diff options
Diffstat (limited to 'arch/x86/kernel/tsc.c')
| -rw-r--r-- | arch/x86/kernel/tsc.c | 958 |
1 files changed, 762 insertions, 196 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 8f98e9de1b8..ea030319b32 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -1,3 +1,5 @@ +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + #include <linux/kernel.h> #include <linux/sched.h> #include <linux/init.h> @@ -5,38 +7,275 @@ #include <linux/timer.h> #include <linux/acpi_pmtmr.h> #include <linux/cpufreq.h> -#include <linux/dmi.h> #include <linux/delay.h> #include <linux/clocksource.h> #include <linux/percpu.h> +#include <linux/timex.h> +#include <linux/static_key.h> #include <asm/hpet.h> #include <asm/timer.h> #include <asm/vgtod.h> #include <asm/time.h> #include <asm/delay.h> +#include <asm/hypervisor.h> +#include <asm/nmi.h> +#include <asm/x86_init.h> -unsigned int cpu_khz; /* TSC clocks / usec, not used here */ +unsigned int __read_mostly cpu_khz; /* TSC clocks / usec, not used here */ EXPORT_SYMBOL(cpu_khz); -unsigned int tsc_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 tsc_unstable; +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 tsc_disabled = -1; +static int __read_mostly tsc_disabled = -1; + +static struct static_key __use_tsc = STATIC_KEY_INIT; + +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 = 0; + 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_notrace(); + 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_notrace(); + + 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 this_offset; + u64 tsc_now; /* * Fall back to jiffies if there's no TSC available: @@ -44,18 +283,18 @@ u64 native_sched_clock(void) * 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 achive it. ) + * can achieve it. ) */ - if (unlikely(tsc_disabled)) { + if (!static_key_false(&__use_tsc)) { /* 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(this_offset); + rdtscll(tsc_now); /* return the value in ns */ - return cycles_2_ns(this_offset); + return cycles_2_ns(tsc_now); } /* We need to define a real function for sched_clock, to override the @@ -70,17 +309,28 @@ 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) { - printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, " - "cannot disable TSC completely.\n"); + pr_warn("Kernel compiled with CONFIG_X86_TSC, cannot disable TSC completely\n"); tsc_disabled = 1; return 1; } @@ -98,13 +348,26 @@ int __init notsc_setup(char *str) __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 *pm, u64 *hpet) +static u64 tsc_read_refs(u64 *p, int hpet) { u64 t1, t2; int i; @@ -112,9 +375,9 @@ static u64 tsc_read_refs(u64 *pm, u64 *hpet) for (i = 0; i < MAX_RETRIES; i++) { t1 = get_cycles(); if (hpet) - *hpet = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF; + *p = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF; else - *pm = acpi_pm_read_early(); + *p = acpi_pm_read_early(); t2 = get_cycles(); if ((t2 - t1) < SMI_TRESHOLD) return t2; @@ -123,13 +386,59 @@ static u64 tsc_read_refs(u64 *pm, u64 *hpet) } /* + * 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(void) +static unsigned long pit_calibrate_tsc(u32 latch, unsigned long ms, int loopmin) { u64 tsc, t1, t2, delta; unsigned long tscmin, tscmax; @@ -144,8 +453,8 @@ 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(latch & 0xff, 0x42); + outb(latch >> 8, 0x42); tsc = t1 = t2 = get_cycles(); @@ -166,31 +475,194 @@ 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 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 < 5000 || tscmax > 10 * tscmin) + if (pitcnt < loopmin || tscmax > 10 * tscmin) return ULONG_MAX; /* Calculate the PIT value */ delta = t2 - t1; - do_div(delta, 50); + 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, pm1, pm2, hpet1, hpet2; + u64 tsc1, tsc2, delta, ref1, ref2; unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX; - unsigned long flags; - int hpet = is_hpet_enabled(), i; + unsigned long flags, latch, ms, fast_calibrate; + int hpet = is_hpet_enabled(), i, loopmin; + + /* Calibrate TSC using MSR for Intel Atom SoCs */ + local_irq_save(flags); + fast_calibrate = try_msr_calibrate_tsc(); + local_irq_restore(flags); + if (fast_calibrate) + return fast_calibrate; + + 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 @@ -204,7 +676,7 @@ unsigned long native_calibrate_tsc(void) * 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 happend between the two reads. If the + * 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. * @@ -216,7 +688,13 @@ unsigned long native_calibrate_tsc(void) * calibration delay loop as we have to wait for a certain * amount of time anyway. */ - for (i = 0; i < 5; i++) { + + /* 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; /* @@ -226,16 +704,16 @@ unsigned long native_calibrate_tsc(void) * read the end value. */ local_irq_save(flags); - tsc1 = tsc_read_refs(&pm1, hpet ? &hpet1 : NULL); - tsc_pit_khz = pit_calibrate_tsc(); - tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL); + 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 (!hpet && !pm1 && !pm2) + if (ref1 == ref2) continue; /* Check, whether the sampling was disturbed by an SMI */ @@ -243,23 +721,40 @@ unsigned long native_calibrate_tsc(void) 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); - if (hpet) { - if (hpet2 < hpet1) - hpet2 += 0x100000000ULL; - hpet2 -= hpet1; - tsc1 = ((u64)hpet2 * hpet_readl(HPET_PERIOD)); - do_div(tsc1, 1000000); - } else { - if (pm2 < pm1) - pm2 += (u64)ACPI_PM_OVRRUN; - pm2 -= pm1; - tsc1 = pm2 * 1000000000LL; - do_div(tsc1, PMTMR_TICKS_PER_SEC); + /* 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; } - do_div(tsc2, tsc1); - tsc_ref_min = min(tsc_ref_min, (unsigned long) tsc2); + /* + * 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; + } } /* @@ -267,80 +762,57 @@ unsigned long native_calibrate_tsc(void) */ if (tsc_pit_min == ULONG_MAX) { /* PIT gave no useful value */ - printk(KERN_WARNING "TSC: Unable to calibrate against PIT\n"); + pr_warn("Unable to calibrate against PIT\n"); /* We don't have an alternative source, disable TSC */ - if (!hpet && !pm1 && !pm2) { - printk("TSC: No reference (HPET/PMTIMER) available\n"); + 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) { - printk(KERN_WARNING "TSC: HPET/PMTIMER calibration " - "failed due to SMI disturbance.\n"); + pr_warn("HPET/PMTIMER calibration failed\n"); return 0; } /* Use the alternative source */ - printk(KERN_INFO "TSC: using %s reference calibration\n", - hpet ? "HPET" : "PMTIMER"); + 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 && !pm1 && !pm2) { - printk(KERN_INFO "TSC: Using PIT calibration value\n"); + 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) { - printk(KERN_WARNING "TSC: HPET/PMTIMER calibration failed due " - "to SMI disturbance. Using PIT calibration\n"); + pr_warn("HPET/PMTIMER calibration failed. Using PIT calibration.\n"); return tsc_pit_min; } - /* Check the reference deviation */ - delta = ((u64) tsc_pit_min) * 100; - do_div(delta, tsc_ref_min); - - /* - * If both calibration results are inside a 5% window, the we - * use the lower frequency of those as it is probably the - * closest estimate. - */ - if (delta >= 95 && delta <= 105) { - printk(KERN_INFO "TSC: PIT calibration confirmed by %s.\n", - hpet ? "HPET" : "PMTIMER"); - printk(KERN_INFO "TSC: using %s calibration value\n", - tsc_pit_min <= tsc_ref_min ? "PIT" : - hpet ? "HPET" : "PMTIMER"); - return tsc_pit_min <= tsc_ref_min ? tsc_pit_min : tsc_ref_min; - } - - printk(KERN_WARNING "TSC: PIT calibration deviates from %s: %lu %lu.\n", - hpet ? "HPET" : "PMTIMER", tsc_pit_min, tsc_ref_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. + * running at double speed. At least we let the user know: */ - printk(KERN_INFO "TSC: Using PIT calibration value\n"); + 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; } -#ifdef CONFIG_X86_32 -/* Only called from the Powernow K7 cpu freq driver */ int recalibrate_cpu_khz(void) { #ifndef CONFIG_SMP unsigned long cpu_khz_old = cpu_khz; if (cpu_has_tsc) { - tsc_khz = calibrate_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, @@ -355,49 +827,52 @@ int recalibrate_cpu_khz(void) EXPORT_SYMBOL(recalibrate_cpu_khz); -#endif /* CONFIG_X86_32 */ -/* 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!" - */ +static unsigned long long cyc2ns_suspend; -DEFINE_PER_CPU(unsigned long, cyc2ns); +void tsc_save_sched_clock_state(void) +{ + if (!sched_clock_stable()) + return; -static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu) + 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 tsc_now, ns_now; - unsigned long flags, *scale; + unsigned long long offset; + unsigned long flags; + int cpu; + + if (!sched_clock_stable()) + return; local_irq_save(flags); - sched_clock_idle_sleep_event(); - scale = &per_cpu(cyc2ns, cpu); + /* + * 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. + */ - rdtscll(tsc_now); - ns_now = __cycles_2_ns(tsc_now); + this_cpu_write(cyc2ns.data[0].cyc2ns_offset, 0); + this_cpu_write(cyc2ns.data[1].cyc2ns_offset, 0); - if (cpu_khz) - *scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz; + 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; + } - sched_clock_idle_wakeup_event(0); local_irq_restore(flags); } @@ -422,17 +897,15 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data) { struct cpufreq_freqs *freq = data; - unsigned long *lpj, dummy; + unsigned long *lpj; if (cpu_has(&cpu_data(freq->cpu), X86_FEATURE_CONSTANT_TSC)) return 0; - lpj = &dummy; - if (!(freq->flags & CPUFREQ_CONST_LOOPS)) + lpj = &boot_cpu_data.loops_per_jiffy; #ifdef CONFIG_SMP + if (!(freq->flags & CPUFREQ_CONST_LOOPS)) lpj = &cpu_data(freq->cpu).loops_per_jiffy; -#else - lpj = &boot_cpu_data.loops_per_jiffy; #endif if (!ref_freq) { @@ -441,16 +914,15 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, 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); + (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); + set_cyc2ns_scale(tsc_khz, freq->cpu); + } return 0; } @@ -490,7 +962,7 @@ static struct clocksource clocksource_tsc; * code, which is necessary to support wrapping clocksources like pm * timer. */ -static cycle_t read_tsc(void) +static cycle_t read_tsc(struct clocksource *cs) { cycle_t ret = (cycle_t)get_cycles(); @@ -498,89 +970,63 @@ static cycle_t read_tsc(void) ret : clocksource_tsc.cycle_last; } -#ifdef CONFIG_X86_64 -static cycle_t __vsyscall_fn vread_tsc(void) +static void resume_tsc(struct clocksource *cs) { - cycle_t ret = (cycle_t)vget_cycles(); - - return ret >= __vsyscall_gtod_data.clock.cycle_last ? - ret : __vsyscall_gtod_data.clock.cycle_last; + if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC_S3)) + clocksource_tsc.cycle_last = 0; } -#endif static struct clocksource clocksource_tsc = { .name = "tsc", .rating = 300, .read = read_tsc, + .resume = resume_tsc, .mask = CLOCKSOURCE_MASK(64), - .shift = 22, .flags = CLOCK_SOURCE_IS_CONTINUOUS | CLOCK_SOURCE_MUST_VERIFY, -#ifdef CONFIG_X86_64 - .vread = vread_tsc, -#endif + .archdata = { .vclock_mode = VCLOCK_TSC }, }; void mark_tsc_unstable(char *reason) { if (!tsc_unstable) { tsc_unstable = 1; - printk("Marking TSC unstable due to %s\n", reason); + clear_sched_clock_stable(); + 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_change_rating(&clocksource_tsc, 0); - else + clocksource_mark_unstable(&clocksource_tsc); + else { + clocksource_tsc.flags |= CLOCK_SOURCE_UNSTABLE; clocksource_tsc.rating = 0; + } } } EXPORT_SYMBOL_GPL(mark_tsc_unstable); -static int __init dmi_mark_tsc_unstable(const struct dmi_system_id *d) +static void __init check_system_tsc_reliable(void) { - printk(KERN_NOTICE "%s detected: marking TSC unstable.\n", - d->ident); - tsc_unstable = 1; - return 0; -} - -/* List of systems that have known TSC problems */ -static struct dmi_system_id __initdata bad_tsc_dmi_table[] = { - { - .callback = dmi_mark_tsc_unstable, - .ident = "IBM Thinkpad 380XD", - .matches = { - DMI_MATCH(DMI_BOARD_VENDOR, "IBM"), - DMI_MATCH(DMI_BOARD_NAME, "2635FA0"), - }, - }, - {} -}; - -/* - * Geode_LX - the OLPC CPU has a possibly a very reliable TSC - */ #ifdef CONFIG_MGEODE_LX -/* RTSC counts during suspend */ + /* RTSC counts during suspend */ #define RTSC_SUSP 0x100 - -static void __init check_geode_tsc_reliable(void) -{ 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) - clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY; -} -#else -static inline void check_geode_tsc_reliable(void) { } + 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. */ -__cpuinit int unsynchronized_tsc(void) +int unsynchronized_tsc(void) { if (!cpu_has_tsc || tsc_unstable) return 1; @@ -592,6 +1038,9 @@ __cpuinit int unsynchronized_tsc(void) 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: @@ -599,33 +1048,132 @@ __cpuinit int unsynchronized_tsc(void) if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) { /* assume multi socket systems are not synchronized: */ if (num_possible_cpus() > 1) - tsc_unstable = 1; + return 1; } - return tsc_unstable; + 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 void __init init_tsc_clocksource(void) + +static int __init init_tsc_clocksource(void) { - clocksource_tsc.mult = clocksource_khz2mult(tsc_khz, - clocksource_tsc.shift); + 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; } - clocksource_register(&clocksource_tsc); + + 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 = calibrate_tsc(); + tsc_khz = x86_platform.calibrate_tsc(); cpu_khz = tsc_khz; if (!tsc_khz) { @@ -633,19 +1181,9 @@ void __init tsc_init(void) return; } -#ifdef CONFIG_X86_64 - if (cpu_has(&boot_cpu_data, X86_FEATURE_CONSTANT_TSC) && - (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)) - cpu_khz = calibrate_cpu(); -#endif - - lpj = ((u64)tsc_khz * 1000); - do_div(lpj, HZ); - lpj_fine = lpj; - - printk("Detected %lu.%03lu MHz processor.\n", - (unsigned long)cpu_khz / 1000, - (unsigned long)cpu_khz % 1000); + 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 @@ -653,23 +1191,51 @@ void __init tsc_init(void) * speed as the bootup CPU. (cpufreq notifiers will fix this * up if their speed diverges) */ - for_each_possible_cpu(cpu) + 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; + static_key_slow_inc(&__use_tsc); + + if (!no_sched_irq_time) + enable_sched_clock_irqtime(); + + lpj = ((u64)tsc_khz * 1000); + do_div(lpj, HZ); + lpj_fine = lpj; use_tsc_delay(); - /* Check and install the TSC clocksource */ - dmi_check_system(bad_tsc_dmi_table); if (unsynchronized_tsc()) mark_tsc_unstable("TSCs unsynchronized"); - check_geode_tsc_reliable(); - init_tsc_clocksource(); + 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 |