Merge git://git.kernel.org/pub/scm/linux/kernel/git/bart/ide-2.6
[linux-2.6] / 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
10 #include <asm/timex.h>
11
12 static int notsc __initdata = 0;
13
14 unsigned int cpu_khz;           /* TSC clocks / usec, not used here */
15 EXPORT_SYMBOL(cpu_khz);
16 unsigned int tsc_khz;
17 EXPORT_SYMBOL(tsc_khz);
18
19 static unsigned int cyc2ns_scale __read_mostly;
20
21 void set_cyc2ns_scale(unsigned long khz)
22 {
23         cyc2ns_scale = (NSEC_PER_MSEC << NS_SCALE) / khz;
24 }
25
26 static unsigned long long cycles_2_ns(unsigned long long cyc)
27 {
28         return (cyc * cyc2ns_scale) >> NS_SCALE;
29 }
30
31 unsigned long long sched_clock(void)
32 {
33         unsigned long a = 0;
34
35         /* Could do CPU core sync here. Opteron can execute rdtsc speculatively,
36          * which means it is not completely exact and may not be monotonous
37          * between CPUs. But the errors should be too small to matter for
38          * scheduling purposes.
39          */
40
41         rdtscll(a);
42         return cycles_2_ns(a);
43 }
44
45 static int tsc_unstable;
46
47 inline int check_tsc_unstable(void)
48 {
49         return tsc_unstable;
50 }
51 #ifdef CONFIG_CPU_FREQ
52
53 /* Frequency scaling support. Adjust the TSC based timer when the cpu frequency
54  * changes.
55  *
56  * RED-PEN: On SMP we assume all CPUs run with the same frequency.  It's
57  * not that important because current Opteron setups do not support
58  * scaling on SMP anyroads.
59  *
60  * Should fix up last_tsc too. Currently gettimeofday in the
61  * first tick after the change will be slightly wrong.
62  */
63
64 static unsigned int  ref_freq;
65 static unsigned long loops_per_jiffy_ref;
66 static unsigned long tsc_khz_ref;
67
68 static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
69                                  void *data)
70 {
71         struct cpufreq_freqs *freq = data;
72         unsigned long *lpj, dummy;
73
74         if (cpu_has(&cpu_data[freq->cpu], X86_FEATURE_CONSTANT_TSC))
75                 return 0;
76
77         lpj = &dummy;
78         if (!(freq->flags & CPUFREQ_CONST_LOOPS))
79 #ifdef CONFIG_SMP
80                 lpj = &cpu_data[freq->cpu].loops_per_jiffy;
81 #else
82                 lpj = &boot_cpu_data.loops_per_jiffy;
83 #endif
84
85         if (!ref_freq) {
86                 ref_freq = freq->old;
87                 loops_per_jiffy_ref = *lpj;
88                 tsc_khz_ref = tsc_khz;
89         }
90         if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
91                 (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
92                 (val == CPUFREQ_RESUMECHANGE)) {
93                 *lpj =
94                 cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new);
95
96                 tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new);
97                 if (!(freq->flags & CPUFREQ_CONST_LOOPS))
98                         mark_tsc_unstable("cpufreq changes");
99         }
100
101         set_cyc2ns_scale(tsc_khz_ref);
102
103         return 0;
104 }
105
106 static struct notifier_block time_cpufreq_notifier_block = {
107         .notifier_call  = time_cpufreq_notifier
108 };
109
110 static int __init cpufreq_tsc(void)
111 {
112         cpufreq_register_notifier(&time_cpufreq_notifier_block,
113                                   CPUFREQ_TRANSITION_NOTIFIER);
114         return 0;
115 }
116
117 core_initcall(cpufreq_tsc);
118
119 #endif
120
121 /*
122  * Make an educated guess if the TSC is trustworthy and synchronized
123  * over all CPUs.
124  */
125 __cpuinit int unsynchronized_tsc(void)
126 {
127         if (tsc_unstable)
128                 return 1;
129
130 #ifdef CONFIG_SMP
131         if (apic_is_clustered_box())
132                 return 1;
133 #endif
134         /* Most intel systems have synchronized TSCs except for
135            multi node systems */
136         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
137 #ifdef CONFIG_ACPI
138                 /* But TSC doesn't tick in C3 so don't use it there */
139                 if (acpi_gbl_FADT.header.length > 0 &&
140                     acpi_gbl_FADT.C3latency < 1000)
141                         return 1;
142 #endif
143                 return 0;
144         }
145
146         /* Assume multi socket systems are not synchronized */
147         return num_present_cpus() > 1;
148 }
149
150 int __init notsc_setup(char *s)
151 {
152         notsc = 1;
153         return 1;
154 }
155
156 __setup("notsc", notsc_setup);
157
158
159 /* clock source code: */
160 static cycle_t read_tsc(void)
161 {
162         cycle_t ret = (cycle_t)get_cycles_sync();
163         return ret;
164 }
165
166 static cycle_t __vsyscall_fn vread_tsc(void)
167 {
168         cycle_t ret = (cycle_t)get_cycles_sync();
169         return ret;
170 }
171
172 static struct clocksource clocksource_tsc = {
173         .name                   = "tsc",
174         .rating                 = 300,
175         .read                   = read_tsc,
176         .mask                   = CLOCKSOURCE_MASK(64),
177         .shift                  = 22,
178         .flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
179                                   CLOCK_SOURCE_MUST_VERIFY,
180         .vread                  = vread_tsc,
181 };
182
183 void mark_tsc_unstable(char *reason)
184 {
185         if (!tsc_unstable) {
186                 tsc_unstable = 1;
187                 printk("Marking TSC unstable due to %s\n", reason);
188                 /* Change only the rating, when not registered */
189                 if (clocksource_tsc.mult)
190                         clocksource_change_rating(&clocksource_tsc, 0);
191                 else
192                         clocksource_tsc.rating = 0;
193         }
194 }
195 EXPORT_SYMBOL_GPL(mark_tsc_unstable);
196
197 void __init init_tsc_clocksource(void)
198 {
199         if (!notsc) {
200                 clocksource_tsc.mult = clocksource_khz2mult(tsc_khz,
201                                                         clocksource_tsc.shift);
202                 if (check_tsc_unstable())
203                         clocksource_tsc.rating = 0;
204
205                 clocksource_register(&clocksource_tsc);
206         }
207 }