Loading...
1// SPDX-License-Identifier: GPL-2.0-only
2#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
3
4#include <linux/kernel.h>
5#include <linux/sched.h>
6#include <linux/sched/clock.h>
7#include <linux/init.h>
8#include <linux/export.h>
9#include <linux/timer.h>
10#include <linux/acpi_pmtmr.h>
11#include <linux/cpufreq.h>
12#include <linux/delay.h>
13#include <linux/clocksource.h>
14#include <linux/percpu.h>
15#include <linux/timex.h>
16#include <linux/static_key.h>
17#include <linux/static_call.h>
18
19#include <asm/hpet.h>
20#include <asm/timer.h>
21#include <asm/vgtod.h>
22#include <asm/time.h>
23#include <asm/delay.h>
24#include <asm/hypervisor.h>
25#include <asm/nmi.h>
26#include <asm/x86_init.h>
27#include <asm/geode.h>
28#include <asm/apic.h>
29#include <asm/intel-family.h>
30#include <asm/i8259.h>
31#include <asm/uv/uv.h>
32
33unsigned int __read_mostly cpu_khz; /* TSC clocks / usec, not used here */
34EXPORT_SYMBOL(cpu_khz);
35
36unsigned int __read_mostly tsc_khz;
37EXPORT_SYMBOL(tsc_khz);
38
39#define KHZ 1000
40
41/*
42 * TSC can be unstable due to cpufreq or due to unsynced TSCs
43 */
44static int __read_mostly tsc_unstable;
45static unsigned int __initdata tsc_early_khz;
46
47static DEFINE_STATIC_KEY_FALSE(__use_tsc);
48
49int tsc_clocksource_reliable;
50
51static u32 art_to_tsc_numerator;
52static u32 art_to_tsc_denominator;
53static u64 art_to_tsc_offset;
54static struct clocksource *art_related_clocksource;
55
56struct cyc2ns {
57 struct cyc2ns_data data[2]; /* 0 + 2*16 = 32 */
58 seqcount_latch_t seq; /* 32 + 4 = 36 */
59
60}; /* fits one cacheline */
61
62static DEFINE_PER_CPU_ALIGNED(struct cyc2ns, cyc2ns);
63
64static int __init tsc_early_khz_setup(char *buf)
65{
66 return kstrtouint(buf, 0, &tsc_early_khz);
67}
68early_param("tsc_early_khz", tsc_early_khz_setup);
69
70__always_inline void cyc2ns_read_begin(struct cyc2ns_data *data)
71{
72 int seq, idx;
73
74 preempt_disable_notrace();
75
76 do {
77 seq = this_cpu_read(cyc2ns.seq.seqcount.sequence);
78 idx = seq & 1;
79
80 data->cyc2ns_offset = this_cpu_read(cyc2ns.data[idx].cyc2ns_offset);
81 data->cyc2ns_mul = this_cpu_read(cyc2ns.data[idx].cyc2ns_mul);
82 data->cyc2ns_shift = this_cpu_read(cyc2ns.data[idx].cyc2ns_shift);
83
84 } while (unlikely(seq != this_cpu_read(cyc2ns.seq.seqcount.sequence)));
85}
86
87__always_inline void cyc2ns_read_end(void)
88{
89 preempt_enable_notrace();
90}
91
92/*
93 * Accelerators for sched_clock()
94 * convert from cycles(64bits) => nanoseconds (64bits)
95 * basic equation:
96 * ns = cycles / (freq / ns_per_sec)
97 * ns = cycles * (ns_per_sec / freq)
98 * ns = cycles * (10^9 / (cpu_khz * 10^3))
99 * ns = cycles * (10^6 / cpu_khz)
100 *
101 * Then we use scaling math (suggested by george@mvista.com) to get:
102 * ns = cycles * (10^6 * SC / cpu_khz) / SC
103 * ns = cycles * cyc2ns_scale / SC
104 *
105 * And since SC is a constant power of two, we can convert the div
106 * into a shift. The larger SC is, the more accurate the conversion, but
107 * cyc2ns_scale needs to be a 32-bit value so that 32-bit multiplication
108 * (64-bit result) can be used.
109 *
110 * We can use khz divisor instead of mhz to keep a better precision.
111 * (mathieu.desnoyers@polymtl.ca)
112 *
113 * -johnstul@us.ibm.com "math is hard, lets go shopping!"
114 */
115
116static __always_inline unsigned long long cycles_2_ns(unsigned long long cyc)
117{
118 struct cyc2ns_data data;
119 unsigned long long ns;
120
121 cyc2ns_read_begin(&data);
122
123 ns = data.cyc2ns_offset;
124 ns += mul_u64_u32_shr(cyc, data.cyc2ns_mul, data.cyc2ns_shift);
125
126 cyc2ns_read_end();
127
128 return ns;
129}
130
131static void __set_cyc2ns_scale(unsigned long khz, int cpu, unsigned long long tsc_now)
132{
133 unsigned long long ns_now;
134 struct cyc2ns_data data;
135 struct cyc2ns *c2n;
136
137 ns_now = cycles_2_ns(tsc_now);
138
139 /*
140 * Compute a new multiplier as per the above comment and ensure our
141 * time function is continuous; see the comment near struct
142 * cyc2ns_data.
143 */
144 clocks_calc_mult_shift(&data.cyc2ns_mul, &data.cyc2ns_shift, khz,
145 NSEC_PER_MSEC, 0);
146
147 /*
148 * cyc2ns_shift is exported via arch_perf_update_userpage() where it is
149 * not expected to be greater than 31 due to the original published
150 * conversion algorithm shifting a 32-bit value (now specifies a 64-bit
151 * value) - refer perf_event_mmap_page documentation in perf_event.h.
152 */
153 if (data.cyc2ns_shift == 32) {
154 data.cyc2ns_shift = 31;
155 data.cyc2ns_mul >>= 1;
156 }
157
158 data.cyc2ns_offset = ns_now -
159 mul_u64_u32_shr(tsc_now, data.cyc2ns_mul, data.cyc2ns_shift);
160
161 c2n = per_cpu_ptr(&cyc2ns, cpu);
162
163 raw_write_seqcount_latch(&c2n->seq);
164 c2n->data[0] = data;
165 raw_write_seqcount_latch(&c2n->seq);
166 c2n->data[1] = data;
167}
168
169static void set_cyc2ns_scale(unsigned long khz, int cpu, unsigned long long tsc_now)
170{
171 unsigned long flags;
172
173 local_irq_save(flags);
174 sched_clock_idle_sleep_event();
175
176 if (khz)
177 __set_cyc2ns_scale(khz, cpu, tsc_now);
178
179 sched_clock_idle_wakeup_event();
180 local_irq_restore(flags);
181}
182
183/*
184 * Initialize cyc2ns for boot cpu
185 */
186static void __init cyc2ns_init_boot_cpu(void)
187{
188 struct cyc2ns *c2n = this_cpu_ptr(&cyc2ns);
189
190 seqcount_latch_init(&c2n->seq);
191 __set_cyc2ns_scale(tsc_khz, smp_processor_id(), rdtsc());
192}
193
194/*
195 * Secondary CPUs do not run through tsc_init(), so set up
196 * all the scale factors for all CPUs, assuming the same
197 * speed as the bootup CPU.
198 */
199static void __init cyc2ns_init_secondary_cpus(void)
200{
201 unsigned int cpu, this_cpu = smp_processor_id();
202 struct cyc2ns *c2n = this_cpu_ptr(&cyc2ns);
203 struct cyc2ns_data *data = c2n->data;
204
205 for_each_possible_cpu(cpu) {
206 if (cpu != this_cpu) {
207 seqcount_latch_init(&c2n->seq);
208 c2n = per_cpu_ptr(&cyc2ns, cpu);
209 c2n->data[0] = data[0];
210 c2n->data[1] = data[1];
211 }
212 }
213}
214
215/*
216 * Scheduler clock - returns current time in nanosec units.
217 */
218u64 native_sched_clock(void)
219{
220 if (static_branch_likely(&__use_tsc)) {
221 u64 tsc_now = rdtsc();
222
223 /* return the value in ns */
224 return cycles_2_ns(tsc_now);
225 }
226
227 /*
228 * Fall back to jiffies if there's no TSC available:
229 * ( But note that we still use it if the TSC is marked
230 * unstable. We do this because unlike Time Of Day,
231 * the scheduler clock tolerates small errors and it's
232 * very important for it to be as fast as the platform
233 * can achieve it. )
234 */
235
236 /* No locking but a rare wrong value is not a big deal: */
237 return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
238}
239
240/*
241 * Generate a sched_clock if you already have a TSC value.
242 */
243u64 native_sched_clock_from_tsc(u64 tsc)
244{
245 return cycles_2_ns(tsc);
246}
247
248/* We need to define a real function for sched_clock, to override the
249 weak default version */
250#ifdef CONFIG_PARAVIRT
251unsigned long long sched_clock(void)
252{
253 return paravirt_sched_clock();
254}
255
256bool using_native_sched_clock(void)
257{
258 return static_call_query(pv_sched_clock) == native_sched_clock;
259}
260#else
261unsigned long long
262sched_clock(void) __attribute__((alias("native_sched_clock")));
263
264bool using_native_sched_clock(void) { return true; }
265#endif
266
267int check_tsc_unstable(void)
268{
269 return tsc_unstable;
270}
271EXPORT_SYMBOL_GPL(check_tsc_unstable);
272
273#ifdef CONFIG_X86_TSC
274int __init notsc_setup(char *str)
275{
276 mark_tsc_unstable("boot parameter notsc");
277 return 1;
278}
279#else
280/*
281 * disable flag for tsc. Takes effect by clearing the TSC cpu flag
282 * in cpu/common.c
283 */
284int __init notsc_setup(char *str)
285{
286 setup_clear_cpu_cap(X86_FEATURE_TSC);
287 return 1;
288}
289#endif
290
291__setup("notsc", notsc_setup);
292
293static int no_sched_irq_time;
294static int no_tsc_watchdog;
295
296static int __init tsc_setup(char *str)
297{
298 if (!strcmp(str, "reliable"))
299 tsc_clocksource_reliable = 1;
300 if (!strncmp(str, "noirqtime", 9))
301 no_sched_irq_time = 1;
302 if (!strcmp(str, "unstable"))
303 mark_tsc_unstable("boot parameter");
304 if (!strcmp(str, "nowatchdog"))
305 no_tsc_watchdog = 1;
306 return 1;
307}
308
309__setup("tsc=", tsc_setup);
310
311#define MAX_RETRIES 5
312#define TSC_DEFAULT_THRESHOLD 0x20000
313
314/*
315 * Read TSC and the reference counters. Take care of any disturbances
316 */
317static u64 tsc_read_refs(u64 *p, int hpet)
318{
319 u64 t1, t2;
320 u64 thresh = tsc_khz ? tsc_khz >> 5 : TSC_DEFAULT_THRESHOLD;
321 int i;
322
323 for (i = 0; i < MAX_RETRIES; i++) {
324 t1 = get_cycles();
325 if (hpet)
326 *p = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF;
327 else
328 *p = acpi_pm_read_early();
329 t2 = get_cycles();
330 if ((t2 - t1) < thresh)
331 return t2;
332 }
333 return ULLONG_MAX;
334}
335
336/*
337 * Calculate the TSC frequency from HPET reference
338 */
339static unsigned long calc_hpet_ref(u64 deltatsc, u64 hpet1, u64 hpet2)
340{
341 u64 tmp;
342
343 if (hpet2 < hpet1)
344 hpet2 += 0x100000000ULL;
345 hpet2 -= hpet1;
346 tmp = ((u64)hpet2 * hpet_readl(HPET_PERIOD));
347 do_div(tmp, 1000000);
348 deltatsc = div64_u64(deltatsc, tmp);
349
350 return (unsigned long) deltatsc;
351}
352
353/*
354 * Calculate the TSC frequency from PMTimer reference
355 */
356static unsigned long calc_pmtimer_ref(u64 deltatsc, u64 pm1, u64 pm2)
357{
358 u64 tmp;
359
360 if (!pm1 && !pm2)
361 return ULONG_MAX;
362
363 if (pm2 < pm1)
364 pm2 += (u64)ACPI_PM_OVRRUN;
365 pm2 -= pm1;
366 tmp = pm2 * 1000000000LL;
367 do_div(tmp, PMTMR_TICKS_PER_SEC);
368 do_div(deltatsc, tmp);
369
370 return (unsigned long) deltatsc;
371}
372
373#define CAL_MS 10
374#define CAL_LATCH (PIT_TICK_RATE / (1000 / CAL_MS))
375#define CAL_PIT_LOOPS 1000
376
377#define CAL2_MS 50
378#define CAL2_LATCH (PIT_TICK_RATE / (1000 / CAL2_MS))
379#define CAL2_PIT_LOOPS 5000
380
381
382/*
383 * Try to calibrate the TSC against the Programmable
384 * Interrupt Timer and return the frequency of the TSC
385 * in kHz.
386 *
387 * Return ULONG_MAX on failure to calibrate.
388 */
389static unsigned long pit_calibrate_tsc(u32 latch, unsigned long ms, int loopmin)
390{
391 u64 tsc, t1, t2, delta;
392 unsigned long tscmin, tscmax;
393 int pitcnt;
394
395 if (!has_legacy_pic()) {
396 /*
397 * Relies on tsc_early_delay_calibrate() to have given us semi
398 * usable udelay(), wait for the same 50ms we would have with
399 * the PIT loop below.
400 */
401 udelay(10 * USEC_PER_MSEC);
402 udelay(10 * USEC_PER_MSEC);
403 udelay(10 * USEC_PER_MSEC);
404 udelay(10 * USEC_PER_MSEC);
405 udelay(10 * USEC_PER_MSEC);
406 return ULONG_MAX;
407 }
408
409 /* Set the Gate high, disable speaker */
410 outb((inb(0x61) & ~0x02) | 0x01, 0x61);
411
412 /*
413 * Setup CTC channel 2* for mode 0, (interrupt on terminal
414 * count mode), binary count. Set the latch register to 50ms
415 * (LSB then MSB) to begin countdown.
416 */
417 outb(0xb0, 0x43);
418 outb(latch & 0xff, 0x42);
419 outb(latch >> 8, 0x42);
420
421 tsc = t1 = t2 = get_cycles();
422
423 pitcnt = 0;
424 tscmax = 0;
425 tscmin = ULONG_MAX;
426 while ((inb(0x61) & 0x20) == 0) {
427 t2 = get_cycles();
428 delta = t2 - tsc;
429 tsc = t2;
430 if ((unsigned long) delta < tscmin)
431 tscmin = (unsigned int) delta;
432 if ((unsigned long) delta > tscmax)
433 tscmax = (unsigned int) delta;
434 pitcnt++;
435 }
436
437 /*
438 * Sanity checks:
439 *
440 * If we were not able to read the PIT more than loopmin
441 * times, then we have been hit by a massive SMI
442 *
443 * If the maximum is 10 times larger than the minimum,
444 * then we got hit by an SMI as well.
445 */
446 if (pitcnt < loopmin || tscmax > 10 * tscmin)
447 return ULONG_MAX;
448
449 /* Calculate the PIT value */
450 delta = t2 - t1;
451 do_div(delta, ms);
452 return delta;
453}
454
455/*
456 * This reads the current MSB of the PIT counter, and
457 * checks if we are running on sufficiently fast and
458 * non-virtualized hardware.
459 *
460 * Our expectations are:
461 *
462 * - the PIT is running at roughly 1.19MHz
463 *
464 * - each IO is going to take about 1us on real hardware,
465 * but we allow it to be much faster (by a factor of 10) or
466 * _slightly_ slower (ie we allow up to a 2us read+counter
467 * update - anything else implies a unacceptably slow CPU
468 * or PIT for the fast calibration to work.
469 *
470 * - with 256 PIT ticks to read the value, we have 214us to
471 * see the same MSB (and overhead like doing a single TSC
472 * read per MSB value etc).
473 *
474 * - We're doing 2 reads per loop (LSB, MSB), and we expect
475 * them each to take about a microsecond on real hardware.
476 * So we expect a count value of around 100. But we'll be
477 * generous, and accept anything over 50.
478 *
479 * - if the PIT is stuck, and we see *many* more reads, we
480 * return early (and the next caller of pit_expect_msb()
481 * then consider it a failure when they don't see the
482 * next expected value).
483 *
484 * These expectations mean that we know that we have seen the
485 * transition from one expected value to another with a fairly
486 * high accuracy, and we didn't miss any events. We can thus
487 * use the TSC value at the transitions to calculate a pretty
488 * good value for the TSC frequency.
489 */
490static inline int pit_verify_msb(unsigned char val)
491{
492 /* Ignore LSB */
493 inb(0x42);
494 return inb(0x42) == val;
495}
496
497static inline int pit_expect_msb(unsigned char val, u64 *tscp, unsigned long *deltap)
498{
499 int count;
500 u64 tsc = 0, prev_tsc = 0;
501
502 for (count = 0; count < 50000; count++) {
503 if (!pit_verify_msb(val))
504 break;
505 prev_tsc = tsc;
506 tsc = get_cycles();
507 }
508 *deltap = get_cycles() - prev_tsc;
509 *tscp = tsc;
510
511 /*
512 * We require _some_ success, but the quality control
513 * will be based on the error terms on the TSC values.
514 */
515 return count > 5;
516}
517
518/*
519 * How many MSB values do we want to see? We aim for
520 * a maximum error rate of 500ppm (in practice the
521 * real error is much smaller), but refuse to spend
522 * more than 50ms on it.
523 */
524#define MAX_QUICK_PIT_MS 50
525#define MAX_QUICK_PIT_ITERATIONS (MAX_QUICK_PIT_MS * PIT_TICK_RATE / 1000 / 256)
526
527static unsigned long quick_pit_calibrate(void)
528{
529 int i;
530 u64 tsc, delta;
531 unsigned long d1, d2;
532
533 if (!has_legacy_pic())
534 return 0;
535
536 /* Set the Gate high, disable speaker */
537 outb((inb(0x61) & ~0x02) | 0x01, 0x61);
538
539 /*
540 * Counter 2, mode 0 (one-shot), binary count
541 *
542 * NOTE! Mode 2 decrements by two (and then the
543 * output is flipped each time, giving the same
544 * final output frequency as a decrement-by-one),
545 * so mode 0 is much better when looking at the
546 * individual counts.
547 */
548 outb(0xb0, 0x43);
549
550 /* Start at 0xffff */
551 outb(0xff, 0x42);
552 outb(0xff, 0x42);
553
554 /*
555 * The PIT starts counting at the next edge, so we
556 * need to delay for a microsecond. The easiest way
557 * to do that is to just read back the 16-bit counter
558 * once from the PIT.
559 */
560 pit_verify_msb(0);
561
562 if (pit_expect_msb(0xff, &tsc, &d1)) {
563 for (i = 1; i <= MAX_QUICK_PIT_ITERATIONS; i++) {
564 if (!pit_expect_msb(0xff-i, &delta, &d2))
565 break;
566
567 delta -= tsc;
568
569 /*
570 * Extrapolate the error and fail fast if the error will
571 * never be below 500 ppm.
572 */
573 if (i == 1 &&
574 d1 + d2 >= (delta * MAX_QUICK_PIT_ITERATIONS) >> 11)
575 return 0;
576
577 /*
578 * Iterate until the error is less than 500 ppm
579 */
580 if (d1+d2 >= delta >> 11)
581 continue;
582
583 /*
584 * Check the PIT one more time to verify that
585 * all TSC reads were stable wrt the PIT.
586 *
587 * This also guarantees serialization of the
588 * last cycle read ('d2') in pit_expect_msb.
589 */
590 if (!pit_verify_msb(0xfe - i))
591 break;
592 goto success;
593 }
594 }
595 pr_info("Fast TSC calibration failed\n");
596 return 0;
597
598success:
599 /*
600 * Ok, if we get here, then we've seen the
601 * MSB of the PIT decrement 'i' times, and the
602 * error has shrunk to less than 500 ppm.
603 *
604 * As a result, we can depend on there not being
605 * any odd delays anywhere, and the TSC reads are
606 * reliable (within the error).
607 *
608 * kHz = ticks / time-in-seconds / 1000;
609 * kHz = (t2 - t1) / (I * 256 / PIT_TICK_RATE) / 1000
610 * kHz = ((t2 - t1) * PIT_TICK_RATE) / (I * 256 * 1000)
611 */
612 delta *= PIT_TICK_RATE;
613 do_div(delta, i*256*1000);
614 pr_info("Fast TSC calibration using PIT\n");
615 return delta;
616}
617
618/**
619 * native_calibrate_tsc
620 * Determine TSC frequency via CPUID, else return 0.
621 */
622unsigned long native_calibrate_tsc(void)
623{
624 unsigned int eax_denominator, ebx_numerator, ecx_hz, edx;
625 unsigned int crystal_khz;
626
627 if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
628 return 0;
629
630 if (boot_cpu_data.cpuid_level < 0x15)
631 return 0;
632
633 eax_denominator = ebx_numerator = ecx_hz = edx = 0;
634
635 /* CPUID 15H TSC/Crystal ratio, plus optionally Crystal Hz */
636 cpuid(0x15, &eax_denominator, &ebx_numerator, &ecx_hz, &edx);
637
638 if (ebx_numerator == 0 || eax_denominator == 0)
639 return 0;
640
641 crystal_khz = ecx_hz / 1000;
642
643 /*
644 * Denverton SoCs don't report crystal clock, and also don't support
645 * CPUID.0x16 for the calculation below, so hardcode the 25MHz crystal
646 * clock.
647 */
648 if (crystal_khz == 0 &&
649 boot_cpu_data.x86_model == INTEL_FAM6_ATOM_GOLDMONT_D)
650 crystal_khz = 25000;
651
652 /*
653 * TSC frequency reported directly by CPUID is a "hardware reported"
654 * frequency and is the most accurate one so far we have. This
655 * is considered a known frequency.
656 */
657 if (crystal_khz != 0)
658 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
659
660 /*
661 * Some Intel SoCs like Skylake and Kabylake don't report the crystal
662 * clock, but we can easily calculate it to a high degree of accuracy
663 * by considering the crystal ratio and the CPU speed.
664 */
665 if (crystal_khz == 0 && boot_cpu_data.cpuid_level >= 0x16) {
666 unsigned int eax_base_mhz, ebx, ecx, edx;
667
668 cpuid(0x16, &eax_base_mhz, &ebx, &ecx, &edx);
669 crystal_khz = eax_base_mhz * 1000 *
670 eax_denominator / ebx_numerator;
671 }
672
673 if (crystal_khz == 0)
674 return 0;
675
676 /*
677 * For Atom SoCs TSC is the only reliable clocksource.
678 * Mark TSC reliable so no watchdog on it.
679 */
680 if (boot_cpu_data.x86_model == INTEL_FAM6_ATOM_GOLDMONT)
681 setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
682
683#ifdef CONFIG_X86_LOCAL_APIC
684 /*
685 * The local APIC appears to be fed by the core crystal clock
686 * (which sounds entirely sensible). We can set the global
687 * lapic_timer_period here to avoid having to calibrate the APIC
688 * timer later.
689 */
690 lapic_timer_period = crystal_khz * 1000 / HZ;
691#endif
692
693 return crystal_khz * ebx_numerator / eax_denominator;
694}
695
696static unsigned long cpu_khz_from_cpuid(void)
697{
698 unsigned int eax_base_mhz, ebx_max_mhz, ecx_bus_mhz, edx;
699
700 if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
701 return 0;
702
703 if (boot_cpu_data.cpuid_level < 0x16)
704 return 0;
705
706 eax_base_mhz = ebx_max_mhz = ecx_bus_mhz = edx = 0;
707
708 cpuid(0x16, &eax_base_mhz, &ebx_max_mhz, &ecx_bus_mhz, &edx);
709
710 return eax_base_mhz * 1000;
711}
712
713/*
714 * calibrate cpu using pit, hpet, and ptimer methods. They are available
715 * later in boot after acpi is initialized.
716 */
717static unsigned long pit_hpet_ptimer_calibrate_cpu(void)
718{
719 u64 tsc1, tsc2, delta, ref1, ref2;
720 unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX;
721 unsigned long flags, latch, ms;
722 int hpet = is_hpet_enabled(), i, loopmin;
723
724 /*
725 * Run 5 calibration loops to get the lowest frequency value
726 * (the best estimate). We use two different calibration modes
727 * here:
728 *
729 * 1) PIT loop. We set the PIT Channel 2 to oneshot mode and
730 * load a timeout of 50ms. We read the time right after we
731 * started the timer and wait until the PIT count down reaches
732 * zero. In each wait loop iteration we read the TSC and check
733 * the delta to the previous read. We keep track of the min
734 * and max values of that delta. The delta is mostly defined
735 * by the IO time of the PIT access, so we can detect when
736 * any disturbance happened between the two reads. If the
737 * maximum time is significantly larger than the minimum time,
738 * then we discard the result and have another try.
739 *
740 * 2) Reference counter. If available we use the HPET or the
741 * PMTIMER as a reference to check the sanity of that value.
742 * We use separate TSC readouts and check inside of the
743 * reference read for any possible disturbance. We discard
744 * disturbed values here as well. We do that around the PIT
745 * calibration delay loop as we have to wait for a certain
746 * amount of time anyway.
747 */
748
749 /* Preset PIT loop values */
750 latch = CAL_LATCH;
751 ms = CAL_MS;
752 loopmin = CAL_PIT_LOOPS;
753
754 for (i = 0; i < 3; i++) {
755 unsigned long tsc_pit_khz;
756
757 /*
758 * Read the start value and the reference count of
759 * hpet/pmtimer when available. Then do the PIT
760 * calibration, which will take at least 50ms, and
761 * read the end value.
762 */
763 local_irq_save(flags);
764 tsc1 = tsc_read_refs(&ref1, hpet);
765 tsc_pit_khz = pit_calibrate_tsc(latch, ms, loopmin);
766 tsc2 = tsc_read_refs(&ref2, hpet);
767 local_irq_restore(flags);
768
769 /* Pick the lowest PIT TSC calibration so far */
770 tsc_pit_min = min(tsc_pit_min, tsc_pit_khz);
771
772 /* hpet or pmtimer available ? */
773 if (ref1 == ref2)
774 continue;
775
776 /* Check, whether the sampling was disturbed */
777 if (tsc1 == ULLONG_MAX || tsc2 == ULLONG_MAX)
778 continue;
779
780 tsc2 = (tsc2 - tsc1) * 1000000LL;
781 if (hpet)
782 tsc2 = calc_hpet_ref(tsc2, ref1, ref2);
783 else
784 tsc2 = calc_pmtimer_ref(tsc2, ref1, ref2);
785
786 tsc_ref_min = min(tsc_ref_min, (unsigned long) tsc2);
787
788 /* Check the reference deviation */
789 delta = ((u64) tsc_pit_min) * 100;
790 do_div(delta, tsc_ref_min);
791
792 /*
793 * If both calibration results are inside a 10% window
794 * then we can be sure, that the calibration
795 * succeeded. We break out of the loop right away. We
796 * use the reference value, as it is more precise.
797 */
798 if (delta >= 90 && delta <= 110) {
799 pr_info("PIT calibration matches %s. %d loops\n",
800 hpet ? "HPET" : "PMTIMER", i + 1);
801 return tsc_ref_min;
802 }
803
804 /*
805 * Check whether PIT failed more than once. This
806 * happens in virtualized environments. We need to
807 * give the virtual PC a slightly longer timeframe for
808 * the HPET/PMTIMER to make the result precise.
809 */
810 if (i == 1 && tsc_pit_min == ULONG_MAX) {
811 latch = CAL2_LATCH;
812 ms = CAL2_MS;
813 loopmin = CAL2_PIT_LOOPS;
814 }
815 }
816
817 /*
818 * Now check the results.
819 */
820 if (tsc_pit_min == ULONG_MAX) {
821 /* PIT gave no useful value */
822 pr_warn("Unable to calibrate against PIT\n");
823
824 /* We don't have an alternative source, disable TSC */
825 if (!hpet && !ref1 && !ref2) {
826 pr_notice("No reference (HPET/PMTIMER) available\n");
827 return 0;
828 }
829
830 /* The alternative source failed as well, disable TSC */
831 if (tsc_ref_min == ULONG_MAX) {
832 pr_warn("HPET/PMTIMER calibration failed\n");
833 return 0;
834 }
835
836 /* Use the alternative source */
837 pr_info("using %s reference calibration\n",
838 hpet ? "HPET" : "PMTIMER");
839
840 return tsc_ref_min;
841 }
842
843 /* We don't have an alternative source, use the PIT calibration value */
844 if (!hpet && !ref1 && !ref2) {
845 pr_info("Using PIT calibration value\n");
846 return tsc_pit_min;
847 }
848
849 /* The alternative source failed, use the PIT calibration value */
850 if (tsc_ref_min == ULONG_MAX) {
851 pr_warn("HPET/PMTIMER calibration failed. Using PIT calibration.\n");
852 return tsc_pit_min;
853 }
854
855 /*
856 * The calibration values differ too much. In doubt, we use
857 * the PIT value as we know that there are PMTIMERs around
858 * running at double speed. At least we let the user know:
859 */
860 pr_warn("PIT calibration deviates from %s: %lu %lu\n",
861 hpet ? "HPET" : "PMTIMER", tsc_pit_min, tsc_ref_min);
862 pr_info("Using PIT calibration value\n");
863 return tsc_pit_min;
864}
865
866/**
867 * native_calibrate_cpu_early - can calibrate the cpu early in boot
868 */
869unsigned long native_calibrate_cpu_early(void)
870{
871 unsigned long flags, fast_calibrate = cpu_khz_from_cpuid();
872
873 if (!fast_calibrate)
874 fast_calibrate = cpu_khz_from_msr();
875 if (!fast_calibrate) {
876 local_irq_save(flags);
877 fast_calibrate = quick_pit_calibrate();
878 local_irq_restore(flags);
879 }
880 return fast_calibrate;
881}
882
883
884/**
885 * native_calibrate_cpu - calibrate the cpu
886 */
887static unsigned long native_calibrate_cpu(void)
888{
889 unsigned long tsc_freq = native_calibrate_cpu_early();
890
891 if (!tsc_freq)
892 tsc_freq = pit_hpet_ptimer_calibrate_cpu();
893
894 return tsc_freq;
895}
896
897void recalibrate_cpu_khz(void)
898{
899#ifndef CONFIG_SMP
900 unsigned long cpu_khz_old = cpu_khz;
901
902 if (!boot_cpu_has(X86_FEATURE_TSC))
903 return;
904
905 cpu_khz = x86_platform.calibrate_cpu();
906 tsc_khz = x86_platform.calibrate_tsc();
907 if (tsc_khz == 0)
908 tsc_khz = cpu_khz;
909 else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
910 cpu_khz = tsc_khz;
911 cpu_data(0).loops_per_jiffy = cpufreq_scale(cpu_data(0).loops_per_jiffy,
912 cpu_khz_old, cpu_khz);
913#endif
914}
915
916EXPORT_SYMBOL(recalibrate_cpu_khz);
917
918
919static unsigned long long cyc2ns_suspend;
920
921void tsc_save_sched_clock_state(void)
922{
923 if (!sched_clock_stable())
924 return;
925
926 cyc2ns_suspend = sched_clock();
927}
928
929/*
930 * Even on processors with invariant TSC, TSC gets reset in some the
931 * ACPI system sleep states. And in some systems BIOS seem to reinit TSC to
932 * arbitrary value (still sync'd across cpu's) during resume from such sleep
933 * states. To cope up with this, recompute the cyc2ns_offset for each cpu so
934 * that sched_clock() continues from the point where it was left off during
935 * suspend.
936 */
937void tsc_restore_sched_clock_state(void)
938{
939 unsigned long long offset;
940 unsigned long flags;
941 int cpu;
942
943 if (!sched_clock_stable())
944 return;
945
946 local_irq_save(flags);
947
948 /*
949 * We're coming out of suspend, there's no concurrency yet; don't
950 * bother being nice about the RCU stuff, just write to both
951 * data fields.
952 */
953
954 this_cpu_write(cyc2ns.data[0].cyc2ns_offset, 0);
955 this_cpu_write(cyc2ns.data[1].cyc2ns_offset, 0);
956
957 offset = cyc2ns_suspend - sched_clock();
958
959 for_each_possible_cpu(cpu) {
960 per_cpu(cyc2ns.data[0].cyc2ns_offset, cpu) = offset;
961 per_cpu(cyc2ns.data[1].cyc2ns_offset, cpu) = offset;
962 }
963
964 local_irq_restore(flags);
965}
966
967#ifdef CONFIG_CPU_FREQ
968/*
969 * Frequency scaling support. Adjust the TSC based timer when the CPU frequency
970 * changes.
971 *
972 * NOTE: On SMP the situation is not fixable in general, so simply mark the TSC
973 * as unstable and give up in those cases.
974 *
975 * Should fix up last_tsc too. Currently gettimeofday in the
976 * first tick after the change will be slightly wrong.
977 */
978
979static unsigned int ref_freq;
980static unsigned long loops_per_jiffy_ref;
981static unsigned long tsc_khz_ref;
982
983static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
984 void *data)
985{
986 struct cpufreq_freqs *freq = data;
987
988 if (num_online_cpus() > 1) {
989 mark_tsc_unstable("cpufreq changes on SMP");
990 return 0;
991 }
992
993 if (!ref_freq) {
994 ref_freq = freq->old;
995 loops_per_jiffy_ref = boot_cpu_data.loops_per_jiffy;
996 tsc_khz_ref = tsc_khz;
997 }
998
999 if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) ||
1000 (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) {
1001 boot_cpu_data.loops_per_jiffy =
1002 cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new);
1003
1004 tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new);
1005 if (!(freq->flags & CPUFREQ_CONST_LOOPS))
1006 mark_tsc_unstable("cpufreq changes");
1007
1008 set_cyc2ns_scale(tsc_khz, freq->policy->cpu, rdtsc());
1009 }
1010
1011 return 0;
1012}
1013
1014static struct notifier_block time_cpufreq_notifier_block = {
1015 .notifier_call = time_cpufreq_notifier
1016};
1017
1018static int __init cpufreq_register_tsc_scaling(void)
1019{
1020 if (!boot_cpu_has(X86_FEATURE_TSC))
1021 return 0;
1022 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
1023 return 0;
1024 cpufreq_register_notifier(&time_cpufreq_notifier_block,
1025 CPUFREQ_TRANSITION_NOTIFIER);
1026 return 0;
1027}
1028
1029core_initcall(cpufreq_register_tsc_scaling);
1030
1031#endif /* CONFIG_CPU_FREQ */
1032
1033#define ART_CPUID_LEAF (0x15)
1034#define ART_MIN_DENOMINATOR (1)
1035
1036
1037/*
1038 * If ART is present detect the numerator:denominator to convert to TSC
1039 */
1040static void __init detect_art(void)
1041{
1042 unsigned int unused[2];
1043
1044 if (boot_cpu_data.cpuid_level < ART_CPUID_LEAF)
1045 return;
1046
1047 /*
1048 * Don't enable ART in a VM, non-stop TSC and TSC_ADJUST required,
1049 * and the TSC counter resets must not occur asynchronously.
1050 */
1051 if (boot_cpu_has(X86_FEATURE_HYPERVISOR) ||
1052 !boot_cpu_has(X86_FEATURE_NONSTOP_TSC) ||
1053 !boot_cpu_has(X86_FEATURE_TSC_ADJUST) ||
1054 tsc_async_resets)
1055 return;
1056
1057 cpuid(ART_CPUID_LEAF, &art_to_tsc_denominator,
1058 &art_to_tsc_numerator, unused, unused+1);
1059
1060 if (art_to_tsc_denominator < ART_MIN_DENOMINATOR)
1061 return;
1062
1063 rdmsrl(MSR_IA32_TSC_ADJUST, art_to_tsc_offset);
1064
1065 /* Make this sticky over multiple CPU init calls */
1066 setup_force_cpu_cap(X86_FEATURE_ART);
1067}
1068
1069
1070/* clocksource code */
1071
1072static void tsc_resume(struct clocksource *cs)
1073{
1074 tsc_verify_tsc_adjust(true);
1075}
1076
1077/*
1078 * We used to compare the TSC to the cycle_last value in the clocksource
1079 * structure to avoid a nasty time-warp. This can be observed in a
1080 * very small window right after one CPU updated cycle_last under
1081 * xtime/vsyscall_gtod lock and the other CPU reads a TSC value which
1082 * is smaller than the cycle_last reference value due to a TSC which
1083 * is slightly behind. This delta is nowhere else observable, but in
1084 * that case it results in a forward time jump in the range of hours
1085 * due to the unsigned delta calculation of the time keeping core
1086 * code, which is necessary to support wrapping clocksources like pm
1087 * timer.
1088 *
1089 * This sanity check is now done in the core timekeeping code.
1090 * checking the result of read_tsc() - cycle_last for being negative.
1091 * That works because CLOCKSOURCE_MASK(64) does not mask out any bit.
1092 */
1093static u64 read_tsc(struct clocksource *cs)
1094{
1095 return (u64)rdtsc_ordered();
1096}
1097
1098static void tsc_cs_mark_unstable(struct clocksource *cs)
1099{
1100 if (tsc_unstable)
1101 return;
1102
1103 tsc_unstable = 1;
1104 if (using_native_sched_clock())
1105 clear_sched_clock_stable();
1106 disable_sched_clock_irqtime();
1107 pr_info("Marking TSC unstable due to clocksource watchdog\n");
1108}
1109
1110static void tsc_cs_tick_stable(struct clocksource *cs)
1111{
1112 if (tsc_unstable)
1113 return;
1114
1115 if (using_native_sched_clock())
1116 sched_clock_tick_stable();
1117}
1118
1119static int tsc_cs_enable(struct clocksource *cs)
1120{
1121 vclocks_set_used(VDSO_CLOCKMODE_TSC);
1122 return 0;
1123}
1124
1125/*
1126 * .mask MUST be CLOCKSOURCE_MASK(64). See comment above read_tsc()
1127 */
1128static struct clocksource clocksource_tsc_early = {
1129 .name = "tsc-early",
1130 .rating = 299,
1131 .uncertainty_margin = 32 * NSEC_PER_MSEC,
1132 .read = read_tsc,
1133 .mask = CLOCKSOURCE_MASK(64),
1134 .flags = CLOCK_SOURCE_IS_CONTINUOUS |
1135 CLOCK_SOURCE_MUST_VERIFY,
1136 .vdso_clock_mode = VDSO_CLOCKMODE_TSC,
1137 .enable = tsc_cs_enable,
1138 .resume = tsc_resume,
1139 .mark_unstable = tsc_cs_mark_unstable,
1140 .tick_stable = tsc_cs_tick_stable,
1141 .list = LIST_HEAD_INIT(clocksource_tsc_early.list),
1142};
1143
1144/*
1145 * Must mark VALID_FOR_HRES early such that when we unregister tsc_early
1146 * this one will immediately take over. We will only register if TSC has
1147 * been found good.
1148 */
1149static struct clocksource clocksource_tsc = {
1150 .name = "tsc",
1151 .rating = 300,
1152 .read = read_tsc,
1153 .mask = CLOCKSOURCE_MASK(64),
1154 .flags = CLOCK_SOURCE_IS_CONTINUOUS |
1155 CLOCK_SOURCE_VALID_FOR_HRES |
1156 CLOCK_SOURCE_MUST_VERIFY |
1157 CLOCK_SOURCE_VERIFY_PERCPU,
1158 .vdso_clock_mode = VDSO_CLOCKMODE_TSC,
1159 .enable = tsc_cs_enable,
1160 .resume = tsc_resume,
1161 .mark_unstable = tsc_cs_mark_unstable,
1162 .tick_stable = tsc_cs_tick_stable,
1163 .list = LIST_HEAD_INIT(clocksource_tsc.list),
1164};
1165
1166void mark_tsc_unstable(char *reason)
1167{
1168 if (tsc_unstable)
1169 return;
1170
1171 tsc_unstable = 1;
1172 if (using_native_sched_clock())
1173 clear_sched_clock_stable();
1174 disable_sched_clock_irqtime();
1175 pr_info("Marking TSC unstable due to %s\n", reason);
1176
1177 clocksource_mark_unstable(&clocksource_tsc_early);
1178 clocksource_mark_unstable(&clocksource_tsc);
1179}
1180
1181EXPORT_SYMBOL_GPL(mark_tsc_unstable);
1182
1183static void __init tsc_disable_clocksource_watchdog(void)
1184{
1185 clocksource_tsc_early.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
1186 clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
1187}
1188
1189static void __init check_system_tsc_reliable(void)
1190{
1191#if defined(CONFIG_MGEODEGX1) || defined(CONFIG_MGEODE_LX) || defined(CONFIG_X86_GENERIC)
1192 if (is_geode_lx()) {
1193 /* RTSC counts during suspend */
1194#define RTSC_SUSP 0x100
1195 unsigned long res_low, res_high;
1196
1197 rdmsr_safe(MSR_GEODE_BUSCONT_CONF0, &res_low, &res_high);
1198 /* Geode_LX - the OLPC CPU has a very reliable TSC */
1199 if (res_low & RTSC_SUSP)
1200 tsc_clocksource_reliable = 1;
1201 }
1202#endif
1203 if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE))
1204 tsc_clocksource_reliable = 1;
1205
1206 /*
1207 * Disable the clocksource watchdog when the system has:
1208 * - TSC running at constant frequency
1209 * - TSC which does not stop in C-States
1210 * - the TSC_ADJUST register which allows to detect even minimal
1211 * modifications
1212 * - not more than two sockets. As the number of sockets cannot be
1213 * evaluated at the early boot stage where this has to be
1214 * invoked, check the number of online memory nodes as a
1215 * fallback solution which is an reasonable estimate.
1216 */
1217 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
1218 boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
1219 boot_cpu_has(X86_FEATURE_TSC_ADJUST) &&
1220 nr_online_nodes <= 2)
1221 tsc_disable_clocksource_watchdog();
1222}
1223
1224/*
1225 * Make an educated guess if the TSC is trustworthy and synchronized
1226 * over all CPUs.
1227 */
1228int unsynchronized_tsc(void)
1229{
1230 if (!boot_cpu_has(X86_FEATURE_TSC) || tsc_unstable)
1231 return 1;
1232
1233#ifdef CONFIG_SMP
1234 if (apic_is_clustered_box())
1235 return 1;
1236#endif
1237
1238 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
1239 return 0;
1240
1241 if (tsc_clocksource_reliable)
1242 return 0;
1243 /*
1244 * Intel systems are normally all synchronized.
1245 * Exceptions must mark TSC as unstable:
1246 */
1247 if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
1248 /* assume multi socket systems are not synchronized: */
1249 if (num_possible_cpus() > 1)
1250 return 1;
1251 }
1252
1253 return 0;
1254}
1255
1256/*
1257 * Convert ART to TSC given numerator/denominator found in detect_art()
1258 */
1259struct system_counterval_t convert_art_to_tsc(u64 art)
1260{
1261 u64 tmp, res, rem;
1262
1263 rem = do_div(art, art_to_tsc_denominator);
1264
1265 res = art * art_to_tsc_numerator;
1266 tmp = rem * art_to_tsc_numerator;
1267
1268 do_div(tmp, art_to_tsc_denominator);
1269 res += tmp + art_to_tsc_offset;
1270
1271 return (struct system_counterval_t) {.cs = art_related_clocksource,
1272 .cycles = res};
1273}
1274EXPORT_SYMBOL(convert_art_to_tsc);
1275
1276/**
1277 * convert_art_ns_to_tsc() - Convert ART in nanoseconds to TSC.
1278 * @art_ns: ART (Always Running Timer) in unit of nanoseconds
1279 *
1280 * PTM requires all timestamps to be in units of nanoseconds. When user
1281 * software requests a cross-timestamp, this function converts system timestamp
1282 * to TSC.
1283 *
1284 * This is valid when CPU feature flag X86_FEATURE_TSC_KNOWN_FREQ is set
1285 * indicating the tsc_khz is derived from CPUID[15H]. Drivers should check
1286 * that this flag is set before conversion to TSC is attempted.
1287 *
1288 * Return:
1289 * struct system_counterval_t - system counter value with the pointer to the
1290 * corresponding clocksource
1291 * @cycles: System counter value
1292 * @cs: Clocksource corresponding to system counter value. Used
1293 * by timekeeping code to verify comparability of two cycle
1294 * values.
1295 */
1296
1297struct system_counterval_t convert_art_ns_to_tsc(u64 art_ns)
1298{
1299 u64 tmp, res, rem;
1300
1301 rem = do_div(art_ns, USEC_PER_SEC);
1302
1303 res = art_ns * tsc_khz;
1304 tmp = rem * tsc_khz;
1305
1306 do_div(tmp, USEC_PER_SEC);
1307 res += tmp;
1308
1309 return (struct system_counterval_t) { .cs = art_related_clocksource,
1310 .cycles = res};
1311}
1312EXPORT_SYMBOL(convert_art_ns_to_tsc);
1313
1314
1315static void tsc_refine_calibration_work(struct work_struct *work);
1316static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work);
1317/**
1318 * tsc_refine_calibration_work - Further refine tsc freq calibration
1319 * @work - ignored.
1320 *
1321 * This functions uses delayed work over a period of a
1322 * second to further refine the TSC freq value. Since this is
1323 * timer based, instead of loop based, we don't block the boot
1324 * process while this longer calibration is done.
1325 *
1326 * If there are any calibration anomalies (too many SMIs, etc),
1327 * or the refined calibration is off by 1% of the fast early
1328 * calibration, we throw out the new calibration and use the
1329 * early calibration.
1330 */
1331static void tsc_refine_calibration_work(struct work_struct *work)
1332{
1333 static u64 tsc_start = ULLONG_MAX, ref_start;
1334 static int hpet;
1335 u64 tsc_stop, ref_stop, delta;
1336 unsigned long freq;
1337 int cpu;
1338
1339 /* Don't bother refining TSC on unstable systems */
1340 if (tsc_unstable)
1341 goto unreg;
1342
1343 /*
1344 * Since the work is started early in boot, we may be
1345 * delayed the first time we expire. So set the workqueue
1346 * again once we know timers are working.
1347 */
1348 if (tsc_start == ULLONG_MAX) {
1349restart:
1350 /*
1351 * Only set hpet once, to avoid mixing hardware
1352 * if the hpet becomes enabled later.
1353 */
1354 hpet = is_hpet_enabled();
1355 tsc_start = tsc_read_refs(&ref_start, hpet);
1356 schedule_delayed_work(&tsc_irqwork, HZ);
1357 return;
1358 }
1359
1360 tsc_stop = tsc_read_refs(&ref_stop, hpet);
1361
1362 /* hpet or pmtimer available ? */
1363 if (ref_start == ref_stop)
1364 goto out;
1365
1366 /* Check, whether the sampling was disturbed */
1367 if (tsc_stop == ULLONG_MAX)
1368 goto restart;
1369
1370 delta = tsc_stop - tsc_start;
1371 delta *= 1000000LL;
1372 if (hpet)
1373 freq = calc_hpet_ref(delta, ref_start, ref_stop);
1374 else
1375 freq = calc_pmtimer_ref(delta, ref_start, ref_stop);
1376
1377 /* Make sure we're within 1% */
1378 if (abs(tsc_khz - freq) > tsc_khz/100)
1379 goto out;
1380
1381 tsc_khz = freq;
1382 pr_info("Refined TSC clocksource calibration: %lu.%03lu MHz\n",
1383 (unsigned long)tsc_khz / 1000,
1384 (unsigned long)tsc_khz % 1000);
1385
1386 /* Inform the TSC deadline clockevent devices about the recalibration */
1387 lapic_update_tsc_freq();
1388
1389 /* Update the sched_clock() rate to match the clocksource one */
1390 for_each_possible_cpu(cpu)
1391 set_cyc2ns_scale(tsc_khz, cpu, tsc_stop);
1392
1393out:
1394 if (tsc_unstable)
1395 goto unreg;
1396
1397 if (boot_cpu_has(X86_FEATURE_ART))
1398 art_related_clocksource = &clocksource_tsc;
1399 clocksource_register_khz(&clocksource_tsc, tsc_khz);
1400unreg:
1401 clocksource_unregister(&clocksource_tsc_early);
1402}
1403
1404
1405static int __init init_tsc_clocksource(void)
1406{
1407 if (!boot_cpu_has(X86_FEATURE_TSC) || !tsc_khz)
1408 return 0;
1409
1410 if (tsc_unstable)
1411 goto unreg;
1412
1413 if (boot_cpu_has(X86_FEATURE_NONSTOP_TSC_S3))
1414 clocksource_tsc.flags |= CLOCK_SOURCE_SUSPEND_NONSTOP;
1415
1416 /*
1417 * When TSC frequency is known (retrieved via MSR or CPUID), we skip
1418 * the refined calibration and directly register it as a clocksource.
1419 */
1420 if (boot_cpu_has(X86_FEATURE_TSC_KNOWN_FREQ)) {
1421 if (boot_cpu_has(X86_FEATURE_ART))
1422 art_related_clocksource = &clocksource_tsc;
1423 clocksource_register_khz(&clocksource_tsc, tsc_khz);
1424unreg:
1425 clocksource_unregister(&clocksource_tsc_early);
1426 return 0;
1427 }
1428
1429 schedule_delayed_work(&tsc_irqwork, 0);
1430 return 0;
1431}
1432/*
1433 * We use device_initcall here, to ensure we run after the hpet
1434 * is fully initialized, which may occur at fs_initcall time.
1435 */
1436device_initcall(init_tsc_clocksource);
1437
1438static bool __init determine_cpu_tsc_frequencies(bool early)
1439{
1440 /* Make sure that cpu and tsc are not already calibrated */
1441 WARN_ON(cpu_khz || tsc_khz);
1442
1443 if (early) {
1444 cpu_khz = x86_platform.calibrate_cpu();
1445 if (tsc_early_khz)
1446 tsc_khz = tsc_early_khz;
1447 else
1448 tsc_khz = x86_platform.calibrate_tsc();
1449 } else {
1450 /* We should not be here with non-native cpu calibration */
1451 WARN_ON(x86_platform.calibrate_cpu != native_calibrate_cpu);
1452 cpu_khz = pit_hpet_ptimer_calibrate_cpu();
1453 }
1454
1455 /*
1456 * Trust non-zero tsc_khz as authoritative,
1457 * and use it to sanity check cpu_khz,
1458 * which will be off if system timer is off.
1459 */
1460 if (tsc_khz == 0)
1461 tsc_khz = cpu_khz;
1462 else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
1463 cpu_khz = tsc_khz;
1464
1465 if (tsc_khz == 0)
1466 return false;
1467
1468 pr_info("Detected %lu.%03lu MHz processor\n",
1469 (unsigned long)cpu_khz / KHZ,
1470 (unsigned long)cpu_khz % KHZ);
1471
1472 if (cpu_khz != tsc_khz) {
1473 pr_info("Detected %lu.%03lu MHz TSC",
1474 (unsigned long)tsc_khz / KHZ,
1475 (unsigned long)tsc_khz % KHZ);
1476 }
1477 return true;
1478}
1479
1480static unsigned long __init get_loops_per_jiffy(void)
1481{
1482 u64 lpj = (u64)tsc_khz * KHZ;
1483
1484 do_div(lpj, HZ);
1485 return lpj;
1486}
1487
1488static void __init tsc_enable_sched_clock(void)
1489{
1490 loops_per_jiffy = get_loops_per_jiffy();
1491 use_tsc_delay();
1492
1493 /* Sanitize TSC ADJUST before cyc2ns gets initialized */
1494 tsc_store_and_check_tsc_adjust(true);
1495 cyc2ns_init_boot_cpu();
1496 static_branch_enable(&__use_tsc);
1497}
1498
1499void __init tsc_early_init(void)
1500{
1501 if (!boot_cpu_has(X86_FEATURE_TSC))
1502 return;
1503 /* Don't change UV TSC multi-chassis synchronization */
1504 if (is_early_uv_system())
1505 return;
1506 if (!determine_cpu_tsc_frequencies(true))
1507 return;
1508 tsc_enable_sched_clock();
1509}
1510
1511void __init tsc_init(void)
1512{
1513 /*
1514 * native_calibrate_cpu_early can only calibrate using methods that are
1515 * available early in boot.
1516 */
1517 if (x86_platform.calibrate_cpu == native_calibrate_cpu_early)
1518 x86_platform.calibrate_cpu = native_calibrate_cpu;
1519
1520 if (!boot_cpu_has(X86_FEATURE_TSC)) {
1521 setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
1522 return;
1523 }
1524
1525 if (!tsc_khz) {
1526 /* We failed to determine frequencies earlier, try again */
1527 if (!determine_cpu_tsc_frequencies(false)) {
1528 mark_tsc_unstable("could not calculate TSC khz");
1529 setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
1530 return;
1531 }
1532 tsc_enable_sched_clock();
1533 }
1534
1535 cyc2ns_init_secondary_cpus();
1536
1537 if (!no_sched_irq_time)
1538 enable_sched_clock_irqtime();
1539
1540 lpj_fine = get_loops_per_jiffy();
1541
1542 check_system_tsc_reliable();
1543
1544 if (unsynchronized_tsc()) {
1545 mark_tsc_unstable("TSCs unsynchronized");
1546 return;
1547 }
1548
1549 if (tsc_clocksource_reliable || no_tsc_watchdog)
1550 tsc_disable_clocksource_watchdog();
1551
1552 clocksource_register_khz(&clocksource_tsc_early, tsc_khz);
1553 detect_art();
1554}
1555
1556#ifdef CONFIG_SMP
1557/*
1558 * If we have a constant TSC and are using the TSC for the delay loop,
1559 * we can skip clock calibration if another cpu in the same socket has already
1560 * been calibrated. This assumes that CONSTANT_TSC applies to all
1561 * cpus in the socket - this should be a safe assumption.
1562 */
1563unsigned long calibrate_delay_is_known(void)
1564{
1565 int sibling, cpu = smp_processor_id();
1566 int constant_tsc = cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC);
1567 const struct cpumask *mask = topology_core_cpumask(cpu);
1568
1569 if (!constant_tsc || !mask)
1570 return 0;
1571
1572 sibling = cpumask_any_but(mask, cpu);
1573 if (sibling < nr_cpu_ids)
1574 return cpu_data(sibling).loops_per_jiffy;
1575 return 0;
1576}
1577#endif
1#include <linux/kernel.h>
2#include <linux/sched.h>
3#include <linux/init.h>
4#include <linux/module.h>
5#include <linux/timer.h>
6#include <linux/acpi_pmtmr.h>
7#include <linux/cpufreq.h>
8#include <linux/delay.h>
9#include <linux/clocksource.h>
10#include <linux/percpu.h>
11#include <linux/timex.h>
12
13#include <asm/hpet.h>
14#include <asm/timer.h>
15#include <asm/vgtod.h>
16#include <asm/time.h>
17#include <asm/delay.h>
18#include <asm/hypervisor.h>
19#include <asm/nmi.h>
20#include <asm/x86_init.h>
21
22unsigned int __read_mostly cpu_khz; /* TSC clocks / usec, not used here */
23EXPORT_SYMBOL(cpu_khz);
24
25unsigned int __read_mostly tsc_khz;
26EXPORT_SYMBOL(tsc_khz);
27
28/*
29 * TSC can be unstable due to cpufreq or due to unsynced TSCs
30 */
31static int __read_mostly tsc_unstable;
32
33/* native_sched_clock() is called before tsc_init(), so
34 we must start with the TSC soft disabled to prevent
35 erroneous rdtsc usage on !cpu_has_tsc processors */
36static int __read_mostly tsc_disabled = -1;
37
38static int tsc_clocksource_reliable;
39/*
40 * Scheduler clock - returns current time in nanosec units.
41 */
42u64 native_sched_clock(void)
43{
44 u64 this_offset;
45
46 /*
47 * Fall back to jiffies if there's no TSC available:
48 * ( But note that we still use it if the TSC is marked
49 * unstable. We do this because unlike Time Of Day,
50 * the scheduler clock tolerates small errors and it's
51 * very important for it to be as fast as the platform
52 * can achieve it. )
53 */
54 if (unlikely(tsc_disabled)) {
55 /* No locking but a rare wrong value is not a big deal: */
56 return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
57 }
58
59 /* read the Time Stamp Counter: */
60 rdtscll(this_offset);
61
62 /* return the value in ns */
63 return __cycles_2_ns(this_offset);
64}
65
66/* We need to define a real function for sched_clock, to override the
67 weak default version */
68#ifdef CONFIG_PARAVIRT
69unsigned long long sched_clock(void)
70{
71 return paravirt_sched_clock();
72}
73#else
74unsigned long long
75sched_clock(void) __attribute__((alias("native_sched_clock")));
76#endif
77
78int check_tsc_unstable(void)
79{
80 return tsc_unstable;
81}
82EXPORT_SYMBOL_GPL(check_tsc_unstable);
83
84#ifdef CONFIG_X86_TSC
85int __init notsc_setup(char *str)
86{
87 printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
88 "cannot disable TSC completely.\n");
89 tsc_disabled = 1;
90 return 1;
91}
92#else
93/*
94 * disable flag for tsc. Takes effect by clearing the TSC cpu flag
95 * in cpu/common.c
96 */
97int __init notsc_setup(char *str)
98{
99 setup_clear_cpu_cap(X86_FEATURE_TSC);
100 return 1;
101}
102#endif
103
104__setup("notsc", notsc_setup);
105
106static int no_sched_irq_time;
107
108static int __init tsc_setup(char *str)
109{
110 if (!strcmp(str, "reliable"))
111 tsc_clocksource_reliable = 1;
112 if (!strncmp(str, "noirqtime", 9))
113 no_sched_irq_time = 1;
114 return 1;
115}
116
117__setup("tsc=", tsc_setup);
118
119#define MAX_RETRIES 5
120#define SMI_TRESHOLD 50000
121
122/*
123 * Read TSC and the reference counters. Take care of SMI disturbance
124 */
125static u64 tsc_read_refs(u64 *p, int hpet)
126{
127 u64 t1, t2;
128 int i;
129
130 for (i = 0; i < MAX_RETRIES; i++) {
131 t1 = get_cycles();
132 if (hpet)
133 *p = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF;
134 else
135 *p = acpi_pm_read_early();
136 t2 = get_cycles();
137 if ((t2 - t1) < SMI_TRESHOLD)
138 return t2;
139 }
140 return ULLONG_MAX;
141}
142
143/*
144 * Calculate the TSC frequency from HPET reference
145 */
146static unsigned long calc_hpet_ref(u64 deltatsc, u64 hpet1, u64 hpet2)
147{
148 u64 tmp;
149
150 if (hpet2 < hpet1)
151 hpet2 += 0x100000000ULL;
152 hpet2 -= hpet1;
153 tmp = ((u64)hpet2 * hpet_readl(HPET_PERIOD));
154 do_div(tmp, 1000000);
155 do_div(deltatsc, tmp);
156
157 return (unsigned long) deltatsc;
158}
159
160/*
161 * Calculate the TSC frequency from PMTimer reference
162 */
163static unsigned long calc_pmtimer_ref(u64 deltatsc, u64 pm1, u64 pm2)
164{
165 u64 tmp;
166
167 if (!pm1 && !pm2)
168 return ULONG_MAX;
169
170 if (pm2 < pm1)
171 pm2 += (u64)ACPI_PM_OVRRUN;
172 pm2 -= pm1;
173 tmp = pm2 * 1000000000LL;
174 do_div(tmp, PMTMR_TICKS_PER_SEC);
175 do_div(deltatsc, tmp);
176
177 return (unsigned long) deltatsc;
178}
179
180#define CAL_MS 10
181#define CAL_LATCH (CLOCK_TICK_RATE / (1000 / CAL_MS))
182#define CAL_PIT_LOOPS 1000
183
184#define CAL2_MS 50
185#define CAL2_LATCH (CLOCK_TICK_RATE / (1000 / CAL2_MS))
186#define CAL2_PIT_LOOPS 5000
187
188
189/*
190 * Try to calibrate the TSC against the Programmable
191 * Interrupt Timer and return the frequency of the TSC
192 * in kHz.
193 *
194 * Return ULONG_MAX on failure to calibrate.
195 */
196static unsigned long pit_calibrate_tsc(u32 latch, unsigned long ms, int loopmin)
197{
198 u64 tsc, t1, t2, delta;
199 unsigned long tscmin, tscmax;
200 int pitcnt;
201
202 /* Set the Gate high, disable speaker */
203 outb((inb(0x61) & ~0x02) | 0x01, 0x61);
204
205 /*
206 * Setup CTC channel 2* for mode 0, (interrupt on terminal
207 * count mode), binary count. Set the latch register to 50ms
208 * (LSB then MSB) to begin countdown.
209 */
210 outb(0xb0, 0x43);
211 outb(latch & 0xff, 0x42);
212 outb(latch >> 8, 0x42);
213
214 tsc = t1 = t2 = get_cycles();
215
216 pitcnt = 0;
217 tscmax = 0;
218 tscmin = ULONG_MAX;
219 while ((inb(0x61) & 0x20) == 0) {
220 t2 = get_cycles();
221 delta = t2 - tsc;
222 tsc = t2;
223 if ((unsigned long) delta < tscmin)
224 tscmin = (unsigned int) delta;
225 if ((unsigned long) delta > tscmax)
226 tscmax = (unsigned int) delta;
227 pitcnt++;
228 }
229
230 /*
231 * Sanity checks:
232 *
233 * If we were not able to read the PIT more than loopmin
234 * times, then we have been hit by a massive SMI
235 *
236 * If the maximum is 10 times larger than the minimum,
237 * then we got hit by an SMI as well.
238 */
239 if (pitcnt < loopmin || tscmax > 10 * tscmin)
240 return ULONG_MAX;
241
242 /* Calculate the PIT value */
243 delta = t2 - t1;
244 do_div(delta, ms);
245 return delta;
246}
247
248/*
249 * This reads the current MSB of the PIT counter, and
250 * checks if we are running on sufficiently fast and
251 * non-virtualized hardware.
252 *
253 * Our expectations are:
254 *
255 * - the PIT is running at roughly 1.19MHz
256 *
257 * - each IO is going to take about 1us on real hardware,
258 * but we allow it to be much faster (by a factor of 10) or
259 * _slightly_ slower (ie we allow up to a 2us read+counter
260 * update - anything else implies a unacceptably slow CPU
261 * or PIT for the fast calibration to work.
262 *
263 * - with 256 PIT ticks to read the value, we have 214us to
264 * see the same MSB (and overhead like doing a single TSC
265 * read per MSB value etc).
266 *
267 * - We're doing 2 reads per loop (LSB, MSB), and we expect
268 * them each to take about a microsecond on real hardware.
269 * So we expect a count value of around 100. But we'll be
270 * generous, and accept anything over 50.
271 *
272 * - if the PIT is stuck, and we see *many* more reads, we
273 * return early (and the next caller of pit_expect_msb()
274 * then consider it a failure when they don't see the
275 * next expected value).
276 *
277 * These expectations mean that we know that we have seen the
278 * transition from one expected value to another with a fairly
279 * high accuracy, and we didn't miss any events. We can thus
280 * use the TSC value at the transitions to calculate a pretty
281 * good value for the TSC frequencty.
282 */
283static inline int pit_verify_msb(unsigned char val)
284{
285 /* Ignore LSB */
286 inb(0x42);
287 return inb(0x42) == val;
288}
289
290static inline int pit_expect_msb(unsigned char val, u64 *tscp, unsigned long *deltap)
291{
292 int count;
293 u64 tsc = 0;
294
295 for (count = 0; count < 50000; count++) {
296 if (!pit_verify_msb(val))
297 break;
298 tsc = get_cycles();
299 }
300 *deltap = get_cycles() - tsc;
301 *tscp = tsc;
302
303 /*
304 * We require _some_ success, but the quality control
305 * will be based on the error terms on the TSC values.
306 */
307 return count > 5;
308}
309
310/*
311 * How many MSB values do we want to see? We aim for
312 * a maximum error rate of 500ppm (in practice the
313 * real error is much smaller), but refuse to spend
314 * more than 25ms on it.
315 */
316#define MAX_QUICK_PIT_MS 25
317#define MAX_QUICK_PIT_ITERATIONS (MAX_QUICK_PIT_MS * PIT_TICK_RATE / 1000 / 256)
318
319static unsigned long quick_pit_calibrate(void)
320{
321 int i;
322 u64 tsc, delta;
323 unsigned long d1, d2;
324
325 /* Set the Gate high, disable speaker */
326 outb((inb(0x61) & ~0x02) | 0x01, 0x61);
327
328 /*
329 * Counter 2, mode 0 (one-shot), binary count
330 *
331 * NOTE! Mode 2 decrements by two (and then the
332 * output is flipped each time, giving the same
333 * final output frequency as a decrement-by-one),
334 * so mode 0 is much better when looking at the
335 * individual counts.
336 */
337 outb(0xb0, 0x43);
338
339 /* Start at 0xffff */
340 outb(0xff, 0x42);
341 outb(0xff, 0x42);
342
343 /*
344 * The PIT starts counting at the next edge, so we
345 * need to delay for a microsecond. The easiest way
346 * to do that is to just read back the 16-bit counter
347 * once from the PIT.
348 */
349 pit_verify_msb(0);
350
351 if (pit_expect_msb(0xff, &tsc, &d1)) {
352 for (i = 1; i <= MAX_QUICK_PIT_ITERATIONS; i++) {
353 if (!pit_expect_msb(0xff-i, &delta, &d2))
354 break;
355
356 /*
357 * Iterate until the error is less than 500 ppm
358 */
359 delta -= tsc;
360 if (d1+d2 >= delta >> 11)
361 continue;
362
363 /*
364 * Check the PIT one more time to verify that
365 * all TSC reads were stable wrt the PIT.
366 *
367 * This also guarantees serialization of the
368 * last cycle read ('d2') in pit_expect_msb.
369 */
370 if (!pit_verify_msb(0xfe - i))
371 break;
372 goto success;
373 }
374 }
375 printk("Fast TSC calibration failed\n");
376 return 0;
377
378success:
379 /*
380 * Ok, if we get here, then we've seen the
381 * MSB of the PIT decrement 'i' times, and the
382 * error has shrunk to less than 500 ppm.
383 *
384 * As a result, we can depend on there not being
385 * any odd delays anywhere, and the TSC reads are
386 * reliable (within the error). We also adjust the
387 * delta to the middle of the error bars, just
388 * because it looks nicer.
389 *
390 * kHz = ticks / time-in-seconds / 1000;
391 * kHz = (t2 - t1) / (I * 256 / PIT_TICK_RATE) / 1000
392 * kHz = ((t2 - t1) * PIT_TICK_RATE) / (I * 256 * 1000)
393 */
394 delta += (long)(d2 - d1)/2;
395 delta *= PIT_TICK_RATE;
396 do_div(delta, i*256*1000);
397 printk("Fast TSC calibration using PIT\n");
398 return delta;
399}
400
401/**
402 * native_calibrate_tsc - calibrate the tsc on boot
403 */
404unsigned long native_calibrate_tsc(void)
405{
406 u64 tsc1, tsc2, delta, ref1, ref2;
407 unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX;
408 unsigned long flags, latch, ms, fast_calibrate;
409 int hpet = is_hpet_enabled(), i, loopmin;
410
411 local_irq_save(flags);
412 fast_calibrate = quick_pit_calibrate();
413 local_irq_restore(flags);
414 if (fast_calibrate)
415 return fast_calibrate;
416
417 /*
418 * Run 5 calibration loops to get the lowest frequency value
419 * (the best estimate). We use two different calibration modes
420 * here:
421 *
422 * 1) PIT loop. We set the PIT Channel 2 to oneshot mode and
423 * load a timeout of 50ms. We read the time right after we
424 * started the timer and wait until the PIT count down reaches
425 * zero. In each wait loop iteration we read the TSC and check
426 * the delta to the previous read. We keep track of the min
427 * and max values of that delta. The delta is mostly defined
428 * by the IO time of the PIT access, so we can detect when a
429 * SMI/SMM disturbance happened between the two reads. If the
430 * maximum time is significantly larger than the minimum time,
431 * then we discard the result and have another try.
432 *
433 * 2) Reference counter. If available we use the HPET or the
434 * PMTIMER as a reference to check the sanity of that value.
435 * We use separate TSC readouts and check inside of the
436 * reference read for a SMI/SMM disturbance. We dicard
437 * disturbed values here as well. We do that around the PIT
438 * calibration delay loop as we have to wait for a certain
439 * amount of time anyway.
440 */
441
442 /* Preset PIT loop values */
443 latch = CAL_LATCH;
444 ms = CAL_MS;
445 loopmin = CAL_PIT_LOOPS;
446
447 for (i = 0; i < 3; i++) {
448 unsigned long tsc_pit_khz;
449
450 /*
451 * Read the start value and the reference count of
452 * hpet/pmtimer when available. Then do the PIT
453 * calibration, which will take at least 50ms, and
454 * read the end value.
455 */
456 local_irq_save(flags);
457 tsc1 = tsc_read_refs(&ref1, hpet);
458 tsc_pit_khz = pit_calibrate_tsc(latch, ms, loopmin);
459 tsc2 = tsc_read_refs(&ref2, hpet);
460 local_irq_restore(flags);
461
462 /* Pick the lowest PIT TSC calibration so far */
463 tsc_pit_min = min(tsc_pit_min, tsc_pit_khz);
464
465 /* hpet or pmtimer available ? */
466 if (ref1 == ref2)
467 continue;
468
469 /* Check, whether the sampling was disturbed by an SMI */
470 if (tsc1 == ULLONG_MAX || tsc2 == ULLONG_MAX)
471 continue;
472
473 tsc2 = (tsc2 - tsc1) * 1000000LL;
474 if (hpet)
475 tsc2 = calc_hpet_ref(tsc2, ref1, ref2);
476 else
477 tsc2 = calc_pmtimer_ref(tsc2, ref1, ref2);
478
479 tsc_ref_min = min(tsc_ref_min, (unsigned long) tsc2);
480
481 /* Check the reference deviation */
482 delta = ((u64) tsc_pit_min) * 100;
483 do_div(delta, tsc_ref_min);
484
485 /*
486 * If both calibration results are inside a 10% window
487 * then we can be sure, that the calibration
488 * succeeded. We break out of the loop right away. We
489 * use the reference value, as it is more precise.
490 */
491 if (delta >= 90 && delta <= 110) {
492 printk(KERN_INFO
493 "TSC: PIT calibration matches %s. %d loops\n",
494 hpet ? "HPET" : "PMTIMER", i + 1);
495 return tsc_ref_min;
496 }
497
498 /*
499 * Check whether PIT failed more than once. This
500 * happens in virtualized environments. We need to
501 * give the virtual PC a slightly longer timeframe for
502 * the HPET/PMTIMER to make the result precise.
503 */
504 if (i == 1 && tsc_pit_min == ULONG_MAX) {
505 latch = CAL2_LATCH;
506 ms = CAL2_MS;
507 loopmin = CAL2_PIT_LOOPS;
508 }
509 }
510
511 /*
512 * Now check the results.
513 */
514 if (tsc_pit_min == ULONG_MAX) {
515 /* PIT gave no useful value */
516 printk(KERN_WARNING "TSC: Unable to calibrate against PIT\n");
517
518 /* We don't have an alternative source, disable TSC */
519 if (!hpet && !ref1 && !ref2) {
520 printk("TSC: No reference (HPET/PMTIMER) available\n");
521 return 0;
522 }
523
524 /* The alternative source failed as well, disable TSC */
525 if (tsc_ref_min == ULONG_MAX) {
526 printk(KERN_WARNING "TSC: HPET/PMTIMER calibration "
527 "failed.\n");
528 return 0;
529 }
530
531 /* Use the alternative source */
532 printk(KERN_INFO "TSC: using %s reference calibration\n",
533 hpet ? "HPET" : "PMTIMER");
534
535 return tsc_ref_min;
536 }
537
538 /* We don't have an alternative source, use the PIT calibration value */
539 if (!hpet && !ref1 && !ref2) {
540 printk(KERN_INFO "TSC: Using PIT calibration value\n");
541 return tsc_pit_min;
542 }
543
544 /* The alternative source failed, use the PIT calibration value */
545 if (tsc_ref_min == ULONG_MAX) {
546 printk(KERN_WARNING "TSC: HPET/PMTIMER calibration failed. "
547 "Using PIT calibration\n");
548 return tsc_pit_min;
549 }
550
551 /*
552 * The calibration values differ too much. In doubt, we use
553 * the PIT value as we know that there are PMTIMERs around
554 * running at double speed. At least we let the user know:
555 */
556 printk(KERN_WARNING "TSC: PIT calibration deviates from %s: %lu %lu.\n",
557 hpet ? "HPET" : "PMTIMER", tsc_pit_min, tsc_ref_min);
558 printk(KERN_INFO "TSC: Using PIT calibration value\n");
559 return tsc_pit_min;
560}
561
562int recalibrate_cpu_khz(void)
563{
564#ifndef CONFIG_SMP
565 unsigned long cpu_khz_old = cpu_khz;
566
567 if (cpu_has_tsc) {
568 tsc_khz = x86_platform.calibrate_tsc();
569 cpu_khz = tsc_khz;
570 cpu_data(0).loops_per_jiffy =
571 cpufreq_scale(cpu_data(0).loops_per_jiffy,
572 cpu_khz_old, cpu_khz);
573 return 0;
574 } else
575 return -ENODEV;
576#else
577 return -ENODEV;
578#endif
579}
580
581EXPORT_SYMBOL(recalibrate_cpu_khz);
582
583
584/* Accelerators for sched_clock()
585 * convert from cycles(64bits) => nanoseconds (64bits)
586 * basic equation:
587 * ns = cycles / (freq / ns_per_sec)
588 * ns = cycles * (ns_per_sec / freq)
589 * ns = cycles * (10^9 / (cpu_khz * 10^3))
590 * ns = cycles * (10^6 / cpu_khz)
591 *
592 * Then we use scaling math (suggested by george@mvista.com) to get:
593 * ns = cycles * (10^6 * SC / cpu_khz) / SC
594 * ns = cycles * cyc2ns_scale / SC
595 *
596 * And since SC is a constant power of two, we can convert the div
597 * into a shift.
598 *
599 * We can use khz divisor instead of mhz to keep a better precision, since
600 * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
601 * (mathieu.desnoyers@polymtl.ca)
602 *
603 * -johnstul@us.ibm.com "math is hard, lets go shopping!"
604 */
605
606DEFINE_PER_CPU(unsigned long, cyc2ns);
607DEFINE_PER_CPU(unsigned long long, cyc2ns_offset);
608
609static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
610{
611 unsigned long long tsc_now, ns_now, *offset;
612 unsigned long flags, *scale;
613
614 local_irq_save(flags);
615 sched_clock_idle_sleep_event();
616
617 scale = &per_cpu(cyc2ns, cpu);
618 offset = &per_cpu(cyc2ns_offset, cpu);
619
620 rdtscll(tsc_now);
621 ns_now = __cycles_2_ns(tsc_now);
622
623 if (cpu_khz) {
624 *scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz;
625 *offset = ns_now - (tsc_now * *scale >> CYC2NS_SCALE_FACTOR);
626 }
627
628 sched_clock_idle_wakeup_event(0);
629 local_irq_restore(flags);
630}
631
632static unsigned long long cyc2ns_suspend;
633
634void save_sched_clock_state(void)
635{
636 if (!sched_clock_stable)
637 return;
638
639 cyc2ns_suspend = sched_clock();
640}
641
642/*
643 * Even on processors with invariant TSC, TSC gets reset in some the
644 * ACPI system sleep states. And in some systems BIOS seem to reinit TSC to
645 * arbitrary value (still sync'd across cpu's) during resume from such sleep
646 * states. To cope up with this, recompute the cyc2ns_offset for each cpu so
647 * that sched_clock() continues from the point where it was left off during
648 * suspend.
649 */
650void restore_sched_clock_state(void)
651{
652 unsigned long long offset;
653 unsigned long flags;
654 int cpu;
655
656 if (!sched_clock_stable)
657 return;
658
659 local_irq_save(flags);
660
661 __this_cpu_write(cyc2ns_offset, 0);
662 offset = cyc2ns_suspend - sched_clock();
663
664 for_each_possible_cpu(cpu)
665 per_cpu(cyc2ns_offset, cpu) = offset;
666
667 local_irq_restore(flags);
668}
669
670#ifdef CONFIG_CPU_FREQ
671
672/* Frequency scaling support. Adjust the TSC based timer when the cpu frequency
673 * changes.
674 *
675 * RED-PEN: On SMP we assume all CPUs run with the same frequency. It's
676 * not that important because current Opteron setups do not support
677 * scaling on SMP anyroads.
678 *
679 * Should fix up last_tsc too. Currently gettimeofday in the
680 * first tick after the change will be slightly wrong.
681 */
682
683static unsigned int ref_freq;
684static unsigned long loops_per_jiffy_ref;
685static unsigned long tsc_khz_ref;
686
687static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
688 void *data)
689{
690 struct cpufreq_freqs *freq = data;
691 unsigned long *lpj;
692
693 if (cpu_has(&cpu_data(freq->cpu), X86_FEATURE_CONSTANT_TSC))
694 return 0;
695
696 lpj = &boot_cpu_data.loops_per_jiffy;
697#ifdef CONFIG_SMP
698 if (!(freq->flags & CPUFREQ_CONST_LOOPS))
699 lpj = &cpu_data(freq->cpu).loops_per_jiffy;
700#endif
701
702 if (!ref_freq) {
703 ref_freq = freq->old;
704 loops_per_jiffy_ref = *lpj;
705 tsc_khz_ref = tsc_khz;
706 }
707 if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) ||
708 (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
709 (val == CPUFREQ_RESUMECHANGE)) {
710 *lpj = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new);
711
712 tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new);
713 if (!(freq->flags & CPUFREQ_CONST_LOOPS))
714 mark_tsc_unstable("cpufreq changes");
715 }
716
717 set_cyc2ns_scale(tsc_khz, freq->cpu);
718
719 return 0;
720}
721
722static struct notifier_block time_cpufreq_notifier_block = {
723 .notifier_call = time_cpufreq_notifier
724};
725
726static int __init cpufreq_tsc(void)
727{
728 if (!cpu_has_tsc)
729 return 0;
730 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
731 return 0;
732 cpufreq_register_notifier(&time_cpufreq_notifier_block,
733 CPUFREQ_TRANSITION_NOTIFIER);
734 return 0;
735}
736
737core_initcall(cpufreq_tsc);
738
739#endif /* CONFIG_CPU_FREQ */
740
741/* clocksource code */
742
743static struct clocksource clocksource_tsc;
744
745/*
746 * We compare the TSC to the cycle_last value in the clocksource
747 * structure to avoid a nasty time-warp. This can be observed in a
748 * very small window right after one CPU updated cycle_last under
749 * xtime/vsyscall_gtod lock and the other CPU reads a TSC value which
750 * is smaller than the cycle_last reference value due to a TSC which
751 * is slighty behind. This delta is nowhere else observable, but in
752 * that case it results in a forward time jump in the range of hours
753 * due to the unsigned delta calculation of the time keeping core
754 * code, which is necessary to support wrapping clocksources like pm
755 * timer.
756 */
757static cycle_t read_tsc(struct clocksource *cs)
758{
759 cycle_t ret = (cycle_t)get_cycles();
760
761 return ret >= clocksource_tsc.cycle_last ?
762 ret : clocksource_tsc.cycle_last;
763}
764
765static void resume_tsc(struct clocksource *cs)
766{
767 clocksource_tsc.cycle_last = 0;
768}
769
770static struct clocksource clocksource_tsc = {
771 .name = "tsc",
772 .rating = 300,
773 .read = read_tsc,
774 .resume = resume_tsc,
775 .mask = CLOCKSOURCE_MASK(64),
776 .flags = CLOCK_SOURCE_IS_CONTINUOUS |
777 CLOCK_SOURCE_MUST_VERIFY,
778#ifdef CONFIG_X86_64
779 .archdata = { .vclock_mode = VCLOCK_TSC },
780#endif
781};
782
783void mark_tsc_unstable(char *reason)
784{
785 if (!tsc_unstable) {
786 tsc_unstable = 1;
787 sched_clock_stable = 0;
788 disable_sched_clock_irqtime();
789 printk(KERN_INFO "Marking TSC unstable due to %s\n", reason);
790 /* Change only the rating, when not registered */
791 if (clocksource_tsc.mult)
792 clocksource_mark_unstable(&clocksource_tsc);
793 else {
794 clocksource_tsc.flags |= CLOCK_SOURCE_UNSTABLE;
795 clocksource_tsc.rating = 0;
796 }
797 }
798}
799
800EXPORT_SYMBOL_GPL(mark_tsc_unstable);
801
802static void __init check_system_tsc_reliable(void)
803{
804#ifdef CONFIG_MGEODE_LX
805 /* RTSC counts during suspend */
806#define RTSC_SUSP 0x100
807 unsigned long res_low, res_high;
808
809 rdmsr_safe(MSR_GEODE_BUSCONT_CONF0, &res_low, &res_high);
810 /* Geode_LX - the OLPC CPU has a very reliable TSC */
811 if (res_low & RTSC_SUSP)
812 tsc_clocksource_reliable = 1;
813#endif
814 if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE))
815 tsc_clocksource_reliable = 1;
816}
817
818/*
819 * Make an educated guess if the TSC is trustworthy and synchronized
820 * over all CPUs.
821 */
822__cpuinit int unsynchronized_tsc(void)
823{
824 if (!cpu_has_tsc || tsc_unstable)
825 return 1;
826
827#ifdef CONFIG_SMP
828 if (apic_is_clustered_box())
829 return 1;
830#endif
831
832 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
833 return 0;
834
835 if (tsc_clocksource_reliable)
836 return 0;
837 /*
838 * Intel systems are normally all synchronized.
839 * Exceptions must mark TSC as unstable:
840 */
841 if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
842 /* assume multi socket systems are not synchronized: */
843 if (num_possible_cpus() > 1)
844 return 1;
845 }
846
847 return 0;
848}
849
850
851static void tsc_refine_calibration_work(struct work_struct *work);
852static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work);
853/**
854 * tsc_refine_calibration_work - Further refine tsc freq calibration
855 * @work - ignored.
856 *
857 * This functions uses delayed work over a period of a
858 * second to further refine the TSC freq value. Since this is
859 * timer based, instead of loop based, we don't block the boot
860 * process while this longer calibration is done.
861 *
862 * If there are any calibration anomalies (too many SMIs, etc),
863 * or the refined calibration is off by 1% of the fast early
864 * calibration, we throw out the new calibration and use the
865 * early calibration.
866 */
867static void tsc_refine_calibration_work(struct work_struct *work)
868{
869 static u64 tsc_start = -1, ref_start;
870 static int hpet;
871 u64 tsc_stop, ref_stop, delta;
872 unsigned long freq;
873
874 /* Don't bother refining TSC on unstable systems */
875 if (check_tsc_unstable())
876 goto out;
877
878 /*
879 * Since the work is started early in boot, we may be
880 * delayed the first time we expire. So set the workqueue
881 * again once we know timers are working.
882 */
883 if (tsc_start == -1) {
884 /*
885 * Only set hpet once, to avoid mixing hardware
886 * if the hpet becomes enabled later.
887 */
888 hpet = is_hpet_enabled();
889 schedule_delayed_work(&tsc_irqwork, HZ);
890 tsc_start = tsc_read_refs(&ref_start, hpet);
891 return;
892 }
893
894 tsc_stop = tsc_read_refs(&ref_stop, hpet);
895
896 /* hpet or pmtimer available ? */
897 if (ref_start == ref_stop)
898 goto out;
899
900 /* Check, whether the sampling was disturbed by an SMI */
901 if (tsc_start == ULLONG_MAX || tsc_stop == ULLONG_MAX)
902 goto out;
903
904 delta = tsc_stop - tsc_start;
905 delta *= 1000000LL;
906 if (hpet)
907 freq = calc_hpet_ref(delta, ref_start, ref_stop);
908 else
909 freq = calc_pmtimer_ref(delta, ref_start, ref_stop);
910
911 /* Make sure we're within 1% */
912 if (abs(tsc_khz - freq) > tsc_khz/100)
913 goto out;
914
915 tsc_khz = freq;
916 printk(KERN_INFO "Refined TSC clocksource calibration: "
917 "%lu.%03lu MHz.\n", (unsigned long)tsc_khz / 1000,
918 (unsigned long)tsc_khz % 1000);
919
920out:
921 clocksource_register_khz(&clocksource_tsc, tsc_khz);
922}
923
924
925static int __init init_tsc_clocksource(void)
926{
927 if (!cpu_has_tsc || tsc_disabled > 0 || !tsc_khz)
928 return 0;
929
930 if (tsc_clocksource_reliable)
931 clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
932 /* lower the rating if we already know its unstable: */
933 if (check_tsc_unstable()) {
934 clocksource_tsc.rating = 0;
935 clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
936 }
937 schedule_delayed_work(&tsc_irqwork, 0);
938 return 0;
939}
940/*
941 * We use device_initcall here, to ensure we run after the hpet
942 * is fully initialized, which may occur at fs_initcall time.
943 */
944device_initcall(init_tsc_clocksource);
945
946void __init tsc_init(void)
947{
948 u64 lpj;
949 int cpu;
950
951 x86_init.timers.tsc_pre_init();
952
953 if (!cpu_has_tsc)
954 return;
955
956 tsc_khz = x86_platform.calibrate_tsc();
957 cpu_khz = tsc_khz;
958
959 if (!tsc_khz) {
960 mark_tsc_unstable("could not calculate TSC khz");
961 return;
962 }
963
964 printk("Detected %lu.%03lu MHz processor.\n",
965 (unsigned long)cpu_khz / 1000,
966 (unsigned long)cpu_khz % 1000);
967
968 /*
969 * Secondary CPUs do not run through tsc_init(), so set up
970 * all the scale factors for all CPUs, assuming the same
971 * speed as the bootup CPU. (cpufreq notifiers will fix this
972 * up if their speed diverges)
973 */
974 for_each_possible_cpu(cpu)
975 set_cyc2ns_scale(cpu_khz, cpu);
976
977 if (tsc_disabled > 0)
978 return;
979
980 /* now allow native_sched_clock() to use rdtsc */
981 tsc_disabled = 0;
982
983 if (!no_sched_irq_time)
984 enable_sched_clock_irqtime();
985
986 lpj = ((u64)tsc_khz * 1000);
987 do_div(lpj, HZ);
988 lpj_fine = lpj;
989
990 use_tsc_delay();
991
992 if (unsynchronized_tsc())
993 mark_tsc_unstable("TSCs unsynchronized");
994
995 check_system_tsc_reliable();
996}
997