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bfc0f594 | 1 | #include <linux/kernel.h> |
0ef95533 AK |
2 | #include <linux/sched.h> |
3 | #include <linux/init.h> | |
4 | #include <linux/module.h> | |
5 | #include <linux/timer.h> | |
bfc0f594 | 6 | #include <linux/acpi_pmtmr.h> |
2dbe06fa | 7 | #include <linux/cpufreq.h> |
8fbbc4b4 AK |
8 | #include <linux/dmi.h> |
9 | #include <linux/delay.h> | |
10 | #include <linux/clocksource.h> | |
11 | #include <linux/percpu.h> | |
08604bd9 | 12 | #include <linux/timex.h> |
bfc0f594 AK |
13 | |
14 | #include <asm/hpet.h> | |
8fbbc4b4 AK |
15 | #include <asm/timer.h> |
16 | #include <asm/vgtod.h> | |
17 | #include <asm/time.h> | |
18 | #include <asm/delay.h> | |
88b094fb | 19 | #include <asm/hypervisor.h> |
0ef95533 | 20 | |
f24ade3a | 21 | unsigned int __read_mostly cpu_khz; /* TSC clocks / usec, not used here */ |
0ef95533 | 22 | EXPORT_SYMBOL(cpu_khz); |
f24ade3a IM |
23 | |
24 | unsigned int __read_mostly tsc_khz; | |
0ef95533 AK |
25 | EXPORT_SYMBOL(tsc_khz); |
26 | ||
27 | /* | |
28 | * TSC can be unstable due to cpufreq or due to unsynced TSCs | |
29 | */ | |
f24ade3a | 30 | static int __read_mostly tsc_unstable; |
0ef95533 AK |
31 | |
32 | /* native_sched_clock() is called before tsc_init(), so | |
33 | we must start with the TSC soft disabled to prevent | |
34 | erroneous rdtsc usage on !cpu_has_tsc processors */ | |
f24ade3a | 35 | static int __read_mostly tsc_disabled = -1; |
0ef95533 | 36 | |
395628ef | 37 | static int tsc_clocksource_reliable; |
0ef95533 AK |
38 | /* |
39 | * Scheduler clock - returns current time in nanosec units. | |
40 | */ | |
41 | u64 native_sched_clock(void) | |
42 | { | |
43 | u64 this_offset; | |
44 | ||
45 | /* | |
46 | * Fall back to jiffies if there's no TSC available: | |
47 | * ( But note that we still use it if the TSC is marked | |
48 | * unstable. We do this because unlike Time Of Day, | |
49 | * the scheduler clock tolerates small errors and it's | |
50 | * very important for it to be as fast as the platform | |
51 | * can achive it. ) | |
52 | */ | |
53 | if (unlikely(tsc_disabled)) { | |
54 | /* No locking but a rare wrong value is not a big deal: */ | |
55 | return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ); | |
56 | } | |
57 | ||
58 | /* read the Time Stamp Counter: */ | |
59 | rdtscll(this_offset); | |
60 | ||
61 | /* return the value in ns */ | |
7cbaef9c | 62 | return __cycles_2_ns(this_offset); |
0ef95533 AK |
63 | } |
64 | ||
65 | /* We need to define a real function for sched_clock, to override the | |
66 | weak default version */ | |
67 | #ifdef CONFIG_PARAVIRT | |
68 | unsigned long long sched_clock(void) | |
69 | { | |
70 | return paravirt_sched_clock(); | |
71 | } | |
72 | #else | |
73 | unsigned long long | |
74 | sched_clock(void) __attribute__((alias("native_sched_clock"))); | |
75 | #endif | |
76 | ||
77 | int check_tsc_unstable(void) | |
78 | { | |
79 | return tsc_unstable; | |
80 | } | |
81 | EXPORT_SYMBOL_GPL(check_tsc_unstable); | |
82 | ||
83 | #ifdef CONFIG_X86_TSC | |
84 | int __init notsc_setup(char *str) | |
85 | { | |
86 | printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, " | |
87 | "cannot disable TSC completely.\n"); | |
88 | tsc_disabled = 1; | |
89 | return 1; | |
90 | } | |
91 | #else | |
92 | /* | |
93 | * disable flag for tsc. Takes effect by clearing the TSC cpu flag | |
94 | * in cpu/common.c | |
95 | */ | |
96 | int __init notsc_setup(char *str) | |
97 | { | |
98 | setup_clear_cpu_cap(X86_FEATURE_TSC); | |
99 | return 1; | |
100 | } | |
101 | #endif | |
102 | ||
103 | __setup("notsc", notsc_setup); | |
bfc0f594 | 104 | |
395628ef AK |
105 | static int __init tsc_setup(char *str) |
106 | { | |
107 | if (!strcmp(str, "reliable")) | |
108 | tsc_clocksource_reliable = 1; | |
109 | return 1; | |
110 | } | |
111 | ||
112 | __setup("tsc=", tsc_setup); | |
113 | ||
bfc0f594 AK |
114 | #define MAX_RETRIES 5 |
115 | #define SMI_TRESHOLD 50000 | |
116 | ||
117 | /* | |
118 | * Read TSC and the reference counters. Take care of SMI disturbance | |
119 | */ | |
827014be | 120 | static u64 tsc_read_refs(u64 *p, int hpet) |
bfc0f594 AK |
121 | { |
122 | u64 t1, t2; | |
123 | int i; | |
124 | ||
125 | for (i = 0; i < MAX_RETRIES; i++) { | |
126 | t1 = get_cycles(); | |
127 | if (hpet) | |
827014be | 128 | *p = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF; |
bfc0f594 | 129 | else |
827014be | 130 | *p = acpi_pm_read_early(); |
bfc0f594 AK |
131 | t2 = get_cycles(); |
132 | if ((t2 - t1) < SMI_TRESHOLD) | |
133 | return t2; | |
134 | } | |
135 | return ULLONG_MAX; | |
136 | } | |
137 | ||
d683ef7a TG |
138 | /* |
139 | * Calculate the TSC frequency from HPET reference | |
bfc0f594 | 140 | */ |
d683ef7a | 141 | static unsigned long calc_hpet_ref(u64 deltatsc, u64 hpet1, u64 hpet2) |
bfc0f594 | 142 | { |
d683ef7a | 143 | u64 tmp; |
bfc0f594 | 144 | |
d683ef7a TG |
145 | if (hpet2 < hpet1) |
146 | hpet2 += 0x100000000ULL; | |
147 | hpet2 -= hpet1; | |
148 | tmp = ((u64)hpet2 * hpet_readl(HPET_PERIOD)); | |
149 | do_div(tmp, 1000000); | |
150 | do_div(deltatsc, tmp); | |
151 | ||
152 | return (unsigned long) deltatsc; | |
153 | } | |
154 | ||
155 | /* | |
156 | * Calculate the TSC frequency from PMTimer reference | |
157 | */ | |
158 | static unsigned long calc_pmtimer_ref(u64 deltatsc, u64 pm1, u64 pm2) | |
159 | { | |
160 | u64 tmp; | |
bfc0f594 | 161 | |
d683ef7a TG |
162 | if (!pm1 && !pm2) |
163 | return ULONG_MAX; | |
164 | ||
165 | if (pm2 < pm1) | |
166 | pm2 += (u64)ACPI_PM_OVRRUN; | |
167 | pm2 -= pm1; | |
168 | tmp = pm2 * 1000000000LL; | |
169 | do_div(tmp, PMTMR_TICKS_PER_SEC); | |
170 | do_div(deltatsc, tmp); | |
171 | ||
172 | return (unsigned long) deltatsc; | |
173 | } | |
174 | ||
a977c400 | 175 | #define CAL_MS 10 |
cce3e057 | 176 | #define CAL_LATCH (CLOCK_TICK_RATE / (1000 / CAL_MS)) |
a977c400 TG |
177 | #define CAL_PIT_LOOPS 1000 |
178 | ||
179 | #define CAL2_MS 50 | |
180 | #define CAL2_LATCH (CLOCK_TICK_RATE / (1000 / CAL2_MS)) | |
181 | #define CAL2_PIT_LOOPS 5000 | |
182 | ||
cce3e057 | 183 | |
ec0c15af LT |
184 | /* |
185 | * Try to calibrate the TSC against the Programmable | |
186 | * Interrupt Timer and return the frequency of the TSC | |
187 | * in kHz. | |
188 | * | |
189 | * Return ULONG_MAX on failure to calibrate. | |
190 | */ | |
a977c400 | 191 | static unsigned long pit_calibrate_tsc(u32 latch, unsigned long ms, int loopmin) |
ec0c15af LT |
192 | { |
193 | u64 tsc, t1, t2, delta; | |
194 | unsigned long tscmin, tscmax; | |
195 | int pitcnt; | |
196 | ||
197 | /* Set the Gate high, disable speaker */ | |
198 | outb((inb(0x61) & ~0x02) | 0x01, 0x61); | |
199 | ||
200 | /* | |
201 | * Setup CTC channel 2* for mode 0, (interrupt on terminal | |
202 | * count mode), binary count. Set the latch register to 50ms | |
203 | * (LSB then MSB) to begin countdown. | |
204 | */ | |
205 | outb(0xb0, 0x43); | |
a977c400 TG |
206 | outb(latch & 0xff, 0x42); |
207 | outb(latch >> 8, 0x42); | |
ec0c15af LT |
208 | |
209 | tsc = t1 = t2 = get_cycles(); | |
210 | ||
211 | pitcnt = 0; | |
212 | tscmax = 0; | |
213 | tscmin = ULONG_MAX; | |
214 | while ((inb(0x61) & 0x20) == 0) { | |
215 | t2 = get_cycles(); | |
216 | delta = t2 - tsc; | |
217 | tsc = t2; | |
218 | if ((unsigned long) delta < tscmin) | |
219 | tscmin = (unsigned int) delta; | |
220 | if ((unsigned long) delta > tscmax) | |
221 | tscmax = (unsigned int) delta; | |
222 | pitcnt++; | |
223 | } | |
224 | ||
225 | /* | |
226 | * Sanity checks: | |
227 | * | |
a977c400 | 228 | * If we were not able to read the PIT more than loopmin |
ec0c15af LT |
229 | * times, then we have been hit by a massive SMI |
230 | * | |
231 | * If the maximum is 10 times larger than the minimum, | |
232 | * then we got hit by an SMI as well. | |
233 | */ | |
a977c400 | 234 | if (pitcnt < loopmin || tscmax > 10 * tscmin) |
ec0c15af LT |
235 | return ULONG_MAX; |
236 | ||
237 | /* Calculate the PIT value */ | |
238 | delta = t2 - t1; | |
a977c400 | 239 | do_div(delta, ms); |
ec0c15af LT |
240 | return delta; |
241 | } | |
242 | ||
6ac40ed0 LT |
243 | /* |
244 | * This reads the current MSB of the PIT counter, and | |
245 | * checks if we are running on sufficiently fast and | |
246 | * non-virtualized hardware. | |
247 | * | |
248 | * Our expectations are: | |
249 | * | |
250 | * - the PIT is running at roughly 1.19MHz | |
251 | * | |
252 | * - each IO is going to take about 1us on real hardware, | |
253 | * but we allow it to be much faster (by a factor of 10) or | |
254 | * _slightly_ slower (ie we allow up to a 2us read+counter | |
255 | * update - anything else implies a unacceptably slow CPU | |
256 | * or PIT for the fast calibration to work. | |
257 | * | |
258 | * - with 256 PIT ticks to read the value, we have 214us to | |
259 | * see the same MSB (and overhead like doing a single TSC | |
260 | * read per MSB value etc). | |
261 | * | |
262 | * - We're doing 2 reads per loop (LSB, MSB), and we expect | |
263 | * them each to take about a microsecond on real hardware. | |
264 | * So we expect a count value of around 100. But we'll be | |
265 | * generous, and accept anything over 50. | |
266 | * | |
267 | * - if the PIT is stuck, and we see *many* more reads, we | |
268 | * return early (and the next caller of pit_expect_msb() | |
269 | * then consider it a failure when they don't see the | |
270 | * next expected value). | |
271 | * | |
272 | * These expectations mean that we know that we have seen the | |
273 | * transition from one expected value to another with a fairly | |
274 | * high accuracy, and we didn't miss any events. We can thus | |
275 | * use the TSC value at the transitions to calculate a pretty | |
276 | * good value for the TSC frequencty. | |
277 | */ | |
b6e61eef LT |
278 | static inline int pit_verify_msb(unsigned char val) |
279 | { | |
280 | /* Ignore LSB */ | |
281 | inb(0x42); | |
282 | return inb(0x42) == val; | |
283 | } | |
284 | ||
9e8912e0 | 285 | static inline int pit_expect_msb(unsigned char val, u64 *tscp, unsigned long *deltap) |
6ac40ed0 | 286 | { |
9e8912e0 LT |
287 | int count; |
288 | u64 tsc = 0; | |
bfc0f594 | 289 | |
6ac40ed0 | 290 | for (count = 0; count < 50000; count++) { |
b6e61eef | 291 | if (!pit_verify_msb(val)) |
6ac40ed0 | 292 | break; |
9e8912e0 | 293 | tsc = get_cycles(); |
6ac40ed0 | 294 | } |
9e8912e0 LT |
295 | *deltap = get_cycles() - tsc; |
296 | *tscp = tsc; | |
297 | ||
298 | /* | |
299 | * We require _some_ success, but the quality control | |
300 | * will be based on the error terms on the TSC values. | |
301 | */ | |
302 | return count > 5; | |
6ac40ed0 LT |
303 | } |
304 | ||
305 | /* | |
9e8912e0 LT |
306 | * How many MSB values do we want to see? We aim for |
307 | * a maximum error rate of 500ppm (in practice the | |
308 | * real error is much smaller), but refuse to spend | |
309 | * more than 25ms on it. | |
6ac40ed0 | 310 | */ |
9e8912e0 LT |
311 | #define MAX_QUICK_PIT_MS 25 |
312 | #define MAX_QUICK_PIT_ITERATIONS (MAX_QUICK_PIT_MS * PIT_TICK_RATE / 1000 / 256) | |
bfc0f594 | 313 | |
6ac40ed0 LT |
314 | static unsigned long quick_pit_calibrate(void) |
315 | { | |
9e8912e0 LT |
316 | int i; |
317 | u64 tsc, delta; | |
318 | unsigned long d1, d2; | |
319 | ||
6ac40ed0 | 320 | /* Set the Gate high, disable speaker */ |
bfc0f594 AK |
321 | outb((inb(0x61) & ~0x02) | 0x01, 0x61); |
322 | ||
6ac40ed0 LT |
323 | /* |
324 | * Counter 2, mode 0 (one-shot), binary count | |
325 | * | |
326 | * NOTE! Mode 2 decrements by two (and then the | |
327 | * output is flipped each time, giving the same | |
328 | * final output frequency as a decrement-by-one), | |
329 | * so mode 0 is much better when looking at the | |
330 | * individual counts. | |
331 | */ | |
bfc0f594 | 332 | outb(0xb0, 0x43); |
bfc0f594 | 333 | |
6ac40ed0 LT |
334 | /* Start at 0xffff */ |
335 | outb(0xff, 0x42); | |
336 | outb(0xff, 0x42); | |
337 | ||
a6a80e1d LT |
338 | /* |
339 | * The PIT starts counting at the next edge, so we | |
340 | * need to delay for a microsecond. The easiest way | |
341 | * to do that is to just read back the 16-bit counter | |
342 | * once from the PIT. | |
343 | */ | |
b6e61eef | 344 | pit_verify_msb(0); |
a6a80e1d | 345 | |
9e8912e0 LT |
346 | if (pit_expect_msb(0xff, &tsc, &d1)) { |
347 | for (i = 1; i <= MAX_QUICK_PIT_ITERATIONS; i++) { | |
348 | if (!pit_expect_msb(0xff-i, &delta, &d2)) | |
349 | break; | |
350 | ||
351 | /* | |
352 | * Iterate until the error is less than 500 ppm | |
353 | */ | |
354 | delta -= tsc; | |
b6e61eef LT |
355 | if (d1+d2 >= delta >> 11) |
356 | continue; | |
357 | ||
358 | /* | |
359 | * Check the PIT one more time to verify that | |
360 | * all TSC reads were stable wrt the PIT. | |
361 | * | |
362 | * This also guarantees serialization of the | |
363 | * last cycle read ('d2') in pit_expect_msb. | |
364 | */ | |
365 | if (!pit_verify_msb(0xfe - i)) | |
366 | break; | |
367 | goto success; | |
6ac40ed0 | 368 | } |
6ac40ed0 | 369 | } |
9e8912e0 | 370 | printk("Fast TSC calibration failed\n"); |
6ac40ed0 | 371 | return 0; |
9e8912e0 LT |
372 | |
373 | success: | |
374 | /* | |
375 | * Ok, if we get here, then we've seen the | |
376 | * MSB of the PIT decrement 'i' times, and the | |
377 | * error has shrunk to less than 500 ppm. | |
378 | * | |
379 | * As a result, we can depend on there not being | |
380 | * any odd delays anywhere, and the TSC reads are | |
381 | * reliable (within the error). We also adjust the | |
382 | * delta to the middle of the error bars, just | |
383 | * because it looks nicer. | |
384 | * | |
385 | * kHz = ticks / time-in-seconds / 1000; | |
386 | * kHz = (t2 - t1) / (I * 256 / PIT_TICK_RATE) / 1000 | |
387 | * kHz = ((t2 - t1) * PIT_TICK_RATE) / (I * 256 * 1000) | |
388 | */ | |
389 | delta += (long)(d2 - d1)/2; | |
390 | delta *= PIT_TICK_RATE; | |
391 | do_div(delta, i*256*1000); | |
392 | printk("Fast TSC calibration using PIT\n"); | |
393 | return delta; | |
6ac40ed0 | 394 | } |
ec0c15af | 395 | |
bfc0f594 | 396 | /** |
e93ef949 | 397 | * native_calibrate_tsc - calibrate the tsc on boot |
bfc0f594 | 398 | */ |
e93ef949 | 399 | unsigned long native_calibrate_tsc(void) |
bfc0f594 | 400 | { |
827014be | 401 | u64 tsc1, tsc2, delta, ref1, ref2; |
fbb16e24 | 402 | unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX; |
2c1b284e | 403 | unsigned long flags, latch, ms, fast_calibrate, hv_tsc_khz; |
a977c400 | 404 | int hpet = is_hpet_enabled(), i, loopmin; |
bfc0f594 | 405 | |
2c1b284e JSR |
406 | hv_tsc_khz = get_hypervisor_tsc_freq(); |
407 | if (hv_tsc_khz) { | |
88b094fb | 408 | printk(KERN_INFO "TSC: Frequency read from the hypervisor\n"); |
2c1b284e | 409 | return hv_tsc_khz; |
88b094fb AK |
410 | } |
411 | ||
6ac40ed0 LT |
412 | local_irq_save(flags); |
413 | fast_calibrate = quick_pit_calibrate(); | |
bfc0f594 | 414 | local_irq_restore(flags); |
6ac40ed0 LT |
415 | if (fast_calibrate) |
416 | return fast_calibrate; | |
bfc0f594 | 417 | |
fbb16e24 TG |
418 | /* |
419 | * Run 5 calibration loops to get the lowest frequency value | |
420 | * (the best estimate). We use two different calibration modes | |
421 | * here: | |
422 | * | |
423 | * 1) PIT loop. We set the PIT Channel 2 to oneshot mode and | |
424 | * load a timeout of 50ms. We read the time right after we | |
425 | * started the timer and wait until the PIT count down reaches | |
426 | * zero. In each wait loop iteration we read the TSC and check | |
427 | * the delta to the previous read. We keep track of the min | |
428 | * and max values of that delta. The delta is mostly defined | |
429 | * by the IO time of the PIT access, so we can detect when a | |
430 | * SMI/SMM disturbance happend between the two reads. If the | |
431 | * maximum time is significantly larger than the minimum time, | |
432 | * then we discard the result and have another try. | |
433 | * | |
434 | * 2) Reference counter. If available we use the HPET or the | |
435 | * PMTIMER as a reference to check the sanity of that value. | |
436 | * We use separate TSC readouts and check inside of the | |
437 | * reference read for a SMI/SMM disturbance. We dicard | |
438 | * disturbed values here as well. We do that around the PIT | |
439 | * calibration delay loop as we have to wait for a certain | |
440 | * amount of time anyway. | |
441 | */ | |
a977c400 TG |
442 | |
443 | /* Preset PIT loop values */ | |
444 | latch = CAL_LATCH; | |
445 | ms = CAL_MS; | |
446 | loopmin = CAL_PIT_LOOPS; | |
447 | ||
448 | for (i = 0; i < 3; i++) { | |
ec0c15af | 449 | unsigned long tsc_pit_khz; |
fbb16e24 TG |
450 | |
451 | /* | |
452 | * Read the start value and the reference count of | |
ec0c15af LT |
453 | * hpet/pmtimer when available. Then do the PIT |
454 | * calibration, which will take at least 50ms, and | |
455 | * read the end value. | |
fbb16e24 | 456 | */ |
ec0c15af | 457 | local_irq_save(flags); |
827014be | 458 | tsc1 = tsc_read_refs(&ref1, hpet); |
a977c400 | 459 | tsc_pit_khz = pit_calibrate_tsc(latch, ms, loopmin); |
827014be | 460 | tsc2 = tsc_read_refs(&ref2, hpet); |
fbb16e24 TG |
461 | local_irq_restore(flags); |
462 | ||
ec0c15af LT |
463 | /* Pick the lowest PIT TSC calibration so far */ |
464 | tsc_pit_min = min(tsc_pit_min, tsc_pit_khz); | |
fbb16e24 TG |
465 | |
466 | /* hpet or pmtimer available ? */ | |
827014be | 467 | if (!hpet && !ref1 && !ref2) |
fbb16e24 TG |
468 | continue; |
469 | ||
470 | /* Check, whether the sampling was disturbed by an SMI */ | |
471 | if (tsc1 == ULLONG_MAX || tsc2 == ULLONG_MAX) | |
472 | continue; | |
473 | ||
474 | tsc2 = (tsc2 - tsc1) * 1000000LL; | |
d683ef7a | 475 | if (hpet) |
827014be | 476 | tsc2 = calc_hpet_ref(tsc2, ref1, ref2); |
d683ef7a | 477 | else |
827014be | 478 | tsc2 = calc_pmtimer_ref(tsc2, ref1, ref2); |
fbb16e24 | 479 | |
fbb16e24 | 480 | tsc_ref_min = min(tsc_ref_min, (unsigned long) tsc2); |
a977c400 TG |
481 | |
482 | /* Check the reference deviation */ | |
483 | delta = ((u64) tsc_pit_min) * 100; | |
484 | do_div(delta, tsc_ref_min); | |
485 | ||
486 | /* | |
487 | * If both calibration results are inside a 10% window | |
488 | * then we can be sure, that the calibration | |
489 | * succeeded. We break out of the loop right away. We | |
490 | * use the reference value, as it is more precise. | |
491 | */ | |
492 | if (delta >= 90 && delta <= 110) { | |
493 | printk(KERN_INFO | |
494 | "TSC: PIT calibration matches %s. %d loops\n", | |
495 | hpet ? "HPET" : "PMTIMER", i + 1); | |
496 | return tsc_ref_min; | |
fbb16e24 TG |
497 | } |
498 | ||
a977c400 TG |
499 | /* |
500 | * Check whether PIT failed more than once. This | |
501 | * happens in virtualized environments. We need to | |
502 | * give the virtual PC a slightly longer timeframe for | |
503 | * the HPET/PMTIMER to make the result precise. | |
504 | */ | |
505 | if (i == 1 && tsc_pit_min == ULONG_MAX) { | |
506 | latch = CAL2_LATCH; | |
507 | ms = CAL2_MS; | |
508 | loopmin = CAL2_PIT_LOOPS; | |
509 | } | |
fbb16e24 | 510 | } |
bfc0f594 AK |
511 | |
512 | /* | |
fbb16e24 | 513 | * Now check the results. |
bfc0f594 | 514 | */ |
fbb16e24 TG |
515 | if (tsc_pit_min == ULONG_MAX) { |
516 | /* PIT gave no useful value */ | |
de014d61 | 517 | printk(KERN_WARNING "TSC: Unable to calibrate against PIT\n"); |
fbb16e24 TG |
518 | |
519 | /* We don't have an alternative source, disable TSC */ | |
827014be | 520 | if (!hpet && !ref1 && !ref2) { |
fbb16e24 TG |
521 | printk("TSC: No reference (HPET/PMTIMER) available\n"); |
522 | return 0; | |
523 | } | |
524 | ||
525 | /* The alternative source failed as well, disable TSC */ | |
526 | if (tsc_ref_min == ULONG_MAX) { | |
527 | printk(KERN_WARNING "TSC: HPET/PMTIMER calibration " | |
a977c400 | 528 | "failed.\n"); |
fbb16e24 TG |
529 | return 0; |
530 | } | |
531 | ||
532 | /* Use the alternative source */ | |
533 | printk(KERN_INFO "TSC: using %s reference calibration\n", | |
534 | hpet ? "HPET" : "PMTIMER"); | |
535 | ||
536 | return tsc_ref_min; | |
537 | } | |
bfc0f594 | 538 | |
fbb16e24 | 539 | /* We don't have an alternative source, use the PIT calibration value */ |
827014be | 540 | if (!hpet && !ref1 && !ref2) { |
fbb16e24 TG |
541 | printk(KERN_INFO "TSC: Using PIT calibration value\n"); |
542 | return tsc_pit_min; | |
bfc0f594 AK |
543 | } |
544 | ||
fbb16e24 TG |
545 | /* The alternative source failed, use the PIT calibration value */ |
546 | if (tsc_ref_min == ULONG_MAX) { | |
a977c400 TG |
547 | printk(KERN_WARNING "TSC: HPET/PMTIMER calibration failed. " |
548 | "Using PIT calibration\n"); | |
fbb16e24 | 549 | return tsc_pit_min; |
bfc0f594 AK |
550 | } |
551 | ||
fbb16e24 TG |
552 | /* |
553 | * The calibration values differ too much. In doubt, we use | |
554 | * the PIT value as we know that there are PMTIMERs around | |
a977c400 | 555 | * running at double speed. At least we let the user know: |
fbb16e24 | 556 | */ |
a977c400 TG |
557 | printk(KERN_WARNING "TSC: PIT calibration deviates from %s: %lu %lu.\n", |
558 | hpet ? "HPET" : "PMTIMER", tsc_pit_min, tsc_ref_min); | |
fbb16e24 TG |
559 | printk(KERN_INFO "TSC: Using PIT calibration value\n"); |
560 | return tsc_pit_min; | |
bfc0f594 AK |
561 | } |
562 | ||
bfc0f594 AK |
563 | int recalibrate_cpu_khz(void) |
564 | { | |
565 | #ifndef CONFIG_SMP | |
566 | unsigned long cpu_khz_old = cpu_khz; | |
567 | ||
568 | if (cpu_has_tsc) { | |
e93ef949 AK |
569 | tsc_khz = calibrate_tsc(); |
570 | cpu_khz = tsc_khz; | |
bfc0f594 AK |
571 | cpu_data(0).loops_per_jiffy = |
572 | cpufreq_scale(cpu_data(0).loops_per_jiffy, | |
573 | cpu_khz_old, cpu_khz); | |
574 | return 0; | |
575 | } else | |
576 | return -ENODEV; | |
577 | #else | |
578 | return -ENODEV; | |
579 | #endif | |
580 | } | |
581 | ||
582 | EXPORT_SYMBOL(recalibrate_cpu_khz); | |
583 | ||
2dbe06fa AK |
584 | |
585 | /* Accelerators for sched_clock() | |
586 | * convert from cycles(64bits) => nanoseconds (64bits) | |
587 | * basic equation: | |
588 | * ns = cycles / (freq / ns_per_sec) | |
589 | * ns = cycles * (ns_per_sec / freq) | |
590 | * ns = cycles * (10^9 / (cpu_khz * 10^3)) | |
591 | * ns = cycles * (10^6 / cpu_khz) | |
592 | * | |
593 | * Then we use scaling math (suggested by george@mvista.com) to get: | |
594 | * ns = cycles * (10^6 * SC / cpu_khz) / SC | |
595 | * ns = cycles * cyc2ns_scale / SC | |
596 | * | |
597 | * And since SC is a constant power of two, we can convert the div | |
598 | * into a shift. | |
599 | * | |
600 | * We can use khz divisor instead of mhz to keep a better precision, since | |
601 | * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits. | |
602 | * (mathieu.desnoyers@polymtl.ca) | |
603 | * | |
604 | * -johnstul@us.ibm.com "math is hard, lets go shopping!" | |
605 | */ | |
606 | ||
607 | DEFINE_PER_CPU(unsigned long, cyc2ns); | |
84599f8a | 608 | DEFINE_PER_CPU(unsigned long long, cyc2ns_offset); |
2dbe06fa | 609 | |
8fbbc4b4 | 610 | static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu) |
2dbe06fa | 611 | { |
84599f8a | 612 | unsigned long long tsc_now, ns_now, *offset; |
2dbe06fa AK |
613 | unsigned long flags, *scale; |
614 | ||
615 | local_irq_save(flags); | |
616 | sched_clock_idle_sleep_event(); | |
617 | ||
618 | scale = &per_cpu(cyc2ns, cpu); | |
84599f8a | 619 | offset = &per_cpu(cyc2ns_offset, cpu); |
2dbe06fa AK |
620 | |
621 | rdtscll(tsc_now); | |
622 | ns_now = __cycles_2_ns(tsc_now); | |
623 | ||
84599f8a | 624 | if (cpu_khz) { |
2dbe06fa | 625 | *scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz; |
84599f8a PZ |
626 | *offset = ns_now - (tsc_now * *scale >> CYC2NS_SCALE_FACTOR); |
627 | } | |
2dbe06fa AK |
628 | |
629 | sched_clock_idle_wakeup_event(0); | |
630 | local_irq_restore(flags); | |
631 | } | |
632 | ||
633 | #ifdef CONFIG_CPU_FREQ | |
634 | ||
635 | /* Frequency scaling support. Adjust the TSC based timer when the cpu frequency | |
636 | * changes. | |
637 | * | |
638 | * RED-PEN: On SMP we assume all CPUs run with the same frequency. It's | |
639 | * not that important because current Opteron setups do not support | |
640 | * scaling on SMP anyroads. | |
641 | * | |
642 | * Should fix up last_tsc too. Currently gettimeofday in the | |
643 | * first tick after the change will be slightly wrong. | |
644 | */ | |
645 | ||
646 | static unsigned int ref_freq; | |
647 | static unsigned long loops_per_jiffy_ref; | |
648 | static unsigned long tsc_khz_ref; | |
649 | ||
650 | static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, | |
651 | void *data) | |
652 | { | |
653 | struct cpufreq_freqs *freq = data; | |
931db6a3 | 654 | unsigned long *lpj; |
2dbe06fa AK |
655 | |
656 | if (cpu_has(&cpu_data(freq->cpu), X86_FEATURE_CONSTANT_TSC)) | |
657 | return 0; | |
658 | ||
931db6a3 | 659 | lpj = &boot_cpu_data.loops_per_jiffy; |
2dbe06fa | 660 | #ifdef CONFIG_SMP |
931db6a3 | 661 | if (!(freq->flags & CPUFREQ_CONST_LOOPS)) |
2dbe06fa | 662 | lpj = &cpu_data(freq->cpu).loops_per_jiffy; |
2dbe06fa AK |
663 | #endif |
664 | ||
665 | if (!ref_freq) { | |
666 | ref_freq = freq->old; | |
667 | loops_per_jiffy_ref = *lpj; | |
668 | tsc_khz_ref = tsc_khz; | |
669 | } | |
670 | if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) || | |
671 | (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) || | |
672 | (val == CPUFREQ_RESUMECHANGE)) { | |
878f4f53 | 673 | *lpj = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new); |
2dbe06fa AK |
674 | |
675 | tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new); | |
676 | if (!(freq->flags & CPUFREQ_CONST_LOOPS)) | |
677 | mark_tsc_unstable("cpufreq changes"); | |
678 | } | |
679 | ||
52a8968c | 680 | set_cyc2ns_scale(tsc_khz, freq->cpu); |
2dbe06fa AK |
681 | |
682 | return 0; | |
683 | } | |
684 | ||
685 | static struct notifier_block time_cpufreq_notifier_block = { | |
686 | .notifier_call = time_cpufreq_notifier | |
687 | }; | |
688 | ||
689 | static int __init cpufreq_tsc(void) | |
690 | { | |
060700b5 LT |
691 | if (!cpu_has_tsc) |
692 | return 0; | |
693 | if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) | |
694 | return 0; | |
2dbe06fa AK |
695 | cpufreq_register_notifier(&time_cpufreq_notifier_block, |
696 | CPUFREQ_TRANSITION_NOTIFIER); | |
697 | return 0; | |
698 | } | |
699 | ||
700 | core_initcall(cpufreq_tsc); | |
701 | ||
702 | #endif /* CONFIG_CPU_FREQ */ | |
8fbbc4b4 AK |
703 | |
704 | /* clocksource code */ | |
705 | ||
706 | static struct clocksource clocksource_tsc; | |
707 | ||
708 | /* | |
709 | * We compare the TSC to the cycle_last value in the clocksource | |
710 | * structure to avoid a nasty time-warp. This can be observed in a | |
711 | * very small window right after one CPU updated cycle_last under | |
712 | * xtime/vsyscall_gtod lock and the other CPU reads a TSC value which | |
713 | * is smaller than the cycle_last reference value due to a TSC which | |
714 | * is slighty behind. This delta is nowhere else observable, but in | |
715 | * that case it results in a forward time jump in the range of hours | |
716 | * due to the unsigned delta calculation of the time keeping core | |
717 | * code, which is necessary to support wrapping clocksources like pm | |
718 | * timer. | |
719 | */ | |
8e19608e | 720 | static cycle_t read_tsc(struct clocksource *cs) |
8fbbc4b4 AK |
721 | { |
722 | cycle_t ret = (cycle_t)get_cycles(); | |
723 | ||
724 | return ret >= clocksource_tsc.cycle_last ? | |
725 | ret : clocksource_tsc.cycle_last; | |
726 | } | |
727 | ||
431ceb83 | 728 | #ifdef CONFIG_X86_64 |
8fbbc4b4 AK |
729 | static cycle_t __vsyscall_fn vread_tsc(void) |
730 | { | |
7d96fd41 PT |
731 | cycle_t ret; |
732 | ||
733 | /* | |
734 | * Surround the RDTSC by barriers, to make sure it's not | |
735 | * speculated to outside the seqlock critical section and | |
736 | * does not cause time warps: | |
737 | */ | |
738 | rdtsc_barrier(); | |
739 | ret = (cycle_t)vget_cycles(); | |
740 | rdtsc_barrier(); | |
8fbbc4b4 AK |
741 | |
742 | return ret >= __vsyscall_gtod_data.clock.cycle_last ? | |
743 | ret : __vsyscall_gtod_data.clock.cycle_last; | |
744 | } | |
431ceb83 | 745 | #endif |
8fbbc4b4 AK |
746 | |
747 | static struct clocksource clocksource_tsc = { | |
748 | .name = "tsc", | |
749 | .rating = 300, | |
750 | .read = read_tsc, | |
751 | .mask = CLOCKSOURCE_MASK(64), | |
752 | .shift = 22, | |
753 | .flags = CLOCK_SOURCE_IS_CONTINUOUS | | |
754 | CLOCK_SOURCE_MUST_VERIFY, | |
755 | #ifdef CONFIG_X86_64 | |
756 | .vread = vread_tsc, | |
757 | #endif | |
758 | }; | |
759 | ||
760 | void mark_tsc_unstable(char *reason) | |
761 | { | |
762 | if (!tsc_unstable) { | |
763 | tsc_unstable = 1; | |
764 | printk("Marking TSC unstable due to %s\n", reason); | |
765 | /* Change only the rating, when not registered */ | |
766 | if (clocksource_tsc.mult) | |
767 | clocksource_change_rating(&clocksource_tsc, 0); | |
768 | else | |
769 | clocksource_tsc.rating = 0; | |
770 | } | |
771 | } | |
772 | ||
773 | EXPORT_SYMBOL_GPL(mark_tsc_unstable); | |
774 | ||
775 | static int __init dmi_mark_tsc_unstable(const struct dmi_system_id *d) | |
776 | { | |
777 | printk(KERN_NOTICE "%s detected: marking TSC unstable.\n", | |
778 | d->ident); | |
779 | tsc_unstable = 1; | |
780 | return 0; | |
781 | } | |
782 | ||
783 | /* List of systems that have known TSC problems */ | |
784 | static struct dmi_system_id __initdata bad_tsc_dmi_table[] = { | |
785 | { | |
786 | .callback = dmi_mark_tsc_unstable, | |
787 | .ident = "IBM Thinkpad 380XD", | |
788 | .matches = { | |
789 | DMI_MATCH(DMI_BOARD_VENDOR, "IBM"), | |
790 | DMI_MATCH(DMI_BOARD_NAME, "2635FA0"), | |
791 | }, | |
792 | }, | |
793 | {} | |
794 | }; | |
795 | ||
395628ef AK |
796 | static void __init check_system_tsc_reliable(void) |
797 | { | |
8fbbc4b4 | 798 | #ifdef CONFIG_MGEODE_LX |
395628ef | 799 | /* RTSC counts during suspend */ |
8fbbc4b4 | 800 | #define RTSC_SUSP 0x100 |
8fbbc4b4 AK |
801 | unsigned long res_low, res_high; |
802 | ||
803 | rdmsr_safe(MSR_GEODE_BUSCONT_CONF0, &res_low, &res_high); | |
395628ef | 804 | /* Geode_LX - the OLPC CPU has a possibly a very reliable TSC */ |
8fbbc4b4 | 805 | if (res_low & RTSC_SUSP) |
395628ef | 806 | tsc_clocksource_reliable = 1; |
8fbbc4b4 | 807 | #endif |
395628ef AK |
808 | if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) |
809 | tsc_clocksource_reliable = 1; | |
810 | } | |
8fbbc4b4 AK |
811 | |
812 | /* | |
813 | * Make an educated guess if the TSC is trustworthy and synchronized | |
814 | * over all CPUs. | |
815 | */ | |
816 | __cpuinit int unsynchronized_tsc(void) | |
817 | { | |
818 | if (!cpu_has_tsc || tsc_unstable) | |
819 | return 1; | |
820 | ||
3e5095d1 | 821 | #ifdef CONFIG_SMP |
8fbbc4b4 AK |
822 | if (apic_is_clustered_box()) |
823 | return 1; | |
824 | #endif | |
825 | ||
826 | if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) | |
827 | return 0; | |
828 | /* | |
829 | * Intel systems are normally all synchronized. | |
830 | * Exceptions must mark TSC as unstable: | |
831 | */ | |
832 | if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) { | |
833 | /* assume multi socket systems are not synchronized: */ | |
834 | if (num_possible_cpus() > 1) | |
835 | tsc_unstable = 1; | |
836 | } | |
837 | ||
838 | return tsc_unstable; | |
839 | } | |
840 | ||
841 | static void __init init_tsc_clocksource(void) | |
842 | { | |
843 | clocksource_tsc.mult = clocksource_khz2mult(tsc_khz, | |
844 | clocksource_tsc.shift); | |
395628ef AK |
845 | if (tsc_clocksource_reliable) |
846 | clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY; | |
8fbbc4b4 AK |
847 | /* lower the rating if we already know its unstable: */ |
848 | if (check_tsc_unstable()) { | |
849 | clocksource_tsc.rating = 0; | |
850 | clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS; | |
851 | } | |
852 | clocksource_register(&clocksource_tsc); | |
853 | } | |
854 | ||
855 | void __init tsc_init(void) | |
856 | { | |
857 | u64 lpj; | |
858 | int cpu; | |
859 | ||
860 | if (!cpu_has_tsc) | |
861 | return; | |
862 | ||
e93ef949 AK |
863 | tsc_khz = calibrate_tsc(); |
864 | cpu_khz = tsc_khz; | |
8fbbc4b4 | 865 | |
e93ef949 | 866 | if (!tsc_khz) { |
8fbbc4b4 AK |
867 | mark_tsc_unstable("could not calculate TSC khz"); |
868 | return; | |
869 | } | |
870 | ||
871 | #ifdef CONFIG_X86_64 | |
872 | if (cpu_has(&boot_cpu_data, X86_FEATURE_CONSTANT_TSC) && | |
873 | (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)) | |
874 | cpu_khz = calibrate_cpu(); | |
875 | #endif | |
876 | ||
8fbbc4b4 AK |
877 | printk("Detected %lu.%03lu MHz processor.\n", |
878 | (unsigned long)cpu_khz / 1000, | |
879 | (unsigned long)cpu_khz % 1000); | |
880 | ||
881 | /* | |
882 | * Secondary CPUs do not run through tsc_init(), so set up | |
883 | * all the scale factors for all CPUs, assuming the same | |
884 | * speed as the bootup CPU. (cpufreq notifiers will fix this | |
885 | * up if their speed diverges) | |
886 | */ | |
887 | for_each_possible_cpu(cpu) | |
888 | set_cyc2ns_scale(cpu_khz, cpu); | |
889 | ||
890 | if (tsc_disabled > 0) | |
891 | return; | |
892 | ||
893 | /* now allow native_sched_clock() to use rdtsc */ | |
894 | tsc_disabled = 0; | |
895 | ||
70de9a97 AK |
896 | lpj = ((u64)tsc_khz * 1000); |
897 | do_div(lpj, HZ); | |
898 | lpj_fine = lpj; | |
899 | ||
8fbbc4b4 AK |
900 | use_tsc_delay(); |
901 | /* Check and install the TSC clocksource */ | |
902 | dmi_check_system(bad_tsc_dmi_table); | |
903 | ||
904 | if (unsynchronized_tsc()) | |
905 | mark_tsc_unstable("TSCs unsynchronized"); | |
906 | ||
395628ef | 907 | check_system_tsc_reliable(); |
8fbbc4b4 AK |
908 | init_tsc_clocksource(); |
909 | } | |
910 |