1 // SPDX-License-Identifier: GPL-2.0-only <<
2 /* 1 /*
3 * linux/arch/arm/kernel/time.c !! 2 * Common time routines among all ppc machines.
4 * 3 *
5 * Copyright (C) 1991, 1992, 1995 Linus Torv !! 4 * Written by Cort Dougan (cort@cs.nmt.edu) to merge
6 * Modifications for ARM (C) 1994-2001 Russel !! 5 * Paul Mackerras' version and mine for PReP and Pmac.
>> 6 * MPC8xx/MBX changes by Dan Malek (dmalek@jlc.net).
7 * 7 *
8 * This file contains the ARM-specific time h !! 8 * First round of bugfixes by Gabriel Paubert (paubert@iram.es)
9 * reading the RTC at bootup, etc... !! 9 * to make clock more stable (2.4.0-test5). The only thing
>> 10 * that this code assumes is that the timebases have been synchronized
>> 11 * by firmware on SMP and are never stopped (never do sleep
>> 12 * on SMP then, nap and doze are OK).
>> 13 *
>> 14 * TODO (not necessarily in this file):
>> 15 * - improve precision and reproducibility of timebase frequency
>> 16 * measurement at boot time.
>> 17 * - get rid of xtime_lock for gettimeofday (generic kernel problem
>> 18 * to be implemented on all architectures for SMP scalability and
>> 19 * eventually implementing gettimeofday without entering the kernel).
>> 20 * - put all time/clock related variables in a single structure
>> 21 * to minimize number of cache lines touched by gettimeofday()
>> 22 * - for astronomical applications: add a new function to get
>> 23 * non ambiguous timestamps even around leap seconds. This needs
>> 24 * a new timestamp format and a good name.
>> 25 *
>> 26 *
>> 27 * The following comment is partially obsolete (at least the long wait
>> 28 * is no more a valid reason):
>> 29 * Since the MPC8xx has a programmable interrupt timer, I decided to
>> 30 * use that rather than the decrementer. Two reasons: 1.) the clock
>> 31 * frequency is low, causing 2.) a long wait in the timer interrupt
>> 32 * while ((d = get_dec()) == dval)
>> 33 * loop. The MPC8xx can be driven from a variety of input clocks,
>> 34 * so a number of assumptions have been made here because the kernel
>> 35 * parameter HZ is a constant. We assume (correctly, today :-) that
>> 36 * the MPC8xx on the MBX board is driven from a 32.768 kHz crystal.
>> 37 * This is then divided by 4, providing a 8192 Hz clock into the PIT.
>> 38 * Since it is not possible to get a nice 100 Hz clock out of this, without
>> 39 * creating a software PLL, I have set HZ to 128. -- Dan
>> 40 *
>> 41 * 1997-09-10 Updated NTP code according to technical memorandum Jan '96
>> 42 * "A Kernel Model for Precision Timekeeping" by Dave Mills
10 */ 43 */
11 #include <linux/clockchips.h> !! 44
12 #include <linux/clocksource.h> !! 45 #include <linux/config.h>
13 #include <linux/errno.h> 46 #include <linux/errno.h>
14 #include <linux/export.h> <<
15 #include <linux/init.h> <<
16 #include <linux/interrupt.h> <<
17 #include <linux/irq.h> <<
18 #include <linux/kernel.h> <<
19 #include <linux/of_clk.h> <<
20 #include <linux/profile.h> <<
21 #include <linux/sched.h> 47 #include <linux/sched.h>
22 #include <linux/sched_clock.h> !! 48 #include <linux/kernel.h>
23 #include <linux/smp.h> !! 49 #include <linux/param.h>
24 #include <linux/time.h> !! 50 #include <linux/string.h>
>> 51 #include <linux/mm.h>
>> 52 #include <linux/module.h>
>> 53 #include <linux/interrupt.h>
25 #include <linux/timex.h> 54 #include <linux/timex.h>
26 #include <linux/timer.h> !! 55 #include <linux/kernel_stat.h>
>> 56 #include <linux/mc146818rtc.h>
>> 57 #include <linux/time.h>
>> 58 #include <linux/init.h>
>> 59
>> 60 #include <asm/segment.h>
>> 61 #include <asm/io.h>
>> 62 #include <asm/nvram.h>
>> 63 #include <asm/cache.h>
>> 64 #include <asm/8xx_immap.h>
>> 65 #include <asm/machdep.h>
>> 66
>> 67 #include <asm/time.h>
>> 68
>> 69 /* XXX false sharing with below? */
>> 70 u64 jiffies_64 = INITIAL_JIFFIES;
>> 71
>> 72 EXPORT_SYMBOL(jiffies_64);
>> 73
>> 74 unsigned long disarm_decr[NR_CPUS];
>> 75
>> 76 extern struct timezone sys_tz;
>> 77
>> 78 /* keep track of when we need to update the rtc */
>> 79 time_t last_rtc_update;
>> 80
>> 81 /* The decrementer counts down by 128 every 128ns on a 601. */
>> 82 #define DECREMENTER_COUNT_601 (1000000000 / HZ)
>> 83
>> 84 unsigned tb_ticks_per_jiffy;
>> 85 unsigned tb_to_us;
>> 86 unsigned tb_last_stamp;
>> 87 unsigned long tb_to_ns_scale;
>> 88
>> 89 extern unsigned long wall_jiffies;
>> 90
>> 91 static long time_offset;
>> 92
>> 93 spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;
27 94
28 #include <asm/mach/arch.h> <<
29 #include <asm/mach/time.h> <<
30 #include <asm/stacktrace.h> <<
31 #include <asm/thread_info.h> <<
32 <<
33 #if defined(CONFIG_RTC_DRV_CMOS) || defined(CO <<
34 defined(CONFIG_NVRAM) || defined(CONFIG_NV <<
35 /* this needs a better home */ <<
36 DEFINE_SPINLOCK(rtc_lock); <<
37 EXPORT_SYMBOL(rtc_lock); 95 EXPORT_SYMBOL(rtc_lock);
38 #endif /* pc-style 'CMOS' RTC support */ <<
39 96
40 /* change this if you have some constant time !! 97 /* Timer interrupt helper function */
41 #define USECS_PER_JIFFY (1000000/HZ) !! 98 static inline int tb_delta(unsigned *jiffy_stamp) {
>> 99 int delta;
>> 100 if (__USE_RTC()) {
>> 101 delta = get_rtcl();
>> 102 if (delta < *jiffy_stamp) *jiffy_stamp -= 1000000000;
>> 103 delta -= *jiffy_stamp;
>> 104 } else {
>> 105 delta = get_tbl() - *jiffy_stamp;
>> 106 }
>> 107 return delta;
>> 108 }
42 109
43 #ifdef CONFIG_SMP !! 110 extern unsigned long prof_cpu_mask;
44 unsigned long profile_pc(struct pt_regs *regs) !! 111 extern unsigned int * prof_buffer;
>> 112 extern unsigned long prof_len;
>> 113 extern unsigned long prof_shift;
>> 114 extern char _stext;
>> 115
>> 116 static inline void ppc_do_profile (unsigned long nip)
45 { 117 {
46 struct stackframe frame; !! 118 if (!prof_buffer)
>> 119 return;
47 120
48 if (!in_lock_functions(regs->ARM_pc)) !! 121 /*
49 return regs->ARM_pc; !! 122 * Only measure the CPUs specified by /proc/irq/prof_cpu_mask.
>> 123 * (default is all CPUs.)
>> 124 */
>> 125 if (!((1<<smp_processor_id()) & prof_cpu_mask))
>> 126 return;
>> 127
>> 128 nip -= (unsigned long) &_stext;
>> 129 nip >>= prof_shift;
>> 130 /*
>> 131 * Don't ignore out-of-bounds EIP values silently,
>> 132 * put them into the last histogram slot, so if
>> 133 * present, they will show up as a sharp peak.
>> 134 */
>> 135 if (nip > prof_len-1)
>> 136 nip = prof_len-1;
>> 137 atomic_inc((atomic_t *)&prof_buffer[nip]);
>> 138 }
50 139
51 arm_get_current_stackframe(regs, &fram !! 140 /*
52 do { !! 141 * timer_interrupt - gets called when the decrementer overflows,
53 int ret = unwind_frame(&frame) !! 142 * with interrupts disabled.
54 if (ret < 0) !! 143 * We set it up to overflow again in 1/HZ seconds.
55 return 0; !! 144 */
56 } while (in_lock_functions(frame.pc)); !! 145 void timer_interrupt(struct pt_regs * regs)
>> 146 {
>> 147 int next_dec;
>> 148 unsigned long cpu = smp_processor_id();
>> 149 unsigned jiffy_stamp = last_jiffy_stamp(cpu);
>> 150 extern void do_IRQ(struct pt_regs *);
>> 151
>> 152 if (atomic_read(&ppc_n_lost_interrupts) != 0)
>> 153 do_IRQ(regs);
>> 154
>> 155 irq_enter();
>> 156
>> 157 while ((next_dec = tb_ticks_per_jiffy - tb_delta(&jiffy_stamp)) < 0) {
>> 158 jiffy_stamp += tb_ticks_per_jiffy;
>> 159 if (!user_mode(regs))
>> 160 ppc_do_profile(instruction_pointer(regs));
>> 161 if (smp_processor_id())
>> 162 continue;
>> 163
>> 164 /* We are in an interrupt, no need to save/restore flags */
>> 165 write_seqlock(&xtime_lock);
>> 166 tb_last_stamp = jiffy_stamp;
>> 167 do_timer(regs);
>> 168
>> 169 /*
>> 170 * update the rtc when needed, this should be performed on the
>> 171 * right fraction of a second. Half or full second ?
>> 172 * Full second works on mk48t59 clocks, others need testing.
>> 173 * Note that this update is basically only used through
>> 174 * the adjtimex system calls. Setting the HW clock in
>> 175 * any other way is a /dev/rtc and userland business.
>> 176 * This is still wrong by -0.5/+1.5 jiffies because of the
>> 177 * timer interrupt resolution and possible delay, but here we
>> 178 * hit a quantization limit which can only be solved by higher
>> 179 * resolution timers and decoupling time management from timer
>> 180 * interrupts. This is also wrong on the clocks
>> 181 * which require being written at the half second boundary.
>> 182 * We should have an rtc call that only sets the minutes and
>> 183 * seconds like on Intel to avoid problems with non UTC clocks.
>> 184 */
>> 185 if ( ppc_md.set_rtc_time && (time_status & STA_UNSYNC) == 0 &&
>> 186 xtime.tv_sec - last_rtc_update >= 659 &&
>> 187 abs((xtime.tv_nsec / 1000) - (1000000-1000000/HZ)) < 500000/HZ &&
>> 188 jiffies - wall_jiffies == 1) {
>> 189 if (ppc_md.set_rtc_time(xtime.tv_sec+1 + time_offset) == 0)
>> 190 last_rtc_update = xtime.tv_sec+1;
>> 191 else
>> 192 /* Try again one minute later */
>> 193 last_rtc_update += 60;
>> 194 }
>> 195 write_sequnlock(&xtime_lock);
>> 196 }
>> 197 if ( !disarm_decr[smp_processor_id()] )
>> 198 set_dec(next_dec);
>> 199 last_jiffy_stamp(cpu) = jiffy_stamp;
>> 200
>> 201 #ifdef CONFIG_SMP
>> 202 smp_local_timer_interrupt(regs);
>> 203 #endif /* CONFIG_SMP */
>> 204
>> 205 if (ppc_md.heartbeat && !ppc_md.heartbeat_count--)
>> 206 ppc_md.heartbeat();
57 207
58 return frame.pc; !! 208 irq_exit();
59 } 209 }
60 EXPORT_SYMBOL(profile_pc); <<
61 #endif <<
62 210
63 static void dummy_clock_access(struct timespec !! 211 /*
>> 212 * This version of gettimeofday has microsecond resolution.
>> 213 */
>> 214 void do_gettimeofday(struct timeval *tv)
64 { 215 {
65 ts->tv_sec = 0; !! 216 unsigned long flags;
66 ts->tv_nsec = 0; !! 217 unsigned long seq;
>> 218 unsigned delta, lost_ticks, usec, sec;
>> 219
>> 220 do {
>> 221 seq = read_seqbegin_irqsave(&xtime_lock, flags);
>> 222 sec = xtime.tv_sec;
>> 223 usec = (xtime.tv_nsec / 1000);
>> 224 delta = tb_ticks_since(tb_last_stamp);
>> 225 #ifdef CONFIG_SMP
>> 226 /* As long as timebases are not in sync, gettimeofday can only
>> 227 * have jiffy resolution on SMP.
>> 228 */
>> 229 if (!smp_tb_synchronized)
>> 230 delta = 0;
>> 231 #endif /* CONFIG_SMP */
>> 232 lost_ticks = jiffies - wall_jiffies;
>> 233 } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
>> 234
>> 235 usec += mulhwu(tb_to_us, tb_ticks_per_jiffy * lost_ticks + delta);
>> 236 while (usec >= 1000000) {
>> 237 sec++;
>> 238 usec -= 1000000;
>> 239 }
>> 240 tv->tv_sec = sec;
>> 241 tv->tv_usec = usec;
67 } 242 }
68 243
69 static clock_access_fn __read_persistent_clock !! 244 EXPORT_SYMBOL(do_gettimeofday);
70 245
71 void read_persistent_clock64(struct timespec64 !! 246 int do_settimeofday(struct timespec *tv)
72 { 247 {
73 __read_persistent_clock(ts); !! 248 time_t wtm_sec, new_sec = tv->tv_sec;
>> 249 long wtm_nsec, new_nsec = tv->tv_nsec;
>> 250 unsigned long flags;
>> 251 int tb_delta;
>> 252
>> 253 if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
>> 254 return -EINVAL;
>> 255
>> 256 write_seqlock_irqsave(&xtime_lock, flags);
>> 257 /* Updating the RTC is not the job of this code. If the time is
>> 258 * stepped under NTP, the RTC will be update after STA_UNSYNC
>> 259 * is cleared. Tool like clock/hwclock either copy the RTC
>> 260 * to the system time, in which case there is no point in writing
>> 261 * to the RTC again, or write to the RTC but then they don't call
>> 262 * settimeofday to perform this operation. Note also that
>> 263 * we don't touch the decrementer since:
>> 264 * a) it would lose timer interrupt synchronization on SMP
>> 265 * (if it is working one day)
>> 266 * b) it could make one jiffy spuriously shorter or longer
>> 267 * which would introduce another source of uncertainty potentially
>> 268 * harmful to relatively short timers.
>> 269 */
>> 270
>> 271 /* This works perfectly on SMP only if the tb are in sync but
>> 272 * guarantees an error < 1 jiffy even if they are off by eons,
>> 273 * still reasonable when gettimeofday resolution is 1 jiffy.
>> 274 */
>> 275 tb_delta = tb_ticks_since(last_jiffy_stamp(smp_processor_id()));
>> 276 tb_delta += (jiffies - wall_jiffies) * tb_ticks_per_jiffy;
>> 277
>> 278 new_nsec -= 1000 * mulhwu(tb_to_us, tb_delta);
>> 279
>> 280 wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - new_sec);
>> 281 wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - new_nsec);
>> 282
>> 283 set_normalized_timespec(&xtime, new_sec, new_nsec);
>> 284 set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
>> 285
>> 286 /* In case of a large backwards jump in time with NTP, we want the
>> 287 * clock to be updated as soon as the PLL is again in lock.
>> 288 */
>> 289 last_rtc_update = new_sec - 658;
>> 290
>> 291 time_adjust = 0; /* stop active adjtime() */
>> 292 time_status |= STA_UNSYNC;
>> 293 time_state = TIME_ERROR; /* p. 24, (a) */
>> 294 time_maxerror = NTP_PHASE_LIMIT;
>> 295 time_esterror = NTP_PHASE_LIMIT;
>> 296 write_sequnlock_irqrestore(&xtime_lock, flags);
>> 297 return 0;
74 } 298 }
75 299
76 int __init register_persistent_clock(clock_acc !! 300 EXPORT_SYMBOL(do_settimeofday);
>> 301
>> 302 /* This function is only called on the boot processor */
>> 303 void __init time_init(void)
77 { 304 {
78 /* Only allow the clockaccess function !! 305 time_t sec, old_sec;
79 if (__read_persistent_clock == dummy_c !! 306 unsigned old_stamp, stamp, elapsed;
80 if (read_persistent) !! 307
81 __read_persistent_cloc !! 308 if (ppc_md.time_init != NULL)
82 return 0; !! 309 time_offset = ppc_md.time_init();
>> 310
>> 311 if (__USE_RTC()) {
>> 312 /* 601 processor: dec counts down by 128 every 128ns */
>> 313 tb_ticks_per_jiffy = DECREMENTER_COUNT_601;
>> 314 /* mulhwu_scale_factor(1000000000, 1000000) is 0x418937 */
>> 315 tb_to_us = 0x418937;
>> 316 } else {
>> 317 ppc_md.calibrate_decr();
>> 318 tb_to_ns_scale = mulhwu(tb_to_us, 1000 << 10);
>> 319 }
>> 320
>> 321 /* Now that the decrementer is calibrated, it can be used in case the
>> 322 * clock is stuck, but the fact that we have to handle the 601
>> 323 * makes things more complex. Repeatedly read the RTC until the
>> 324 * next second boundary to try to achieve some precision. If there
>> 325 * is no RTC, we still need to set tb_last_stamp and
>> 326 * last_jiffy_stamp(cpu 0) to the current stamp.
>> 327 */
>> 328 stamp = get_native_tbl();
>> 329 if (ppc_md.get_rtc_time) {
>> 330 sec = ppc_md.get_rtc_time();
>> 331 elapsed = 0;
>> 332 do {
>> 333 old_stamp = stamp;
>> 334 old_sec = sec;
>> 335 stamp = get_native_tbl();
>> 336 if (__USE_RTC() && stamp < old_stamp)
>> 337 old_stamp -= 1000000000;
>> 338 elapsed += stamp - old_stamp;
>> 339 sec = ppc_md.get_rtc_time();
>> 340 } while ( sec == old_sec && elapsed < 2*HZ*tb_ticks_per_jiffy);
>> 341 if (sec==old_sec)
>> 342 printk("Warning: real time clock seems stuck!\n");
>> 343 xtime.tv_sec = sec;
>> 344 xtime.tv_nsec = 0;
>> 345 /* No update now, we just read the time from the RTC ! */
>> 346 last_rtc_update = xtime.tv_sec;
83 } 347 }
>> 348 last_jiffy_stamp(0) = tb_last_stamp = stamp;
84 349
85 return -EINVAL; !! 350 /* Not exact, but the timer interrupt takes care of this */
>> 351 set_dec(tb_ticks_per_jiffy);
>> 352
>> 353 /* If platform provided a timezone (pmac), we correct the time */
>> 354 if (time_offset) {
>> 355 sys_tz.tz_minuteswest = -time_offset / 60;
>> 356 sys_tz.tz_dsttime = 0;
>> 357 xtime.tv_sec -= time_offset;
>> 358 }
>> 359 set_normalized_timespec(&wall_to_monotonic,
>> 360 -xtime.tv_sec, -xtime.tv_nsec);
86 } 361 }
87 362
88 void __init time_init(void) !! 363 #define FEBRUARY 2
>> 364 #define STARTOFTIME 1970
>> 365 #define SECDAY 86400L
>> 366 #define SECYR (SECDAY * 365)
>> 367
>> 368 /*
>> 369 * Note: this is wrong for 2100, but our signed 32-bit time_t will
>> 370 * have overflowed long before that, so who cares. -- paulus
>> 371 */
>> 372 #define leapyear(year) ((year) % 4 == 0)
>> 373 #define days_in_year(a) (leapyear(a) ? 366 : 365)
>> 374 #define days_in_month(a) (month_days[(a) - 1])
>> 375
>> 376 static int month_days[12] = {
>> 377 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
>> 378 };
>> 379
>> 380 void to_tm(int tim, struct rtc_time * tm)
>> 381 {
>> 382 register int i;
>> 383 register long hms, day, gday;
>> 384
>> 385 gday = day = tim / SECDAY;
>> 386 hms = tim % SECDAY;
>> 387
>> 388 /* Hours, minutes, seconds are easy */
>> 389 tm->tm_hour = hms / 3600;
>> 390 tm->tm_min = (hms % 3600) / 60;
>> 391 tm->tm_sec = (hms % 3600) % 60;
>> 392
>> 393 /* Number of years in days */
>> 394 for (i = STARTOFTIME; day >= days_in_year(i); i++)
>> 395 day -= days_in_year(i);
>> 396 tm->tm_year = i;
>> 397
>> 398 /* Number of months in days left */
>> 399 if (leapyear(tm->tm_year))
>> 400 days_in_month(FEBRUARY) = 29;
>> 401 for (i = 1; day >= days_in_month(i); i++)
>> 402 day -= days_in_month(i);
>> 403 days_in_month(FEBRUARY) = 28;
>> 404 tm->tm_mon = i;
>> 405
>> 406 /* Days are what is left over (+1) from all that. */
>> 407 tm->tm_mday = day + 1;
>> 408
>> 409 /*
>> 410 * Determine the day of week. Jan. 1, 1970 was a Thursday.
>> 411 */
>> 412 tm->tm_wday = (gday + 4) % 7;
>> 413 }
>> 414
>> 415 /* Auxiliary function to compute scaling factors */
>> 416 /* Actually the choice of a timebase running at 1/4 the of the bus
>> 417 * frequency giving resolution of a few tens of nanoseconds is quite nice.
>> 418 * It makes this computation very precise (27-28 bits typically) which
>> 419 * is optimistic considering the stability of most processor clock
>> 420 * oscillators and the precision with which the timebase frequency
>> 421 * is measured but does not harm.
>> 422 */
>> 423 unsigned mulhwu_scale_factor(unsigned inscale, unsigned outscale) {
>> 424 unsigned mlt=0, tmp, err;
>> 425 /* No concern for performance, it's done once: use a stupid
>> 426 * but safe and compact method to find the multiplier.
>> 427 */
>> 428 for (tmp = 1U<<31; tmp != 0; tmp >>= 1) {
>> 429 if (mulhwu(inscale, mlt|tmp) < outscale) mlt|=tmp;
>> 430 }
>> 431 /* We might still be off by 1 for the best approximation.
>> 432 * A side effect of this is that if outscale is too large
>> 433 * the returned value will be zero.
>> 434 * Many corner cases have been checked and seem to work,
>> 435 * some might have been forgotten in the test however.
>> 436 */
>> 437 err = inscale*(mlt+1);
>> 438 if (err <= inscale/2) mlt++;
>> 439 return mlt;
>> 440 }
>> 441
>> 442 unsigned long long sched_clock(void)
89 { 443 {
90 if (machine_desc->init_time) { !! 444 unsigned long lo, hi, hi2;
91 machine_desc->init_time(); !! 445 unsigned long long tb;
>> 446
>> 447 if (!__USE_RTC()) {
>> 448 do {
>> 449 hi = get_tbu();
>> 450 lo = get_tbl();
>> 451 hi2 = get_tbu();
>> 452 } while (hi2 != hi);
>> 453 tb = ((unsigned long long) hi << 32) | lo;
>> 454 tb = (tb * tb_to_ns_scale) >> 10;
92 } else { 455 } else {
93 #ifdef CONFIG_COMMON_CLK !! 456 do {
94 of_clk_init(NULL); !! 457 hi = get_rtcu();
95 #endif !! 458 lo = get_rtcl();
96 timer_probe(); !! 459 hi2 = get_rtcu();
97 tick_setup_hrtimer_broadcast() !! 460 } while (hi2 != hi);
>> 461 tb = ((unsigned long long) hi) * 1000000000 + lo;
98 } 462 }
>> 463 return tb;
99 } 464 }
100 465
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