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>
17 #include <asm/timer.h>
19 #include "mach_timer.h"
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
31 static int __init
tsc_setup(char *str
)
33 printk(KERN_WARNING
"notsc: Kernel compiled with CONFIG_X86_TSC, "
34 "cannot disable TSC.\n");
39 * disable flag for tsc. Takes effect by clearing the TSC cpu flag
42 static int __init
tsc_setup(char *str
)
50 __setup("notsc", tsc_setup
);
53 * code to mark and check if the TSC is unstable
54 * due to cpufreq or due to unsynced TSCs
56 static int tsc_unstable
;
58 static inline int check_tsc_unstable(void)
63 /* Accellerators for sched_clock()
64 * convert from cycles(64bits) => nanoseconds (64bits)
66 * ns = cycles / (freq / ns_per_sec)
67 * ns = cycles * (ns_per_sec / freq)
68 * ns = cycles * (10^9 / (cpu_khz * 10^3))
69 * ns = cycles * (10^6 / cpu_khz)
71 * Then we use scaling math (suggested by george@mvista.com) to get:
72 * ns = cycles * (10^6 * SC / cpu_khz) / SC
73 * ns = cycles * cyc2ns_scale / SC
75 * And since SC is a constant power of two, we can convert the div
78 * We can use khz divisor instead of mhz to keep a better percision, since
79 * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
80 * (mathieu.desnoyers@polymtl.ca)
82 * -johnstul@us.ibm.com "math is hard, lets go shopping!"
84 static unsigned long cyc2ns_scale __read_mostly
;
86 #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
88 static inline void set_cyc2ns_scale(unsigned long cpu_khz
)
90 cyc2ns_scale
= (1000000 << CYC2NS_SCALE_FACTOR
)/cpu_khz
;
93 static inline unsigned long long cycles_2_ns(unsigned long long cyc
)
95 return (cyc
* cyc2ns_scale
) >> CYC2NS_SCALE_FACTOR
;
99 * Scheduler clock - returns current time in nanosec units.
101 unsigned long long sched_clock(void)
103 unsigned long long this_offset
;
106 * Fall back to jiffies if there's no TSC available:
108 if (unlikely(tsc_disable
))
109 /* No locking but a rare wrong value is not a big deal: */
110 return (jiffies_64
- INITIAL_JIFFIES
) * (1000000000 / HZ
);
112 /* read the Time Stamp Counter: */
113 get_scheduled_cycles(this_offset
);
115 /* return the value in ns */
116 return cycles_2_ns(this_offset
);
119 unsigned long native_calculate_cpu_khz(void)
121 unsigned long long start
, end
;
127 local_irq_save(flags
);
129 /* run 3 times to ensure the cache is warm */
130 for (i
= 0; i
< 3; i
++) {
131 mach_prepare_counter();
133 mach_countup(&count
);
137 * Error: ECTCNEVERSET
138 * The CTC wasn't reliable: we got a hit on the very first read,
139 * or the CPU was so fast/slow that the quotient wouldn't fit in
145 delta64
= end
- start
;
147 /* cpu freq too fast: */
148 if (delta64
> (1ULL<<32))
151 /* cpu freq too slow: */
152 if (delta64
<= CALIBRATE_TIME_MSEC
)
155 delta64
+= CALIBRATE_TIME_MSEC
/2; /* round for do_div */
156 do_div(delta64
,CALIBRATE_TIME_MSEC
);
158 local_irq_restore(flags
);
159 return (unsigned long)delta64
;
161 local_irq_restore(flags
);
165 int recalibrate_cpu_khz(void)
168 unsigned long cpu_khz_old
= cpu_khz
;
171 cpu_khz
= calculate_cpu_khz();
173 cpu_data
[0].loops_per_jiffy
=
174 cpufreq_scale(cpu_data
[0].loops_per_jiffy
,
175 cpu_khz_old
, cpu_khz
);
184 EXPORT_SYMBOL(recalibrate_cpu_khz
);
186 #ifdef CONFIG_CPU_FREQ
189 * if the CPU frequency is scaled, TSC-based delays will need a different
190 * loops_per_jiffy value to function properly.
192 static unsigned int ref_freq
= 0;
193 static unsigned long loops_per_jiffy_ref
= 0;
194 static unsigned long cpu_khz_ref
= 0;
197 time_cpufreq_notifier(struct notifier_block
*nb
, unsigned long val
, void *data
)
199 struct cpufreq_freqs
*freq
= data
;
201 if (val
!= CPUFREQ_RESUMECHANGE
&& val
!= CPUFREQ_SUSPENDCHANGE
)
202 write_seqlock_irq(&xtime_lock
);
206 ref_freq
= freq
->new;
209 ref_freq
= freq
->old
;
210 loops_per_jiffy_ref
= cpu_data
[freq
->cpu
].loops_per_jiffy
;
211 cpu_khz_ref
= cpu_khz
;
214 if ((val
== CPUFREQ_PRECHANGE
&& freq
->old
< freq
->new) ||
215 (val
== CPUFREQ_POSTCHANGE
&& freq
->old
> freq
->new) ||
216 (val
== CPUFREQ_RESUMECHANGE
)) {
217 if (!(freq
->flags
& CPUFREQ_CONST_LOOPS
))
218 cpu_data
[freq
->cpu
].loops_per_jiffy
=
219 cpufreq_scale(loops_per_jiffy_ref
,
220 ref_freq
, freq
->new);
224 if (num_online_cpus() == 1)
225 cpu_khz
= cpufreq_scale(cpu_khz_ref
,
226 ref_freq
, freq
->new);
227 if (!(freq
->flags
& CPUFREQ_CONST_LOOPS
)) {
229 set_cyc2ns_scale(cpu_khz
);
231 * TSC based sched_clock turns
239 if (val
!= CPUFREQ_RESUMECHANGE
&& val
!= CPUFREQ_SUSPENDCHANGE
)
240 write_sequnlock_irq(&xtime_lock
);
245 static struct notifier_block time_cpufreq_notifier_block
= {
246 .notifier_call
= time_cpufreq_notifier
249 static int __init
cpufreq_tsc(void)
251 return cpufreq_register_notifier(&time_cpufreq_notifier_block
,
252 CPUFREQ_TRANSITION_NOTIFIER
);
254 core_initcall(cpufreq_tsc
);
258 /* clock source code */
260 static unsigned long current_tsc_khz
= 0;
262 static cycle_t
read_tsc(void)
271 static struct clocksource clocksource_tsc
= {
275 .mask
= CLOCKSOURCE_MASK(64),
276 .mult
= 0, /* to be set */
278 .flags
= CLOCK_SOURCE_IS_CONTINUOUS
|
279 CLOCK_SOURCE_MUST_VERIFY
,
282 void mark_tsc_unstable(void)
286 /* Can be called before registration */
287 if (clocksource_tsc
.mult
)
288 clocksource_change_rating(&clocksource_tsc
, 0);
290 clocksource_tsc
.rating
= 0;
293 EXPORT_SYMBOL_GPL(mark_tsc_unstable
);
295 static int __init
dmi_mark_tsc_unstable(struct dmi_system_id
*d
)
297 printk(KERN_NOTICE
"%s detected: marking TSC unstable.\n",
303 /* List of systems that have known TSC problems */
304 static struct dmi_system_id __initdata bad_tsc_dmi_table
[] = {
306 .callback
= dmi_mark_tsc_unstable
,
307 .ident
= "IBM Thinkpad 380XD",
309 DMI_MATCH(DMI_BOARD_VENDOR
, "IBM"),
310 DMI_MATCH(DMI_BOARD_NAME
, "2635FA0"),
317 * Make an educated guess if the TSC is trustworthy and synchronized
320 __cpuinit
int unsynchronized_tsc(void)
322 if (!cpu_has_tsc
|| tsc_unstable
)
325 * Intel systems are normally all synchronized.
326 * Exceptions must mark TSC as unstable:
328 if (boot_cpu_data
.x86_vendor
!= X86_VENDOR_INTEL
) {
329 /* assume multi socket systems are not synchronized: */
330 if (num_possible_cpus() > 1)
337 * Geode_LX - the OLPC CPU has a possibly a very reliable TSC
339 #ifdef CONFIG_MGEODE_LX
340 /* RTSC counts during suspend */
341 #define RTSC_SUSP 0x100
343 static void __init
check_geode_tsc_reliable(void)
347 rdmsrl(MSR_GEODE_BUSCONT_CONF0
, val
);
348 if ((val
& RTSC_SUSP
))
349 clocksource_tsc
.flags
&= ~CLOCK_SOURCE_MUST_VERIFY
;
352 static inline void check_geode_tsc_reliable(void) { }
356 void __init
tsc_init(void)
358 if (!cpu_has_tsc
|| tsc_disable
)
361 cpu_khz
= calculate_cpu_khz();
367 printk("Detected %lu.%03lu MHz processor.\n",
368 (unsigned long)cpu_khz
/ 1000,
369 (unsigned long)cpu_khz
% 1000);
371 set_cyc2ns_scale(cpu_khz
);
374 /* Check and install the TSC clocksource */
375 dmi_check_system(bad_tsc_dmi_table
);
377 unsynchronized_tsc();
378 check_geode_tsc_reliable();
379 current_tsc_khz
= tsc_khz
;
380 clocksource_tsc
.mult
= clocksource_khz2mult(current_tsc_khz
,
381 clocksource_tsc
.shift
);
382 /* lower the rating if we already know its unstable: */
383 if (check_tsc_unstable()) {
384 clocksource_tsc
.rating
= 0;
385 clocksource_tsc
.flags
&= ~CLOCK_SOURCE_IS_CONTINUOUS
;
387 clocksource_register(&clocksource_tsc
);
393 * Set the tsc_disable flag if there's no TSC support, this
394 * makes it a fast flag for the kernel to see whether it
395 * should be using the TSC.