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
58 #if defined(__i386__) || defined(__x86_64__)
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.
70 void outb(int a
__attribute__ ((__unused__
)),
71 int b
__attribute__ ((__unused__
)))
75 int inb(int c
__attribute__ ((__unused__
)))
79 #endif /* __i386__ __x86_64__ */
81 #elif defined(__alpha__)
82 /* <asm/io.h> fails to compile, probably because of u8 etc */
83 extern unsigned int inb(unsigned long port
);
84 extern void outb(unsigned char b
, unsigned long port
);
86 static void outb(int a
__attribute__ ((__unused__
)),
87 int b
__attribute__ ((__unused__
)))
91 static int inb(int c
__attribute__ ((__unused__
)))
95 #endif /* __alpha__ */
99 #define BCD_TO_BIN(val) ((val)=((val)&15) + ((val)>>4)*10)
100 #define BIN_TO_BCD(val) ((val)=(((val)/10)<<4) + (val)%10)
105 * Unix uses 1900 as epoch for a struct tm, and 1970 for a time_t. But what
106 * was written to CMOS?
108 * Digital DECstations use 1928 - this is on a mips or alpha Digital Unix
109 * uses 1952, e.g. on AXPpxi33. Windows NT uses 1980. The ARC console
110 * expects to boot Windows NT and uses 1980. (But a Ruffian uses 1900, just
111 * like SRM.) It is reported that ALPHA_PRE_V1_2_SRM_CONSOLE uses 1958.
113 #define TM_EPOCH 1900
114 int cmos_epoch
= 1900;
117 * Martin Ostermann writes:
119 * The problem with the Jensen is twofold: First, it has the clock at a
120 * different address. Secondly, it has a distinction between "local" and
121 * normal bus addresses. The local ones pertain to the hardware integrated
122 * into the chipset, like serial/parallel ports and of course, the RTC.
123 * Those need to be addressed differently. This is handled fine in the
124 * kernel, and it's not a problem, since this usually gets totally optimized
125 * by the compile. But the i/o routines of (g)libc lack this support so far.
126 * The result of this is, that the old clock program worked only on the
127 * Jensen when USE_DEV_PORT was defined, but not with the normal inb/outb
130 int use_dev_port
= 0; /* 1 for Jensen */
132 unsigned short clock_ctl_addr
= 0x70; /* 0x170 for Jensen */
133 unsigned short clock_data_addr
= 0x71; /* 0x171 for Jensen */
135 int century_byte
= 0; /* 0: don't access a century byte
136 * 50 (0x32): usual PC value
141 int funkyTOY
= 0; /* 1 for PC164/LX164/SX164 type alpha */
146 static int is_in_cpuinfo(char *fmt
, char *str
)
153 sprintf(format
, "%s : %s", fmt
, "%255s");
155 cpuinfo
= fopen("/proc/cpuinfo", "r");
158 if (fscanf(cpuinfo
, format
, field
) == 1) {
159 if (strncmp(field
, str
, strlen(str
)) == 0)
163 } while (fgets(field
, 256, cpuinfo
));
170 * Set cmos_epoch, either from user options, or by asking the kernel, or by
171 * looking at /proc/cpu_info
173 void set_cmos_epoch(int ARCconsole
, int SRM
)
177 /* Believe the user */
178 if (epoch_option
!= -1) {
179 cmos_epoch
= epoch_option
;
186 if (ARCconsole
|| SRM
)
191 * If we can ask the kernel, we don't need guessing from
194 if (get_epoch_rtc(&epoch
, 1) == 0) {
201 * The kernel source today says: read the year.
203 * If it is in 0-19 then the epoch is 2000.
204 * If it is in 20-47 then the epoch is 1980.
205 * If it is in 48-69 then the epoch is 1952.
206 * If it is in 70-99 then the epoch is 1928.
208 * Otherwise the epoch is 1900.
209 * TODO: Clearly, this must be changed before 2019.
212 * See whether we are dealing with SRM or MILO, as they have
213 * different "epoch" ideas.
215 if (is_in_cpuinfo("system serial number", "MILO")) {
218 printf(_("booted from MILO\n"));
222 * See whether we are dealing with a RUFFIAN aka Alpha PC-164 UX (or
223 * BX), as they have REALLY different TOY (TimeOfYear) format: BCD,
224 * and not an ARC-style epoch. BCD is detected dynamically, but we
225 * must NOT adjust like ARC.
227 if (ARCconsole
&& is_in_cpuinfo("system type", "Ruffian")) {
230 printf(_("Ruffian BCD clock\n"));
237 void set_cmos_access(int Jensen
, int funky_toy
)
241 * See whether we're dealing with a Jensen---it has a weird I/O
242 * system. DEC was just learning how to build Alpha PCs.
244 if (Jensen
|| is_in_cpuinfo("system type", "Jensen")) {
246 clock_ctl_addr
= 0x170;
247 clock_data_addr
= 0x171;
249 printf(_("clockport adjusted to 0x%x\n"),
254 * See whether we are dealing with PC164/LX164/SX164, as they have a
255 * TOY that must be accessed differently to work correctly.
257 /* Nautilus stuff reported by Neoklis Kyriazis */
259 is_in_cpuinfo("system variation", "PC164") ||
260 is_in_cpuinfo("system variation", "LX164") ||
261 is_in_cpuinfo("system variation", "SX164") ||
262 is_in_cpuinfo("system type", "Nautilus")) {
265 printf(_("funky TOY!\n"));
272 * The Alpha doesn't allow user-level code to disable interrupts (for good
273 * reasons). Instead, we ensure atomic operation by performing the operation
274 * and checking whether the high 32 bits of the cycle counter changed. If
275 * they did, a context switch must have occurred and we redo the operation.
276 * As long as the operation is reasonably short, it will complete
277 * atomically, eventually.
280 atomic(const char *name
, unsigned long (*op
) (unsigned long), unsigned long arg
)
282 unsigned long ts1
, ts2
, n
, v
;
284 for (n
= 0; n
< 1000; ++n
) {
285 asm volatile ("rpcc %0":"r=" (ts1
));
287 asm volatile ("rpcc %0":"r=" (ts2
));
289 if ((ts1
^ ts2
) >> 32 == 0) {
293 errx(EXIT_FAILURE
, _("atomic %s failed for 1000 iterations!"),
299 * Hmmh, this isn't very atomic. Maybe we should force an error instead?
301 * TODO: optimize the access to CMOS by mlockall(MCL_CURRENT) and SCHED_FIFO
304 atomic(const char *name
__attribute__ ((__unused__
)),
305 unsigned long (*op
) (unsigned long),
313 static inline unsigned long cmos_read(unsigned long reg
)
316 unsigned char v
= reg
| 0x80;
317 lseek(dev_port_fd
, clock_ctl_addr
, 0);
318 if (write(dev_port_fd
, &v
, 1) == -1 && debug
)
319 warn(_("cmos_read(): write to control address %X failed"),
321 lseek(dev_port_fd
, clock_data_addr
, 0);
322 if (read(dev_port_fd
, &v
, 1) == -1 && debug
)
323 warn(_("cmos_read(): read from data address %X failed"),
328 * We only want to read CMOS data, but unfortunately writing
329 * to bit 7 disables (1) or enables (0) NMI; since this bit
330 * is read-only we have to guess the old status. Various
331 * docs suggest that one should disable NMI while
332 * reading/writing CMOS data, and enable it again
333 * afterwards. This would yield the sequence
335 * outb (reg | 0x80, 0x70);
337 * outb (0x0d, 0x70); // 0x0d: random read-only location
339 * Other docs state that "any write to 0x70 should be
340 * followed by an action to 0x71 or the RTC wil be left in
341 * an unknown state". Most docs say that it doesn't matter at
345 * bit 0x80: disable NMI while reading - should we? Let us
346 * follow the kernel and not disable. Called only with 0 <=
349 outb(reg
, clock_ctl_addr
);
350 return inb(clock_data_addr
);
354 static inline unsigned long cmos_write(unsigned long reg
, unsigned long val
)
357 unsigned char v
= reg
| 0x80;
358 lseek(dev_port_fd
, clock_ctl_addr
, 0);
359 if (write(dev_port_fd
, &v
, 1) == -1 && debug
)
360 warn(_("cmos_write(): write to control address %X failed"),
363 lseek(dev_port_fd
, clock_data_addr
, 0);
364 if (write(dev_port_fd
, &v
, 1) == -1 && debug
)
365 warn(_("cmos_write(): write to data address %X failed"),
368 outb(reg
, clock_ctl_addr
);
369 outb(val
, clock_data_addr
);
374 static unsigned long cmos_set_time(unsigned long arg
)
376 unsigned char save_control
, save_freq_select
, pmbit
= 0;
377 struct tm tm
= *(struct tm
*)arg
;
378 unsigned int century
;
381 * CMOS byte 10 (clock status register A) has 3 bitfields:
382 * bit 7: 1 if data invalid, update in progress (read-only bit)
383 * (this is raised 224 us before the actual update starts)
384 * 6-4 select base frequency
385 * 010: 32768 Hz time base (default)
387 * all other combinations are manufacturer-dependent
388 * (e.g.: DS1287: 010 = start oscillator, anything else = stop)
389 * 3-0 rate selection bits for interrupt
390 * 0000 none (may stop RTC)
391 * 0001, 0010 give same frequency as 1000, 1001
392 * 0011 122 microseconds (minimum, 8192 Hz)
393 * .... each increase by 1 halves the frequency, doubles the period
394 * 1111 500 milliseconds (maximum, 2 Hz)
395 * 0110 976.562 microseconds (default 1024 Hz)
397 save_control
= cmos_read(11); /* tell the clock it's being set */
398 cmos_write(11, (save_control
| 0x80));
399 save_freq_select
= cmos_read(10); /* stop and reset prescaler */
400 cmos_write(10, (save_freq_select
| 0x70));
402 tm
.tm_year
+= TM_EPOCH
;
403 century
= tm
.tm_year
/ 100;
404 tm
.tm_year
-= cmos_epoch
;
409 if (!(save_control
& 0x02)) { /* 12hr mode; the default is 24hr mode */
412 if (tm
.tm_hour
> 12) {
418 if (!(save_control
& 0x04)) { /* BCD mode - the default */
419 BIN_TO_BCD(tm
.tm_sec
);
420 BIN_TO_BCD(tm
.tm_min
);
421 BIN_TO_BCD(tm
.tm_hour
);
422 BIN_TO_BCD(tm
.tm_wday
);
423 BIN_TO_BCD(tm
.tm_mday
);
424 BIN_TO_BCD(tm
.tm_mon
);
425 BIN_TO_BCD(tm
.tm_year
);
429 cmos_write(0, tm
.tm_sec
);
430 cmos_write(2, tm
.tm_min
);
431 cmos_write(4, tm
.tm_hour
| pmbit
);
432 cmos_write(6, tm
.tm_wday
);
433 cmos_write(7, tm
.tm_mday
);
434 cmos_write(8, tm
.tm_mon
);
435 cmos_write(9, tm
.tm_year
);
437 cmos_write(century_byte
, century
);
440 * The kernel sources, linux/arch/i386/kernel/time.c, have the
443 * The following flags have to be released exactly in this order,
444 * otherwise the DS12887 (popular MC146818A clone with integrated
445 * battery and quartz) will not reset the oscillator and will not
446 * update precisely 500 ms later. You won't find this mentioned in
447 * the Dallas Semiconductor data sheets, but who believes data
448 * sheets anyway ... -- Markus Kuhn
450 cmos_write(11, save_control
);
451 cmos_write(10, save_freq_select
);
455 static int hclock_read(unsigned long reg
)
457 return atomic("clock read", cmos_read
, (reg
));
460 static void hclock_set_time(const struct tm
*tm
)
462 atomic("set time", cmos_set_time
, (unsigned long)(tm
));
465 static inline int cmos_clock_busy(void)
469 /* poll bit 4 (UF) of Control Register C */
470 funkyTOY
? (hclock_read(12) & 0x10) :
472 /* poll bit 7 (UIP) of Control Register A */
473 (hclock_read(10) & 0x80);
476 static int synchronize_to_clock_tick_cmos(void)
481 * Wait for rise. Should be within a second, but in case something
482 * weird happens, we have a limit on this loop to reduce the impact
485 for (i
= 0; !cmos_clock_busy(); i
++)
489 /* Wait for fall. Should be within 2.228 ms. */
490 for (i
= 0; cmos_clock_busy(); i
++)
497 * Read the hardware clock and return the current time via <tm> argument.
498 * Assume we have an ISA machine and read the clock directly with CPU I/O
501 * This function is not totally reliable. It takes a finite and
502 * unpredictable amount of time to execute the code below. During that time,
503 * the clock may change and we may even read an invalid value in the middle
504 * of an update. We do a few checks to minimize this possibility, but only
505 * the kernel can actually read the clock properly, since it can execute
506 * code in a short and predictable amount of time (by turning of
509 * In practice, the chance of this function returning the wrong time is
512 static int read_hardware_clock_cmos(struct tm
*tm
)
514 bool got_time
= FALSE
;
515 unsigned char status
, pmbit
;
517 status
= pmbit
= 0; /* just for gcc */
521 * Bit 7 of Byte 10 of the Hardware Clock value is the
522 * Update In Progress (UIP) bit, which is on while and 244
523 * uS before the Hardware Clock updates itself. It updates
524 * the counters individually, so reading them during an
525 * update would produce garbage. The update takes 2mS, so we
526 * could be spinning here that long waiting for this bit to
529 * Furthermore, it is pathologically possible for us to be
530 * in this code so long that even if the UIP bit is not on
531 * at first, the clock has changed while we were running. We
532 * check for that too, and if it happens, we start over.
534 if (!cmos_clock_busy()) {
535 /* No clock update in progress, go ahead and read */
536 tm
->tm_sec
= hclock_read(0);
537 tm
->tm_min
= hclock_read(2);
538 tm
->tm_hour
= hclock_read(4);
539 tm
->tm_wday
= hclock_read(6);
540 tm
->tm_mday
= hclock_read(7);
541 tm
->tm_mon
= hclock_read(8);
542 tm
->tm_year
= hclock_read(9);
543 status
= hclock_read(11);
546 century
= hclock_read(century_byte
);
549 * Unless the clock changed while we were reading,
550 * consider this a good clock read .
552 if (tm
->tm_sec
== hclock_read(0))
556 * Yes, in theory we could have been running for 60 seconds
557 * and the above test wouldn't work!
561 if (!(status
& 0x04)) { /* BCD mode - the default */
562 BCD_TO_BIN(tm
->tm_sec
);
563 BCD_TO_BIN(tm
->tm_min
);
564 pmbit
= (tm
->tm_hour
& 0x80);
566 BCD_TO_BIN(tm
->tm_hour
);
567 BCD_TO_BIN(tm
->tm_wday
);
568 BCD_TO_BIN(tm
->tm_mday
);
569 BCD_TO_BIN(tm
->tm_mon
);
570 BCD_TO_BIN(tm
->tm_year
);
577 * We don't use the century byte of the Hardware Clock since we
578 * don't know its address (usually 50 or 55). Here, we follow the
579 * advice of the X/Open Base Working Group: "if century is not
580 * specified, then values in the range [69-99] refer to years in the
581 * twentieth century (1969 to 1999 inclusive), and values in the
582 * range [00-68] refer to years in the twenty-first century (2000 to
587 tm
->tm_year
+= (cmos_epoch
- TM_EPOCH
);
588 if (tm
->tm_year
< 69)
592 if (tm
->tm_hour
== 24)
596 tm
->tm_isdst
= -1; /* don't know whether it's daylight */
600 static int set_hardware_clock_cmos(const struct tm
*new_broken_time
)
603 hclock_set_time(new_broken_time
);
607 #if defined(__i386__) || defined(__alpha__) || defined(__x86_64__)
608 # if defined(HAVE_IOPL)
609 static int i386_iopl(const int level
)
614 static int i386_iopl(const int level
__attribute__ ((__unused__
)))
616 extern int ioperm(unsigned long from
, unsigned long num
, int turn_on
);
617 return ioperm(clock_ctl_addr
, 2, 1);
621 static int i386_iopl(const int level
__attribute__ ((__unused__
)))
627 static int get_permissions_cmos(void)
632 if ((dev_port_fd
= open("/dev/port", O_RDWR
)) < 0) {
633 warn(_("cannot open %s"), "/dev/port");
640 warnx(_("I failed to get permission because I didn't try."));
641 } else if (rc
!= 0) {
643 warn(_("unable to get I/O port access: "
644 "the iopl(3) call failed."));
645 if (rc
== EPERM
&& geteuid())
646 warnx(_("Probably you need root privileges.\n"));
652 static struct clock_ops cmos
= {
653 N_("Using direct I/O instructions to ISA clock."),
654 get_permissions_cmos
,
655 read_hardware_clock_cmos
,
656 set_hardware_clock_cmos
,
657 synchronize_to_clock_tick_cmos
,
661 * return &cmos if cmos clock present, NULL otherwise choose this
662 * construction to avoid gcc messages about unused variables
664 struct clock_ops
*probe_for_cmos_clock(void)
667 #if defined(__i386__) || defined(__alpha__) || defined(__x86_64__)
672 return have_cmos
? &cmos
: NULL
;