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 int __read_mostly tsc_force_recalibrate;
52
53static u32 art_to_tsc_numerator;
54static u32 art_to_tsc_denominator;
55static u64 art_to_tsc_offset;
56static bool have_art;
57
58struct cyc2ns {
59 struct cyc2ns_data data[2]; /* 0 + 2*16 = 32 */
60 seqcount_latch_t seq; /* 32 + 4 = 36 */
61
62}; /* fits one cacheline */
63
64static DEFINE_PER_CPU_ALIGNED(struct cyc2ns, cyc2ns);
65
66static int __init tsc_early_khz_setup(char *buf)
67{
68 return kstrtouint(s: buf, base: 0, res: &tsc_early_khz);
69}
70early_param("tsc_early_khz", tsc_early_khz_setup);
71
72__always_inline void __cyc2ns_read(struct cyc2ns_data *data)
73{
74 int seq, idx;
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_begin(struct cyc2ns_data *data)
88{
89 preempt_disable_notrace();
90 __cyc2ns_read(data);
91}
92
93__always_inline void cyc2ns_read_end(void)
94{
95 preempt_enable_notrace();
96}
97
98/*
99 * Accelerators for sched_clock()
100 * convert from cycles(64bits) => nanoseconds (64bits)
101 * basic equation:
102 * ns = cycles / (freq / ns_per_sec)
103 * ns = cycles * (ns_per_sec / freq)
104 * ns = cycles * (10^9 / (cpu_khz * 10^3))
105 * ns = cycles * (10^6 / cpu_khz)
106 *
107 * Then we use scaling math (suggested by george@mvista.com) to get:
108 * ns = cycles * (10^6 * SC / cpu_khz) / SC
109 * ns = cycles * cyc2ns_scale / SC
110 *
111 * And since SC is a constant power of two, we can convert the div
112 * into a shift. The larger SC is, the more accurate the conversion, but
113 * cyc2ns_scale needs to be a 32-bit value so that 32-bit multiplication
114 * (64-bit result) can be used.
115 *
116 * We can use khz divisor instead of mhz to keep a better precision.
117 * (mathieu.desnoyers@polymtl.ca)
118 *
119 * -johnstul@us.ibm.com "math is hard, lets go shopping!"
120 */
121
122static __always_inline unsigned long long __cycles_2_ns(unsigned long long cyc)
123{
124 struct cyc2ns_data data;
125 unsigned long long ns;
126
127 __cyc2ns_read(data: &data);
128
129 ns = data.cyc2ns_offset;
130 ns += mul_u64_u32_shr(a: cyc, mul: data.cyc2ns_mul, shift: data.cyc2ns_shift);
131
132 return ns;
133}
134
135static __always_inline unsigned long long cycles_2_ns(unsigned long long cyc)
136{
137 unsigned long long ns;
138 preempt_disable_notrace();
139 ns = __cycles_2_ns(cyc);
140 preempt_enable_notrace();
141 return ns;
142}
143
144static void __set_cyc2ns_scale(unsigned long khz, int cpu, unsigned long long tsc_now)
145{
146 unsigned long long ns_now;
147 struct cyc2ns_data data;
148 struct cyc2ns *c2n;
149
150 ns_now = cycles_2_ns(cyc: tsc_now);
151
152 /*
153 * Compute a new multiplier as per the above comment and ensure our
154 * time function is continuous; see the comment near struct
155 * cyc2ns_data.
156 */
157 clocks_calc_mult_shift(mult: &data.cyc2ns_mul, shift: &data.cyc2ns_shift, from: khz,
158 NSEC_PER_MSEC, minsec: 0);
159
160 /*
161 * cyc2ns_shift is exported via arch_perf_update_userpage() where it is
162 * not expected to be greater than 31 due to the original published
163 * conversion algorithm shifting a 32-bit value (now specifies a 64-bit
164 * value) - refer perf_event_mmap_page documentation in perf_event.h.
165 */
166 if (data.cyc2ns_shift == 32) {
167 data.cyc2ns_shift = 31;
168 data.cyc2ns_mul >>= 1;
169 }
170
171 data.cyc2ns_offset = ns_now -
172 mul_u64_u32_shr(a: tsc_now, mul: data.cyc2ns_mul, shift: data.cyc2ns_shift);
173
174 c2n = per_cpu_ptr(&cyc2ns, cpu);
175
176 raw_write_seqcount_latch(s: &c2n->seq);
177 c2n->data[0] = data;
178 raw_write_seqcount_latch(s: &c2n->seq);
179 c2n->data[1] = data;
180}
181
182static void set_cyc2ns_scale(unsigned long khz, int cpu, unsigned long long tsc_now)
183{
184 unsigned long flags;
185
186 local_irq_save(flags);
187 sched_clock_idle_sleep_event();
188
189 if (khz)
190 __set_cyc2ns_scale(khz, cpu, tsc_now);
191
192 sched_clock_idle_wakeup_event();
193 local_irq_restore(flags);
194}
195
196/*
197 * Initialize cyc2ns for boot cpu
198 */
199static void __init cyc2ns_init_boot_cpu(void)
200{
201 struct cyc2ns *c2n = this_cpu_ptr(&cyc2ns);
202
203 seqcount_latch_init(&c2n->seq);
204 __set_cyc2ns_scale(khz: tsc_khz, smp_processor_id(), tsc_now: rdtsc());
205}
206
207/*
208 * Secondary CPUs do not run through tsc_init(), so set up
209 * all the scale factors for all CPUs, assuming the same
210 * speed as the bootup CPU.
211 */
212static void __init cyc2ns_init_secondary_cpus(void)
213{
214 unsigned int cpu, this_cpu = smp_processor_id();
215 struct cyc2ns *c2n = this_cpu_ptr(&cyc2ns);
216 struct cyc2ns_data *data = c2n->data;
217
218 for_each_possible_cpu(cpu) {
219 if (cpu != this_cpu) {
220 seqcount_latch_init(&c2n->seq);
221 c2n = per_cpu_ptr(&cyc2ns, cpu);
222 c2n->data[0] = data[0];
223 c2n->data[1] = data[1];
224 }
225 }
226}
227
228/*
229 * Scheduler clock - returns current time in nanosec units.
230 */
231noinstr u64 native_sched_clock(void)
232{
233 if (static_branch_likely(&__use_tsc)) {
234 u64 tsc_now = rdtsc();
235
236 /* return the value in ns */
237 return __cycles_2_ns(cyc: tsc_now);
238 }
239
240 /*
241 * Fall back to jiffies if there's no TSC available:
242 * ( But note that we still use it if the TSC is marked
243 * unstable. We do this because unlike Time Of Day,
244 * the scheduler clock tolerates small errors and it's
245 * very important for it to be as fast as the platform
246 * can achieve it. )
247 */
248
249 /* No locking but a rare wrong value is not a big deal: */
250 return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
251}
252
253/*
254 * Generate a sched_clock if you already have a TSC value.
255 */
256u64 native_sched_clock_from_tsc(u64 tsc)
257{
258 return cycles_2_ns(cyc: tsc);
259}
260
261/* We need to define a real function for sched_clock, to override the
262 weak default version */
263#ifdef CONFIG_PARAVIRT
264noinstr u64 sched_clock_noinstr(void)
265{
266 return paravirt_sched_clock();
267}
268
269bool using_native_sched_clock(void)
270{
271 return static_call_query(pv_sched_clock) == native_sched_clock;
272}
273#else
274u64 sched_clock_noinstr(void) __attribute__((alias("native_sched_clock")));
275
276bool using_native_sched_clock(void) { return true; }
277#endif
278
279notrace u64 sched_clock(void)
280{
281 u64 now;
282 preempt_disable_notrace();
283 now = sched_clock_noinstr();
284 preempt_enable_notrace();
285 return now;
286}
287
288int check_tsc_unstable(void)
289{
290 return tsc_unstable;
291}
292EXPORT_SYMBOL_GPL(check_tsc_unstable);
293
294#ifdef CONFIG_X86_TSC
295int __init notsc_setup(char *str)
296{
297 mark_tsc_unstable(reason: "boot parameter notsc");
298 return 1;
299}
300#else
301/*
302 * disable flag for tsc. Takes effect by clearing the TSC cpu flag
303 * in cpu/common.c
304 */
305int __init notsc_setup(char *str)
306{
307 setup_clear_cpu_cap(X86_FEATURE_TSC);
308 return 1;
309}
310#endif
311
312__setup("notsc", notsc_setup);
313
314static int no_sched_irq_time;
315static int no_tsc_watchdog;
316static int tsc_as_watchdog;
317
318static int __init tsc_setup(char *str)
319{
320 if (!strcmp(str, "reliable"))
321 tsc_clocksource_reliable = 1;
322 if (!strncmp(str, "noirqtime", 9))
323 no_sched_irq_time = 1;
324 if (!strcmp(str, "unstable"))
325 mark_tsc_unstable(reason: "boot parameter");
326 if (!strcmp(str, "nowatchdog")) {
327 no_tsc_watchdog = 1;
328 if (tsc_as_watchdog)
329 pr_alert("%s: Overriding earlier tsc=watchdog with tsc=nowatchdog\n",
330 __func__);
331 tsc_as_watchdog = 0;
332 }
333 if (!strcmp(str, "recalibrate"))
334 tsc_force_recalibrate = 1;
335 if (!strcmp(str, "watchdog")) {
336 if (no_tsc_watchdog)
337 pr_alert("%s: tsc=watchdog overridden by earlier tsc=nowatchdog\n",
338 __func__);
339 else
340 tsc_as_watchdog = 1;
341 }
342 return 1;
343}
344
345__setup("tsc=", tsc_setup);
346
347#define MAX_RETRIES 5
348#define TSC_DEFAULT_THRESHOLD 0x20000
349
350/*
351 * Read TSC and the reference counters. Take care of any disturbances
352 */
353static u64 tsc_read_refs(u64 *p, int hpet)
354{
355 u64 t1, t2;
356 u64 thresh = tsc_khz ? tsc_khz >> 5 : TSC_DEFAULT_THRESHOLD;
357 int i;
358
359 for (i = 0; i < MAX_RETRIES; i++) {
360 t1 = get_cycles();
361 if (hpet)
362 *p = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF;
363 else
364 *p = acpi_pm_read_early();
365 t2 = get_cycles();
366 if ((t2 - t1) < thresh)
367 return t2;
368 }
369 return ULLONG_MAX;
370}
371
372/*
373 * Calculate the TSC frequency from HPET reference
374 */
375static unsigned long calc_hpet_ref(u64 deltatsc, u64 hpet1, u64 hpet2)
376{
377 u64 tmp;
378
379 if (hpet2 < hpet1)
380 hpet2 += 0x100000000ULL;
381 hpet2 -= hpet1;
382 tmp = ((u64)hpet2 * hpet_readl(HPET_PERIOD));
383 do_div(tmp, 1000000);
384 deltatsc = div64_u64(dividend: deltatsc, divisor: tmp);
385
386 return (unsigned long) deltatsc;
387}
388
389/*
390 * Calculate the TSC frequency from PMTimer reference
391 */
392static unsigned long calc_pmtimer_ref(u64 deltatsc, u64 pm1, u64 pm2)
393{
394 u64 tmp;
395
396 if (!pm1 && !pm2)
397 return ULONG_MAX;
398
399 if (pm2 < pm1)
400 pm2 += (u64)ACPI_PM_OVRRUN;
401 pm2 -= pm1;
402 tmp = pm2 * 1000000000LL;
403 do_div(tmp, PMTMR_TICKS_PER_SEC);
404 do_div(deltatsc, tmp);
405
406 return (unsigned long) deltatsc;
407}
408
409#define CAL_MS 10
410#define CAL_LATCH (PIT_TICK_RATE / (1000 / CAL_MS))
411#define CAL_PIT_LOOPS 1000
412
413#define CAL2_MS 50
414#define CAL2_LATCH (PIT_TICK_RATE / (1000 / CAL2_MS))
415#define CAL2_PIT_LOOPS 5000
416
417
418/*
419 * Try to calibrate the TSC against the Programmable
420 * Interrupt Timer and return the frequency of the TSC
421 * in kHz.
422 *
423 * Return ULONG_MAX on failure to calibrate.
424 */
425static unsigned long pit_calibrate_tsc(u32 latch, unsigned long ms, int loopmin)
426{
427 u64 tsc, t1, t2, delta;
428 unsigned long tscmin, tscmax;
429 int pitcnt;
430
431 if (!has_legacy_pic()) {
432 /*
433 * Relies on tsc_early_delay_calibrate() to have given us semi
434 * usable udelay(), wait for the same 50ms we would have with
435 * the PIT loop below.
436 */
437 udelay(10 * USEC_PER_MSEC);
438 udelay(10 * USEC_PER_MSEC);
439 udelay(10 * USEC_PER_MSEC);
440 udelay(10 * USEC_PER_MSEC);
441 udelay(10 * USEC_PER_MSEC);
442 return ULONG_MAX;
443 }
444
445 /* Set the Gate high, disable speaker */
446 outb(value: (inb(port: 0x61) & ~0x02) | 0x01, port: 0x61);
447
448 /*
449 * Setup CTC channel 2* for mode 0, (interrupt on terminal
450 * count mode), binary count. Set the latch register to 50ms
451 * (LSB then MSB) to begin countdown.
452 */
453 outb(value: 0xb0, port: 0x43);
454 outb(value: latch & 0xff, port: 0x42);
455 outb(value: latch >> 8, port: 0x42);
456
457 tsc = t1 = t2 = get_cycles();
458
459 pitcnt = 0;
460 tscmax = 0;
461 tscmin = ULONG_MAX;
462 while ((inb(port: 0x61) & 0x20) == 0) {
463 t2 = get_cycles();
464 delta = t2 - tsc;
465 tsc = t2;
466 if ((unsigned long) delta < tscmin)
467 tscmin = (unsigned int) delta;
468 if ((unsigned long) delta > tscmax)
469 tscmax = (unsigned int) delta;
470 pitcnt++;
471 }
472
473 /*
474 * Sanity checks:
475 *
476 * If we were not able to read the PIT more than loopmin
477 * times, then we have been hit by a massive SMI
478 *
479 * If the maximum is 10 times larger than the minimum,
480 * then we got hit by an SMI as well.
481 */
482 if (pitcnt < loopmin || tscmax > 10 * tscmin)
483 return ULONG_MAX;
484
485 /* Calculate the PIT value */
486 delta = t2 - t1;
487 do_div(delta, ms);
488 return delta;
489}
490
491/*
492 * This reads the current MSB of the PIT counter, and
493 * checks if we are running on sufficiently fast and
494 * non-virtualized hardware.
495 *
496 * Our expectations are:
497 *
498 * - the PIT is running at roughly 1.19MHz
499 *
500 * - each IO is going to take about 1us on real hardware,
501 * but we allow it to be much faster (by a factor of 10) or
502 * _slightly_ slower (ie we allow up to a 2us read+counter
503 * update - anything else implies a unacceptably slow CPU
504 * or PIT for the fast calibration to work.
505 *
506 * - with 256 PIT ticks to read the value, we have 214us to
507 * see the same MSB (and overhead like doing a single TSC
508 * read per MSB value etc).
509 *
510 * - We're doing 2 reads per loop (LSB, MSB), and we expect
511 * them each to take about a microsecond on real hardware.
512 * So we expect a count value of around 100. But we'll be
513 * generous, and accept anything over 50.
514 *
515 * - if the PIT is stuck, and we see *many* more reads, we
516 * return early (and the next caller of pit_expect_msb()
517 * then consider it a failure when they don't see the
518 * next expected value).
519 *
520 * These expectations mean that we know that we have seen the
521 * transition from one expected value to another with a fairly
522 * high accuracy, and we didn't miss any events. We can thus
523 * use the TSC value at the transitions to calculate a pretty
524 * good value for the TSC frequency.
525 */
526static inline int pit_verify_msb(unsigned char val)
527{
528 /* Ignore LSB */
529 inb(port: 0x42);
530 return inb(port: 0x42) == val;
531}
532
533static inline int pit_expect_msb(unsigned char val, u64 *tscp, unsigned long *deltap)
534{
535 int count;
536 u64 tsc = 0, prev_tsc = 0;
537
538 for (count = 0; count < 50000; count++) {
539 if (!pit_verify_msb(val))
540 break;
541 prev_tsc = tsc;
542 tsc = get_cycles();
543 }
544 *deltap = get_cycles() - prev_tsc;
545 *tscp = tsc;
546
547 /*
548 * We require _some_ success, but the quality control
549 * will be based on the error terms on the TSC values.
550 */
551 return count > 5;
552}
553
554/*
555 * How many MSB values do we want to see? We aim for
556 * a maximum error rate of 500ppm (in practice the
557 * real error is much smaller), but refuse to spend
558 * more than 50ms on it.
559 */
560#define MAX_QUICK_PIT_MS 50
561#define MAX_QUICK_PIT_ITERATIONS (MAX_QUICK_PIT_MS * PIT_TICK_RATE / 1000 / 256)
562
563static unsigned long quick_pit_calibrate(void)
564{
565 int i;
566 u64 tsc, delta;
567 unsigned long d1, d2;
568
569 if (!has_legacy_pic())
570 return 0;
571
572 /* Set the Gate high, disable speaker */
573 outb(value: (inb(port: 0x61) & ~0x02) | 0x01, port: 0x61);
574
575 /*
576 * Counter 2, mode 0 (one-shot), binary count
577 *
578 * NOTE! Mode 2 decrements by two (and then the
579 * output is flipped each time, giving the same
580 * final output frequency as a decrement-by-one),
581 * so mode 0 is much better when looking at the
582 * individual counts.
583 */
584 outb(value: 0xb0, port: 0x43);
585
586 /* Start at 0xffff */
587 outb(value: 0xff, port: 0x42);
588 outb(value: 0xff, port: 0x42);
589
590 /*
591 * The PIT starts counting at the next edge, so we
592 * need to delay for a microsecond. The easiest way
593 * to do that is to just read back the 16-bit counter
594 * once from the PIT.
595 */
596 pit_verify_msb(val: 0);
597
598 if (pit_expect_msb(val: 0xff, tscp: &tsc, deltap: &d1)) {
599 for (i = 1; i <= MAX_QUICK_PIT_ITERATIONS; i++) {
600 if (!pit_expect_msb(val: 0xff-i, tscp: &delta, deltap: &d2))
601 break;
602
603 delta -= tsc;
604
605 /*
606 * Extrapolate the error and fail fast if the error will
607 * never be below 500 ppm.
608 */
609 if (i == 1 &&
610 d1 + d2 >= (delta * MAX_QUICK_PIT_ITERATIONS) >> 11)
611 return 0;
612
613 /*
614 * Iterate until the error is less than 500 ppm
615 */
616 if (d1+d2 >= delta >> 11)
617 continue;
618
619 /*
620 * Check the PIT one more time to verify that
621 * all TSC reads were stable wrt the PIT.
622 *
623 * This also guarantees serialization of the
624 * last cycle read ('d2') in pit_expect_msb.
625 */
626 if (!pit_verify_msb(val: 0xfe - i))
627 break;
628 goto success;
629 }
630 }
631 pr_info("Fast TSC calibration failed\n");
632 return 0;
633
634success:
635 /*
636 * Ok, if we get here, then we've seen the
637 * MSB of the PIT decrement 'i' times, and the
638 * error has shrunk to less than 500 ppm.
639 *
640 * As a result, we can depend on there not being
641 * any odd delays anywhere, and the TSC reads are
642 * reliable (within the error).
643 *
644 * kHz = ticks / time-in-seconds / 1000;
645 * kHz = (t2 - t1) / (I * 256 / PIT_TICK_RATE) / 1000
646 * kHz = ((t2 - t1) * PIT_TICK_RATE) / (I * 256 * 1000)
647 */
648 delta *= PIT_TICK_RATE;
649 do_div(delta, i*256*1000);
650 pr_info("Fast TSC calibration using PIT\n");
651 return delta;
652}
653
654/**
655 * native_calibrate_tsc - determine TSC frequency
656 * Determine TSC frequency via CPUID, else return 0.
657 */
658unsigned long native_calibrate_tsc(void)
659{
660 unsigned int eax_denominator, ebx_numerator, ecx_hz, edx;
661 unsigned int crystal_khz;
662
663 if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
664 return 0;
665
666 if (boot_cpu_data.cpuid_level < 0x15)
667 return 0;
668
669 eax_denominator = ebx_numerator = ecx_hz = edx = 0;
670
671 /* CPUID 15H TSC/Crystal ratio, plus optionally Crystal Hz */
672 cpuid(op: 0x15, eax: &eax_denominator, ebx: &ebx_numerator, ecx: &ecx_hz, edx: &edx);
673
674 if (ebx_numerator == 0 || eax_denominator == 0)
675 return 0;
676
677 crystal_khz = ecx_hz / 1000;
678
679 /*
680 * Denverton SoCs don't report crystal clock, and also don't support
681 * CPUID.0x16 for the calculation below, so hardcode the 25MHz crystal
682 * clock.
683 */
684 if (crystal_khz == 0 &&
685 boot_cpu_data.x86_model == INTEL_FAM6_ATOM_GOLDMONT_D)
686 crystal_khz = 25000;
687
688 /*
689 * TSC frequency reported directly by CPUID is a "hardware reported"
690 * frequency and is the most accurate one so far we have. This
691 * is considered a known frequency.
692 */
693 if (crystal_khz != 0)
694 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
695
696 /*
697 * Some Intel SoCs like Skylake and Kabylake don't report the crystal
698 * clock, but we can easily calculate it to a high degree of accuracy
699 * by considering the crystal ratio and the CPU speed.
700 */
701 if (crystal_khz == 0 && boot_cpu_data.cpuid_level >= 0x16) {
702 unsigned int eax_base_mhz, ebx, ecx, edx;
703
704 cpuid(op: 0x16, eax: &eax_base_mhz, ebx: &ebx, ecx: &ecx, edx: &edx);
705 crystal_khz = eax_base_mhz * 1000 *
706 eax_denominator / ebx_numerator;
707 }
708
709 if (crystal_khz == 0)
710 return 0;
711
712 /*
713 * For Atom SoCs TSC is the only reliable clocksource.
714 * Mark TSC reliable so no watchdog on it.
715 */
716 if (boot_cpu_data.x86_model == INTEL_FAM6_ATOM_GOLDMONT)
717 setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
718
719#ifdef CONFIG_X86_LOCAL_APIC
720 /*
721 * The local APIC appears to be fed by the core crystal clock
722 * (which sounds entirely sensible). We can set the global
723 * lapic_timer_period here to avoid having to calibrate the APIC
724 * timer later.
725 */
726 lapic_timer_period = crystal_khz * 1000 / HZ;
727#endif
728
729 return crystal_khz * ebx_numerator / eax_denominator;
730}
731
732static unsigned long cpu_khz_from_cpuid(void)
733{
734 unsigned int eax_base_mhz, ebx_max_mhz, ecx_bus_mhz, edx;
735
736 if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
737 return 0;
738
739 if (boot_cpu_data.cpuid_level < 0x16)
740 return 0;
741
742 eax_base_mhz = ebx_max_mhz = ecx_bus_mhz = edx = 0;
743
744 cpuid(op: 0x16, eax: &eax_base_mhz, ebx: &ebx_max_mhz, ecx: &ecx_bus_mhz, edx: &edx);
745
746 return eax_base_mhz * 1000;
747}
748
749/*
750 * calibrate cpu using pit, hpet, and ptimer methods. They are available
751 * later in boot after acpi is initialized.
752 */
753static unsigned long pit_hpet_ptimer_calibrate_cpu(void)
754{
755 u64 tsc1, tsc2, delta, ref1, ref2;
756 unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX;
757 unsigned long flags, latch, ms;
758 int hpet = is_hpet_enabled(), i, loopmin;
759
760 /*
761 * Run 5 calibration loops to get the lowest frequency value
762 * (the best estimate). We use two different calibration modes
763 * here:
764 *
765 * 1) PIT loop. We set the PIT Channel 2 to oneshot mode and
766 * load a timeout of 50ms. We read the time right after we
767 * started the timer and wait until the PIT count down reaches
768 * zero. In each wait loop iteration we read the TSC and check
769 * the delta to the previous read. We keep track of the min
770 * and max values of that delta. The delta is mostly defined
771 * by the IO time of the PIT access, so we can detect when
772 * any disturbance happened between the two reads. If the
773 * maximum time is significantly larger than the minimum time,
774 * then we discard the result and have another try.
775 *
776 * 2) Reference counter. If available we use the HPET or the
777 * PMTIMER as a reference to check the sanity of that value.
778 * We use separate TSC readouts and check inside of the
779 * reference read for any possible disturbance. We discard
780 * disturbed values here as well. We do that around the PIT
781 * calibration delay loop as we have to wait for a certain
782 * amount of time anyway.
783 */
784
785 /* Preset PIT loop values */
786 latch = CAL_LATCH;
787 ms = CAL_MS;
788 loopmin = CAL_PIT_LOOPS;
789
790 for (i = 0; i < 3; i++) {
791 unsigned long tsc_pit_khz;
792
793 /*
794 * Read the start value and the reference count of
795 * hpet/pmtimer when available. Then do the PIT
796 * calibration, which will take at least 50ms, and
797 * read the end value.
798 */
799 local_irq_save(flags);
800 tsc1 = tsc_read_refs(p: &ref1, hpet);
801 tsc_pit_khz = pit_calibrate_tsc(latch, ms, loopmin);
802 tsc2 = tsc_read_refs(p: &ref2, hpet);
803 local_irq_restore(flags);
804
805 /* Pick the lowest PIT TSC calibration so far */
806 tsc_pit_min = min(tsc_pit_min, tsc_pit_khz);
807
808 /* hpet or pmtimer available ? */
809 if (ref1 == ref2)
810 continue;
811
812 /* Check, whether the sampling was disturbed */
813 if (tsc1 == ULLONG_MAX || tsc2 == ULLONG_MAX)
814 continue;
815
816 tsc2 = (tsc2 - tsc1) * 1000000LL;
817 if (hpet)
818 tsc2 = calc_hpet_ref(deltatsc: tsc2, hpet1: ref1, hpet2: ref2);
819 else
820 tsc2 = calc_pmtimer_ref(deltatsc: tsc2, pm1: ref1, pm2: ref2);
821
822 tsc_ref_min = min(tsc_ref_min, (unsigned long) tsc2);
823
824 /* Check the reference deviation */
825 delta = ((u64) tsc_pit_min) * 100;
826 do_div(delta, tsc_ref_min);
827
828 /*
829 * If both calibration results are inside a 10% window
830 * then we can be sure, that the calibration
831 * succeeded. We break out of the loop right away. We
832 * use the reference value, as it is more precise.
833 */
834 if (delta >= 90 && delta <= 110) {
835 pr_info("PIT calibration matches %s. %d loops\n",
836 hpet ? "HPET" : "PMTIMER", i + 1);
837 return tsc_ref_min;
838 }
839
840 /*
841 * Check whether PIT failed more than once. This
842 * happens in virtualized environments. We need to
843 * give the virtual PC a slightly longer timeframe for
844 * the HPET/PMTIMER to make the result precise.
845 */
846 if (i == 1 && tsc_pit_min == ULONG_MAX) {
847 latch = CAL2_LATCH;
848 ms = CAL2_MS;
849 loopmin = CAL2_PIT_LOOPS;
850 }
851 }
852
853 /*
854 * Now check the results.
855 */
856 if (tsc_pit_min == ULONG_MAX) {
857 /* PIT gave no useful value */
858 pr_warn("Unable to calibrate against PIT\n");
859
860 /* We don't have an alternative source, disable TSC */
861 if (!hpet && !ref1 && !ref2) {
862 pr_notice("No reference (HPET/PMTIMER) available\n");
863 return 0;
864 }
865
866 /* The alternative source failed as well, disable TSC */
867 if (tsc_ref_min == ULONG_MAX) {
868 pr_warn("HPET/PMTIMER calibration failed\n");
869 return 0;
870 }
871
872 /* Use the alternative source */
873 pr_info("using %s reference calibration\n",
874 hpet ? "HPET" : "PMTIMER");
875
876 return tsc_ref_min;
877 }
878
879 /* We don't have an alternative source, use the PIT calibration value */
880 if (!hpet && !ref1 && !ref2) {
881 pr_info("Using PIT calibration value\n");
882 return tsc_pit_min;
883 }
884
885 /* The alternative source failed, use the PIT calibration value */
886 if (tsc_ref_min == ULONG_MAX) {
887 pr_warn("HPET/PMTIMER calibration failed. Using PIT calibration.\n");
888 return tsc_pit_min;
889 }
890
891 /*
892 * The calibration values differ too much. In doubt, we use
893 * the PIT value as we know that there are PMTIMERs around
894 * running at double speed. At least we let the user know:
895 */
896 pr_warn("PIT calibration deviates from %s: %lu %lu\n",
897 hpet ? "HPET" : "PMTIMER", tsc_pit_min, tsc_ref_min);
898 pr_info("Using PIT calibration value\n");
899 return tsc_pit_min;
900}
901
902/**
903 * native_calibrate_cpu_early - can calibrate the cpu early in boot
904 */
905unsigned long native_calibrate_cpu_early(void)
906{
907 unsigned long flags, fast_calibrate = cpu_khz_from_cpuid();
908
909 if (!fast_calibrate)
910 fast_calibrate = cpu_khz_from_msr();
911 if (!fast_calibrate) {
912 local_irq_save(flags);
913 fast_calibrate = quick_pit_calibrate();
914 local_irq_restore(flags);
915 }
916 return fast_calibrate;
917}
918
919
920/**
921 * native_calibrate_cpu - calibrate the cpu
922 */
923static unsigned long native_calibrate_cpu(void)
924{
925 unsigned long tsc_freq = native_calibrate_cpu_early();
926
927 if (!tsc_freq)
928 tsc_freq = pit_hpet_ptimer_calibrate_cpu();
929
930 return tsc_freq;
931}
932
933void recalibrate_cpu_khz(void)
934{
935#ifndef CONFIG_SMP
936 unsigned long cpu_khz_old = cpu_khz;
937
938 if (!boot_cpu_has(X86_FEATURE_TSC))
939 return;
940
941 cpu_khz = x86_platform.calibrate_cpu();
942 tsc_khz = x86_platform.calibrate_tsc();
943 if (tsc_khz == 0)
944 tsc_khz = cpu_khz;
945 else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
946 cpu_khz = tsc_khz;
947 cpu_data(0).loops_per_jiffy = cpufreq_scale(cpu_data(0).loops_per_jiffy,
948 cpu_khz_old, cpu_khz);
949#endif
950}
951EXPORT_SYMBOL_GPL(recalibrate_cpu_khz);
952
953
954static unsigned long long cyc2ns_suspend;
955
956void tsc_save_sched_clock_state(void)
957{
958 if (!sched_clock_stable())
959 return;
960
961 cyc2ns_suspend = sched_clock();
962}
963
964/*
965 * Even on processors with invariant TSC, TSC gets reset in some the
966 * ACPI system sleep states. And in some systems BIOS seem to reinit TSC to
967 * arbitrary value (still sync'd across cpu's) during resume from such sleep
968 * states. To cope up with this, recompute the cyc2ns_offset for each cpu so
969 * that sched_clock() continues from the point where it was left off during
970 * suspend.
971 */
972void tsc_restore_sched_clock_state(void)
973{
974 unsigned long long offset;
975 unsigned long flags;
976 int cpu;
977
978 if (!sched_clock_stable())
979 return;
980
981 local_irq_save(flags);
982
983 /*
984 * We're coming out of suspend, there's no concurrency yet; don't
985 * bother being nice about the RCU stuff, just write to both
986 * data fields.
987 */
988
989 this_cpu_write(cyc2ns.data[0].cyc2ns_offset, 0);
990 this_cpu_write(cyc2ns.data[1].cyc2ns_offset, 0);
991
992 offset = cyc2ns_suspend - sched_clock();
993
994 for_each_possible_cpu(cpu) {
995 per_cpu(cyc2ns.data[0].cyc2ns_offset, cpu) = offset;
996 per_cpu(cyc2ns.data[1].cyc2ns_offset, cpu) = offset;
997 }
998
999 local_irq_restore(flags);
1000}
1001
1002#ifdef CONFIG_CPU_FREQ
1003/*
1004 * Frequency scaling support. Adjust the TSC based timer when the CPU frequency
1005 * changes.
1006 *
1007 * NOTE: On SMP the situation is not fixable in general, so simply mark the TSC
1008 * as unstable and give up in those cases.
1009 *
1010 * Should fix up last_tsc too. Currently gettimeofday in the
1011 * first tick after the change will be slightly wrong.
1012 */
1013
1014static unsigned int ref_freq;
1015static unsigned long loops_per_jiffy_ref;
1016static unsigned long tsc_khz_ref;
1017
1018static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
1019 void *data)
1020{
1021 struct cpufreq_freqs *freq = data;
1022
1023 if (num_online_cpus() > 1) {
1024 mark_tsc_unstable(reason: "cpufreq changes on SMP");
1025 return 0;
1026 }
1027
1028 if (!ref_freq) {
1029 ref_freq = freq->old;
1030 loops_per_jiffy_ref = boot_cpu_data.loops_per_jiffy;
1031 tsc_khz_ref = tsc_khz;
1032 }
1033
1034 if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) ||
1035 (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) {
1036 boot_cpu_data.loops_per_jiffy =
1037 cpufreq_scale(old: loops_per_jiffy_ref, div: ref_freq, mult: freq->new);
1038
1039 tsc_khz = cpufreq_scale(old: tsc_khz_ref, div: ref_freq, mult: freq->new);
1040 if (!(freq->flags & CPUFREQ_CONST_LOOPS))
1041 mark_tsc_unstable(reason: "cpufreq changes");
1042
1043 set_cyc2ns_scale(khz: tsc_khz, cpu: freq->policy->cpu, tsc_now: rdtsc());
1044 }
1045
1046 return 0;
1047}
1048
1049static struct notifier_block time_cpufreq_notifier_block = {
1050 .notifier_call = time_cpufreq_notifier
1051};
1052
1053static int __init cpufreq_register_tsc_scaling(void)
1054{
1055 if (!boot_cpu_has(X86_FEATURE_TSC))
1056 return 0;
1057 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
1058 return 0;
1059 cpufreq_register_notifier(nb: &time_cpufreq_notifier_block,
1060 CPUFREQ_TRANSITION_NOTIFIER);
1061 return 0;
1062}
1063
1064core_initcall(cpufreq_register_tsc_scaling);
1065
1066#endif /* CONFIG_CPU_FREQ */
1067
1068#define ART_CPUID_LEAF (0x15)
1069#define ART_MIN_DENOMINATOR (1)
1070
1071
1072/*
1073 * If ART is present detect the numerator:denominator to convert to TSC
1074 */
1075static void __init detect_art(void)
1076{
1077 unsigned int unused[2];
1078
1079 if (boot_cpu_data.cpuid_level < ART_CPUID_LEAF)
1080 return;
1081
1082 /*
1083 * Don't enable ART in a VM, non-stop TSC and TSC_ADJUST required,
1084 * and the TSC counter resets must not occur asynchronously.
1085 */
1086 if (boot_cpu_has(X86_FEATURE_HYPERVISOR) ||
1087 !boot_cpu_has(X86_FEATURE_NONSTOP_TSC) ||
1088 !boot_cpu_has(X86_FEATURE_TSC_ADJUST) ||
1089 tsc_async_resets)
1090 return;
1091
1092 cpuid(ART_CPUID_LEAF, eax: &art_to_tsc_denominator,
1093 ebx: &art_to_tsc_numerator, ecx: unused, edx: unused+1);
1094
1095 if (art_to_tsc_denominator < ART_MIN_DENOMINATOR)
1096 return;
1097
1098 rdmsrl(MSR_IA32_TSC_ADJUST, art_to_tsc_offset);
1099
1100 /* Make this sticky over multiple CPU init calls */
1101 setup_force_cpu_cap(X86_FEATURE_ART);
1102}
1103
1104
1105/* clocksource code */
1106
1107static void tsc_resume(struct clocksource *cs)
1108{
1109 tsc_verify_tsc_adjust(resume: true);
1110}
1111
1112/*
1113 * We used to compare the TSC to the cycle_last value in the clocksource
1114 * structure to avoid a nasty time-warp. This can be observed in a
1115 * very small window right after one CPU updated cycle_last under
1116 * xtime/vsyscall_gtod lock and the other CPU reads a TSC value which
1117 * is smaller than the cycle_last reference value due to a TSC which
1118 * is slightly behind. This delta is nowhere else observable, but in
1119 * that case it results in a forward time jump in the range of hours
1120 * due to the unsigned delta calculation of the time keeping core
1121 * code, which is necessary to support wrapping clocksources like pm
1122 * timer.
1123 *
1124 * This sanity check is now done in the core timekeeping code.
1125 * checking the result of read_tsc() - cycle_last for being negative.
1126 * That works because CLOCKSOURCE_MASK(64) does not mask out any bit.
1127 */
1128static u64 read_tsc(struct clocksource *cs)
1129{
1130 return (u64)rdtsc_ordered();
1131}
1132
1133static void tsc_cs_mark_unstable(struct clocksource *cs)
1134{
1135 if (tsc_unstable)
1136 return;
1137
1138 tsc_unstable = 1;
1139 if (using_native_sched_clock())
1140 clear_sched_clock_stable();
1141 disable_sched_clock_irqtime();
1142 pr_info("Marking TSC unstable due to clocksource watchdog\n");
1143}
1144
1145static void tsc_cs_tick_stable(struct clocksource *cs)
1146{
1147 if (tsc_unstable)
1148 return;
1149
1150 if (using_native_sched_clock())
1151 sched_clock_tick_stable();
1152}
1153
1154static int tsc_cs_enable(struct clocksource *cs)
1155{
1156 vclocks_set_used(which: VDSO_CLOCKMODE_TSC);
1157 return 0;
1158}
1159
1160/*
1161 * .mask MUST be CLOCKSOURCE_MASK(64). See comment above read_tsc()
1162 */
1163static struct clocksource clocksource_tsc_early = {
1164 .name = "tsc-early",
1165 .rating = 299,
1166 .uncertainty_margin = 32 * NSEC_PER_MSEC,
1167 .read = read_tsc,
1168 .mask = CLOCKSOURCE_MASK(64),
1169 .flags = CLOCK_SOURCE_IS_CONTINUOUS |
1170 CLOCK_SOURCE_MUST_VERIFY,
1171 .id = CSID_X86_TSC_EARLY,
1172 .vdso_clock_mode = VDSO_CLOCKMODE_TSC,
1173 .enable = tsc_cs_enable,
1174 .resume = tsc_resume,
1175 .mark_unstable = tsc_cs_mark_unstable,
1176 .tick_stable = tsc_cs_tick_stable,
1177 .list = LIST_HEAD_INIT(clocksource_tsc_early.list),
1178};
1179
1180/*
1181 * Must mark VALID_FOR_HRES early such that when we unregister tsc_early
1182 * this one will immediately take over. We will only register if TSC has
1183 * been found good.
1184 */
1185static struct clocksource clocksource_tsc = {
1186 .name = "tsc",
1187 .rating = 300,
1188 .read = read_tsc,
1189 .mask = CLOCKSOURCE_MASK(64),
1190 .flags = CLOCK_SOURCE_IS_CONTINUOUS |
1191 CLOCK_SOURCE_VALID_FOR_HRES |
1192 CLOCK_SOURCE_MUST_VERIFY |
1193 CLOCK_SOURCE_VERIFY_PERCPU,
1194 .id = CSID_X86_TSC,
1195 .vdso_clock_mode = VDSO_CLOCKMODE_TSC,
1196 .enable = tsc_cs_enable,
1197 .resume = tsc_resume,
1198 .mark_unstable = tsc_cs_mark_unstable,
1199 .tick_stable = tsc_cs_tick_stable,
1200 .list = LIST_HEAD_INIT(clocksource_tsc.list),
1201};
1202
1203void mark_tsc_unstable(char *reason)
1204{
1205 if (tsc_unstable)
1206 return;
1207
1208 tsc_unstable = 1;
1209 if (using_native_sched_clock())
1210 clear_sched_clock_stable();
1211 disable_sched_clock_irqtime();
1212 pr_info("Marking TSC unstable due to %s\n", reason);
1213
1214 clocksource_mark_unstable(cs: &clocksource_tsc_early);
1215 clocksource_mark_unstable(cs: &clocksource_tsc);
1216}
1217
1218EXPORT_SYMBOL_GPL(mark_tsc_unstable);
1219
1220static void __init tsc_disable_clocksource_watchdog(void)
1221{
1222 clocksource_tsc_early.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
1223 clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
1224}
1225
1226bool tsc_clocksource_watchdog_disabled(void)
1227{
1228 return !(clocksource_tsc.flags & CLOCK_SOURCE_MUST_VERIFY) &&
1229 tsc_as_watchdog && !no_tsc_watchdog;
1230}
1231
1232static void __init check_system_tsc_reliable(void)
1233{
1234#if defined(CONFIG_MGEODEGX1) || defined(CONFIG_MGEODE_LX) || defined(CONFIG_X86_GENERIC)
1235 if (is_geode_lx()) {
1236 /* RTSC counts during suspend */
1237#define RTSC_SUSP 0x100
1238 unsigned long res_low, res_high;
1239
1240 rdmsr_safe(MSR_GEODE_BUSCONT_CONF0, &res_low, &res_high);
1241 /* Geode_LX - the OLPC CPU has a very reliable TSC */
1242 if (res_low & RTSC_SUSP)
1243 tsc_clocksource_reliable = 1;
1244 }
1245#endif
1246 if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE))
1247 tsc_clocksource_reliable = 1;
1248
1249 /*
1250 * Disable the clocksource watchdog when the system has:
1251 * - TSC running at constant frequency
1252 * - TSC which does not stop in C-States
1253 * - the TSC_ADJUST register which allows to detect even minimal
1254 * modifications
1255 * - not more than two sockets. As the number of sockets cannot be
1256 * evaluated at the early boot stage where this has to be
1257 * invoked, check the number of online memory nodes as a
1258 * fallback solution which is an reasonable estimate.
1259 */
1260 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
1261 boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
1262 boot_cpu_has(X86_FEATURE_TSC_ADJUST) &&
1263 nr_online_nodes <= 4)
1264 tsc_disable_clocksource_watchdog();
1265}
1266
1267/*
1268 * Make an educated guess if the TSC is trustworthy and synchronized
1269 * over all CPUs.
1270 */
1271int unsynchronized_tsc(void)
1272{
1273 if (!boot_cpu_has(X86_FEATURE_TSC) || tsc_unstable)
1274 return 1;
1275
1276#ifdef CONFIG_SMP
1277 if (apic_is_clustered_box())
1278 return 1;
1279#endif
1280
1281 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
1282 return 0;
1283
1284 if (tsc_clocksource_reliable)
1285 return 0;
1286 /*
1287 * Intel systems are normally all synchronized.
1288 * Exceptions must mark TSC as unstable:
1289 */
1290 if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
1291 /* assume multi socket systems are not synchronized: */
1292 if (num_possible_cpus() > 1)
1293 return 1;
1294 }
1295
1296 return 0;
1297}
1298
1299/*
1300 * Convert ART to TSC given numerator/denominator found in detect_art()
1301 */
1302struct system_counterval_t convert_art_to_tsc(u64 art)
1303{
1304 u64 tmp, res, rem;
1305
1306 rem = do_div(art, art_to_tsc_denominator);
1307
1308 res = art * art_to_tsc_numerator;
1309 tmp = rem * art_to_tsc_numerator;
1310
1311 do_div(tmp, art_to_tsc_denominator);
1312 res += tmp + art_to_tsc_offset;
1313
1314 return (struct system_counterval_t) {
1315 .cs_id = have_art ? CSID_X86_TSC : CSID_GENERIC,
1316 .cycles = res,
1317 };
1318}
1319EXPORT_SYMBOL(convert_art_to_tsc);
1320
1321/**
1322 * convert_art_ns_to_tsc() - Convert ART in nanoseconds to TSC.
1323 * @art_ns: ART (Always Running Timer) in unit of nanoseconds
1324 *
1325 * PTM requires all timestamps to be in units of nanoseconds. When user
1326 * software requests a cross-timestamp, this function converts system timestamp
1327 * to TSC.
1328 *
1329 * This is valid when CPU feature flag X86_FEATURE_TSC_KNOWN_FREQ is set
1330 * indicating the tsc_khz is derived from CPUID[15H]. Drivers should check
1331 * that this flag is set before conversion to TSC is attempted.
1332 *
1333 * Return:
1334 * struct system_counterval_t - system counter value with the ID of the
1335 * corresponding clocksource:
1336 * cycles: System counter value
1337 * cs_id: The clocksource ID for validating comparability
1338 */
1339
1340struct system_counterval_t convert_art_ns_to_tsc(u64 art_ns)
1341{
1342 u64 tmp, res, rem;
1343
1344 rem = do_div(art_ns, USEC_PER_SEC);
1345
1346 res = art_ns * tsc_khz;
1347 tmp = rem * tsc_khz;
1348
1349 do_div(tmp, USEC_PER_SEC);
1350 res += tmp;
1351
1352 return (struct system_counterval_t) {
1353 .cs_id = have_art ? CSID_X86_TSC : CSID_GENERIC,
1354 .cycles = res,
1355 };
1356}
1357EXPORT_SYMBOL(convert_art_ns_to_tsc);
1358
1359
1360static void tsc_refine_calibration_work(struct work_struct *work);
1361static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work);
1362/**
1363 * tsc_refine_calibration_work - Further refine tsc freq calibration
1364 * @work: ignored.
1365 *
1366 * This functions uses delayed work over a period of a
1367 * second to further refine the TSC freq value. Since this is
1368 * timer based, instead of loop based, we don't block the boot
1369 * process while this longer calibration is done.
1370 *
1371 * If there are any calibration anomalies (too many SMIs, etc),
1372 * or the refined calibration is off by 1% of the fast early
1373 * calibration, we throw out the new calibration and use the
1374 * early calibration.
1375 */
1376static void tsc_refine_calibration_work(struct work_struct *work)
1377{
1378 static u64 tsc_start = ULLONG_MAX, ref_start;
1379 static int hpet;
1380 u64 tsc_stop, ref_stop, delta;
1381 unsigned long freq;
1382 int cpu;
1383
1384 /* Don't bother refining TSC on unstable systems */
1385 if (tsc_unstable)
1386 goto unreg;
1387
1388 /*
1389 * Since the work is started early in boot, we may be
1390 * delayed the first time we expire. So set the workqueue
1391 * again once we know timers are working.
1392 */
1393 if (tsc_start == ULLONG_MAX) {
1394restart:
1395 /*
1396 * Only set hpet once, to avoid mixing hardware
1397 * if the hpet becomes enabled later.
1398 */
1399 hpet = is_hpet_enabled();
1400 tsc_start = tsc_read_refs(p: &ref_start, hpet);
1401 schedule_delayed_work(dwork: &tsc_irqwork, HZ);
1402 return;
1403 }
1404
1405 tsc_stop = tsc_read_refs(p: &ref_stop, hpet);
1406
1407 /* hpet or pmtimer available ? */
1408 if (ref_start == ref_stop)
1409 goto out;
1410
1411 /* Check, whether the sampling was disturbed */
1412 if (tsc_stop == ULLONG_MAX)
1413 goto restart;
1414
1415 delta = tsc_stop - tsc_start;
1416 delta *= 1000000LL;
1417 if (hpet)
1418 freq = calc_hpet_ref(deltatsc: delta, hpet1: ref_start, hpet2: ref_stop);
1419 else
1420 freq = calc_pmtimer_ref(deltatsc: delta, pm1: ref_start, pm2: ref_stop);
1421
1422 /* Will hit this only if tsc_force_recalibrate has been set */
1423 if (boot_cpu_has(X86_FEATURE_TSC_KNOWN_FREQ)) {
1424
1425 /* Warn if the deviation exceeds 500 ppm */
1426 if (abs(tsc_khz - freq) > (tsc_khz >> 11)) {
1427 pr_warn("Warning: TSC freq calibrated by CPUID/MSR differs from what is calibrated by HW timer, please check with vendor!!\n");
1428 pr_info("Previous calibrated TSC freq:\t %lu.%03lu MHz\n",
1429 (unsigned long)tsc_khz / 1000,
1430 (unsigned long)tsc_khz % 1000);
1431 }
1432
1433 pr_info("TSC freq recalibrated by [%s]:\t %lu.%03lu MHz\n",
1434 hpet ? "HPET" : "PM_TIMER",
1435 (unsigned long)freq / 1000,
1436 (unsigned long)freq % 1000);
1437
1438 return;
1439 }
1440
1441 /* Make sure we're within 1% */
1442 if (abs(tsc_khz - freq) > tsc_khz/100)
1443 goto out;
1444
1445 tsc_khz = freq;
1446 pr_info("Refined TSC clocksource calibration: %lu.%03lu MHz\n",
1447 (unsigned long)tsc_khz / 1000,
1448 (unsigned long)tsc_khz % 1000);
1449
1450 /* Inform the TSC deadline clockevent devices about the recalibration */
1451 lapic_update_tsc_freq();
1452
1453 /* Update the sched_clock() rate to match the clocksource one */
1454 for_each_possible_cpu(cpu)
1455 set_cyc2ns_scale(khz: tsc_khz, cpu, tsc_now: tsc_stop);
1456
1457out:
1458 if (tsc_unstable)
1459 goto unreg;
1460
1461 if (boot_cpu_has(X86_FEATURE_ART))
1462 have_art = true;
1463 clocksource_register_khz(cs: &clocksource_tsc, khz: tsc_khz);
1464unreg:
1465 clocksource_unregister(&clocksource_tsc_early);
1466}
1467
1468
1469static int __init init_tsc_clocksource(void)
1470{
1471 if (!boot_cpu_has(X86_FEATURE_TSC) || !tsc_khz)
1472 return 0;
1473
1474 if (tsc_unstable) {
1475 clocksource_unregister(&clocksource_tsc_early);
1476 return 0;
1477 }
1478
1479 if (boot_cpu_has(X86_FEATURE_NONSTOP_TSC_S3))
1480 clocksource_tsc.flags |= CLOCK_SOURCE_SUSPEND_NONSTOP;
1481
1482 /*
1483 * When TSC frequency is known (retrieved via MSR or CPUID), we skip
1484 * the refined calibration and directly register it as a clocksource.
1485 */
1486 if (boot_cpu_has(X86_FEATURE_TSC_KNOWN_FREQ)) {
1487 if (boot_cpu_has(X86_FEATURE_ART))
1488 have_art = true;
1489 clocksource_register_khz(cs: &clocksource_tsc, khz: tsc_khz);
1490 clocksource_unregister(&clocksource_tsc_early);
1491
1492 if (!tsc_force_recalibrate)
1493 return 0;
1494 }
1495
1496 schedule_delayed_work(dwork: &tsc_irqwork, delay: 0);
1497 return 0;
1498}
1499/*
1500 * We use device_initcall here, to ensure we run after the hpet
1501 * is fully initialized, which may occur at fs_initcall time.
1502 */
1503device_initcall(init_tsc_clocksource);
1504
1505static bool __init determine_cpu_tsc_frequencies(bool early)
1506{
1507 /* Make sure that cpu and tsc are not already calibrated */
1508 WARN_ON(cpu_khz || tsc_khz);
1509
1510 if (early) {
1511 cpu_khz = x86_platform.calibrate_cpu();
1512 if (tsc_early_khz)
1513 tsc_khz = tsc_early_khz;
1514 else
1515 tsc_khz = x86_platform.calibrate_tsc();
1516 } else {
1517 /* We should not be here with non-native cpu calibration */
1518 WARN_ON(x86_platform.calibrate_cpu != native_calibrate_cpu);
1519 cpu_khz = pit_hpet_ptimer_calibrate_cpu();
1520 }
1521
1522 /*
1523 * Trust non-zero tsc_khz as authoritative,
1524 * and use it to sanity check cpu_khz,
1525 * which will be off if system timer is off.
1526 */
1527 if (tsc_khz == 0)
1528 tsc_khz = cpu_khz;
1529 else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
1530 cpu_khz = tsc_khz;
1531
1532 if (tsc_khz == 0)
1533 return false;
1534
1535 pr_info("Detected %lu.%03lu MHz processor\n",
1536 (unsigned long)cpu_khz / KHZ,
1537 (unsigned long)cpu_khz % KHZ);
1538
1539 if (cpu_khz != tsc_khz) {
1540 pr_info("Detected %lu.%03lu MHz TSC",
1541 (unsigned long)tsc_khz / KHZ,
1542 (unsigned long)tsc_khz % KHZ);
1543 }
1544 return true;
1545}
1546
1547static unsigned long __init get_loops_per_jiffy(void)
1548{
1549 u64 lpj = (u64)tsc_khz * KHZ;
1550
1551 do_div(lpj, HZ);
1552 return lpj;
1553}
1554
1555static void __init tsc_enable_sched_clock(void)
1556{
1557 loops_per_jiffy = get_loops_per_jiffy();
1558 use_tsc_delay();
1559
1560 /* Sanitize TSC ADJUST before cyc2ns gets initialized */
1561 tsc_store_and_check_tsc_adjust(bootcpu: true);
1562 cyc2ns_init_boot_cpu();
1563 static_branch_enable(&__use_tsc);
1564}
1565
1566void __init tsc_early_init(void)
1567{
1568 if (!boot_cpu_has(X86_FEATURE_TSC))
1569 return;
1570 /* Don't change UV TSC multi-chassis synchronization */
1571 if (is_early_uv_system())
1572 return;
1573 if (!determine_cpu_tsc_frequencies(early: true))
1574 return;
1575 tsc_enable_sched_clock();
1576}
1577
1578void __init tsc_init(void)
1579{
1580 if (!cpu_feature_enabled(X86_FEATURE_TSC)) {
1581 setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
1582 return;
1583 }
1584
1585 /*
1586 * native_calibrate_cpu_early can only calibrate using methods that are
1587 * available early in boot.
1588 */
1589 if (x86_platform.calibrate_cpu == native_calibrate_cpu_early)
1590 x86_platform.calibrate_cpu = native_calibrate_cpu;
1591
1592 if (!tsc_khz) {
1593 /* We failed to determine frequencies earlier, try again */
1594 if (!determine_cpu_tsc_frequencies(early: false)) {
1595 mark_tsc_unstable("could not calculate TSC khz");
1596 setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
1597 return;
1598 }
1599 tsc_enable_sched_clock();
1600 }
1601
1602 cyc2ns_init_secondary_cpus();
1603
1604 if (!no_sched_irq_time)
1605 enable_sched_clock_irqtime();
1606
1607 lpj_fine = get_loops_per_jiffy();
1608
1609 check_system_tsc_reliable();
1610
1611 if (unsynchronized_tsc()) {
1612 mark_tsc_unstable("TSCs unsynchronized");
1613 return;
1614 }
1615
1616 if (tsc_clocksource_reliable || no_tsc_watchdog)
1617 tsc_disable_clocksource_watchdog();
1618
1619 clocksource_register_khz(cs: &clocksource_tsc_early, khz: tsc_khz);
1620 detect_art();
1621}
1622
1623#ifdef CONFIG_SMP
1624/*
1625 * Check whether existing calibration data can be reused.
1626 */
1627unsigned long calibrate_delay_is_known(void)
1628{
1629 int sibling, cpu = smp_processor_id();
1630 int constant_tsc = cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC);
1631 const struct cpumask *mask = topology_core_cpumask(cpu);
1632
1633 /*
1634 * If TSC has constant frequency and TSC is synchronized across
1635 * sockets then reuse CPU0 calibration.
1636 */
1637 if (constant_tsc && !tsc_unstable)
1638 return cpu_data(0).loops_per_jiffy;
1639
1640 /*
1641 * If TSC has constant frequency and TSC is not synchronized across
1642 * sockets and this is not the first CPU in the socket, then reuse
1643 * the calibration value of an already online CPU on that socket.
1644 *
1645 * This assumes that CONSTANT_TSC is consistent for all CPUs in a
1646 * socket.
1647 */
1648 if (!constant_tsc || !mask)
1649 return 0;
1650
1651 sibling = cpumask_any_but(mask, cpu);
1652 if (sibling < nr_cpu_ids)
1653 return cpu_data(sibling).loops_per_jiffy;
1654 return 0;
1655}
1656#endif
1657

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source code of linux/arch/x86/kernel/tsc.c