time.c 12 KB

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400401402403404405406407408409410411412413414415416417418419420421422423424425426427428429430431432433434435436437438439440441442443444445446447448449450451452453454
  1. /*
  2. * linux/arch/ia64/kernel/time.c
  3. *
  4. * Copyright (C) 1998-2003 Hewlett-Packard Co
  5. * Stephane Eranian <eranian@hpl.hp.com>
  6. * David Mosberger <davidm@hpl.hp.com>
  7. * Copyright (C) 1999 Don Dugger <don.dugger@intel.com>
  8. * Copyright (C) 1999-2000 VA Linux Systems
  9. * Copyright (C) 1999-2000 Walt Drummond <drummond@valinux.com>
  10. */
  11. #include <linux/cpu.h>
  12. #include <linux/init.h>
  13. #include <linux/kernel.h>
  14. #include <linux/module.h>
  15. #include <linux/profile.h>
  16. #include <linux/sched.h>
  17. #include <linux/time.h>
  18. #include <linux/interrupt.h>
  19. #include <linux/efi.h>
  20. #include <linux/timex.h>
  21. #include <linux/clocksource.h>
  22. #include <asm/machvec.h>
  23. #include <asm/delay.h>
  24. #include <asm/hw_irq.h>
  25. #include <asm/ptrace.h>
  26. #include <asm/sal.h>
  27. #include <asm/sections.h>
  28. #include <asm/system.h>
  29. #include "fsyscall_gtod_data.h"
  30. static cycle_t itc_get_cycles(void);
  31. struct fsyscall_gtod_data_t fsyscall_gtod_data = {
  32. .lock = SEQLOCK_UNLOCKED,
  33. };
  34. struct itc_jitter_data_t itc_jitter_data;
  35. volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
  36. #ifdef CONFIG_IA64_DEBUG_IRQ
  37. unsigned long last_cli_ip;
  38. EXPORT_SYMBOL(last_cli_ip);
  39. #endif
  40. static struct clocksource clocksource_itc = {
  41. .name = "itc",
  42. .rating = 350,
  43. .read = itc_get_cycles,
  44. .mask = CLOCKSOURCE_MASK(64),
  45. .mult = 0, /*to be calculated*/
  46. .shift = 16,
  47. .flags = CLOCK_SOURCE_IS_CONTINUOUS,
  48. };
  49. static struct clocksource *itc_clocksource;
  50. #ifdef CONFIG_VIRT_CPU_ACCOUNTING
  51. #include <linux/kernel_stat.h>
  52. extern cputime_t cycle_to_cputime(u64 cyc);
  53. /*
  54. * Called from the context switch with interrupts disabled, to charge all
  55. * accumulated times to the current process, and to prepare accounting on
  56. * the next process.
  57. */
  58. void ia64_account_on_switch(struct task_struct *prev, struct task_struct *next)
  59. {
  60. struct thread_info *pi = task_thread_info(prev);
  61. struct thread_info *ni = task_thread_info(next);
  62. cputime_t delta_stime, delta_utime;
  63. __u64 now;
  64. now = ia64_get_itc();
  65. delta_stime = cycle_to_cputime(pi->ac_stime + (now - pi->ac_stamp));
  66. account_system_time(prev, 0, delta_stime);
  67. account_system_time_scaled(prev, delta_stime);
  68. if (pi->ac_utime) {
  69. delta_utime = cycle_to_cputime(pi->ac_utime);
  70. account_user_time(prev, delta_utime);
  71. account_user_time_scaled(prev, delta_utime);
  72. }
  73. pi->ac_stamp = ni->ac_stamp = now;
  74. ni->ac_stime = ni->ac_utime = 0;
  75. }
  76. /*
  77. * Account time for a transition between system, hard irq or soft irq state.
  78. * Note that this function is called with interrupts enabled.
  79. */
  80. void account_system_vtime(struct task_struct *tsk)
  81. {
  82. struct thread_info *ti = task_thread_info(tsk);
  83. unsigned long flags;
  84. cputime_t delta_stime;
  85. __u64 now;
  86. local_irq_save(flags);
  87. now = ia64_get_itc();
  88. delta_stime = cycle_to_cputime(ti->ac_stime + (now - ti->ac_stamp));
  89. account_system_time(tsk, 0, delta_stime);
  90. account_system_time_scaled(tsk, delta_stime);
  91. ti->ac_stime = 0;
  92. ti->ac_stamp = now;
  93. local_irq_restore(flags);
  94. }
  95. /*
  96. * Called from the timer interrupt handler to charge accumulated user time
  97. * to the current process. Must be called with interrupts disabled.
  98. */
  99. void account_process_tick(struct task_struct *p, int user_tick)
  100. {
  101. struct thread_info *ti = task_thread_info(p);
  102. cputime_t delta_utime;
  103. if (ti->ac_utime) {
  104. delta_utime = cycle_to_cputime(ti->ac_utime);
  105. account_user_time(p, delta_utime);
  106. account_user_time_scaled(p, delta_utime);
  107. ti->ac_utime = 0;
  108. }
  109. }
  110. #endif /* CONFIG_VIRT_CPU_ACCOUNTING */
  111. static irqreturn_t
  112. timer_interrupt (int irq, void *dev_id)
  113. {
  114. unsigned long new_itm;
  115. if (unlikely(cpu_is_offline(smp_processor_id()))) {
  116. return IRQ_HANDLED;
  117. }
  118. platform_timer_interrupt(irq, dev_id);
  119. new_itm = local_cpu_data->itm_next;
  120. if (!time_after(ia64_get_itc(), new_itm))
  121. printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
  122. ia64_get_itc(), new_itm);
  123. profile_tick(CPU_PROFILING);
  124. while (1) {
  125. update_process_times(user_mode(get_irq_regs()));
  126. new_itm += local_cpu_data->itm_delta;
  127. if (smp_processor_id() == time_keeper_id) {
  128. /*
  129. * Here we are in the timer irq handler. We have irqs locally
  130. * disabled, but we don't know if the timer_bh is running on
  131. * another CPU. We need to avoid to SMP race by acquiring the
  132. * xtime_lock.
  133. */
  134. write_seqlock(&xtime_lock);
  135. do_timer(1);
  136. local_cpu_data->itm_next = new_itm;
  137. write_sequnlock(&xtime_lock);
  138. } else
  139. local_cpu_data->itm_next = new_itm;
  140. if (time_after(new_itm, ia64_get_itc()))
  141. break;
  142. /*
  143. * Allow IPIs to interrupt the timer loop.
  144. */
  145. local_irq_enable();
  146. local_irq_disable();
  147. }
  148. do {
  149. /*
  150. * If we're too close to the next clock tick for
  151. * comfort, we increase the safety margin by
  152. * intentionally dropping the next tick(s). We do NOT
  153. * update itm.next because that would force us to call
  154. * do_timer() which in turn would let our clock run
  155. * too fast (with the potentially devastating effect
  156. * of losing monotony of time).
  157. */
  158. while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
  159. new_itm += local_cpu_data->itm_delta;
  160. ia64_set_itm(new_itm);
  161. /* double check, in case we got hit by a (slow) PMI: */
  162. } while (time_after_eq(ia64_get_itc(), new_itm));
  163. return IRQ_HANDLED;
  164. }
  165. /*
  166. * Encapsulate access to the itm structure for SMP.
  167. */
  168. void
  169. ia64_cpu_local_tick (void)
  170. {
  171. int cpu = smp_processor_id();
  172. unsigned long shift = 0, delta;
  173. /* arrange for the cycle counter to generate a timer interrupt: */
  174. ia64_set_itv(IA64_TIMER_VECTOR);
  175. delta = local_cpu_data->itm_delta;
  176. /*
  177. * Stagger the timer tick for each CPU so they don't occur all at (almost) the
  178. * same time:
  179. */
  180. if (cpu) {
  181. unsigned long hi = 1UL << ia64_fls(cpu);
  182. shift = (2*(cpu - hi) + 1) * delta/hi/2;
  183. }
  184. local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
  185. ia64_set_itm(local_cpu_data->itm_next);
  186. }
  187. static int nojitter;
  188. static int __init nojitter_setup(char *str)
  189. {
  190. nojitter = 1;
  191. printk("Jitter checking for ITC timers disabled\n");
  192. return 1;
  193. }
  194. __setup("nojitter", nojitter_setup);
  195. void __devinit
  196. ia64_init_itm (void)
  197. {
  198. unsigned long platform_base_freq, itc_freq;
  199. struct pal_freq_ratio itc_ratio, proc_ratio;
  200. long status, platform_base_drift, itc_drift;
  201. /*
  202. * According to SAL v2.6, we need to use a SAL call to determine the platform base
  203. * frequency and then a PAL call to determine the frequency ratio between the ITC
  204. * and the base frequency.
  205. */
  206. status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
  207. &platform_base_freq, &platform_base_drift);
  208. if (status != 0) {
  209. printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
  210. } else {
  211. status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
  212. if (status != 0)
  213. printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
  214. }
  215. if (status != 0) {
  216. /* invent "random" values */
  217. printk(KERN_ERR
  218. "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
  219. platform_base_freq = 100000000;
  220. platform_base_drift = -1; /* no drift info */
  221. itc_ratio.num = 3;
  222. itc_ratio.den = 1;
  223. }
  224. if (platform_base_freq < 40000000) {
  225. printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
  226. platform_base_freq);
  227. platform_base_freq = 75000000;
  228. platform_base_drift = -1;
  229. }
  230. if (!proc_ratio.den)
  231. proc_ratio.den = 1; /* avoid division by zero */
  232. if (!itc_ratio.den)
  233. itc_ratio.den = 1; /* avoid division by zero */
  234. itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
  235. local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
  236. printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
  237. "ITC freq=%lu.%03luMHz", smp_processor_id(),
  238. platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
  239. itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
  240. if (platform_base_drift != -1) {
  241. itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
  242. printk("+/-%ldppm\n", itc_drift);
  243. } else {
  244. itc_drift = -1;
  245. printk("\n");
  246. }
  247. local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
  248. local_cpu_data->itc_freq = itc_freq;
  249. local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
  250. local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
  251. + itc_freq/2)/itc_freq;
  252. if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
  253. #ifdef CONFIG_SMP
  254. /* On IA64 in an SMP configuration ITCs are never accurately synchronized.
  255. * Jitter compensation requires a cmpxchg which may limit
  256. * the scalability of the syscalls for retrieving time.
  257. * The ITC synchronization is usually successful to within a few
  258. * ITC ticks but this is not a sure thing. If you need to improve
  259. * timer performance in SMP situations then boot the kernel with the
  260. * "nojitter" option. However, doing so may result in time fluctuating (maybe
  261. * even going backward) if the ITC offsets between the individual CPUs
  262. * are too large.
  263. */
  264. if (!nojitter)
  265. itc_jitter_data.itc_jitter = 1;
  266. #endif
  267. } else
  268. /*
  269. * ITC is drifty and we have not synchronized the ITCs in smpboot.c.
  270. * ITC values may fluctuate significantly between processors.
  271. * Clock should not be used for hrtimers. Mark itc as only
  272. * useful for boot and testing.
  273. *
  274. * Note that jitter compensation is off! There is no point of
  275. * synchronizing ITCs since they may be large differentials
  276. * that change over time.
  277. *
  278. * The only way to fix this would be to repeatedly sync the
  279. * ITCs. Until that time we have to avoid ITC.
  280. */
  281. clocksource_itc.rating = 50;
  282. /* Setup the CPU local timer tick */
  283. ia64_cpu_local_tick();
  284. if (!itc_clocksource) {
  285. /* Sort out mult/shift values: */
  286. clocksource_itc.mult =
  287. clocksource_hz2mult(local_cpu_data->itc_freq,
  288. clocksource_itc.shift);
  289. clocksource_register(&clocksource_itc);
  290. itc_clocksource = &clocksource_itc;
  291. }
  292. }
  293. static cycle_t itc_get_cycles(void)
  294. {
  295. u64 lcycle, now, ret;
  296. if (!itc_jitter_data.itc_jitter)
  297. return get_cycles();
  298. lcycle = itc_jitter_data.itc_lastcycle;
  299. now = get_cycles();
  300. if (lcycle && time_after(lcycle, now))
  301. return lcycle;
  302. /*
  303. * Keep track of the last timer value returned.
  304. * In an SMP environment, you could lose out in contention of
  305. * cmpxchg. If so, your cmpxchg returns new value which the
  306. * winner of contention updated to. Use the new value instead.
  307. */
  308. ret = cmpxchg(&itc_jitter_data.itc_lastcycle, lcycle, now);
  309. if (unlikely(ret != lcycle))
  310. return ret;
  311. return now;
  312. }
  313. static struct irqaction timer_irqaction = {
  314. .handler = timer_interrupt,
  315. .flags = IRQF_DISABLED | IRQF_IRQPOLL,
  316. .name = "timer"
  317. };
  318. void __init
  319. time_init (void)
  320. {
  321. register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
  322. efi_gettimeofday(&xtime);
  323. ia64_init_itm();
  324. /*
  325. * Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
  326. * tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
  327. */
  328. set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
  329. }
  330. /*
  331. * Generic udelay assumes that if preemption is allowed and the thread
  332. * migrates to another CPU, that the ITC values are synchronized across
  333. * all CPUs.
  334. */
  335. static void
  336. ia64_itc_udelay (unsigned long usecs)
  337. {
  338. unsigned long start = ia64_get_itc();
  339. unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;
  340. while (time_before(ia64_get_itc(), end))
  341. cpu_relax();
  342. }
  343. void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;
  344. void
  345. udelay (unsigned long usecs)
  346. {
  347. (*ia64_udelay)(usecs);
  348. }
  349. EXPORT_SYMBOL(udelay);
  350. /* IA64 doesn't cache the timezone */
  351. void update_vsyscall_tz(void)
  352. {
  353. }
  354. void update_vsyscall(struct timespec *wall, struct clocksource *c)
  355. {
  356. unsigned long flags;
  357. write_seqlock_irqsave(&fsyscall_gtod_data.lock, flags);
  358. /* copy fsyscall clock data */
  359. fsyscall_gtod_data.clk_mask = c->mask;
  360. fsyscall_gtod_data.clk_mult = c->mult;
  361. fsyscall_gtod_data.clk_shift = c->shift;
  362. fsyscall_gtod_data.clk_fsys_mmio = c->fsys_mmio;
  363. fsyscall_gtod_data.clk_cycle_last = c->cycle_last;
  364. /* copy kernel time structures */
  365. fsyscall_gtod_data.wall_time.tv_sec = wall->tv_sec;
  366. fsyscall_gtod_data.wall_time.tv_nsec = wall->tv_nsec;
  367. fsyscall_gtod_data.monotonic_time.tv_sec = wall_to_monotonic.tv_sec
  368. + wall->tv_sec;
  369. fsyscall_gtod_data.monotonic_time.tv_nsec = wall_to_monotonic.tv_nsec
  370. + wall->tv_nsec;
  371. /* normalize */
  372. while (fsyscall_gtod_data.monotonic_time.tv_nsec >= NSEC_PER_SEC) {
  373. fsyscall_gtod_data.monotonic_time.tv_nsec -= NSEC_PER_SEC;
  374. fsyscall_gtod_data.monotonic_time.tv_sec++;
  375. }
  376. write_sequnlock_irqrestore(&fsyscall_gtod_data.lock, flags);
  377. }