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TOMOYO Linux Cross Reference
Linux/arch/s390/kernel/time.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  *    Time of day based timer functions.
  4  *
  5  *  S390 version
  6  *    Copyright IBM Corp. 1999, 2008
  7  *    Author(s): Hartmut Penner (hp@de.ibm.com),
  8  *               Martin Schwidefsky (schwidefsky@de.ibm.com),
  9  *               Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
 10  *
 11  *  Derived from "arch/i386/kernel/time.c"
 12  *    Copyright (C) 1991, 1992, 1995  Linus Torvalds
 13  */
 14 
 15 #define KMSG_COMPONENT "time"
 16 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
 17 
 18 #include <linux/kernel_stat.h>
 19 #include <linux/errno.h>
 20 #include <linux/export.h>
 21 #include <linux/sched.h>
 22 #include <linux/sched/clock.h>
 23 #include <linux/kernel.h>
 24 #include <linux/param.h>
 25 #include <linux/string.h>
 26 #include <linux/mm.h>
 27 #include <linux/interrupt.h>
 28 #include <linux/cpu.h>
 29 #include <linux/stop_machine.h>
 30 #include <linux/time.h>
 31 #include <linux/device.h>
 32 #include <linux/delay.h>
 33 #include <linux/init.h>
 34 #include <linux/smp.h>
 35 #include <linux/types.h>
 36 #include <linux/profile.h>
 37 #include <linux/timex.h>
 38 #include <linux/notifier.h>
 39 #include <linux/timekeeper_internal.h>
 40 #include <linux/clockchips.h>
 41 #include <linux/gfp.h>
 42 #include <linux/kprobes.h>
 43 #include <linux/uaccess.h>
 44 #include <asm/facility.h>
 45 #include <asm/delay.h>
 46 #include <asm/div64.h>
 47 #include <asm/vdso.h>
 48 #include <asm/irq.h>
 49 #include <asm/irq_regs.h>
 50 #include <asm/vtimer.h>
 51 #include <asm/stp.h>
 52 #include <asm/cio.h>
 53 #include "entry.h"
 54 
 55 unsigned char tod_clock_base[16] __aligned(8) = {
 56         /* Force to data section. */
 57         0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
 58         0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
 59 };
 60 EXPORT_SYMBOL_GPL(tod_clock_base);
 61 
 62 u64 clock_comparator_max = -1ULL;
 63 EXPORT_SYMBOL_GPL(clock_comparator_max);
 64 
 65 static DEFINE_PER_CPU(struct clock_event_device, comparators);
 66 
 67 ATOMIC_NOTIFIER_HEAD(s390_epoch_delta_notifier);
 68 EXPORT_SYMBOL(s390_epoch_delta_notifier);
 69 
 70 unsigned char ptff_function_mask[16];
 71 
 72 static unsigned long long lpar_offset;
 73 static unsigned long long initial_leap_seconds;
 74 static unsigned long long tod_steering_end;
 75 static long long tod_steering_delta;
 76 
 77 /*
 78  * Get time offsets with PTFF
 79  */
 80 void __init time_early_init(void)
 81 {
 82         struct ptff_qto qto;
 83         struct ptff_qui qui;
 84 
 85         /* Initialize TOD steering parameters */
 86         tod_steering_end = *(unsigned long long *) &tod_clock_base[1];
 87         vdso_data->ts_end = tod_steering_end;
 88 
 89         if (!test_facility(28))
 90                 return;
 91 
 92         ptff(&ptff_function_mask, sizeof(ptff_function_mask), PTFF_QAF);
 93 
 94         /* get LPAR offset */
 95         if (ptff_query(PTFF_QTO) && ptff(&qto, sizeof(qto), PTFF_QTO) == 0)
 96                 lpar_offset = qto.tod_epoch_difference;
 97 
 98         /* get initial leap seconds */
 99         if (ptff_query(PTFF_QUI) && ptff(&qui, sizeof(qui), PTFF_QUI) == 0)
100                 initial_leap_seconds = (unsigned long long)
101                         ((long) qui.old_leap * 4096000000L);
102 }
103 
104 /*
105  * Scheduler clock - returns current time in nanosec units.
106  */
107 unsigned long long notrace sched_clock(void)
108 {
109         return tod_to_ns(get_tod_clock_monotonic());
110 }
111 NOKPROBE_SYMBOL(sched_clock);
112 
113 /*
114  * Monotonic_clock - returns # of nanoseconds passed since time_init()
115  */
116 unsigned long long monotonic_clock(void)
117 {
118         return sched_clock();
119 }
120 EXPORT_SYMBOL(monotonic_clock);
121 
122 static void ext_to_timespec64(unsigned char *clk, struct timespec64 *xt)
123 {
124         unsigned long long high, low, rem, sec, nsec;
125 
126         /* Split extendnd TOD clock to micro-seconds and sub-micro-seconds */
127         high = (*(unsigned long long *) clk) >> 4;
128         low = (*(unsigned long long *)&clk[7]) << 4;
129         /* Calculate seconds and nano-seconds */
130         sec = high;
131         rem = do_div(sec, 1000000);
132         nsec = (((low >> 32) + (rem << 32)) * 1000) >> 32;
133 
134         xt->tv_sec = sec;
135         xt->tv_nsec = nsec;
136 }
137 
138 void clock_comparator_work(void)
139 {
140         struct clock_event_device *cd;
141 
142         S390_lowcore.clock_comparator = clock_comparator_max;
143         cd = this_cpu_ptr(&comparators);
144         cd->event_handler(cd);
145 }
146 
147 static int s390_next_event(unsigned long delta,
148                            struct clock_event_device *evt)
149 {
150         S390_lowcore.clock_comparator = get_tod_clock() + delta;
151         set_clock_comparator(S390_lowcore.clock_comparator);
152         return 0;
153 }
154 
155 /*
156  * Set up lowcore and control register of the current cpu to
157  * enable TOD clock and clock comparator interrupts.
158  */
159 void init_cpu_timer(void)
160 {
161         struct clock_event_device *cd;
162         int cpu;
163 
164         S390_lowcore.clock_comparator = clock_comparator_max;
165         set_clock_comparator(S390_lowcore.clock_comparator);
166 
167         cpu = smp_processor_id();
168         cd = &per_cpu(comparators, cpu);
169         cd->name                = "comparator";
170         cd->features            = CLOCK_EVT_FEAT_ONESHOT;
171         cd->mult                = 16777;
172         cd->shift               = 12;
173         cd->min_delta_ns        = 1;
174         cd->min_delta_ticks     = 1;
175         cd->max_delta_ns        = LONG_MAX;
176         cd->max_delta_ticks     = ULONG_MAX;
177         cd->rating              = 400;
178         cd->cpumask             = cpumask_of(cpu);
179         cd->set_next_event      = s390_next_event;
180 
181         clockevents_register_device(cd);
182 
183         /* Enable clock comparator timer interrupt. */
184         __ctl_set_bit(0,11);
185 
186         /* Always allow the timing alert external interrupt. */
187         __ctl_set_bit(0, 4);
188 }
189 
190 static void clock_comparator_interrupt(struct ext_code ext_code,
191                                        unsigned int param32,
192                                        unsigned long param64)
193 {
194         inc_irq_stat(IRQEXT_CLK);
195         if (S390_lowcore.clock_comparator == clock_comparator_max)
196                 set_clock_comparator(S390_lowcore.clock_comparator);
197 }
198 
199 static void stp_timing_alert(struct stp_irq_parm *);
200 
201 static void timing_alert_interrupt(struct ext_code ext_code,
202                                    unsigned int param32, unsigned long param64)
203 {
204         inc_irq_stat(IRQEXT_TLA);
205         if (param32 & 0x00038000)
206                 stp_timing_alert((struct stp_irq_parm *) &param32);
207 }
208 
209 static void stp_reset(void);
210 
211 void read_persistent_clock64(struct timespec64 *ts)
212 {
213         unsigned char clk[STORE_CLOCK_EXT_SIZE];
214         __u64 delta;
215 
216         delta = initial_leap_seconds + TOD_UNIX_EPOCH;
217         get_tod_clock_ext(clk);
218         *(__u64 *) &clk[1] -= delta;
219         if (*(__u64 *) &clk[1] > delta)
220                 clk[0]--;
221         ext_to_timespec64(clk, ts);
222 }
223 
224 void read_boot_clock64(struct timespec64 *ts)
225 {
226         unsigned char clk[STORE_CLOCK_EXT_SIZE];
227         __u64 delta;
228 
229         delta = initial_leap_seconds + TOD_UNIX_EPOCH;
230         memcpy(clk, tod_clock_base, 16);
231         *(__u64 *) &clk[1] -= delta;
232         if (*(__u64 *) &clk[1] > delta)
233                 clk[0]--;
234         ext_to_timespec64(clk, ts);
235 }
236 
237 static u64 read_tod_clock(struct clocksource *cs)
238 {
239         unsigned long long now, adj;
240 
241         preempt_disable(); /* protect from changes to steering parameters */
242         now = get_tod_clock();
243         adj = tod_steering_end - now;
244         if (unlikely((s64) adj >= 0))
245                 /*
246                  * manually steer by 1 cycle every 2^16 cycles. This
247                  * corresponds to shifting the tod delta by 15. 1s is
248                  * therefore steered in ~9h. The adjust will decrease
249                  * over time, until it finally reaches 0.
250                  */
251                 now += (tod_steering_delta < 0) ? (adj >> 15) : -(adj >> 15);
252         preempt_enable();
253         return now;
254 }
255 
256 static struct clocksource clocksource_tod = {
257         .name           = "tod",
258         .rating         = 400,
259         .read           = read_tod_clock,
260         .mask           = -1ULL,
261         .mult           = 1000,
262         .shift          = 12,
263         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
264 };
265 
266 struct clocksource * __init clocksource_default_clock(void)
267 {
268         return &clocksource_tod;
269 }
270 
271 void update_vsyscall(struct timekeeper *tk)
272 {
273         u64 nsecps;
274 
275         if (tk->tkr_mono.clock != &clocksource_tod)
276                 return;
277 
278         /* Make userspace gettimeofday spin until we're done. */
279         ++vdso_data->tb_update_count;
280         smp_wmb();
281         vdso_data->xtime_tod_stamp = tk->tkr_mono.cycle_last;
282         vdso_data->xtime_clock_sec = tk->xtime_sec;
283         vdso_data->xtime_clock_nsec = tk->tkr_mono.xtime_nsec;
284         vdso_data->wtom_clock_sec =
285                 tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
286         vdso_data->wtom_clock_nsec = tk->tkr_mono.xtime_nsec +
287                 + ((u64) tk->wall_to_monotonic.tv_nsec << tk->tkr_mono.shift);
288         nsecps = (u64) NSEC_PER_SEC << tk->tkr_mono.shift;
289         while (vdso_data->wtom_clock_nsec >= nsecps) {
290                 vdso_data->wtom_clock_nsec -= nsecps;
291                 vdso_data->wtom_clock_sec++;
292         }
293 
294         vdso_data->xtime_coarse_sec = tk->xtime_sec;
295         vdso_data->xtime_coarse_nsec =
296                 (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
297         vdso_data->wtom_coarse_sec =
298                 vdso_data->xtime_coarse_sec + tk->wall_to_monotonic.tv_sec;
299         vdso_data->wtom_coarse_nsec =
300                 vdso_data->xtime_coarse_nsec + tk->wall_to_monotonic.tv_nsec;
301         while (vdso_data->wtom_coarse_nsec >= NSEC_PER_SEC) {
302                 vdso_data->wtom_coarse_nsec -= NSEC_PER_SEC;
303                 vdso_data->wtom_coarse_sec++;
304         }
305 
306         vdso_data->tk_mult = tk->tkr_mono.mult;
307         vdso_data->tk_shift = tk->tkr_mono.shift;
308         smp_wmb();
309         ++vdso_data->tb_update_count;
310 }
311 
312 extern struct timezone sys_tz;
313 
314 void update_vsyscall_tz(void)
315 {
316         vdso_data->tz_minuteswest = sys_tz.tz_minuteswest;
317         vdso_data->tz_dsttime = sys_tz.tz_dsttime;
318 }
319 
320 /*
321  * Initialize the TOD clock and the CPU timer of
322  * the boot cpu.
323  */
324 void __init time_init(void)
325 {
326         /* Reset time synchronization interfaces. */
327         stp_reset();
328 
329         /* request the clock comparator external interrupt */
330         if (register_external_irq(EXT_IRQ_CLK_COMP, clock_comparator_interrupt))
331                 panic("Couldn't request external interrupt 0x1004");
332 
333         /* request the timing alert external interrupt */
334         if (register_external_irq(EXT_IRQ_TIMING_ALERT, timing_alert_interrupt))
335                 panic("Couldn't request external interrupt 0x1406");
336 
337         if (__clocksource_register(&clocksource_tod) != 0)
338                 panic("Could not register TOD clock source");
339 
340         /* Enable TOD clock interrupts on the boot cpu. */
341         init_cpu_timer();
342 
343         /* Enable cpu timer interrupts on the boot cpu. */
344         vtime_init();
345 }
346 
347 static DEFINE_PER_CPU(atomic_t, clock_sync_word);
348 static DEFINE_MUTEX(clock_sync_mutex);
349 static unsigned long clock_sync_flags;
350 
351 #define CLOCK_SYNC_HAS_STP      0
352 #define CLOCK_SYNC_STP          1
353 
354 /*
355  * The get_clock function for the physical clock. It will get the current
356  * TOD clock, subtract the LPAR offset and write the result to *clock.
357  * The function returns 0 if the clock is in sync with the external time
358  * source. If the clock mode is local it will return -EOPNOTSUPP and
359  * -EAGAIN if the clock is not in sync with the external reference.
360  */
361 int get_phys_clock(unsigned long *clock)
362 {
363         atomic_t *sw_ptr;
364         unsigned int sw0, sw1;
365 
366         sw_ptr = &get_cpu_var(clock_sync_word);
367         sw0 = atomic_read(sw_ptr);
368         *clock = get_tod_clock() - lpar_offset;
369         sw1 = atomic_read(sw_ptr);
370         put_cpu_var(clock_sync_word);
371         if (sw0 == sw1 && (sw0 & 0x80000000U))
372                 /* Success: time is in sync. */
373                 return 0;
374         if (!test_bit(CLOCK_SYNC_HAS_STP, &clock_sync_flags))
375                 return -EOPNOTSUPP;
376         if (!test_bit(CLOCK_SYNC_STP, &clock_sync_flags))
377                 return -EACCES;
378         return -EAGAIN;
379 }
380 EXPORT_SYMBOL(get_phys_clock);
381 
382 /*
383  * Make get_phys_clock() return -EAGAIN.
384  */
385 static void disable_sync_clock(void *dummy)
386 {
387         atomic_t *sw_ptr = this_cpu_ptr(&clock_sync_word);
388         /*
389          * Clear the in-sync bit 2^31. All get_phys_clock calls will
390          * fail until the sync bit is turned back on. In addition
391          * increase the "sequence" counter to avoid the race of an
392          * stp event and the complete recovery against get_phys_clock.
393          */
394         atomic_andnot(0x80000000, sw_ptr);
395         atomic_inc(sw_ptr);
396 }
397 
398 /*
399  * Make get_phys_clock() return 0 again.
400  * Needs to be called from a context disabled for preemption.
401  */
402 static void enable_sync_clock(void)
403 {
404         atomic_t *sw_ptr = this_cpu_ptr(&clock_sync_word);
405         atomic_or(0x80000000, sw_ptr);
406 }
407 
408 /*
409  * Function to check if the clock is in sync.
410  */
411 static inline int check_sync_clock(void)
412 {
413         atomic_t *sw_ptr;
414         int rc;
415 
416         sw_ptr = &get_cpu_var(clock_sync_word);
417         rc = (atomic_read(sw_ptr) & 0x80000000U) != 0;
418         put_cpu_var(clock_sync_word);
419         return rc;
420 }
421 
422 /*
423  * Apply clock delta to the global data structures.
424  * This is called once on the CPU that performed the clock sync.
425  */
426 static void clock_sync_global(unsigned long long delta)
427 {
428         unsigned long now, adj;
429         struct ptff_qto qto;
430 
431         /* Fixup the monotonic sched clock. */
432         *(unsigned long long *) &tod_clock_base[1] += delta;
433         if (*(unsigned long long *) &tod_clock_base[1] < delta)
434                 /* Epoch overflow */
435                 tod_clock_base[0]++;
436         /* Adjust TOD steering parameters. */
437         vdso_data->tb_update_count++;
438         now = get_tod_clock();
439         adj = tod_steering_end - now;
440         if (unlikely((s64) adj >= 0))
441                 /* Calculate how much of the old adjustment is left. */
442                 tod_steering_delta = (tod_steering_delta < 0) ?
443                         -(adj >> 15) : (adj >> 15);
444         tod_steering_delta += delta;
445         if ((abs(tod_steering_delta) >> 48) != 0)
446                 panic("TOD clock sync offset %lli is too large to drift\n",
447                       tod_steering_delta);
448         tod_steering_end = now + (abs(tod_steering_delta) << 15);
449         vdso_data->ts_dir = (tod_steering_delta < 0) ? 0 : 1;
450         vdso_data->ts_end = tod_steering_end;
451         vdso_data->tb_update_count++;
452         /* Update LPAR offset. */
453         if (ptff_query(PTFF_QTO) && ptff(&qto, sizeof(qto), PTFF_QTO) == 0)
454                 lpar_offset = qto.tod_epoch_difference;
455         /* Call the TOD clock change notifier. */
456         atomic_notifier_call_chain(&s390_epoch_delta_notifier, 0, &delta);
457 }
458 
459 /*
460  * Apply clock delta to the per-CPU data structures of this CPU.
461  * This is called for each online CPU after the call to clock_sync_global.
462  */
463 static void clock_sync_local(unsigned long long delta)
464 {
465         /* Add the delta to the clock comparator. */
466         if (S390_lowcore.clock_comparator != clock_comparator_max) {
467                 S390_lowcore.clock_comparator += delta;
468                 set_clock_comparator(S390_lowcore.clock_comparator);
469         }
470         /* Adjust the last_update_clock time-stamp. */
471         S390_lowcore.last_update_clock += delta;
472 }
473 
474 /* Single threaded workqueue used for stp sync events */
475 static struct workqueue_struct *time_sync_wq;
476 
477 static void __init time_init_wq(void)
478 {
479         if (time_sync_wq)
480                 return;
481         time_sync_wq = create_singlethread_workqueue("timesync");
482 }
483 
484 struct clock_sync_data {
485         atomic_t cpus;
486         int in_sync;
487         unsigned long long clock_delta;
488 };
489 
490 /*
491  * Server Time Protocol (STP) code.
492  */
493 static bool stp_online;
494 static struct stp_sstpi stp_info;
495 static void *stp_page;
496 
497 static void stp_work_fn(struct work_struct *work);
498 static DEFINE_MUTEX(stp_work_mutex);
499 static DECLARE_WORK(stp_work, stp_work_fn);
500 static struct timer_list stp_timer;
501 
502 static int __init early_parse_stp(char *p)
503 {
504         return kstrtobool(p, &stp_online);
505 }
506 early_param("stp", early_parse_stp);
507 
508 /*
509  * Reset STP attachment.
510  */
511 static void __init stp_reset(void)
512 {
513         int rc;
514 
515         stp_page = (void *) get_zeroed_page(GFP_ATOMIC);
516         rc = chsc_sstpc(stp_page, STP_OP_CTRL, 0x0000, NULL);
517         if (rc == 0)
518                 set_bit(CLOCK_SYNC_HAS_STP, &clock_sync_flags);
519         else if (stp_online) {
520                 pr_warn("The real or virtual hardware system does not provide an STP interface\n");
521                 free_page((unsigned long) stp_page);
522                 stp_page = NULL;
523                 stp_online = false;
524         }
525 }
526 
527 static void stp_timeout(struct timer_list *unused)
528 {
529         queue_work(time_sync_wq, &stp_work);
530 }
531 
532 static int __init stp_init(void)
533 {
534         if (!test_bit(CLOCK_SYNC_HAS_STP, &clock_sync_flags))
535                 return 0;
536         timer_setup(&stp_timer, stp_timeout, 0);
537         time_init_wq();
538         if (!stp_online)
539                 return 0;
540         queue_work(time_sync_wq, &stp_work);
541         return 0;
542 }
543 
544 arch_initcall(stp_init);
545 
546 /*
547  * STP timing alert. There are three causes:
548  * 1) timing status change
549  * 2) link availability change
550  * 3) time control parameter change
551  * In all three cases we are only interested in the clock source state.
552  * If a STP clock source is now available use it.
553  */
554 static void stp_timing_alert(struct stp_irq_parm *intparm)
555 {
556         if (intparm->tsc || intparm->lac || intparm->tcpc)
557                 queue_work(time_sync_wq, &stp_work);
558 }
559 
560 /*
561  * STP sync check machine check. This is called when the timing state
562  * changes from the synchronized state to the unsynchronized state.
563  * After a STP sync check the clock is not in sync. The machine check
564  * is broadcasted to all cpus at the same time.
565  */
566 int stp_sync_check(void)
567 {
568         disable_sync_clock(NULL);
569         return 1;
570 }
571 
572 /*
573  * STP island condition machine check. This is called when an attached
574  * server  attempts to communicate over an STP link and the servers
575  * have matching CTN ids and have a valid stratum-1 configuration
576  * but the configurations do not match.
577  */
578 int stp_island_check(void)
579 {
580         disable_sync_clock(NULL);
581         return 1;
582 }
583 
584 void stp_queue_work(void)
585 {
586         queue_work(time_sync_wq, &stp_work);
587 }
588 
589 static int stp_sync_clock(void *data)
590 {
591         struct clock_sync_data *sync = data;
592         unsigned long long clock_delta;
593         static int first;
594         int rc;
595 
596         enable_sync_clock();
597         if (xchg(&first, 1) == 0) {
598                 /* Wait until all other cpus entered the sync function. */
599                 while (atomic_read(&sync->cpus) != 0)
600                         cpu_relax();
601                 rc = 0;
602                 if (stp_info.todoff[0] || stp_info.todoff[1] ||
603                     stp_info.todoff[2] || stp_info.todoff[3] ||
604                     stp_info.tmd != 2) {
605                         rc = chsc_sstpc(stp_page, STP_OP_SYNC, 0,
606                                         &clock_delta);
607                         if (rc == 0) {
608                                 sync->clock_delta = clock_delta;
609                                 clock_sync_global(clock_delta);
610                                 rc = chsc_sstpi(stp_page, &stp_info,
611                                                 sizeof(struct stp_sstpi));
612                                 if (rc == 0 && stp_info.tmd != 2)
613                                         rc = -EAGAIN;
614                         }
615                 }
616                 sync->in_sync = rc ? -EAGAIN : 1;
617                 xchg(&first, 0);
618         } else {
619                 /* Slave */
620                 atomic_dec(&sync->cpus);
621                 /* Wait for in_sync to be set. */
622                 while (READ_ONCE(sync->in_sync) == 0)
623                         __udelay(1);
624         }
625         if (sync->in_sync != 1)
626                 /* Didn't work. Clear per-cpu in sync bit again. */
627                 disable_sync_clock(NULL);
628         /* Apply clock delta to per-CPU fields of this CPU. */
629         clock_sync_local(sync->clock_delta);
630 
631         return 0;
632 }
633 
634 /*
635  * STP work. Check for the STP state and take over the clock
636  * synchronization if the STP clock source is usable.
637  */
638 static void stp_work_fn(struct work_struct *work)
639 {
640         struct clock_sync_data stp_sync;
641         int rc;
642 
643         /* prevent multiple execution. */
644         mutex_lock(&stp_work_mutex);
645 
646         if (!stp_online) {
647                 chsc_sstpc(stp_page, STP_OP_CTRL, 0x0000, NULL);
648                 del_timer_sync(&stp_timer);
649                 goto out_unlock;
650         }
651 
652         rc = chsc_sstpc(stp_page, STP_OP_CTRL, 0xb0e0, NULL);
653         if (rc)
654                 goto out_unlock;
655 
656         rc = chsc_sstpi(stp_page, &stp_info, sizeof(struct stp_sstpi));
657         if (rc || stp_info.c == 0)
658                 goto out_unlock;
659 
660         /* Skip synchronization if the clock is already in sync. */
661         if (check_sync_clock())
662                 goto out_unlock;
663 
664         memset(&stp_sync, 0, sizeof(stp_sync));
665         cpus_read_lock();
666         atomic_set(&stp_sync.cpus, num_online_cpus() - 1);
667         stop_machine_cpuslocked(stp_sync_clock, &stp_sync, cpu_online_mask);
668         cpus_read_unlock();
669 
670         if (!check_sync_clock())
671                 /*
672                  * There is a usable clock but the synchonization failed.
673                  * Retry after a second.
674                  */
675                 mod_timer(&stp_timer, jiffies + HZ);
676 
677 out_unlock:
678         mutex_unlock(&stp_work_mutex);
679 }
680 
681 /*
682  * STP subsys sysfs interface functions
683  */
684 static struct bus_type stp_subsys = {
685         .name           = "stp",
686         .dev_name       = "stp",
687 };
688 
689 static ssize_t stp_ctn_id_show(struct device *dev,
690                                 struct device_attribute *attr,
691                                 char *buf)
692 {
693         if (!stp_online)
694                 return -ENODATA;
695         return sprintf(buf, "%016llx\n",
696                        *(unsigned long long *) stp_info.ctnid);
697 }
698 
699 static DEVICE_ATTR(ctn_id, 0400, stp_ctn_id_show, NULL);
700 
701 static ssize_t stp_ctn_type_show(struct device *dev,
702                                 struct device_attribute *attr,
703                                 char *buf)
704 {
705         if (!stp_online)
706                 return -ENODATA;
707         return sprintf(buf, "%i\n", stp_info.ctn);
708 }
709 
710 static DEVICE_ATTR(ctn_type, 0400, stp_ctn_type_show, NULL);
711 
712 static ssize_t stp_dst_offset_show(struct device *dev,
713                                    struct device_attribute *attr,
714                                    char *buf)
715 {
716         if (!stp_online || !(stp_info.vbits & 0x2000))
717                 return -ENODATA;
718         return sprintf(buf, "%i\n", (int)(s16) stp_info.dsto);
719 }
720 
721 static DEVICE_ATTR(dst_offset, 0400, stp_dst_offset_show, NULL);
722 
723 static ssize_t stp_leap_seconds_show(struct device *dev,
724                                         struct device_attribute *attr,
725                                         char *buf)
726 {
727         if (!stp_online || !(stp_info.vbits & 0x8000))
728                 return -ENODATA;
729         return sprintf(buf, "%i\n", (int)(s16) stp_info.leaps);
730 }
731 
732 static DEVICE_ATTR(leap_seconds, 0400, stp_leap_seconds_show, NULL);
733 
734 static ssize_t stp_stratum_show(struct device *dev,
735                                 struct device_attribute *attr,
736                                 char *buf)
737 {
738         if (!stp_online)
739                 return -ENODATA;
740         return sprintf(buf, "%i\n", (int)(s16) stp_info.stratum);
741 }
742 
743 static DEVICE_ATTR(stratum, 0400, stp_stratum_show, NULL);
744 
745 static ssize_t stp_time_offset_show(struct device *dev,
746                                 struct device_attribute *attr,
747                                 char *buf)
748 {
749         if (!stp_online || !(stp_info.vbits & 0x0800))
750                 return -ENODATA;
751         return sprintf(buf, "%i\n", (int) stp_info.tto);
752 }
753 
754 static DEVICE_ATTR(time_offset, 0400, stp_time_offset_show, NULL);
755 
756 static ssize_t stp_time_zone_offset_show(struct device *dev,
757                                 struct device_attribute *attr,
758                                 char *buf)
759 {
760         if (!stp_online || !(stp_info.vbits & 0x4000))
761                 return -ENODATA;
762         return sprintf(buf, "%i\n", (int)(s16) stp_info.tzo);
763 }
764 
765 static DEVICE_ATTR(time_zone_offset, 0400,
766                          stp_time_zone_offset_show, NULL);
767 
768 static ssize_t stp_timing_mode_show(struct device *dev,
769                                 struct device_attribute *attr,
770                                 char *buf)
771 {
772         if (!stp_online)
773                 return -ENODATA;
774         return sprintf(buf, "%i\n", stp_info.tmd);
775 }
776 
777 static DEVICE_ATTR(timing_mode, 0400, stp_timing_mode_show, NULL);
778 
779 static ssize_t stp_timing_state_show(struct device *dev,
780                                 struct device_attribute *attr,
781                                 char *buf)
782 {
783         if (!stp_online)
784                 return -ENODATA;
785         return sprintf(buf, "%i\n", stp_info.tst);
786 }
787 
788 static DEVICE_ATTR(timing_state, 0400, stp_timing_state_show, NULL);
789 
790 static ssize_t stp_online_show(struct device *dev,
791                                 struct device_attribute *attr,
792                                 char *buf)
793 {
794         return sprintf(buf, "%i\n", stp_online);
795 }
796 
797 static ssize_t stp_online_store(struct device *dev,
798                                 struct device_attribute *attr,
799                                 const char *buf, size_t count)
800 {
801         unsigned int value;
802 
803         value = simple_strtoul(buf, NULL, 0);
804         if (value != 0 && value != 1)
805                 return -EINVAL;
806         if (!test_bit(CLOCK_SYNC_HAS_STP, &clock_sync_flags))
807                 return -EOPNOTSUPP;
808         mutex_lock(&clock_sync_mutex);
809         stp_online = value;
810         if (stp_online)
811                 set_bit(CLOCK_SYNC_STP, &clock_sync_flags);
812         else
813                 clear_bit(CLOCK_SYNC_STP, &clock_sync_flags);
814         queue_work(time_sync_wq, &stp_work);
815         mutex_unlock(&clock_sync_mutex);
816         return count;
817 }
818 
819 /*
820  * Can't use DEVICE_ATTR because the attribute should be named
821  * stp/online but dev_attr_online already exists in this file ..
822  */
823 static struct device_attribute dev_attr_stp_online = {
824         .attr = { .name = "online", .mode = 0600 },
825         .show   = stp_online_show,
826         .store  = stp_online_store,
827 };
828 
829 static struct device_attribute *stp_attributes[] = {
830         &dev_attr_ctn_id,
831         &dev_attr_ctn_type,
832         &dev_attr_dst_offset,
833         &dev_attr_leap_seconds,
834         &dev_attr_stp_online,
835         &dev_attr_stratum,
836         &dev_attr_time_offset,
837         &dev_attr_time_zone_offset,
838         &dev_attr_timing_mode,
839         &dev_attr_timing_state,
840         NULL
841 };
842 
843 static int __init stp_init_sysfs(void)
844 {
845         struct device_attribute **attr;
846         int rc;
847 
848         rc = subsys_system_register(&stp_subsys, NULL);
849         if (rc)
850                 goto out;
851         for (attr = stp_attributes; *attr; attr++) {
852                 rc = device_create_file(stp_subsys.dev_root, *attr);
853                 if (rc)
854                         goto out_unreg;
855         }
856         return 0;
857 out_unreg:
858         for (; attr >= stp_attributes; attr--)
859                 device_remove_file(stp_subsys.dev_root, *attr);
860         bus_unregister(&stp_subsys);
861 out:
862         return rc;
863 }
864 
865 device_initcall(stp_init_sysfs);
866 

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