fbc95828cd7493082aeeedc0396a762db056097b
[linux-3.10.git] / arch / i386 / kernel / tsc.c
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
7 #include <linux/clocksource.h>
8 #include <linux/workqueue.h>
9 #include <linux/cpufreq.h>
10 #include <linux/jiffies.h>
11 #include <linux/init.h>
12 #include <linux/dmi.h>
13
14 #include <asm/delay.h>
15 #include <asm/tsc.h>
16 #include <asm/delay.h>
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
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
195 void __init tsc_init(void)
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);
211         use_tsc_delay();
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
220 static void handle_cpufreq_delayed_get(void *v)
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
309         INIT_WORK(&cpufreq_delayed_get_work, handle_cpufreq_delayed_get, NULL);
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
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,
340         .mask                   = CLOCKSOURCE_MASK(64),
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: */
352         if (clocksource_tsc.rating != 0 && check_tsc_unstable()) {
353                 clocksource_tsc.rating = 0;
354                 clocksource_reselect();
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())
464                         clocksource_tsc.rating = 0;
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
472                 return clocksource_register(&clocksource_tsc);
473         }
474
475         return 0;
476 }
477
478 module_init(init_tsc_clocksource);