c62f3b6eacc090e6408361a2f78eb10121cfe94a
[sfrench/cifs-2.6.git] / arch / x86 / kernel / tsc_64.c
1 #include <linux/kernel.h>
2 #include <linux/sched.h>
3 #include <linux/interrupt.h>
4 #include <linux/init.h>
5 #include <linux/clocksource.h>
6 #include <linux/time.h>
7 #include <linux/acpi.h>
8 #include <linux/cpufreq.h>
9 #include <linux/acpi_pmtmr.h>
10
11 #include <asm/hpet.h>
12 #include <asm/timex.h>
13 #include <asm/timer.h>
14
15 static int notsc __initdata = 0;
16
17 unsigned int cpu_khz;           /* TSC clocks / usec, not used here */
18 EXPORT_SYMBOL(cpu_khz);
19 unsigned int tsc_khz;
20 EXPORT_SYMBOL(tsc_khz);
21
22 /* Accelerators for sched_clock()
23  * convert from cycles(64bits) => nanoseconds (64bits)
24  *  basic equation:
25  *              ns = cycles / (freq / ns_per_sec)
26  *              ns = cycles * (ns_per_sec / freq)
27  *              ns = cycles * (10^9 / (cpu_khz * 10^3))
28  *              ns = cycles * (10^6 / cpu_khz)
29  *
30  *      Then we use scaling math (suggested by george@mvista.com) to get:
31  *              ns = cycles * (10^6 * SC / cpu_khz) / SC
32  *              ns = cycles * cyc2ns_scale / SC
33  *
34  *      And since SC is a constant power of two, we can convert the div
35  *  into a shift.
36  *
37  *  We can use khz divisor instead of mhz to keep a better precision, since
38  *  cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
39  *  (mathieu.desnoyers@polymtl.ca)
40  *
41  *                      -johnstul@us.ibm.com "math is hard, lets go shopping!"
42  */
43 DEFINE_PER_CPU(unsigned long, cyc2ns);
44
45 static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
46 {
47         unsigned long flags, prev_scale, *scale;
48         unsigned long long tsc_now, ns_now;
49
50         local_irq_save(flags);
51         sched_clock_idle_sleep_event();
52
53         scale = &per_cpu(cyc2ns, cpu);
54
55         rdtscll(tsc_now);
56         ns_now = __cycles_2_ns(tsc_now);
57
58         prev_scale = *scale;
59         if (cpu_khz)
60                 *scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz;
61
62         sched_clock_idle_wakeup_event(0);
63         local_irq_restore(flags);
64 }
65
66 unsigned long long native_sched_clock(void)
67 {
68         unsigned long a = 0;
69
70         /* Could do CPU core sync here. Opteron can execute rdtsc speculatively,
71          * which means it is not completely exact and may not be monotonous
72          * between CPUs. But the errors should be too small to matter for
73          * scheduling purposes.
74          */
75
76         rdtscll(a);
77         return cycles_2_ns(a);
78 }
79
80 /* We need to define a real function for sched_clock, to override the
81    weak default version */
82 #ifdef CONFIG_PARAVIRT
83 unsigned long long sched_clock(void)
84 {
85         return paravirt_sched_clock();
86 }
87 #else
88 unsigned long long
89 sched_clock(void) __attribute__((alias("native_sched_clock")));
90 #endif
91
92
93 static int tsc_unstable;
94
95 inline int check_tsc_unstable(void)
96 {
97         return tsc_unstable;
98 }
99 #ifdef CONFIG_CPU_FREQ
100
101 /* Frequency scaling support. Adjust the TSC based timer when the cpu frequency
102  * changes.
103  *
104  * RED-PEN: On SMP we assume all CPUs run with the same frequency.  It's
105  * not that important because current Opteron setups do not support
106  * scaling on SMP anyroads.
107  *
108  * Should fix up last_tsc too. Currently gettimeofday in the
109  * first tick after the change will be slightly wrong.
110  */
111
112 static unsigned int  ref_freq;
113 static unsigned long loops_per_jiffy_ref;
114 static unsigned long tsc_khz_ref;
115
116 static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
117                                  void *data)
118 {
119         struct cpufreq_freqs *freq = data;
120         unsigned long *lpj, dummy;
121
122         if (cpu_has(&cpu_data(freq->cpu), X86_FEATURE_CONSTANT_TSC))
123                 return 0;
124
125         lpj = &dummy;
126         if (!(freq->flags & CPUFREQ_CONST_LOOPS))
127 #ifdef CONFIG_SMP
128                 lpj = &cpu_data(freq->cpu).loops_per_jiffy;
129 #else
130                 lpj = &boot_cpu_data.loops_per_jiffy;
131 #endif
132
133         if (!ref_freq) {
134                 ref_freq = freq->old;
135                 loops_per_jiffy_ref = *lpj;
136                 tsc_khz_ref = tsc_khz;
137         }
138         if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
139                 (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
140                 (val == CPUFREQ_RESUMECHANGE)) {
141                 *lpj =
142                 cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new);
143
144                 tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new);
145                 if (!(freq->flags & CPUFREQ_CONST_LOOPS))
146                         mark_tsc_unstable("cpufreq changes");
147         }
148
149         preempt_disable();
150         set_cyc2ns_scale(tsc_khz_ref, smp_processor_id());
151         preempt_enable();
152
153         return 0;
154 }
155
156 static struct notifier_block time_cpufreq_notifier_block = {
157         .notifier_call  = time_cpufreq_notifier
158 };
159
160 static int __init cpufreq_tsc(void)
161 {
162         cpufreq_register_notifier(&time_cpufreq_notifier_block,
163                                   CPUFREQ_TRANSITION_NOTIFIER);
164         return 0;
165 }
166
167 core_initcall(cpufreq_tsc);
168
169 #endif
170
171 #define MAX_RETRIES     5
172 #define SMI_TRESHOLD    50000
173
174 /*
175  * Read TSC and the reference counters. Take care of SMI disturbance
176  */
177 static unsigned long __init tsc_read_refs(unsigned long *pm,
178                                           unsigned long *hpet)
179 {
180         unsigned long t1, t2;
181         int i;
182
183         for (i = 0; i < MAX_RETRIES; i++) {
184                 t1 = get_cycles();
185                 if (hpet)
186                         *hpet = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF;
187                 else
188                         *pm = acpi_pm_read_early();
189                 t2 = get_cycles();
190                 if ((t2 - t1) < SMI_TRESHOLD)
191                         return t2;
192         }
193         return ULONG_MAX;
194 }
195
196 /**
197  * tsc_calibrate - calibrate the tsc on boot
198  */
199 void __init tsc_calibrate(void)
200 {
201         unsigned long flags, tsc1, tsc2, tr1, tr2, pm1, pm2, hpet1, hpet2;
202         int hpet = is_hpet_enabled(), cpu;
203
204         local_irq_save(flags);
205
206         tsc1 = tsc_read_refs(&pm1, hpet ? &hpet1 : NULL);
207
208         outb((inb(0x61) & ~0x02) | 0x01, 0x61);
209
210         outb(0xb0, 0x43);
211         outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42);
212         outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42);
213         tr1 = get_cycles();
214         while ((inb(0x61) & 0x20) == 0);
215         tr2 = get_cycles();
216
217         tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL);
218
219         local_irq_restore(flags);
220
221         /*
222          * Preset the result with the raw and inaccurate PIT
223          * calibration value
224          */
225         tsc_khz = (tr2 - tr1) / 50;
226
227         /* hpet or pmtimer available ? */
228         if (!hpet && !pm1 && !pm2) {
229                 printk(KERN_INFO "TSC calibrated against PIT\n");
230                 return;
231         }
232
233         /* Check, whether the sampling was disturbed by an SMI */
234         if (tsc1 == ULONG_MAX || tsc2 == ULONG_MAX) {
235                 printk(KERN_WARNING "TSC calibration disturbed by SMI, "
236                        "using PIT calibration result\n");
237                 return;
238         }
239
240         tsc2 = (tsc2 - tsc1) * 1000000L;
241
242         if (hpet) {
243                 printk(KERN_INFO "TSC calibrated against HPET\n");
244                 if (hpet2 < hpet1)
245                         hpet2 += 0x100000000;
246                 hpet2 -= hpet1;
247                 tsc1 = (hpet2 * hpet_readl(HPET_PERIOD)) / 1000000;
248         } else {
249                 printk(KERN_INFO "TSC calibrated against PM_TIMER\n");
250                 if (pm2 < pm1)
251                         pm2 += ACPI_PM_OVRRUN;
252                 pm2 -= pm1;
253                 tsc1 = (pm2 * 1000000000) / PMTMR_TICKS_PER_SEC;
254         }
255
256         tsc_khz = tsc2 / tsc1;
257
258         for_each_possible_cpu(cpu)
259                 set_cyc2ns_scale(tsc_khz, cpu);
260 }
261
262 /*
263  * Make an educated guess if the TSC is trustworthy and synchronized
264  * over all CPUs.
265  */
266 __cpuinit int unsynchronized_tsc(void)
267 {
268         if (tsc_unstable)
269                 return 1;
270
271 #ifdef CONFIG_SMP
272         if (apic_is_clustered_box())
273                 return 1;
274 #endif
275
276         if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
277                 return 0;
278
279         /* Assume multi socket systems are not synchronized */
280         return num_present_cpus() > 1;
281 }
282
283 int __init notsc_setup(char *s)
284 {
285         notsc = 1;
286         return 1;
287 }
288
289 __setup("notsc", notsc_setup);
290
291
292 /* clock source code: */
293 static cycle_t read_tsc(void)
294 {
295         cycle_t ret = (cycle_t)get_cycles();
296         return ret;
297 }
298
299 static cycle_t __vsyscall_fn vread_tsc(void)
300 {
301         cycle_t ret = (cycle_t)vget_cycles();
302         return ret;
303 }
304
305 static struct clocksource clocksource_tsc = {
306         .name                   = "tsc",
307         .rating                 = 300,
308         .read                   = read_tsc,
309         .mask                   = CLOCKSOURCE_MASK(64),
310         .shift                  = 22,
311         .flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
312                                   CLOCK_SOURCE_MUST_VERIFY,
313         .vread                  = vread_tsc,
314 };
315
316 void mark_tsc_unstable(char *reason)
317 {
318         if (!tsc_unstable) {
319                 tsc_unstable = 1;
320                 printk("Marking TSC unstable due to %s\n", reason);
321                 /* Change only the rating, when not registered */
322                 if (clocksource_tsc.mult)
323                         clocksource_change_rating(&clocksource_tsc, 0);
324                 else
325                         clocksource_tsc.rating = 0;
326         }
327 }
328 EXPORT_SYMBOL_GPL(mark_tsc_unstable);
329
330 void __init init_tsc_clocksource(void)
331 {
332         if (!notsc) {
333                 clocksource_tsc.mult = clocksource_khz2mult(tsc_khz,
334                                                         clocksource_tsc.shift);
335                 if (check_tsc_unstable())
336                         clocksource_tsc.rating = 0;
337
338                 clocksource_register(&clocksource_tsc);
339         }
340 }