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.
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>
14 #include <asm/delay.h>
18 #include "mach_timer.h"
21 * On some systems the TSC frequency does not
22 * change with the cpu frequency. So we need
23 * an extra value to store the TSC freq
27 int tsc_disable __cpuinitdata
= 0;
30 static int __init
tsc_setup(char *str
)
32 printk(KERN_WARNING
"notsc: Kernel compiled with CONFIG_X86_TSC, "
33 "cannot disable TSC.\n");
38 * disable flag for tsc. Takes effect by clearing the TSC cpu flag
41 static int __init
tsc_setup(char *str
)
49 __setup("notsc", tsc_setup
);
52 * code to mark and check if the TSC is unstable
53 * due to cpufreq or due to unsynced TSCs
55 static int tsc_unstable
;
57 static inline int check_tsc_unstable(void)
62 void mark_tsc_unstable(void)
66 EXPORT_SYMBOL_GPL(mark_tsc_unstable
);
68 /* Accellerators for sched_clock()
69 * convert from cycles(64bits) => nanoseconds (64bits)
71 * ns = cycles / (freq / ns_per_sec)
72 * ns = cycles * (ns_per_sec / freq)
73 * ns = cycles * (10^9 / (cpu_khz * 10^3))
74 * ns = cycles * (10^6 / cpu_khz)
76 * Then we use scaling math (suggested by george@mvista.com) to get:
77 * ns = cycles * (10^6 * SC / cpu_khz) / SC
78 * ns = cycles * cyc2ns_scale / SC
80 * And since SC is a constant power of two, we can convert the div
83 * We can use khz divisor instead of mhz to keep a better percision, since
84 * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
85 * (mathieu.desnoyers@polymtl.ca)
87 * -johnstul@us.ibm.com "math is hard, lets go shopping!"
89 static unsigned long cyc2ns_scale __read_mostly
;
91 #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
93 static inline void set_cyc2ns_scale(unsigned long cpu_khz
)
95 cyc2ns_scale
= (1000000 << CYC2NS_SCALE_FACTOR
)/cpu_khz
;
98 static inline unsigned long long cycles_2_ns(unsigned long long cyc
)
100 return (cyc
* cyc2ns_scale
) >> CYC2NS_SCALE_FACTOR
;
104 * Scheduler clock - returns current time in nanosec units.
106 unsigned long long sched_clock(void)
108 unsigned long long this_offset
;
111 * in the NUMA case we dont use the TSC as they are not
112 * synchronized across all CPUs.
115 if (!cpu_khz
|| check_tsc_unstable())
117 /* no locking but a rare wrong value is not a big deal */
118 return (jiffies_64
- INITIAL_JIFFIES
) * (1000000000 / HZ
);
120 /* read the Time Stamp Counter: */
121 rdtscll(this_offset
);
123 /* return the value in ns */
124 return cycles_2_ns(this_offset
);
127 static unsigned long calculate_cpu_khz(void)
129 unsigned long long start
, end
;
135 local_irq_save(flags
);
137 /* run 3 times to ensure the cache is warm */
138 for (i
= 0; i
< 3; i
++) {
139 mach_prepare_counter();
141 mach_countup(&count
);
145 * Error: ECTCNEVERSET
146 * The CTC wasn't reliable: we got a hit on the very first read,
147 * or the CPU was so fast/slow that the quotient wouldn't fit in
153 delta64
= end
- start
;
155 /* cpu freq too fast: */
156 if (delta64
> (1ULL<<32))
159 /* cpu freq too slow: */
160 if (delta64
<= CALIBRATE_TIME_MSEC
)
163 delta64
+= CALIBRATE_TIME_MSEC
/2; /* round for do_div */
164 do_div(delta64
,CALIBRATE_TIME_MSEC
);
166 local_irq_restore(flags
);
167 return (unsigned long)delta64
;
169 local_irq_restore(flags
);
173 int recalibrate_cpu_khz(void)
176 unsigned long cpu_khz_old
= cpu_khz
;
179 cpu_khz
= calculate_cpu_khz();
181 cpu_data
[0].loops_per_jiffy
=
182 cpufreq_scale(cpu_data
[0].loops_per_jiffy
,
183 cpu_khz_old
, cpu_khz
);
192 EXPORT_SYMBOL(recalibrate_cpu_khz
);
194 void __init
tsc_init(void)
196 if (!cpu_has_tsc
|| tsc_disable
)
199 cpu_khz
= calculate_cpu_khz();
205 printk("Detected %lu.%03lu MHz processor.\n",
206 (unsigned long)cpu_khz
/ 1000,
207 (unsigned long)cpu_khz
% 1000);
209 set_cyc2ns_scale(cpu_khz
);
213 #ifdef CONFIG_CPU_FREQ
215 static unsigned int cpufreq_delayed_issched
= 0;
216 static unsigned int cpufreq_init
= 0;
217 static struct work_struct cpufreq_delayed_get_work
;
219 static void handle_cpufreq_delayed_get(void *v
)
223 for_each_online_cpu(cpu
)
226 cpufreq_delayed_issched
= 0;
230 * if we notice cpufreq oddness, schedule a call to cpufreq_get() as it tries
231 * to verify the CPU frequency the timing core thinks the CPU is running
232 * at is still correct.
234 static inline void cpufreq_delayed_get(void)
236 if (cpufreq_init
&& !cpufreq_delayed_issched
) {
237 cpufreq_delayed_issched
= 1;
238 printk(KERN_DEBUG
"Checking if CPU frequency changed.\n");
239 schedule_work(&cpufreq_delayed_get_work
);
244 * if the CPU frequency is scaled, TSC-based delays will need a different
245 * loops_per_jiffy value to function properly.
247 static unsigned int ref_freq
= 0;
248 static unsigned long loops_per_jiffy_ref
= 0;
249 static unsigned long cpu_khz_ref
= 0;
252 time_cpufreq_notifier(struct notifier_block
*nb
, unsigned long val
, void *data
)
254 struct cpufreq_freqs
*freq
= data
;
256 if (val
!= CPUFREQ_RESUMECHANGE
&& val
!= CPUFREQ_SUSPENDCHANGE
)
257 write_seqlock_irq(&xtime_lock
);
261 ref_freq
= freq
->new;
264 ref_freq
= freq
->old
;
265 loops_per_jiffy_ref
= cpu_data
[freq
->cpu
].loops_per_jiffy
;
266 cpu_khz_ref
= cpu_khz
;
269 if ((val
== CPUFREQ_PRECHANGE
&& freq
->old
< freq
->new) ||
270 (val
== CPUFREQ_POSTCHANGE
&& freq
->old
> freq
->new) ||
271 (val
== CPUFREQ_RESUMECHANGE
)) {
272 if (!(freq
->flags
& CPUFREQ_CONST_LOOPS
))
273 cpu_data
[freq
->cpu
].loops_per_jiffy
=
274 cpufreq_scale(loops_per_jiffy_ref
,
275 ref_freq
, freq
->new);
279 if (num_online_cpus() == 1)
280 cpu_khz
= cpufreq_scale(cpu_khz_ref
,
281 ref_freq
, freq
->new);
282 if (!(freq
->flags
& CPUFREQ_CONST_LOOPS
)) {
284 set_cyc2ns_scale(cpu_khz
);
286 * TSC based sched_clock turns
294 if (val
!= CPUFREQ_RESUMECHANGE
&& val
!= CPUFREQ_SUSPENDCHANGE
)
295 write_sequnlock_irq(&xtime_lock
);
300 static struct notifier_block time_cpufreq_notifier_block
= {
301 .notifier_call
= time_cpufreq_notifier
304 static int __init
cpufreq_tsc(void)
308 INIT_WORK(&cpufreq_delayed_get_work
, handle_cpufreq_delayed_get
, NULL
);
309 ret
= cpufreq_register_notifier(&time_cpufreq_notifier_block
,
310 CPUFREQ_TRANSITION_NOTIFIER
);
317 core_initcall(cpufreq_tsc
);
321 /* clock source code */
323 static unsigned long current_tsc_khz
= 0;
324 static int tsc_update_callback(void);
326 static cycle_t
read_tsc(void)
335 static struct clocksource clocksource_tsc
= {
339 .mask
= CLOCKSOURCE_MASK(64),
340 .mult
= 0, /* to be set */
342 .update_callback
= tsc_update_callback
,
346 static int tsc_update_callback(void)
350 /* check to see if we should switch to the safe clocksource: */
351 if (clocksource_tsc
.rating
!= 0 && check_tsc_unstable()) {
352 clocksource_tsc
.rating
= 0;
353 clocksource_reselect();
357 /* only update if tsc_khz has changed: */
358 if (current_tsc_khz
!= tsc_khz
) {
359 current_tsc_khz
= tsc_khz
;
360 clocksource_tsc
.mult
= clocksource_khz2mult(current_tsc_khz
,
361 clocksource_tsc
.shift
);
368 static int __init
dmi_mark_tsc_unstable(struct dmi_system_id
*d
)
370 printk(KERN_NOTICE
"%s detected: marking TSC unstable.\n",
376 /* List of systems that have known TSC problems */
377 static struct dmi_system_id __initdata bad_tsc_dmi_table
[] = {
379 .callback
= dmi_mark_tsc_unstable
,
380 .ident
= "IBM Thinkpad 380XD",
382 DMI_MATCH(DMI_BOARD_VENDOR
, "IBM"),
383 DMI_MATCH(DMI_BOARD_NAME
, "2635FA0"),
389 #define TSC_FREQ_CHECK_INTERVAL (10*MSEC_PER_SEC) /* 10sec in MS */
390 static struct timer_list verify_tsc_freq_timer
;
392 /* XXX - Probably should add locking */
393 static void verify_tsc_freq(unsigned long unused
)
396 static unsigned long last_jiffies
;
398 u64 now_tsc
, interval_tsc
;
399 unsigned long now_jiffies
, interval_jiffies
;
402 if (check_tsc_unstable())
406 now_jiffies
= jiffies
;
412 interval_jiffies
= now_jiffies
- last_jiffies
;
413 interval_tsc
= now_tsc
- last_tsc
;
415 do_div(interval_tsc
, cpu_khz
*1000);
417 if (interval_tsc
< (interval_jiffies
* 3 / 4)) {
418 printk("TSC appears to be running slowly. "
419 "Marking it as unstable\n");
426 last_jiffies
= now_jiffies
;
427 /* set us up to go off on the next interval: */
428 mod_timer(&verify_tsc_freq_timer
,
429 jiffies
+ msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL
));
433 * Make an educated guess if the TSC is trustworthy and synchronized
436 static __init
int unsynchronized_tsc(void)
439 * Intel systems are normally all synchronized.
440 * Exceptions must mark TSC as unstable:
442 if (boot_cpu_data
.x86_vendor
== X86_VENDOR_INTEL
)
445 /* assume multi socket systems are not synchronized: */
446 return num_possible_cpus() > 1;
449 static int __init
init_tsc_clocksource(void)
452 if (cpu_has_tsc
&& tsc_khz
&& !tsc_disable
) {
453 /* check blacklist */
454 dmi_check_system(bad_tsc_dmi_table
);
456 if (unsynchronized_tsc()) /* mark unstable if unsynced */
458 current_tsc_khz
= tsc_khz
;
459 clocksource_tsc
.mult
= clocksource_khz2mult(current_tsc_khz
,
460 clocksource_tsc
.shift
);
461 /* lower the rating if we already know its unstable: */
462 if (check_tsc_unstable())
463 clocksource_tsc
.rating
= 0;
465 init_timer(&verify_tsc_freq_timer
);
466 verify_tsc_freq_timer
.function
= verify_tsc_freq
;
467 verify_tsc_freq_timer
.expires
=
468 jiffies
+ msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL
);
469 add_timer(&verify_tsc_freq_timer
);
471 return clocksource_register(&clocksource_tsc
);
477 module_init(init_tsc_clocksource
);