aboutsummaryrefslogtreecommitdiffstats
path: root/arch/i386/kernel/tsc.c
diff options
context:
space:
mode:
authorThomas Gleixner <tglx@linutronix.de>2007-10-11 05:13:09 -0400
committerThomas Gleixner <tglx@linutronix.de>2007-10-11 05:13:09 -0400
commit76ea2ec68b54acc13ee1bfbb9a4e3aad370a374f (patch)
tree32e289c7d4e82403951c4004e5ff1dece31d1816 /arch/i386/kernel/tsc.c
parent668a3bf76e56f019fee46210531f94cf6b418bbd (diff)
i386: prepare shared kernel/tsc.c
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/i386/kernel/tsc.c')
-rw-r--r--arch/i386/kernel/tsc.c413
1 files changed, 0 insertions, 413 deletions
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c
deleted file mode 100644
index a39280b4dd3a..000000000000
--- a/arch/i386/kernel/tsc.c
+++ /dev/null
@@ -1,413 +0,0 @@
1/*
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.
5 */
6
7#include <linux/sched.h>
8#include <linux/clocksource.h>
9#include <linux/workqueue.h>
10#include <linux/cpufreq.h>
11#include <linux/jiffies.h>
12#include <linux/init.h>
13#include <linux/dmi.h>
14
15#include <asm/delay.h>
16#include <asm/tsc.h>
17#include <asm/io.h>
18#include <asm/timer.h>
19
20#include "mach_timer.h"
21
22static int tsc_enabled;
23
24/*
25 * On some systems the TSC frequency does not
26 * change with the cpu frequency. So we need
27 * an extra value to store the TSC freq
28 */
29unsigned int tsc_khz;
30EXPORT_SYMBOL_GPL(tsc_khz);
31
32int tsc_disable;
33
34#ifdef CONFIG_X86_TSC
35static int __init tsc_setup(char *str)
36{
37 printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
38 "cannot disable TSC.\n");
39 return 1;
40}
41#else
42/*
43 * disable flag for tsc. Takes effect by clearing the TSC cpu flag
44 * in cpu/common.c
45 */
46static int __init tsc_setup(char *str)
47{
48 tsc_disable = 1;
49
50 return 1;
51}
52#endif
53
54__setup("notsc", tsc_setup);
55
56/*
57 * code to mark and check if the TSC is unstable
58 * due to cpufreq or due to unsynced TSCs
59 */
60static int tsc_unstable;
61
62int check_tsc_unstable(void)
63{
64 return tsc_unstable;
65}
66EXPORT_SYMBOL_GPL(check_tsc_unstable);
67
68/* Accellerators for sched_clock()
69 * convert from cycles(64bits) => nanoseconds (64bits)
70 * basic equation:
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)
75 *
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
79 *
80 * And since SC is a constant power of two, we can convert the div
81 * into a shift.
82 *
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)
86 *
87 * -johnstul@us.ibm.com "math is hard, lets go shopping!"
88 */
89unsigned long cyc2ns_scale __read_mostly;
90
91#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
92
93static inline void set_cyc2ns_scale(unsigned long cpu_khz)
94{
95 cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz;
96}
97
98/*
99 * Scheduler clock - returns current time in nanosec units.
100 */
101unsigned long long native_sched_clock(void)
102{
103 unsigned long long this_offset;
104
105 /*
106 * Fall back to jiffies if there's no TSC available:
107 * ( But note that we still use it if the TSC is marked
108 * unstable. We do this because unlike Time Of Day,
109 * the scheduler clock tolerates small errors and it's
110 * very important for it to be as fast as the platform
111 * can achive it. )
112 */
113 if (unlikely(!tsc_enabled && !tsc_unstable))
114 /* No locking but a rare wrong value is not a big deal: */
115 return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
116
117 /* read the Time Stamp Counter: */
118 rdtscll(this_offset);
119
120 /* return the value in ns */
121 return cycles_2_ns(this_offset);
122}
123
124/* We need to define a real function for sched_clock, to override the
125 weak default version */
126#ifdef CONFIG_PARAVIRT
127unsigned long long sched_clock(void)
128{
129 return paravirt_sched_clock();
130}
131#else
132unsigned long long sched_clock(void)
133 __attribute__((alias("native_sched_clock")));
134#endif
135
136unsigned long native_calculate_cpu_khz(void)
137{
138 unsigned long long start, end;
139 unsigned long count;
140 u64 delta64;
141 int i;
142 unsigned long flags;
143
144 local_irq_save(flags);
145
146 /* run 3 times to ensure the cache is warm */
147 for (i = 0; i < 3; i++) {
148 mach_prepare_counter();
149 rdtscll(start);
150 mach_countup(&count);
151 rdtscll(end);
152 }
153 /*
154 * Error: ECTCNEVERSET
155 * The CTC wasn't reliable: we got a hit on the very first read,
156 * or the CPU was so fast/slow that the quotient wouldn't fit in
157 * 32 bits..
158 */
159 if (count <= 1)
160 goto err;
161
162 delta64 = end - start;
163
164 /* cpu freq too fast: */
165 if (delta64 > (1ULL<<32))
166 goto err;
167
168 /* cpu freq too slow: */
169 if (delta64 <= CALIBRATE_TIME_MSEC)
170 goto err;
171
172 delta64 += CALIBRATE_TIME_MSEC/2; /* round for do_div */
173 do_div(delta64,CALIBRATE_TIME_MSEC);
174
175 local_irq_restore(flags);
176 return (unsigned long)delta64;
177err:
178 local_irq_restore(flags);
179 return 0;
180}
181
182int recalibrate_cpu_khz(void)
183{
184#ifndef CONFIG_SMP
185 unsigned long cpu_khz_old = cpu_khz;
186
187 if (cpu_has_tsc) {
188 cpu_khz = calculate_cpu_khz();
189 tsc_khz = cpu_khz;
190 cpu_data[0].loops_per_jiffy =
191 cpufreq_scale(cpu_data[0].loops_per_jiffy,
192 cpu_khz_old, cpu_khz);
193 return 0;
194 } else
195 return -ENODEV;
196#else
197 return -ENODEV;
198#endif
199}
200
201EXPORT_SYMBOL(recalibrate_cpu_khz);
202
203#ifdef CONFIG_CPU_FREQ
204
205/*
206 * if the CPU frequency is scaled, TSC-based delays will need a different
207 * loops_per_jiffy value to function properly.
208 */
209static unsigned int ref_freq = 0;
210static unsigned long loops_per_jiffy_ref = 0;
211static unsigned long cpu_khz_ref = 0;
212
213static int
214time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data)
215{
216 struct cpufreq_freqs *freq = data;
217
218 if (!ref_freq) {
219 if (!freq->old){
220 ref_freq = freq->new;
221 return 0;
222 }
223 ref_freq = freq->old;
224 loops_per_jiffy_ref = cpu_data[freq->cpu].loops_per_jiffy;
225 cpu_khz_ref = cpu_khz;
226 }
227
228 if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) ||
229 (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
230 (val == CPUFREQ_RESUMECHANGE)) {
231 if (!(freq->flags & CPUFREQ_CONST_LOOPS))
232 cpu_data[freq->cpu].loops_per_jiffy =
233 cpufreq_scale(loops_per_jiffy_ref,
234 ref_freq, freq->new);
235
236 if (cpu_khz) {
237
238 if (num_online_cpus() == 1)
239 cpu_khz = cpufreq_scale(cpu_khz_ref,
240 ref_freq, freq->new);
241 if (!(freq->flags & CPUFREQ_CONST_LOOPS)) {
242 tsc_khz = cpu_khz;
243 set_cyc2ns_scale(cpu_khz);
244 /*
245 * TSC based sched_clock turns
246 * to junk w/ cpufreq
247 */
248 mark_tsc_unstable("cpufreq changes");
249 }
250 }
251 }
252
253 return 0;
254}
255
256static struct notifier_block time_cpufreq_notifier_block = {
257 .notifier_call = time_cpufreq_notifier
258};
259
260static int __init cpufreq_tsc(void)
261{
262 return cpufreq_register_notifier(&time_cpufreq_notifier_block,
263 CPUFREQ_TRANSITION_NOTIFIER);
264}
265core_initcall(cpufreq_tsc);
266
267#endif
268
269/* clock source code */
270
271static unsigned long current_tsc_khz = 0;
272
273static cycle_t read_tsc(void)
274{
275 cycle_t ret;
276
277 rdtscll(ret);
278
279 return ret;
280}
281
282static struct clocksource clocksource_tsc = {
283 .name = "tsc",
284 .rating = 300,
285 .read = read_tsc,
286 .mask = CLOCKSOURCE_MASK(64),
287 .mult = 0, /* to be set */
288 .shift = 22,
289 .flags = CLOCK_SOURCE_IS_CONTINUOUS |
290 CLOCK_SOURCE_MUST_VERIFY,
291};
292
293void mark_tsc_unstable(char *reason)
294{
295 if (!tsc_unstable) {
296 tsc_unstable = 1;
297 tsc_enabled = 0;
298 printk("Marking TSC unstable due to: %s.\n", reason);
299 /* Can be called before registration */
300 if (clocksource_tsc.mult)
301 clocksource_change_rating(&clocksource_tsc, 0);
302 else
303 clocksource_tsc.rating = 0;
304 }
305}
306EXPORT_SYMBOL_GPL(mark_tsc_unstable);
307
308static int __init dmi_mark_tsc_unstable(struct dmi_system_id *d)
309{
310 printk(KERN_NOTICE "%s detected: marking TSC unstable.\n",
311 d->ident);
312 tsc_unstable = 1;
313 return 0;
314}
315
316/* List of systems that have known TSC problems */
317static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
318 {
319 .callback = dmi_mark_tsc_unstable,
320 .ident = "IBM Thinkpad 380XD",
321 .matches = {
322 DMI_MATCH(DMI_BOARD_VENDOR, "IBM"),
323 DMI_MATCH(DMI_BOARD_NAME, "2635FA0"),
324 },
325 },
326 {}
327};
328
329/*
330 * Make an educated guess if the TSC is trustworthy and synchronized
331 * over all CPUs.
332 */
333__cpuinit int unsynchronized_tsc(void)
334{
335 if (!cpu_has_tsc || tsc_unstable)
336 return 1;
337 /*
338 * Intel systems are normally all synchronized.
339 * Exceptions must mark TSC as unstable:
340 */
341 if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
342 /* assume multi socket systems are not synchronized: */
343 if (num_possible_cpus() > 1)
344 tsc_unstable = 1;
345 }
346 return tsc_unstable;
347}
348
349/*
350 * Geode_LX - the OLPC CPU has a possibly a very reliable TSC
351 */
352#ifdef CONFIG_MGEODE_LX
353/* RTSC counts during suspend */
354#define RTSC_SUSP 0x100
355
356static void __init check_geode_tsc_reliable(void)
357{
358 unsigned long val;
359
360 rdmsrl(MSR_GEODE_BUSCONT_CONF0, val);
361 if ((val & RTSC_SUSP))
362 clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
363}
364#else
365static inline void check_geode_tsc_reliable(void) { }
366#endif
367
368
369void __init tsc_init(void)
370{
371 if (!cpu_has_tsc || tsc_disable)
372 goto out_no_tsc;
373
374 cpu_khz = calculate_cpu_khz();
375 tsc_khz = cpu_khz;
376
377 if (!cpu_khz)
378 goto out_no_tsc;
379
380 printk("Detected %lu.%03lu MHz processor.\n",
381 (unsigned long)cpu_khz / 1000,
382 (unsigned long)cpu_khz % 1000);
383
384 set_cyc2ns_scale(cpu_khz);
385 use_tsc_delay();
386
387 /* Check and install the TSC clocksource */
388 dmi_check_system(bad_tsc_dmi_table);
389
390 unsynchronized_tsc();
391 check_geode_tsc_reliable();
392 current_tsc_khz = tsc_khz;
393 clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
394 clocksource_tsc.shift);
395 /* lower the rating if we already know its unstable: */
396 if (check_tsc_unstable()) {
397 clocksource_tsc.rating = 0;
398 clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
399 } else
400 tsc_enabled = 1;
401
402 clocksource_register(&clocksource_tsc);
403
404 return;
405
406out_no_tsc:
407 /*
408 * Set the tsc_disable flag if there's no TSC support, this
409 * makes it a fast flag for the kernel to see whether it
410 * should be using the TSC.
411 */
412 tsc_disable = 1;
413}
generated by cgit v1.2.2 (git 2.25.0) at 2024-11-15 01:00:36 -0500