[PATCH] Time: i386 Conversion - part 3: Enable Generic Timekeeping
[linux-2.6.git] / arch / i386 / kernel / tsc.c
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/workqueue.h>
8 #include <linux/cpufreq.h>
9 #include <linux/jiffies.h>
10 #include <linux/init.h>
11
12 #include <asm/tsc.h>
13 #include <asm/delay.h>
14 #include <asm/io.h>
15
16 #include "mach_timer.h"
17
18 /*
19  * On some systems the TSC frequency does not
20  * change with the cpu frequency. So we need
21  * an extra value to store the TSC freq
22  */
23 unsigned int tsc_khz;
24
25 int tsc_disable __cpuinitdata = 0;
26
27 #ifdef CONFIG_X86_TSC
28 static int __init tsc_setup(char *str)
29 {
30         printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
31                                 "cannot disable TSC.\n");
32         return 1;
33 }
34 #else
35 /*
36  * disable flag for tsc. Takes effect by clearing the TSC cpu flag
37  * in cpu/common.c
38  */
39 static int __init tsc_setup(char *str)
40 {
41         tsc_disable = 1;
42
43         return 1;
44 }
45 #endif
46
47 __setup("notsc", tsc_setup);
48
49 /*
50  * code to mark and check if the TSC is unstable
51  * due to cpufreq or due to unsynced TSCs
52  */
53 static int tsc_unstable;
54
55 static inline int check_tsc_unstable(void)
56 {
57         return tsc_unstable;
58 }
59
60 void mark_tsc_unstable(void)
61 {
62         tsc_unstable = 1;
63 }
64 EXPORT_SYMBOL_GPL(mark_tsc_unstable);
65
66 /* Accellerators for sched_clock()
67  * convert from cycles(64bits) => nanoseconds (64bits)
68  *  basic equation:
69  *              ns = cycles / (freq / ns_per_sec)
70  *              ns = cycles * (ns_per_sec / freq)
71  *              ns = cycles * (10^9 / (cpu_khz * 10^3))
72  *              ns = cycles * (10^6 / cpu_khz)
73  *
74  *      Then we use scaling math (suggested by george@mvista.com) to get:
75  *              ns = cycles * (10^6 * SC / cpu_khz) / SC
76  *              ns = cycles * cyc2ns_scale / SC
77  *
78  *      And since SC is a constant power of two, we can convert the div
79  *  into a shift.
80  *
81  *  We can use khz divisor instead of mhz to keep a better percision, since
82  *  cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
83  *  (mathieu.desnoyers@polymtl.ca)
84  *
85  *                      -johnstul@us.ibm.com "math is hard, lets go shopping!"
86  */
87 static unsigned long cyc2ns_scale __read_mostly;
88
89 #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
90
91 static inline void set_cyc2ns_scale(unsigned long cpu_khz)
92 {
93         cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz;
94 }
95
96 static inline unsigned long long cycles_2_ns(unsigned long long cyc)
97 {
98         return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR;
99 }
100
101 /*
102  * Scheduler clock - returns current time in nanosec units.
103  */
104 unsigned long long sched_clock(void)
105 {
106         unsigned long long this_offset;
107
108         /*
109          * in the NUMA case we dont use the TSC as they are not
110          * synchronized across all CPUs.
111          */
112 #ifndef CONFIG_NUMA
113         if (!cpu_khz || check_tsc_unstable())
114 #endif
115                 /* no locking but a rare wrong value is not a big deal */
116                 return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
117
118         /* read the Time Stamp Counter: */
119         rdtscll(this_offset);
120
121         /* return the value in ns */
122         return cycles_2_ns(this_offset);
123 }
124
125 static unsigned long calculate_cpu_khz(void)
126 {
127         unsigned long long start, end;
128         unsigned long count;
129         u64 delta64;
130         int i;
131         unsigned long flags;
132
133         local_irq_save(flags);
134
135         /* run 3 times to ensure the cache is warm */
136         for (i = 0; i < 3; i++) {
137                 mach_prepare_counter();
138                 rdtscll(start);
139                 mach_countup(&count);
140                 rdtscll(end);
141         }
142         /*
143          * Error: ECTCNEVERSET
144          * The CTC wasn't reliable: we got a hit on the very first read,
145          * or the CPU was so fast/slow that the quotient wouldn't fit in
146          * 32 bits..
147          */
148         if (count <= 1)
149                 goto err;
150
151         delta64 = end - start;
152
153         /* cpu freq too fast: */
154         if (delta64 > (1ULL<<32))
155                 goto err;
156
157         /* cpu freq too slow: */
158         if (delta64 <= CALIBRATE_TIME_MSEC)
159                 goto err;
160
161         delta64 += CALIBRATE_TIME_MSEC/2; /* round for do_div */
162         do_div(delta64,CALIBRATE_TIME_MSEC);
163
164         local_irq_restore(flags);
165         return (unsigned long)delta64;
166 err:
167         local_irq_restore(flags);
168         return 0;
169 }
170
171 int recalibrate_cpu_khz(void)
172 {
173 #ifndef CONFIG_SMP
174         unsigned long cpu_khz_old = cpu_khz;
175
176         if (cpu_has_tsc) {
177                 cpu_khz = calculate_cpu_khz();
178                 tsc_khz = cpu_khz;
179                 cpu_data[0].loops_per_jiffy =
180                         cpufreq_scale(cpu_data[0].loops_per_jiffy,
181                                         cpu_khz_old, cpu_khz);
182                 return 0;
183         } else
184                 return -ENODEV;
185 #else
186         return -ENODEV;
187 #endif
188 }
189
190 EXPORT_SYMBOL(recalibrate_cpu_khz);
191
192 void tsc_init(void)
193 {
194         if (!cpu_has_tsc || tsc_disable)
195                 return;
196
197         cpu_khz = calculate_cpu_khz();
198         tsc_khz = cpu_khz;
199
200         if (!cpu_khz)
201                 return;
202
203         printk("Detected %lu.%03lu MHz processor.\n",
204                                 (unsigned long)cpu_khz / 1000,
205                                 (unsigned long)cpu_khz % 1000);
206
207         set_cyc2ns_scale(cpu_khz);
208         use_tsc_delay();
209 }
210
211 #ifdef CONFIG_CPU_FREQ
212
213 static unsigned int cpufreq_delayed_issched = 0;
214 static unsigned int cpufreq_init = 0;
215 static struct work_struct cpufreq_delayed_get_work;
216
217 static void handle_cpufreq_delayed_get(void *v)
218 {
219         unsigned int cpu;
220
221         for_each_online_cpu(cpu)
222                 cpufreq_get(cpu);
223
224         cpufreq_delayed_issched = 0;
225 }
226
227 /*
228  * if we notice cpufreq oddness, schedule a call to cpufreq_get() as it tries
229  * to verify the CPU frequency the timing core thinks the CPU is running
230  * at is still correct.
231  */
232 static inline void cpufreq_delayed_get(void)
233 {
234         if (cpufreq_init && !cpufreq_delayed_issched) {
235                 cpufreq_delayed_issched = 1;
236                 printk(KERN_DEBUG "Checking if CPU frequency changed.\n");
237                 schedule_work(&cpufreq_delayed_get_work);
238         }
239 }
240
241 /*
242  * if the CPU frequency is scaled, TSC-based delays will need a different
243  * loops_per_jiffy value to function properly.
244  */
245 static unsigned int ref_freq = 0;
246 static unsigned long loops_per_jiffy_ref = 0;
247 static unsigned long cpu_khz_ref = 0;
248
249 static int
250 time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data)
251 {
252         struct cpufreq_freqs *freq = data;
253
254         if (val != CPUFREQ_RESUMECHANGE && val != CPUFREQ_SUSPENDCHANGE)
255                 write_seqlock_irq(&xtime_lock);
256
257         if (!ref_freq) {
258                 if (!freq->old){
259                         ref_freq = freq->new;
260                         goto end;
261                 }
262                 ref_freq = freq->old;
263                 loops_per_jiffy_ref = cpu_data[freq->cpu].loops_per_jiffy;
264                 cpu_khz_ref = cpu_khz;
265         }
266
267         if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
268             (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
269             (val == CPUFREQ_RESUMECHANGE)) {
270                 if (!(freq->flags & CPUFREQ_CONST_LOOPS))
271                         cpu_data[freq->cpu].loops_per_jiffy =
272                                 cpufreq_scale(loops_per_jiffy_ref,
273                                                 ref_freq, freq->new);
274
275                 if (cpu_khz) {
276
277                         if (num_online_cpus() == 1)
278                                 cpu_khz = cpufreq_scale(cpu_khz_ref,
279                                                 ref_freq, freq->new);
280                         if (!(freq->flags & CPUFREQ_CONST_LOOPS)) {
281                                 tsc_khz = cpu_khz;
282                                 set_cyc2ns_scale(cpu_khz);
283                                 /*
284                                  * TSC based sched_clock turns
285                                  * to junk w/ cpufreq
286                                  */
287                                 mark_tsc_unstable();
288                         }
289                 }
290         }
291 end:
292         if (val != CPUFREQ_RESUMECHANGE && val != CPUFREQ_SUSPENDCHANGE)
293                 write_sequnlock_irq(&xtime_lock);
294
295         return 0;
296 }
297
298 static struct notifier_block time_cpufreq_notifier_block = {
299         .notifier_call  = time_cpufreq_notifier
300 };
301
302 static int __init cpufreq_tsc(void)
303 {
304         int ret;
305
306         INIT_WORK(&cpufreq_delayed_get_work, handle_cpufreq_delayed_get, NULL);
307         ret = cpufreq_register_notifier(&time_cpufreq_notifier_block,
308                                         CPUFREQ_TRANSITION_NOTIFIER);
309         if (!ret)
310                 cpufreq_init = 1;
311
312         return ret;
313 }
314
315 core_initcall(cpufreq_tsc);
316
317 #endif