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>
10 #include <asm/timex.h>
12 static int notsc __initdata
= 0;
14 unsigned int cpu_khz
; /* TSC clocks / usec, not used here */
15 EXPORT_SYMBOL(cpu_khz
);
17 EXPORT_SYMBOL(tsc_khz
);
19 static unsigned int cyc2ns_scale __read_mostly
;
21 void set_cyc2ns_scale(unsigned long khz
)
23 cyc2ns_scale
= (NSEC_PER_MSEC
<< NS_SCALE
) / khz
;
26 static unsigned long long cycles_2_ns(unsigned long long cyc
)
28 return (cyc
* cyc2ns_scale
) >> NS_SCALE
;
31 unsigned long long sched_clock(void)
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.
42 return cycles_2_ns(a
);
45 static int tsc_unstable
;
47 static inline int check_tsc_unstable(void)
51 #ifdef CONFIG_CPU_FREQ
53 /* Frequency scaling support. Adjust the TSC based timer when the cpu frequency
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.
60 * Should fix up last_tsc too. Currently gettimeofday in the
61 * first tick after the change will be slightly wrong.
64 #include <linux/workqueue.h>
66 static unsigned int cpufreq_delayed_issched
= 0;
67 static unsigned int cpufreq_init
= 0;
68 static struct work_struct cpufreq_delayed_get_work
;
70 static void handle_cpufreq_delayed_get(struct work_struct
*v
)
73 for_each_online_cpu(cpu
) {
76 cpufreq_delayed_issched
= 0;
79 static unsigned int ref_freq
= 0;
80 static unsigned long loops_per_jiffy_ref
= 0;
82 static unsigned long tsc_khz_ref
= 0;
84 static int time_cpufreq_notifier(struct notifier_block
*nb
, unsigned long val
,
87 struct cpufreq_freqs
*freq
= data
;
88 unsigned long *lpj
, dummy
;
90 if (cpu_has(&cpu_data
[freq
->cpu
], X86_FEATURE_CONSTANT_TSC
))
94 if (!(freq
->flags
& CPUFREQ_CONST_LOOPS
))
96 lpj
= &cpu_data
[freq
->cpu
].loops_per_jiffy
;
98 lpj
= &boot_cpu_data
.loops_per_jiffy
;
102 ref_freq
= freq
->old
;
103 loops_per_jiffy_ref
= *lpj
;
104 tsc_khz_ref
= tsc_khz
;
106 if ((val
== CPUFREQ_PRECHANGE
&& freq
->old
< freq
->new) ||
107 (val
== CPUFREQ_POSTCHANGE
&& freq
->old
> freq
->new) ||
108 (val
== CPUFREQ_RESUMECHANGE
)) {
110 cpufreq_scale(loops_per_jiffy_ref
, ref_freq
, freq
->new);
112 tsc_khz
= cpufreq_scale(tsc_khz_ref
, ref_freq
, freq
->new);
113 if (!(freq
->flags
& CPUFREQ_CONST_LOOPS
))
114 mark_tsc_unstable("cpufreq changes");
117 set_cyc2ns_scale(tsc_khz_ref
);
122 static struct notifier_block time_cpufreq_notifier_block
= {
123 .notifier_call
= time_cpufreq_notifier
126 static int __init
cpufreq_tsc(void)
128 INIT_WORK(&cpufreq_delayed_get_work
, handle_cpufreq_delayed_get
);
129 if (!cpufreq_register_notifier(&time_cpufreq_notifier_block
,
130 CPUFREQ_TRANSITION_NOTIFIER
))
135 core_initcall(cpufreq_tsc
);
139 static int tsc_unstable
= 0;
142 * Make an educated guess if the TSC is trustworthy and synchronized
145 __cpuinit
int unsynchronized_tsc(void)
151 if (apic_is_clustered_box())
154 /* Most intel systems have synchronized TSCs except for
155 multi node systems */
156 if (boot_cpu_data
.x86_vendor
== X86_VENDOR_INTEL
) {
158 /* But TSC doesn't tick in C3 so don't use it there */
159 if (acpi_gbl_FADT
.header
.length
> 0 && acpi_gbl_FADT
.C3latency
< 1000)
165 /* Assume multi socket systems are not synchronized */
166 return num_present_cpus() > 1;
169 int __init
notsc_setup(char *s
)
175 __setup("notsc", notsc_setup
);
178 /* clock source code: */
179 static cycle_t
read_tsc(void)
181 cycle_t ret
= (cycle_t
)get_cycles_sync();
185 static cycle_t __vsyscall_fn
vread_tsc(void)
187 cycle_t ret
= (cycle_t
)get_cycles_sync();
191 static struct clocksource clocksource_tsc
= {
195 .mask
= CLOCKSOURCE_MASK(64),
197 .flags
= CLOCK_SOURCE_IS_CONTINUOUS
|
198 CLOCK_SOURCE_MUST_VERIFY
,
202 void mark_tsc_unstable(char *reason
)
206 printk("Marking TSC unstable due to %s\n", reason
);
207 /* Change only the rating, when not registered */
208 if (clocksource_tsc
.mult
)
209 clocksource_change_rating(&clocksource_tsc
, 0);
211 clocksource_tsc
.rating
= 0;
214 EXPORT_SYMBOL_GPL(mark_tsc_unstable
);
216 void __init
init_tsc_clocksource(void)
219 clocksource_tsc
.mult
= clocksource_khz2mult(tsc_khz
,
220 clocksource_tsc
.shift
);
221 if (check_tsc_unstable())
222 clocksource_tsc
.rating
= 0;
224 clocksource_register(&clocksource_tsc
);