(latch, ms, loopmin); tsc2 = tsc_read_refs(&ref2, hpet); local_irq_restore(flags); /* Pick the lowest PIT TSC calibration so far */ tsc_pit_min = min(tsc_pit_min, tsc_pit_khz); /* hpet or pmtimer available ? */ if (ref1 == ref2) continue; /* Check, whether the sampling was disturbed by an SMI */ if (tsc1 == ULLONG_MAX || tsc2 == ULLONG_MAX) continue; tsc2 = (tsc2 - tsc1) * 1000000LL; if (hpet) tsc2 = calc_hpet_ref(tsc2, ref1, ref2); else tsc2 = calc_pmtimer_ref(tsc2, ref1, ref2); tsc_ref_min = min(tsc_ref_min, (unsigned long) tsc2); /* Check the reference deviation */ delta = ((u64) tsc_pit_min) * 100; do_div(delta, tsc_ref_min); /* * If both calibration results are inside a 10% window * then we can be sure, that the calibration * succeeded. We break out of the loop right away. We * use the reference value, as it is more precise. */ if (delta >= 90 && delta <= 110) { pr_info("PIT calibration matches %s. %d loops\n", hpet ? "HPET" : "PMTIMER", i + 1); return tsc_ref_min; } /* * Check whether PIT failed more than once. This * happens in virtualized environments. We need to * give the virtual PC a slightly longer timeframe for * the HPET/PMTIMER to make the result precise. */ if (i == 1 && tsc_pit_min == ULONG_MAX) { latch = CAL2_LATCH; ms = CAL2_MS; loopmin = CAL2_PIT_LOOPS; } } /* * Now check the results. */ if (tsc_pit_min == ULONG_MAX) { /* PIT gave no useful value */ pr_warn("Unable to calibrate against PIT\n"); /* We don't have an alternative source, disable TSC */ if (!hpet && !ref1 && !ref2) { pr_notice("No reference (HPET/PMTIMER) available\n"); return 0; } /* The alternative source failed as well, disable TSC */ if (tsc_ref_min == ULONG_MAX) { pr_warn("HPET/PMTIMER calibration failed\n"); return 0; } /* Use the alternative source */ pr_info("using %s reference calibration\n", hpet ? "HPET" : "PMTIMER"); return tsc_ref_min; } /* We don't have an alternative source, use the PIT calibration value */ if (!hpet && !ref1 && !ref2) { pr_info("Using PIT calibration value\n"); return tsc_pit_min; } /* The alternative source failed, use the PIT calibration value */ if (tsc_ref_min == ULONG_MAX) { pr_warn("HPET/PMTIMER calibration failed. Using PIT calibration.\n"); return tsc_pit_min; } /* * The calibration values differ too much. In doubt, we use * the PIT value as we know that there are PMTIMERs around * running at double speed. At least we let the user know: */ pr_warn("PIT calibration deviates from %s: %lu %lu\n", hpet ? "HPET" : "PMTIMER", tsc_pit_min, tsc_ref_min); pr_info("Using PIT calibration value\n"); return tsc_pit_min; } int recalibrate_cpu_khz(void) { #ifndef CONFIG_SMP unsigned long cpu_khz_old = cpu_khz; if (cpu_has_tsc) { tsc_khz = x86_platform.calibrate_tsc(); cpu_khz = tsc_khz; cpu_data(0).loops_per_jiffy = cpufreq_scale(cpu_data(0).loops_per_jiffy, cpu_khz_old, cpu_khz); return 0; } else return -ENODEV; #else return -ENODEV; #endif } EXPORT_SYMBOL(recalibrate_cpu_khz); static unsigned long long cyc2ns_suspend; void tsc_save_sched_clock_state(void) { if (!sched_clock_stable) return; cyc2ns_suspend = sched_clock(); } /* * Even on processors with invariant TSC, TSC gets reset in some the * ACPI system sleep states. And in some systems BIOS seem to reinit TSC to * arbitrary value (still sync'd across cpu's) during resume from such sleep * states. To cope up with this, recompute the cyc2ns_offset for each cpu so * that sched_clock() continues from the point where it was left off during * suspend. */ void tsc_restore_sched_clock_state(void) { unsigned long long offset; unsigned long flags; int cpu; if (!sched_clock_stable) return; local_irq_save(flags); /* * We're comming out of suspend, there's no concurrency yet; don't * bother being nice about the RCU stuff, just write to both * data fields. */ this_cpu_write(cyc2ns.data[0].cyc2ns_offset, 0); this_cpu_write(cyc2ns.data[1].cyc2ns_offset, 0); offset = cyc2ns_suspend - sched_clock(); for_each_possible_cpu(cpu) { per_cpu(cyc2ns.data[0].cyc2ns_offset, cpu) = offset; per_cpu(cyc2ns.data[1].cyc2ns_offset, cpu) = offset; } local_irq_restore(flags); } #ifdef CONFIG_CPU_FREQ /* Frequency scaling support. Adjust the TSC based timer when the cpu frequency * changes. * * RED-PEN: On SMP we assume all CPUs run with the same frequency. It's * not that important because current Opteron setups do not support * scaling on SMP anyroads. * * Should fix up last_tsc too. Currently gettimeofday in the * first tick after the change will be slightly wrong. */ static unsigned int ref_freq; static unsigned long loops_per_jiffy_ref; static unsigned long tsc_khz_ref; static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data) { struct cpufreq_freqs *freq = data; unsigned long *lpj; if (cpu_has(&cpu_data(freq->cpu), X86_FEATURE_CONSTANT_TSC)) return 0; lpj = &boot_cpu_data.loops_per_jiffy; #ifdef CONFIG_SMP if (!(freq->flags & CPUFREQ_CONST_LOOPS)) lpj = &cpu_data(freq->cpu).loops_per_jiffy; #endif if (!ref_freq) { ref_freq = freq->old; loops_per_jiffy_ref = *lpj; tsc_khz_ref = tsc_khz; } if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) || (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) || (val == CPUFREQ_RESUMECHANGE)) { *lpj = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new); tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new); if (!(freq->flags & CPUFREQ_CONST_LOOPS)) mark_tsc_unstable("cpufreq changes"); } set_cyc2ns_scale(tsc_khz, freq->cpu); return 0; } static struct notifier_block time_cpufreq_notifier_block = { .notifier_call = time_cpufreq_notifier }; static int __init cpufreq_tsc(void) { if (!cpu_has_tsc) return 0; if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) return 0; cpufreq_register_notifier(&time_cpufreq_notifier_block, CPUFREQ_TRANSITION_NOTIFIER); return 0; } core_initcall(cpufreq_tsc); #endif /* CONFIG_CPU_FREQ */ /* clocksource code */ static struct clocksource clocksource_tsc; /* * We compare the TSC to the cycle_last value in the clocksource * structure to avoid a nasty time-warp. This can be observed in a * very small window right after one CPU updated cycle_last under * xtime/vsyscall_gtod lock and the other CPU reads a TSC value which * is smaller than the cycle_last reference value due to a TSC which * is slighty behind. This delta is nowhere else observable, but in * that case it results in a forward time jump in the range of hours * due to the unsigned delta calculation of the time keeping core * code, which is necessary to support wrapping clocksources like pm * timer. */ static cycle_t read_tsc(struct clocksource *cs) { cycle_t ret = (cycle_t)get_cycles(); return ret >= clocksource_tsc.cycle_last ? ret : clocksource_tsc.cycle_last; } static void resume_tsc(struct clocksource *cs) { if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC_S3)) clocksource_tsc.cycle_last = 0; } static struct clocksource clocksource_tsc = { .name = "tsc", .rating = 300, .read = read_tsc, .resume = resume_tsc, .mask = CLOCKSOURCE_MASK(64), .flags = CLOCK_SOURCE_IS_CONTINUOUS | CLOCK_SOURCE_MUST_VERIFY, #ifdef CONFIG_X86_64 .archdata = { .vclock_mode = VCLOCK_TSC }, #endif }; void mark_tsc_unstable(char *reason) { if (!tsc_unstable) { tsc_unstable = 1; sched_clock_stable = 0; disable_sched_clock_irqtime(); pr_info("Marking TSC unstable due to %s\n", reason); /* Change only the rating, when not registered */ if (clocksource_tsc.mult) clocksource_mark_unstable(&clocksource_tsc); else { clocksource_tsc.flags |= CLOCK_SOURCE_UNSTABLE; clocksource_tsc.rating = 0; } } } EXPORT_SYMBOL_GPL(mark_tsc_unstable); static void __init check_system_tsc_reliable(void) { #ifdef CONFIG_MGEODE_LX /* RTSC counts during suspend */ #define RTSC_SUSP 0x100 unsigned long res_low, res_high; rdmsr_safe(MSR_GEODE_BUSCONT_CONF0, &res_low, &res_high); /* Geode_LX - the OLPC CPU has a very reliable TSC */ if (res_low & RTSC_SUSP) tsc_clocksource_reliable = 1; #endif if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) tsc_clocksource_reliable = 1; } /* * Make an educated guess if the TSC is trustworthy and synchronized * over all CPUs. */ int unsynchronized_tsc(void) { if (!cpu_has_tsc || tsc_unstable) return 1; #ifdef CONFIG_SMP if (apic_is_clustered_box()) return 1; #endif if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) return 0; if (tsc_clocksource_reliable) return 0; /* * Intel systems are normally all synchronized. * Exceptions must mark TSC as unstable: */ if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) { /* assume multi socket systems are not synchronized: */ if (num_possible_cpus() > 1) return 1; } return 0; } static void tsc_refine_calibration_work(struct work_struct *work); static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work); /** * tsc_refine_calibration_work - Further refine tsc freq calibration * @work - ignored. * * This functions uses delayed work over a period of a * second to further refine the TSC freq value. Since this is * timer based, instead of loop based, we don't block the boot * process while this longer calibration is done. * * If there are any calibration anomalies (too many SMIs, etc), * or the refined calibration is off by 1% of the fast early * calibration, we throw out the new calibration and use the * early calibration. */ static void tsc_refine_calibration_work(struct work_struct *work) { static u64 tsc_start = -1, ref_start; static int hpet; u64 tsc_stop, ref_stop, delta; unsigned long freq; /* Don't bother refining TSC on unstable systems */ if (check_tsc_unstable()) goto out; /* * Since the work is started early in boot, we may be * delayed the first time we expire. So set the workqueue * again once we know timers are working. */ if (tsc_start == -1) { /* * Only set hpet once, to avoid mixing hardware * if the hpet becomes enabled later. */ hpet = is_hpet_enabled(); schedule_delayed_work(&tsc_irqwork, HZ); tsc_start = tsc_read_refs(&ref_start, hpet); return; } tsc_stop = tsc_read_refs(&ref_stop, hpet); /* hpet or pmtimer available ? */ if (ref_start == ref_stop) goto out; /* Check, whether the sampling was disturbed by an SMI */ if (tsc_start == ULLONG_MAX || tsc_stop == ULLONG_MAX) goto out; delta = tsc_stop - tsc_start; delta *= 1000000LL; if (hpet) freq = calc_hpet_ref(delta, ref_start, ref_stop); else freq = calc_pmtimer_ref(delta, ref_start, ref_stop); /* Make sure we're within 1% */ if (abs(tsc_khz - freq) > tsc_khz/100) goto out; tsc_khz = freq; pr_info("Refined TSC clocksource calibration: %lu.%03lu MHz\n", (unsigned long)tsc_khz / 1000, (unsigned long)tsc_khz % 1000); out: clocksource_register_khz(&clocksource_tsc, tsc_khz); } static int __init init_tsc_clocksource(void) { if (!cpu_has_tsc || tsc_disabled > 0 || !tsc_khz) return 0; if (tsc_clocksource_reliable) clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY; /* lower the rating if we already know its unstable: */ if (check_tsc_unstable()) { clocksource_tsc.rating = 0; clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS; } if (boot_cpu_has(X86_FEATURE_NONSTOP_TSC_S3)) clocksource_tsc.flags |= CLOCK_SOURCE_SUSPEND_NONSTOP; /* * Trust the results of the earlier calibration on systems * exporting a reliable TSC. */ if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) { clocksource_register_khz(&clocksource_tsc, tsc_khz); return 0; } schedule_delayed_work(&tsc_irqwork, 0); return 0; } /* * We use device_initcall here, to ensure we run after the hpet * is fully initialized, which may occur at fs_initcall time. */ device_initcall(init_tsc_clocksource); void __init tsc_init(void) { u64 lpj; int cpu; x86_init.timers.tsc_pre_init(); if (!cpu_has_tsc) return; tsc_khz = x86_platform.calibrate_tsc(); cpu_khz = tsc_khz; if (!tsc_khz) { mark_tsc_unstable("could not calculate TSC khz"); return; } pr_info("Detected %lu.%03lu MHz processor\n", (unsigned long)cpu_khz / 1000, (unsigned long)cpu_khz % 1000); /* * Secondary CPUs do not run through tsc_init(), so set up * all the scale factors for all CPUs, assuming the same * speed as the bootup CPU. (cpufreq notifiers will fix this * up if their speed diverges) */ for_each_possible_cpu(cpu) { cyc2ns_init(cpu); set_cyc2ns_scale(cpu_khz, cpu); } if (tsc_disabled > 0) return; /* now allow native_sched_clock() to use rdtsc */ tsc_disabled = 0; if (!no_sched_irq_time) enable_sched_clock_irqtime(); lpj = ((u64)tsc_khz * 1000); do_div(lpj, HZ); lpj_fine = lpj; use_tsc_delay(); if (unsynchronized_tsc()) mark_tsc_unstable("TSCs unsynchronized"); check_system_tsc_reliable(); } #ifdef CONFIG_SMP /* * If we have a constant TSC and are using the TSC for the delay loop, * we can skip clock calibration if another cpu in the same socket has already * been calibrated. This assumes that CONSTANT_TSC applies to all * cpus in the socket - this should be a safe assumption. */ unsigned long calibrate_delay_is_known(void) { int i, cpu = smp_processor_id(); if (!tsc_disabled && !cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC)) return 0; for_each_online_cpu(i) if (cpu_data(i).phys_proc_id == cpu_data(cpu).phys_proc_id) return cpu_data(i).loops_per_jiffy; return 0; } #endif