539eb11e |
1 | /* |
2 | * This code largely moved from arch/i386/kernel/timer/timer_tsc.c |
3 | * which was originally moved from arch/i386/kernel/time.c. |
4 | * See comments there for proper credits. |
5 | */ |
6 | |
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7 | #include <linux/clocksource.h> |
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8 | #include <linux/workqueue.h> |
9 | #include <linux/cpufreq.h> |
10 | #include <linux/jiffies.h> |
11 | #include <linux/init.h> |
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12 | #include <linux/dmi.h> |
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13 | |
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14 | #include <asm/delay.h> |
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15 | #include <asm/tsc.h> |
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16 | #include <asm/delay.h> |
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17 | #include <asm/io.h> |
18 | |
19 | #include "mach_timer.h" |
20 | |
21 | /* |
22 | * On some systems the TSC frequency does not |
23 | * change with the cpu frequency. So we need |
24 | * an extra value to store the TSC freq |
25 | */ |
26 | unsigned int tsc_khz; |
27 | |
28 | int tsc_disable __cpuinitdata = 0; |
29 | |
30 | #ifdef CONFIG_X86_TSC |
31 | static int __init tsc_setup(char *str) |
32 | { |
33 | printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, " |
34 | "cannot disable TSC.\n"); |
35 | return 1; |
36 | } |
37 | #else |
38 | /* |
39 | * disable flag for tsc. Takes effect by clearing the TSC cpu flag |
40 | * in cpu/common.c |
41 | */ |
42 | static int __init tsc_setup(char *str) |
43 | { |
44 | tsc_disable = 1; |
45 | |
46 | return 1; |
47 | } |
48 | #endif |
49 | |
50 | __setup("notsc", tsc_setup); |
51 | |
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52 | /* |
53 | * code to mark and check if the TSC is unstable |
54 | * due to cpufreq or due to unsynced TSCs |
55 | */ |
56 | static int tsc_unstable; |
57 | |
58 | static inline int check_tsc_unstable(void) |
59 | { |
60 | return tsc_unstable; |
61 | } |
62 | |
63 | void mark_tsc_unstable(void) |
64 | { |
65 | tsc_unstable = 1; |
66 | } |
67 | EXPORT_SYMBOL_GPL(mark_tsc_unstable); |
68 | |
69 | /* Accellerators for sched_clock() |
70 | * convert from cycles(64bits) => nanoseconds (64bits) |
71 | * basic equation: |
72 | * ns = cycles / (freq / ns_per_sec) |
73 | * ns = cycles * (ns_per_sec / freq) |
74 | * ns = cycles * (10^9 / (cpu_khz * 10^3)) |
75 | * ns = cycles * (10^6 / cpu_khz) |
76 | * |
77 | * Then we use scaling math (suggested by george@mvista.com) to get: |
78 | * ns = cycles * (10^6 * SC / cpu_khz) / SC |
79 | * ns = cycles * cyc2ns_scale / SC |
80 | * |
81 | * And since SC is a constant power of two, we can convert the div |
82 | * into a shift. |
83 | * |
84 | * We can use khz divisor instead of mhz to keep a better percision, since |
85 | * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits. |
86 | * (mathieu.desnoyers@polymtl.ca) |
87 | * |
88 | * -johnstul@us.ibm.com "math is hard, lets go shopping!" |
89 | */ |
90 | static unsigned long cyc2ns_scale __read_mostly; |
91 | |
92 | #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */ |
93 | |
94 | static inline void set_cyc2ns_scale(unsigned long cpu_khz) |
95 | { |
96 | cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz; |
97 | } |
98 | |
99 | static inline unsigned long long cycles_2_ns(unsigned long long cyc) |
100 | { |
101 | return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR; |
102 | } |
103 | |
104 | /* |
105 | * Scheduler clock - returns current time in nanosec units. |
106 | */ |
107 | unsigned long long sched_clock(void) |
108 | { |
109 | unsigned long long this_offset; |
110 | |
111 | /* |
112 | * in the NUMA case we dont use the TSC as they are not |
113 | * synchronized across all CPUs. |
114 | */ |
115 | #ifndef CONFIG_NUMA |
116 | if (!cpu_khz || check_tsc_unstable()) |
117 | #endif |
118 | /* no locking but a rare wrong value is not a big deal */ |
119 | return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ); |
120 | |
121 | /* read the Time Stamp Counter: */ |
122 | rdtscll(this_offset); |
123 | |
124 | /* return the value in ns */ |
125 | return cycles_2_ns(this_offset); |
126 | } |
127 | |
128 | static unsigned long calculate_cpu_khz(void) |
129 | { |
130 | unsigned long long start, end; |
131 | unsigned long count; |
132 | u64 delta64; |
133 | int i; |
134 | unsigned long flags; |
135 | |
136 | local_irq_save(flags); |
137 | |
138 | /* run 3 times to ensure the cache is warm */ |
139 | for (i = 0; i < 3; i++) { |
140 | mach_prepare_counter(); |
141 | rdtscll(start); |
142 | mach_countup(&count); |
143 | rdtscll(end); |
144 | } |
145 | /* |
146 | * Error: ECTCNEVERSET |
147 | * The CTC wasn't reliable: we got a hit on the very first read, |
148 | * or the CPU was so fast/slow that the quotient wouldn't fit in |
149 | * 32 bits.. |
150 | */ |
151 | if (count <= 1) |
152 | goto err; |
153 | |
154 | delta64 = end - start; |
155 | |
156 | /* cpu freq too fast: */ |
157 | if (delta64 > (1ULL<<32)) |
158 | goto err; |
159 | |
160 | /* cpu freq too slow: */ |
161 | if (delta64 <= CALIBRATE_TIME_MSEC) |
162 | goto err; |
163 | |
164 | delta64 += CALIBRATE_TIME_MSEC/2; /* round for do_div */ |
165 | do_div(delta64,CALIBRATE_TIME_MSEC); |
166 | |
167 | local_irq_restore(flags); |
168 | return (unsigned long)delta64; |
169 | err: |
170 | local_irq_restore(flags); |
171 | return 0; |
172 | } |
173 | |
174 | int recalibrate_cpu_khz(void) |
175 | { |
176 | #ifndef CONFIG_SMP |
177 | unsigned long cpu_khz_old = cpu_khz; |
178 | |
179 | if (cpu_has_tsc) { |
180 | cpu_khz = calculate_cpu_khz(); |
181 | tsc_khz = cpu_khz; |
182 | cpu_data[0].loops_per_jiffy = |
183 | cpufreq_scale(cpu_data[0].loops_per_jiffy, |
184 | cpu_khz_old, cpu_khz); |
185 | return 0; |
186 | } else |
187 | return -ENODEV; |
188 | #else |
189 | return -ENODEV; |
190 | #endif |
191 | } |
192 | |
193 | EXPORT_SYMBOL(recalibrate_cpu_khz); |
194 | |
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195 | void __init tsc_init(void) |
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196 | { |
197 | if (!cpu_has_tsc || tsc_disable) |
198 | return; |
199 | |
200 | cpu_khz = calculate_cpu_khz(); |
201 | tsc_khz = cpu_khz; |
202 | |
203 | if (!cpu_khz) |
204 | return; |
205 | |
206 | printk("Detected %lu.%03lu MHz processor.\n", |
207 | (unsigned long)cpu_khz / 1000, |
208 | (unsigned long)cpu_khz % 1000); |
209 | |
210 | set_cyc2ns_scale(cpu_khz); |
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211 | use_tsc_delay(); |
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212 | } |
213 | |
214 | #ifdef CONFIG_CPU_FREQ |
215 | |
216 | static unsigned int cpufreq_delayed_issched = 0; |
217 | static unsigned int cpufreq_init = 0; |
218 | static struct work_struct cpufreq_delayed_get_work; |
219 | |
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220 | static void handle_cpufreq_delayed_get(struct work_struct *work) |
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221 | { |
222 | unsigned int cpu; |
223 | |
224 | for_each_online_cpu(cpu) |
225 | cpufreq_get(cpu); |
226 | |
227 | cpufreq_delayed_issched = 0; |
228 | } |
229 | |
230 | /* |
231 | * if we notice cpufreq oddness, schedule a call to cpufreq_get() as it tries |
232 | * to verify the CPU frequency the timing core thinks the CPU is running |
233 | * at is still correct. |
234 | */ |
235 | static inline void cpufreq_delayed_get(void) |
236 | { |
237 | if (cpufreq_init && !cpufreq_delayed_issched) { |
238 | cpufreq_delayed_issched = 1; |
239 | printk(KERN_DEBUG "Checking if CPU frequency changed.\n"); |
240 | schedule_work(&cpufreq_delayed_get_work); |
241 | } |
242 | } |
243 | |
244 | /* |
245 | * if the CPU frequency is scaled, TSC-based delays will need a different |
246 | * loops_per_jiffy value to function properly. |
247 | */ |
248 | static unsigned int ref_freq = 0; |
249 | static unsigned long loops_per_jiffy_ref = 0; |
250 | static unsigned long cpu_khz_ref = 0; |
251 | |
252 | static int |
253 | time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data) |
254 | { |
255 | struct cpufreq_freqs *freq = data; |
256 | |
257 | if (val != CPUFREQ_RESUMECHANGE && val != CPUFREQ_SUSPENDCHANGE) |
258 | write_seqlock_irq(&xtime_lock); |
259 | |
260 | if (!ref_freq) { |
261 | if (!freq->old){ |
262 | ref_freq = freq->new; |
263 | goto end; |
264 | } |
265 | ref_freq = freq->old; |
266 | loops_per_jiffy_ref = cpu_data[freq->cpu].loops_per_jiffy; |
267 | cpu_khz_ref = cpu_khz; |
268 | } |
269 | |
270 | if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) || |
271 | (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) || |
272 | (val == CPUFREQ_RESUMECHANGE)) { |
273 | if (!(freq->flags & CPUFREQ_CONST_LOOPS)) |
274 | cpu_data[freq->cpu].loops_per_jiffy = |
275 | cpufreq_scale(loops_per_jiffy_ref, |
276 | ref_freq, freq->new); |
277 | |
278 | if (cpu_khz) { |
279 | |
280 | if (num_online_cpus() == 1) |
281 | cpu_khz = cpufreq_scale(cpu_khz_ref, |
282 | ref_freq, freq->new); |
283 | if (!(freq->flags & CPUFREQ_CONST_LOOPS)) { |
284 | tsc_khz = cpu_khz; |
285 | set_cyc2ns_scale(cpu_khz); |
286 | /* |
287 | * TSC based sched_clock turns |
288 | * to junk w/ cpufreq |
289 | */ |
290 | mark_tsc_unstable(); |
291 | } |
292 | } |
293 | } |
294 | end: |
295 | if (val != CPUFREQ_RESUMECHANGE && val != CPUFREQ_SUSPENDCHANGE) |
296 | write_sequnlock_irq(&xtime_lock); |
297 | |
298 | return 0; |
299 | } |
300 | |
301 | static struct notifier_block time_cpufreq_notifier_block = { |
302 | .notifier_call = time_cpufreq_notifier |
303 | }; |
304 | |
305 | static int __init cpufreq_tsc(void) |
306 | { |
307 | int ret; |
308 | |
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309 | INIT_WORK(&cpufreq_delayed_get_work, handle_cpufreq_delayed_get); |
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310 | ret = cpufreq_register_notifier(&time_cpufreq_notifier_block, |
311 | CPUFREQ_TRANSITION_NOTIFIER); |
312 | if (!ret) |
313 | cpufreq_init = 1; |
314 | |
315 | return ret; |
316 | } |
317 | |
318 | core_initcall(cpufreq_tsc); |
319 | |
320 | #endif |
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321 | |
322 | /* clock source code */ |
323 | |
324 | static unsigned long current_tsc_khz = 0; |
325 | static int tsc_update_callback(void); |
326 | |
327 | static cycle_t read_tsc(void) |
328 | { |
329 | cycle_t ret; |
330 | |
331 | rdtscll(ret); |
332 | |
333 | return ret; |
334 | } |
335 | |
336 | static struct clocksource clocksource_tsc = { |
337 | .name = "tsc", |
338 | .rating = 300, |
339 | .read = read_tsc, |
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340 | .mask = CLOCKSOURCE_MASK(64), |
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341 | .mult = 0, /* to be set */ |
342 | .shift = 22, |
343 | .update_callback = tsc_update_callback, |
344 | .is_continuous = 1, |
345 | }; |
346 | |
347 | static int tsc_update_callback(void) |
348 | { |
349 | int change = 0; |
350 | |
351 | /* check to see if we should switch to the safe clocksource: */ |
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352 | if (clocksource_tsc.rating != 0 && check_tsc_unstable()) { |
353 | clocksource_tsc.rating = 0; |
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354 | clocksource_reselect(); |
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355 | change = 1; |
356 | } |
357 | |
358 | /* only update if tsc_khz has changed: */ |
359 | if (current_tsc_khz != tsc_khz) { |
360 | current_tsc_khz = tsc_khz; |
361 | clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz, |
362 | clocksource_tsc.shift); |
363 | change = 1; |
364 | } |
365 | |
366 | return change; |
367 | } |
368 | |
369 | static int __init dmi_mark_tsc_unstable(struct dmi_system_id *d) |
370 | { |
371 | printk(KERN_NOTICE "%s detected: marking TSC unstable.\n", |
372 | d->ident); |
373 | mark_tsc_unstable(); |
374 | return 0; |
375 | } |
376 | |
377 | /* List of systems that have known TSC problems */ |
378 | static struct dmi_system_id __initdata bad_tsc_dmi_table[] = { |
379 | { |
380 | .callback = dmi_mark_tsc_unstable, |
381 | .ident = "IBM Thinkpad 380XD", |
382 | .matches = { |
383 | DMI_MATCH(DMI_BOARD_VENDOR, "IBM"), |
384 | DMI_MATCH(DMI_BOARD_NAME, "2635FA0"), |
385 | }, |
386 | }, |
387 | {} |
388 | }; |
389 | |
390 | #define TSC_FREQ_CHECK_INTERVAL (10*MSEC_PER_SEC) /* 10sec in MS */ |
391 | static struct timer_list verify_tsc_freq_timer; |
392 | |
393 | /* XXX - Probably should add locking */ |
394 | static void verify_tsc_freq(unsigned long unused) |
395 | { |
396 | static u64 last_tsc; |
397 | static unsigned long last_jiffies; |
398 | |
399 | u64 now_tsc, interval_tsc; |
400 | unsigned long now_jiffies, interval_jiffies; |
401 | |
402 | |
403 | if (check_tsc_unstable()) |
404 | return; |
405 | |
406 | rdtscll(now_tsc); |
407 | now_jiffies = jiffies; |
408 | |
409 | if (!last_jiffies) { |
410 | goto out; |
411 | } |
412 | |
413 | interval_jiffies = now_jiffies - last_jiffies; |
414 | interval_tsc = now_tsc - last_tsc; |
415 | interval_tsc *= HZ; |
416 | do_div(interval_tsc, cpu_khz*1000); |
417 | |
418 | if (interval_tsc < (interval_jiffies * 3 / 4)) { |
419 | printk("TSC appears to be running slowly. " |
420 | "Marking it as unstable\n"); |
421 | mark_tsc_unstable(); |
422 | return; |
423 | } |
424 | |
425 | out: |
426 | last_tsc = now_tsc; |
427 | last_jiffies = now_jiffies; |
428 | /* set us up to go off on the next interval: */ |
429 | mod_timer(&verify_tsc_freq_timer, |
430 | jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL)); |
431 | } |
432 | |
433 | /* |
434 | * Make an educated guess if the TSC is trustworthy and synchronized |
435 | * over all CPUs. |
436 | */ |
437 | static __init int unsynchronized_tsc(void) |
438 | { |
439 | /* |
440 | * Intel systems are normally all synchronized. |
441 | * Exceptions must mark TSC as unstable: |
442 | */ |
443 | if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) |
444 | return 0; |
445 | |
446 | /* assume multi socket systems are not synchronized: */ |
447 | return num_possible_cpus() > 1; |
448 | } |
449 | |
450 | static int __init init_tsc_clocksource(void) |
451 | { |
452 | |
453 | if (cpu_has_tsc && tsc_khz && !tsc_disable) { |
454 | /* check blacklist */ |
455 | dmi_check_system(bad_tsc_dmi_table); |
456 | |
457 | if (unsynchronized_tsc()) /* mark unstable if unsynced */ |
458 | mark_tsc_unstable(); |
459 | current_tsc_khz = tsc_khz; |
460 | clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz, |
461 | clocksource_tsc.shift); |
462 | /* lower the rating if we already know its unstable: */ |
463 | if (check_tsc_unstable()) |
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464 | clocksource_tsc.rating = 0; |
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465 | |
466 | init_timer(&verify_tsc_freq_timer); |
467 | verify_tsc_freq_timer.function = verify_tsc_freq; |
468 | verify_tsc_freq_timer.expires = |
469 | jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL); |
470 | add_timer(&verify_tsc_freq_timer); |
471 | |
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472 | return clocksource_register(&clocksource_tsc); |
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473 | } |
474 | |
475 | return 0; |
476 | } |
477 | |
478 | module_init(init_tsc_clocksource); |