2 * i386 CMOS starts out with 14 bytes clock data alpha has something
3 * similar, but with details depending on the machine type.
7 * byte 4: hours 0-23 in 24hr mode,
8 * 1-12 in 12hr mode, with high bit unset/set
10 * byte 6: weekday 1-7, Sunday=1
11 * byte 7: day of the month 1-31
15 * Numbers are stored in BCD/binary if bit 2 of byte 11 is unset/set The
16 * clock is in 12hr/24hr mode if bit 1 of byte 11 is unset/set The clock is
17 * undefined (being updated) if bit 7 of byte 10 is set. The clock is frozen
18 * (to be updated) by setting bit 7 of byte 11 Bit 7 of byte 14 indicates
19 * whether the CMOS clock is reliable: it is 1 if RTC power has been good
20 * since this bit was last read; it is 0 when the battery is dead and system
23 * Avoid setting the RTC clock within 2 seconds of the day rollover that
24 * starts a new month or enters daylight saving time.
26 * The century situation is messy:
28 * Usually byte 50 (0x32) gives the century (in BCD, so 19 or 20 hex), but
29 * IBM PS/2 has (part of) a checksum there and uses byte 55 (0x37).
30 * Sometimes byte 127 (0x7f) or Bank 1, byte 0x48 gives the century. The
31 * original RTC will not access any century byte; some modern versions will.
32 * If a modern RTC or BIOS increments the century byte it may go from 0x19
33 * to 0x20, but in some buggy cases 0x1a is produced.
36 * A struct tm has int fields
37 * tm_sec 0-59, 60 or 61 only for leap seconds
42 * tm_year number of years since 1900
43 * tm_wday 0-6, 0=Sunday
45 * tm_isdst >0: yes, 0: no, <0: unknown
61 # elif defined(HAVE_ASM_IO_H)
62 # include <asm/io.h> /* for inb, outb */
65 * Disable cmos access; we can no longer use asm/io.h, since the kernel does
66 * not export that header.
69 void outb(int a
__attribute__ ((__unused__
)),
70 int b
__attribute__ ((__unused__
)))
74 int inb(int c
__attribute__ ((__unused__
)))
80 #elif defined(__alpha__)
81 /* <asm/io.h> fails to compile, probably because of u8 etc */
82 extern unsigned int inb(unsigned long port
);
83 extern void outb(unsigned char b
, unsigned long port
);
85 void outb(int a
__attribute__ ((__unused__
)),
86 int b
__attribute__ ((__unused__
)))
90 int inb(int c
__attribute__ ((__unused__
)))
94 #endif /* __alpha__ */
98 #define BCD_TO_BIN(val) ((val)=((val)&15) + ((val)>>4)*10)
99 #define BIN_TO_BCD(val) ((val)=(((val)/10)<<4) + (val)%10)
104 * Unix uses 1900 as epoch for a struct tm, and 1970 for a time_t. But what
105 * was written to CMOS?
107 * Digital DECstations use 1928 - this is on a mips or alpha Digital Unix
108 * uses 1952, e.g. on AXPpxi33. Windows NT uses 1980. The ARC console
109 * expects to boot Windows NT and uses 1980. (But a Ruffian uses 1900, just
110 * like SRM.) It is reported that ALPHA_PRE_V1_2_SRM_CONSOLE uses 1958.
112 #define TM_EPOCH 1900
113 int cmos_epoch
= 1900;
116 * Martin Ostermann writes:
118 * The problem with the Jensen is twofold: First, it has the clock at a
119 * different address. Secondly, it has a distinction between "local" and
120 * normal bus addresses. The local ones pertain to the hardware integrated
121 * into the chipset, like serial/parallel ports and of course, the RTC.
122 * Those need to be addressed differently. This is handled fine in the
123 * kernel, and it's not a problem, since this usually gets totally optimized
124 * by the compile. But the i/o routines of (g)libc lack this support so far.
125 * The result of this is, that the old clock program worked only on the
126 * Jensen when USE_DEV_PORT was defined, but not with the normal inb/outb
129 int use_dev_port
= 0; /* 1 for Jensen */
131 unsigned short clock_ctl_addr
= 0x70; /* 0x170 for Jensen */
132 unsigned short clock_data_addr
= 0x71; /* 0x171 for Jensen */
134 int century_byte
= 0; /* 0: don't access a century byte
135 * 50 (0x32): usual PC value
140 int funkyTOY
= 0; /* 1 for PC164/LX164/SX164 type alpha */
145 static int is_in_cpuinfo(char *fmt
, char *str
)
152 sprintf(format
, "%s : %s", fmt
, "%255s");
154 if ((cpuinfo
= fopen("/proc/cpuinfo", "r")) != NULL
) {
155 while (!feof(cpuinfo
)) {
156 if (fscanf(cpuinfo
, format
, field
) == 1) {
157 if (strncmp(field
, str
, strlen(str
)) == 0)
161 fgets(field
, 256, cpuinfo
);
169 * Set cmos_epoch, either from user options, or by asking the kernel, or by
170 * looking at /proc/cpu_info
172 void set_cmos_epoch(int ARCconsole
, int SRM
)
176 /* Believe the user */
177 if (epoch_option
!= -1) {
178 cmos_epoch
= epoch_option
;
185 if (ARCconsole
|| SRM
)
190 * If we can ask the kernel, we don't need guessing from
193 if (get_epoch_rtc(&epoch
, 1) == 0) {
200 * The kernel source today says: read the year.
202 * If it is in 0-19 then the epoch is 2000.
203 * If it is in 20-47 then the epoch is 1980.
204 * If it is in 48-69 then the epoch is 1952.
205 * If it is in 70-99 then the epoch is 1928.
207 * Otherwise the epoch is 1900.
208 * TODO: Clearly, this must be changed before 2019.
211 * See whether we are dealing with SRM or MILO, as they have
212 * different "epoch" ideas.
214 if (is_in_cpuinfo("system serial number", "MILO")) {
217 printf(_("booted from MILO\n"));
221 * See whether we are dealing with a RUFFIAN aka Alpha PC-164 UX (or
222 * BX), as they have REALLY different TOY (TimeOfYear) format: BCD,
223 * and not an ARC-style epoch. BCD is detected dynamically, but we
224 * must NOT adjust like ARC.
226 if (ARCconsole
&& is_in_cpuinfo("system type", "Ruffian")) {
229 printf(_("Ruffian BCD clock\n"));
236 void set_cmos_access(int Jensen
, int funky_toy
)
240 * See whether we're dealing with a Jensen---it has a weird I/O
241 * system. DEC was just learning how to build Alpha PCs.
243 if (Jensen
|| is_in_cpuinfo("system type", "Jensen")) {
245 clock_ctl_addr
= 0x170;
246 clock_data_addr
= 0x171;
248 printf(_("clockport adjusted to 0x%x\n"),
253 * See whether we are dealing with PC164/LX164/SX164, as they have a
254 * TOY that must be accessed differently to work correctly.
256 /* Nautilus stuff reported by Neoklis Kyriazis */
258 is_in_cpuinfo("system variation", "PC164") ||
259 is_in_cpuinfo("system variation", "LX164") ||
260 is_in_cpuinfo("system variation", "SX164") ||
261 is_in_cpuinfo("system type", "Nautilus")) {
264 printf(_("funky TOY!\n"));
271 * The Alpha doesn't allow user-level code to disable interrupts (for good
272 * reasons). Instead, we ensure atomic operation by performing the operation
273 * and checking whether the high 32 bits of the cycle counter changed. If
274 * they did, a context switch must have occurred and we redo the operation.
275 * As long as the operation is reasonably short, it will complete
276 * atomically, eventually.
279 atomic(const char *name
, unsigned long (*op
) (unsigned long), unsigned long arg
)
281 unsigned long ts1
, ts2
, n
, v
;
283 for (n
= 0; n
< 1000; ++n
) {
284 asm volatile ("rpcc %0":"r=" (ts1
));
286 asm volatile ("rpcc %0":"r=" (ts2
));
288 if ((ts1
^ ts2
) >> 32 == 0) {
292 errx(EXIT_FAILURE
, _("atomic %s failed for 1000 iterations!"),
298 * Hmmh, this isn't very atomic. Maybe we should force an error instead?
300 * TODO: optimize the access to CMOS by mlockall(MCL_CURRENT) and SCHED_FIFO
303 atomic(const char *name
__attribute__ ((__unused__
)),
304 unsigned long (*op
) (unsigned long),
312 static inline unsigned long cmos_read(unsigned long reg
)
315 unsigned char v
= reg
| 0x80;
316 lseek(dev_port_fd
, clock_ctl_addr
, 0);
317 if (write(dev_port_fd
, &v
, 1) == -1 && debug
)
319 ("cmos_read(): write to control address %X failed: %m\n"),
321 lseek(dev_port_fd
, clock_data_addr
, 0);
322 if (read(dev_port_fd
, &v
, 1) == -1 && debug
)
324 ("cmos_read(): read data address %X failed: %m\n"),
329 * We only want to read CMOS data, but unfortunately writing
330 * to bit 7 disables (1) or enables (0) NMI; since this bit
331 * is read-only we have to guess the old status. Various
332 * docs suggest that one should disable NMI while
333 * reading/writing CMOS data, and enable it again
334 * afterwards. This would yield the sequence
336 * outb (reg | 0x80, 0x70);
338 * outb (0x0d, 0x70); // 0x0d: random read-only location
340 * Other docs state that "any write to 0x70 should be
341 * followed by an action to 0x71 or the RTC wil be left in
342 * an unknown state". Most docs say that it doesn't matter at
346 * bit 0x80: disable NMI while reading - should we? Let us
347 * follow the kernel and not disable. Called only with 0 <=
350 outb(reg
, clock_ctl_addr
);
351 return inb(clock_data_addr
);
355 static inline unsigned long cmos_write(unsigned long reg
, unsigned long val
)
358 unsigned char v
= reg
| 0x80;
359 lseek(dev_port_fd
, clock_ctl_addr
, 0);
360 if (write(dev_port_fd
, &v
, 1) == -1 && debug
)
362 ("cmos_write(): write to control address %X failed: %m\n"),
365 lseek(dev_port_fd
, clock_data_addr
, 0);
366 if (write(dev_port_fd
, &v
, 1) == -1 && debug
)
368 ("cmos_write(): write to data address %X failed: %m\n"),
371 outb(reg
, clock_ctl_addr
);
372 outb(val
, clock_data_addr
);
377 static unsigned long cmos_set_time(unsigned long arg
)
379 unsigned char save_control
, save_freq_select
, pmbit
= 0;
380 struct tm tm
= *(struct tm
*)arg
;
381 unsigned int century
;
384 * CMOS byte 10 (clock status register A) has 3 bitfields:
385 * bit 7: 1 if data invalid, update in progress (read-only bit)
386 * (this is raised 224 us before the actual update starts)
387 * 6-4 select base frequency
388 * 010: 32768 Hz time base (default)
390 * all other combinations are manufacturer-dependent
391 * (e.g.: DS1287: 010 = start oscillator, anything else = stop)
392 * 3-0 rate selection bits for interrupt
393 * 0000 none (may stop RTC)
394 * 0001, 0010 give same frequency as 1000, 1001
395 * 0011 122 microseconds (minimum, 8192 Hz)
396 * .... each increase by 1 halves the frequency, doubles the period
397 * 1111 500 milliseconds (maximum, 2 Hz)
398 * 0110 976.562 microseconds (default 1024 Hz)
400 save_control
= cmos_read(11); /* tell the clock it's being set */
401 cmos_write(11, (save_control
| 0x80));
402 save_freq_select
= cmos_read(10); /* stop and reset prescaler */
403 cmos_write(10, (save_freq_select
| 0x70));
405 tm
.tm_year
+= TM_EPOCH
;
406 century
= tm
.tm_year
/ 100;
407 tm
.tm_year
-= cmos_epoch
;
412 if (!(save_control
& 0x02)) { /* 12hr mode; the default is 24hr mode */
415 if (tm
.tm_hour
> 12) {
421 if (!(save_control
& 0x04)) { /* BCD mode - the default */
422 BIN_TO_BCD(tm
.tm_sec
);
423 BIN_TO_BCD(tm
.tm_min
);
424 BIN_TO_BCD(tm
.tm_hour
);
425 BIN_TO_BCD(tm
.tm_wday
);
426 BIN_TO_BCD(tm
.tm_mday
);
427 BIN_TO_BCD(tm
.tm_mon
);
428 BIN_TO_BCD(tm
.tm_year
);
432 cmos_write(0, tm
.tm_sec
);
433 cmos_write(2, tm
.tm_min
);
434 cmos_write(4, tm
.tm_hour
| pmbit
);
435 cmos_write(6, tm
.tm_wday
);
436 cmos_write(7, tm
.tm_mday
);
437 cmos_write(8, tm
.tm_mon
);
438 cmos_write(9, tm
.tm_year
);
440 cmos_write(century_byte
, century
);
443 * The kernel sources, linux/arch/i386/kernel/time.c, have the
446 * The following flags have to be released exactly in this order,
447 * otherwise the DS12887 (popular MC146818A clone with integrated
448 * battery and quartz) will not reset the oscillator and will not
449 * update precisely 500 ms later. You won't find this mentioned in
450 * the Dallas Semiconductor data sheets, but who believes data
451 * sheets anyway ... -- Markus Kuhn
453 cmos_write(11, save_control
);
454 cmos_write(10, save_freq_select
);
458 static int hclock_read(unsigned long reg
)
460 return atomic("clock read", cmos_read
, (reg
));
463 static void hclock_set_time(const struct tm
*tm
)
465 atomic("set time", cmos_set_time
, (unsigned long)(tm
));
468 static inline int cmos_clock_busy(void)
472 /* poll bit 4 (UF) of Control Register C */
473 funkyTOY
? (hclock_read(12) & 0x10) :
475 /* poll bit 7 (UIP) of Control Register A */
476 (hclock_read(10) & 0x80);
479 static int synchronize_to_clock_tick_cmos(void)
484 * Wait for rise. Should be within a second, but in case something
485 * weird happens, we have a limit on this loop to reduce the impact
488 for (i
= 0; !cmos_clock_busy(); i
++)
492 /* Wait for fall. Should be within 2.228 ms. */
493 for (i
= 0; cmos_clock_busy(); i
++)
500 * Read the hardware clock and return the current time via <tm> argument.
501 * Assume we have an ISA machine and read the clock directly with CPU I/O
504 * This function is not totally reliable. It takes a finite and
505 * unpredictable amount of time to execute the code below. During that time,
506 * the clock may change and we may even read an invalid value in the middle
507 * of an update. We do a few checks to minimize this possibility, but only
508 * the kernel can actually read the clock properly, since it can execute
509 * code in a short and predictable amount of time (by turning of
512 * In practice, the chance of this function returning the wrong time is
515 static int read_hardware_clock_cmos(struct tm
*tm
)
517 bool got_time
= FALSE
;
518 unsigned char status
, pmbit
;
520 status
= pmbit
= 0; /* just for gcc */
524 * Bit 7 of Byte 10 of the Hardware Clock value is the
525 * Update In Progress (UIP) bit, which is on while and 244
526 * uS before the Hardware Clock updates itself. It updates
527 * the counters individually, so reading them during an
528 * update would produce garbage. The update takes 2mS, so we
529 * could be spinning here that long waiting for this bit to
532 * Furthermore, it is pathologically possible for us to be
533 * in this code so long that even if the UIP bit is not on
534 * at first, the clock has changed while we were running. We
535 * check for that too, and if it happens, we start over.
537 if (!cmos_clock_busy()) {
538 /* No clock update in progress, go ahead and read */
539 tm
->tm_sec
= hclock_read(0);
540 tm
->tm_min
= hclock_read(2);
541 tm
->tm_hour
= hclock_read(4);
542 tm
->tm_wday
= hclock_read(6);
543 tm
->tm_mday
= hclock_read(7);
544 tm
->tm_mon
= hclock_read(8);
545 tm
->tm_year
= hclock_read(9);
546 status
= hclock_read(11);
549 century
= hclock_read(century_byte
);
552 * Unless the clock changed while we were reading,
553 * consider this a good clock read .
555 if (tm
->tm_sec
== hclock_read(0))
559 * Yes, in theory we could have been running for 60 seconds
560 * and the above test wouldn't work!
564 if (!(status
& 0x04)) { /* BCD mode - the default */
565 BCD_TO_BIN(tm
->tm_sec
);
566 BCD_TO_BIN(tm
->tm_min
);
567 pmbit
= (tm
->tm_hour
& 0x80);
569 BCD_TO_BIN(tm
->tm_hour
);
570 BCD_TO_BIN(tm
->tm_wday
);
571 BCD_TO_BIN(tm
->tm_mday
);
572 BCD_TO_BIN(tm
->tm_mon
);
573 BCD_TO_BIN(tm
->tm_year
);
580 * We don't use the century byte of the Hardware Clock since we
581 * don't know its address (usually 50 or 55). Here, we follow the
582 * advice of the X/Open Base Working Group: "if century is not
583 * specified, then values in the range [69-99] refer to years in the
584 * twentieth century (1969 to 1999 inclusive), and values in the
585 * range [00-68] refer to years in the twenty-first century (2000 to
590 tm
->tm_year
+= (cmos_epoch
- TM_EPOCH
);
591 if (tm
->tm_year
< 69)
595 if (tm
->tm_hour
== 24)
599 tm
->tm_isdst
= -1; /* don't know whether it's daylight */
603 static int set_hardware_clock_cmos(const struct tm
*new_broken_time
)
606 hclock_set_time(new_broken_time
);
610 #if defined(__i386__) || defined(__alpha__)
611 # if defined(HAVE_IOPL)
612 static int i386_iopl(const int level
)
614 extern int iopl(const int lvl
);
618 static int i386_iopl(const int level
__attribute__ ((__unused__
)))
620 extern int ioperm(unsigned long from
, unsigned long num
, int turn_on
);
621 return ioperm(clock_ctl_addr
, 2, 1);
625 static int i386_iopl(const int level
__attribute__ ((__unused__
)))
631 static int get_permissions_cmos(void)
636 if ((dev_port_fd
= open("/dev/port", O_RDWR
)) < 0) {
637 warn(_("Cannot open /dev/port"));
644 warnx(_("I failed to get permission because I didn't try."));
645 } else if (rc
!= 0) {
647 warn(_("unable to get I/O port access: "
648 "the iopl(3) call failed."));
649 if (rc
== EPERM
&& geteuid())
650 warnx(_("Probably you need root privileges.\n"));
656 static struct clock_ops cmos
= {
657 "direct I/O instructions to ISA clock",
658 get_permissions_cmos
,
659 read_hardware_clock_cmos
,
660 set_hardware_clock_cmos
,
661 synchronize_to_clock_tick_cmos
,
665 * return &cmos if cmos clock present, NULL otherwise choose this
666 * construction to avoid gcc messages about unused variables
668 struct clock_ops
*probe_for_cmos_clock(void)
671 #if defined(__i386__) || defined(__alpha__)
676 return have_cmos
? &cmos
: NULL
;