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