#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 #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); #define KHZ 1000 /* * TSC can be unstable due to cpufreq or due to unsynced TSCs */ static int __read_mostly tsc_unstable; static DEFINE_STATIC_KEY_FALSE(__use_tsc); int tsc_clocksource_reliable; static u32 art_to_tsc_numerator; static u32 art_to_tsc_denominator; static u64 art_to_tsc_offset; struct clocksource *art_related_clocksource; struct cyc2ns { struct cyc2ns_data data[2]; /* 0 + 2*16 = 32 */ seqcount_t seq; /* 32 + 4 = 36 */ }; /* fits one cacheline */ static DEFINE_PER_CPU_ALIGNED(struct cyc2ns, cyc2ns); void cyc2ns_read_begin(struct cyc2ns_data *data) { int seq, idx; preempt_disable_notrace(); do { seq = this_cpu_read(cyc2ns.seq.sequence); idx = seq & 1; data->cyc2ns_offset = this_cpu_read(cyc2ns.data[idx].cyc2ns_offset); data->cyc2ns_mul = this_cpu_read(cyc2ns.data[idx].cyc2ns_mul); data->cyc2ns_shift = this_cpu_read(cyc2ns.data[idx].cyc2ns_shift); } while (unlikely(seq != this_cpu_read(cyc2ns.seq.sequence))); } void cyc2ns_read_end(void) { preempt_enable_notrace(); } /* * 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. The larger SC is, the more accurate the conversion, but * cyc2ns_scale needs to be a 32-bit value so that 32-bit multiplication * (64-bit result) can be used. * * We can use khz divisor instead of mhz to keep a better precision. * (mathieu.desnoyers@polymtl.ca) * * -johnstul@us.ibm.com "math is hard, lets go shopping!" */ static inline unsigned long long cycles_2_ns(unsigned long long cyc) { struct cyc2ns_data data; unsigned long long ns; cyc2ns_read_begin(&data); ns = data.cyc2ns_offset; ns += mul_u64_u32_shr(cyc, data.cyc2ns_mul, data.cyc2ns_shift); cyc2ns_read_end(); return ns; } static void __set_cyc2ns_scale(unsigned long khz, int cpu, unsigned long long tsc_now) { unsigned long long ns_now; struct cyc2ns_data data; struct cyc2ns *c2n; 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. */ clocks_calc_mult_shift(&data.cyc2ns_mul, &data.cyc2ns_shift, khz, NSEC_PER_MSEC, 0); /* * cyc2ns_shift is exported via arch_perf_update_userpage() where it is * not expected to be greater than 31 due to the original published * conversion algorithm shifting a 32-bit value (now specifies a 64-bit * value) - refer perf_event_mmap_page documentation in perf_event.h. */ if (data.cyc2ns_shift == 32) { data.cyc2ns_shift = 31; data.cyc2ns_mul >>= 1; } data.cyc2ns_offset = ns_now - mul_u64_u32_shr(tsc_now, data.cyc2ns_mul, data.cyc2ns_shift); c2n = per_cpu_ptr(&cyc2ns, cpu); raw_write_seqcount_latch(&c2n->seq); c2n->data[0] = data; raw_write_seqcount_latch(&c2n->seq); c2n->data[1] = data; } static void set_cyc2ns_scale(unsigned long khz, int cpu, unsigned long long tsc_now) { unsigned long flags; local_irq_save(flags); sched_clock_idle_sleep_event(); if (khz) __set_cyc2ns_scale(khz, cpu, tsc_now); sched_clock_idle_wakeup_event(); local_irq_restore(flags); } /* * Initialize cyc2ns for boot cpu */ static void __init cyc2ns_init_boot_cpu(void) { struct cyc2ns *c2n = this_cpu_ptr(&cyc2ns); seqcount_init(&c2n->seq); __set_cyc2ns_scale(tsc_khz, smp_processor_id(), rdtsc()); } /* * 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) */ static void __init cyc2ns_init_secondary_cpus(void) { unsigned int cpu, this_cpu = smp_processor_id(); struct cyc2ns *c2n = this_cpu_ptr(&cyc2ns); struct cyc2ns_data *data = c2n->data; for_each_possible_cpu(cpu) { if (cpu != this_cpu) { seqcount_init(&c2n->seq); c2n = per_cpu_ptr(&cyc2ns, cpu); c2n->data[0] = data[0]; c2n->data[1] = data[1]; } } } /* * Scheduler clock - returns current time in nanosec units. */ u64 native_sched_clock(void) { if (static_branch_likely(&__use_tsc)) { u64 tsc_now = rdtsc(); /* return the value in ns */ return cycles_2_ns(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. ) */ /* No locking but a rare wrong value is not a big deal: */ return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ); } /* * Generate a sched_clock if you already have a TSC value. */ u64 native_sched_clock_from_tsc(u64 tsc) { return cycles_2_ns(tsc); } /* 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(); } bool using_native_sched_clock(void) { return pv_time_ops.sched_clock == native_sched_clock; } #else unsigned long long sched_clock(void) __attribute__((alias("native_sched_clock"))); bool using_native_sched_clock(void) { return true; } #endif int check_tsc_unstable(void) { return tsc_unstable; } EXPORT_SYMBOL_GPL(check_tsc_unstable); #ifdef CONFIG_X86_TSC int __init notsc_setup(char *str) { mark_tsc_unstable("boot parameter notsc"); 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; if (!strcmp(str, "unstable")) mark_tsc_unstable("boot parameter"); 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); deltatsc = div64_u64(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; if (!has_legacy_pic()) { /* * Relies on tsc_early_delay_calibrate() to have given us semi * usable udelay(), wait for the same 50ms we would have with * the PIT loop below. */ udelay(10 * USEC_PER_MSEC); udelay(10 * USEC_PER_MSEC); udelay(10 * USEC_PER_MSEC); udelay(10 * USEC_PER_MSEC); udelay(10 * USEC_PER_MSEC); return ULONG_MAX; } /* 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; if (!has_legacy_pic()) return 0; /* 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; delta -= tsc; /* * Extrapolate the error and fail fast if the error will * never be below 500 ppm. */ if (i == 1 && d1 + d2 >= (delta * MAX_QUICK_PIT_ITERATIONS) >> 11) return 0; /* * Iterate until the error is less than 500 ppm */ 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_info("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 * Determine TSC frequency via CPUID, else return 0. */ unsigned long native_calibrate_tsc(void) { unsigned int eax_denominator, ebx_numerator, ecx_hz, edx; unsigned int crystal_khz; if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) return 0; if (boot_cpu_data.cpuid_level < 0x15) return 0; eax_denominator = ebx_numerator = ecx_hz = edx = 0; /* CPUID 15H TSC/Crystal ratio, plus optionally Crystal Hz */ cpuid(0x15, &eax_denominator, &ebx_numerator, &ecx_hz, &edx); if (ebx_numerator == 0 || eax_denominator == 0) return 0; crystal_khz = ecx_hz / 1000; if (crystal_khz == 0) { switch (boot_cpu_data.x86_model) { case INTEL_FAM6_SKYLAKE_MOBILE: case INTEL_FAM6_SKYLAKE_DESKTOP: case INTEL_FAM6_KABYLAKE_MOBILE: case INTEL_FAM6_KABYLAKE_DESKTOP: crystal_khz = 24000; /* 24.0 MHz */ break; case INTEL_FAM6_ATOM_DENVERTON: crystal_khz = 25000; /* 25.0 MHz */ break; case INTEL_FAM6_ATOM_GOLDMONT: crystal_khz = 19200; /* 19.2 MHz */ break; } } if (crystal_khz == 0) return 0; /* * TSC frequency determined by CPUID is a "hardware reported" * frequency and is the most accurate one so far we have. This * is considered a known frequency. */ setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); /* * For Atom SoCs TSC is the only reliable clocksource. * Mark TSC reliable so no watchdog on it. */ if (boot_cpu_data.x86_model == INTEL_FAM6_ATOM_GOLDMONT) setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE); return crystal_khz * ebx_numerator / eax_denominator; } static unsigned long cpu_khz_from_cpuid(void) { unsigned int eax_base_mhz, ebx_max_mhz, ecx_bus_mhz, edx; if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) return 0; if (boot_cpu_data.cpuid_level < 0x16) return 0; eax_base_mhz = ebx_max_mhz = ecx_bus_mhz = edx = 0; cpuid(0x16, &eax_base_mhz, &ebx_max_mhz, &ecx_bus_mhz, &edx); return eax_base_mhz * 1000; } /* * calibrate cpu using pit, hpet, and ptimer methods. They are available * later in boot after acpi is initialized. */ static unsigned long pit_hpet_ptimer_calibrate_cpu(void) { u64 tsc1, tsc2, delta, ref1, ref2; unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX; unsigned long flags, latch, ms; int hpet = is_hpet_enabled(), i, loopmin; /* * 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; } /** * native_calibrate_cpu_early - can calibrate the cpu early in boot */ unsigned long native_calibrate_cpu_early(void) { unsigned long flags, fast_calibrate = cpu_khz_from_cpuid(); if (!fast_calibrate) fast_calibrate = cpu_khz_from_msr(); if (!fast_calibrate) { local_irq_save(flags); fast_calibrate = quick_pit_calibrate(); local_irq_restore(flags); } return fast_calibrate; } /** * native_calibrate_cpu - calibrate the cpu */ static unsigned long native_calibrate_cpu(void) { unsigned long tsc_freq = native_calibrate_cpu_early(); if (!tsc_freq) tsc_freq = pit_hpet_ptimer_calibrate_cpu(); return tsc_freq; } void recalibrate_cpu_khz(void) { #ifndef CONFIG_SMP unsigned long cpu_khz_old = cpu_khz; if (!boot_cpu_has(X86_FEATURE_TSC)) return; cpu_khz = x86_platform.calibrate_cpu(); tsc_khz = x86_platform.calibrate_tsc(); if (tsc_khz == 0) tsc_khz = cpu_khz; else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz) cpu_khz = tsc_khz; cpu_data(0).loops_per_jiffy = cpufreq_scale(cpu_data(0).loops_per_jiffy, cpu_khz_old, cpu_khz); #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 coming 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; 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)) { *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, rdtsc()); } return 0; } static struct notifier_block time_cpufreq_notifier_block = { .notifier_call = time_cpufreq_notifier }; static int __init cpufreq_register_tsc_scaling(void) { if (!boot_cpu_has(X86_FEATURE_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_register_tsc_scaling); #endif /* CONFIG_CPU_FREQ */ #define ART_CPUID_LEAF (0x15) #define ART_MIN_DENOMINATOR (1) /* * If ART is present detect the numerator:denominator to convert to TSC */ static void __init detect_art(void) { unsigned int unused[2]; if (boot_cpu_data.cpuid_level < ART_CPUID_LEAF) return; /* * Don't enable ART in a VM, non-stop TSC and TSC_ADJUST required, * and the TSC counter resets must not occur asynchronously. */ if (boot_cpu_has(X86_FEATURE_HYPERVISOR) || !boot_cpu_has(X86_FEATURE_NONSTOP_TSC) || !boot_cpu_has(X86_FEATURE_TSC_ADJUST) || tsc_async_resets) return; cpuid(ART_CPUID_LEAF, &art_to_tsc_denominator, &art_to_tsc_numerator, unused, unused+1); if (art_to_tsc_denominator < ART_MIN_DENOMINATOR) return; rdmsrl(MSR_IA32_TSC_ADJUST, art_to_tsc_offset); /* Make this sticky over multiple CPU init calls */ setup_force_cpu_cap(X86_FEATURE_ART); } /* clocksource code */ static void tsc_resume(struct clocksource *cs) { tsc_verify_tsc_adjust(true); } /* * We used to 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. * * This sanity check is now done in the core timekeeping code. * checking the result of read_tsc() - cycle_last for being negative. * That works because CLOCKSOURCE_MASK(64) does not mask out any bit. */ static u64 read_tsc(struct clocksource *cs) { return (u64)rdtsc_ordered(); } static void tsc_cs_mark_unstable(struct clocksource *cs) { if (tsc_unstable) return; tsc_unstable = 1; if (using_native_sched_clock()) clear_sched_clock_stable(); disable_sched_clock_irqtime(); pr_info("Marking TSC unstable due to clocksource watchdog\n"); } static void tsc_cs_tick_stable(struct clocksource *cs) { if (tsc_unstable) return; if (using_native_sched_clock()) sched_clock_tick_stable(); } /* * .mask MUST be CLOCKSOURCE_MASK(64). See comment above read_tsc() */ static struct clocksource clocksource_tsc_early = { .name = "tsc-early", .rating = 299, .read = read_tsc, .mask = CLOCKSOURCE_MASK(64), .flags = CLOCK_SOURCE_IS_CONTINUOUS | CLOCK_SOURCE_MUST_VERIFY, .archdata = { .vclock_mode = VCLOCK_TSC }, .resume = tsc_resume, .mark_unstable = tsc_cs_mark_unstable, .tick_stable = tsc_cs_tick_stable, .list = LIST_HEAD_INIT(clocksource_tsc_early.list), }; /* * Must mark VALID_FOR_HRES early such that when we unregister tsc_early * this one will immediately take over. We will only register if TSC has * been found good. */ static struct clocksource clocksource_tsc = { .name = "tsc", .rating = 300, .read = read_tsc, .mask = CLOCKSOURCE_MASK(64), .flags = CLOCK_SOURCE_IS_CONTINUOUS | CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_MUST_VERIFY, .archdata = { .vclock_mode = VCLOCK_TSC }, .resume = tsc_resume, .mark_unstable = tsc_cs_mark_unstable, .tick_stable = tsc_cs_tick_stable, .list = LIST_HEAD_INIT(clocksource_tsc.list), }; void mark_tsc_unstable(char *reason) { if (tsc_unstable) return; tsc_unstable = 1; if (using_native_sched_clock()) clear_sched_clock_stable(); disable_sched_clock_irqtime(); pr_info("Marking TSC unstable due to %s\n", reason); clocksource_mark_unstable(&clocksource_tsc_early); clocksource_mark_unstable(&clocksource_tsc); } EXPORT_SYMBOL_GPL(mark_tsc_unstable); static void __init check_system_tsc_reliable(void) { #if defined(CONFIG_MGEODEGX1) || defined(CONFIG_MGEODE_LX) || defined(CONFIG_X86_GENERIC) if (is_geode_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 (!boot_cpu_has(X86_FEATURE_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; } /* * Convert ART to TSC given numerator/denominator found in detect_art() */ struct system_counterval_t convert_art_to_tsc(u64 art) { u64 tmp, res, rem; rem = do_div(art, art_to_tsc_denominator); res = art * art_to_tsc_numerator; tmp = rem * art_to_tsc_numerator; do_div(tmp, art_to_tsc_denominator); res += tmp + art_to_tsc_offset; return (struct system_counterval_t) {.cs = art_related_clocksource, .cycles = res}; } EXPORT_SYMBOL(convert_art_to_tsc); /** * convert_art_ns_to_tsc() - Convert ART in nanoseconds to TSC. * @art_ns: ART (Always Running Timer) in unit of nanoseconds * * PTM requires all timestamps to be in units of nanoseconds. When user * software requests a cross-timestamp, this function converts system timestamp * to TSC. * * This is valid when CPU feature flag X86_FEATURE_TSC_KNOWN_FREQ is set * indicating the tsc_khz is derived from CPUID[15H]. Drivers should check * that this flag is set before conversion to TSC is attempted. * * Return: * struct system_counterval_t - system counter value with the pointer to the * corresponding clocksource * @cycles: System counter value * @cs: Clocksource corresponding to system counter value. Used * by timekeeping code to verify comparibility of two cycle * values. */ struct system_counterval_t convert_art_ns_to_tsc(u64 art_ns) { u64 tmp, res, rem; rem = do_div(art_ns, USEC_PER_SEC); res = art_ns * tsc_khz; tmp = rem * tsc_khz; do_div(tmp, USEC_PER_SEC); res += tmp; return (struct system_counterval_t) { .cs = art_related_clocksource, .cycles = res}; } EXPORT_SYMBOL(convert_art_ns_to_tsc); 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; int cpu; /* Don't bother refining TSC on unstable systems */ if (tsc_unstable) goto unreg; /* * 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); /* Inform the TSC deadline clockevent devices about the recalibration */ lapic_update_tsc_freq(); /* Update the sched_clock() rate to match the clocksource one */ for_each_possible_cpu(cpu) set_cyc2ns_scale(tsc_khz, cpu, tsc_stop); out: if (tsc_unstable) goto unreg; if (boot_cpu_has(X86_FEATURE_ART)) art_related_clocksource = &clocksource_tsc; clocksource_register_khz(&clocksource_tsc, tsc_khz); unreg: clocksource_unregister(&clocksource_tsc_early); } static int __init init_tsc_clocksource(void) { if (!boot_cpu_has(X86_FEATURE_TSC) || !tsc_khz) return 0; if (tsc_unstable) goto unreg; if (tsc_clocksource_reliable) clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY; if (boot_cpu_has(X86_FEATURE_NONSTOP_TSC_S3)) clocksource_tsc.flags |= CLOCK_SOURCE_SUSPEND_NONSTOP; /* * When TSC frequency is known (retrieved via MSR or CPUID), we skip * the refined calibration and directly register it as a clocksource. */ if (boot_cpu_has(X86_FEATURE_TSC_KNOWN_FREQ)) { if (boot_cpu_has(X86_FEATURE_ART)) art_related_clocksource = &clocksource_tsc; clocksource_register_khz(&clocksource_tsc, tsc_khz); unreg: clocksource_unregister(&clocksource_tsc_early); 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); static bool __init determine_cpu_tsc_frequencies(bool early) { /* Make sure that cpu and tsc are not already calibrated */ WARN_ON(cpu_khz || tsc_khz); if (early) { cpu_khz = x86_platform.calibrate_cpu(); tsc_khz = x86_platform.calibrate_tsc(); } else { /* We should not be here with non-native cpu calibration */ WARN_ON(x86_platform.calibrate_cpu != native_calibrate_cpu); cpu_khz = pit_hpet_ptimer_calibrate_cpu(); } /* * Trust non-zero tsc_khz as authoritative, * and use it to sanity check cpu_khz, * which will be off if system timer is off. */ if (tsc_khz == 0) tsc_khz = cpu_khz; else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz) cpu_khz = tsc_khz; if (tsc_khz == 0) return false; pr_info("Detected %lu.%03lu MHz processor\n", (unsigned long)cpu_khz / KHZ, (unsigned long)cpu_khz % KHZ); if (cpu_khz != tsc_khz) { pr_info("Detected %lu.%03lu MHz TSC", (unsigned long)tsc_khz / KHZ, (unsigned long)tsc_khz % KHZ); } return true; } static unsigned long __init get_loops_per_jiffy(void) { u64 lpj = (u64)tsc_khz * KHZ; do_div(lpj, HZ); return lpj; } static void __init tsc_enable_sched_clock(void) { /* Sanitize TSC ADJUST before cyc2ns gets initialized */ tsc_store_and_check_tsc_adjust(true); cyc2ns_init_boot_cpu(); static_branch_enable(&__use_tsc); } void __init tsc_early_init(void) { if (!boot_cpu_has(X86_FEATURE_TSC)) return; /* Don't change UV TSC multi-chassis synchronization */ if (is_early_uv_system()) return; if (!determine_cpu_tsc_frequencies(true)) return; loops_per_jiffy = get_loops_per_jiffy(); tsc_enable_sched_clock(); } void __init tsc_init(void) { /* * native_calibrate_cpu_early can only calibrate using methods that are * available early in boot. */ if (x86_platform.calibrate_cpu == native_calibrate_cpu_early) x86_platform.calibrate_cpu = native_calibrate_cpu; if (!boot_cpu_has(X86_FEATURE_TSC)) { setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER); return; } if (!tsc_khz) { /* We failed to determine frequencies earlier, try again */ if (!determine_cpu_tsc_frequencies(false)) { mark_tsc_unstable("could not calculate TSC khz"); setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER); return; } tsc_enable_sched_clock(); } cyc2ns_init_secondary_cpus(); if (!no_sched_irq_time) enable_sched_clock_irqtime(); lpj_fine = get_loops_per_jiffy(); use_tsc_delay(); check_system_tsc_reliable(); if (unsynchronized_tsc()) { mark_tsc_unstable("TSCs unsynchronized"); return; } clocksource_register_khz(&clocksource_tsc_early, tsc_khz); detect_art(); } #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 sibling, cpu = smp_processor_id(); int constant_tsc = cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC); const struct cpumask *mask = topology_core_cpumask(cpu); if (!constant_tsc || !mask) return 0; sibling = cpumask_any_but(mask, cpu); if (sibling < nr_cpu_ids) return cpu_data(sibling).loops_per_jiffy; return 0; } #endif