path: root/hwclock/cmos.c

/*
 * i386 CMOS starts out with 14 bytes clock data
 * alpha has something similar, but with details
 * depending on the machine type.
 *
 * byte 0: seconds (0-59)
 * byte 2: minutes (0-59)
 * byte 4: hours (0-23 in 24hr mode,
 *                1-12 in 12hr mode, with high bit unset/set if am/pm)
 * byte 6: weekday (1-7, Sunday=1)
 * byte 7: day of the month (1-31)
 * byte 8: month (1-12)
 * byte 9: year (0-99)
 * Numbers are stored in BCD/binary if bit 2 of byte 11 is unset/set
 * The clock is in 12hr/24hr mode if bit 1 of byte 11 is unset/set
 * The clock is undefined (being updated) if bit 7 of byte 10 is set.
 * The clock is frozen (to be updated) by setting bit 7 of byte 11
 * Bit 7 of byte 14 indicates whether the CMOS clock is reliable:
 * it is 1 if RTC power has been good since this bit was last read;
 * it is 0 when the battery is dead and system power has been off.
 *
 * Avoid setting the RTC clock within 2 seconds of the day rollover
 * that starts a new month or enters daylight saving time.
 *
 * The century situation is messy:
 * Usually byte 50 (0x32) gives the century (in BCD, so 19 or 20 hex),
 * but IBM PS/2 has (part of) a checksum there and uses byte 55 (0x37).
 * Sometimes byte 127 (0x7f) or Bank 1, byte 0x48 gives the century.
 * The original RTC will not access any century byte; some modern
 * versions will. If a modern RTC or BIOS increments the century byte
 * it may go from 0x19 to 0x20, but in some buggy cases 0x1a is produced.
 */

/*
 * A struct tm has int fields
 *   tm_sec (0-59, 60 or 61 only for leap seconds)
 *   tm_min (0-59)
 *   tm_hour (0-23)
 *   tm_mday (1-31)
 *   tm_mon (0-11)
 *   tm_year (number of years since 1900)
 *   tm_wday (0-6, 0=Sunday)
 *   tm_yday (0-365)
 *   tm_isdst (>0: yes, 0: no, <0: unknown)
 */

#include <unistd.h>		/* for geteuid() */
#include <fcntl.h>		/* for O_RDWR */
#include <errno.h>
#include "nls.h"

#if defined(__i386__)
#ifdef HAVE_SYS_IO_H
#include <sys/io.h>
#else
#include <asm/io.h>		/* for inb, outb */
#endif
#elif defined(__alpha__)
/* <asm/io.h> fails to compile, probably because of u8 etc */
extern unsigned int     inb(unsigned long port);
extern void             outb(unsigned char b,unsigned long port);
#else
void outb(int a, int b){}
int inb(int c){ return 0; }
#endif

#include "clock.h"

#define BCD_TO_BIN(val) ((val)=((val)&15) + ((val)>>4)*10)
#define BIN_TO_BCD(val) ((val)=(((val)/10)<<4) + (val)%10)

/*
 * The epoch.
 *
 * Unix uses 1900 as epoch for a struct tm, and 1970 for a time_t.
 * But what was written to CMOS?
 * Digital DECstations use 1928 - this is on a mips or alpha
 * Digital Unix uses 1952, e.g. on AXPpxi33
 * Windows NT uses 1980.
 * The ARC console expects to boot Windows NT and uses 1980.
 * (But a Ruffian uses 1900, just like SRM.)
 * It is reported that ALPHA_PRE_V1_2_SRM_CONSOLE uses 1958.
 */
#define TM_EPOCH 1900
int cmos_epoch = 1900;

/* Martin Ostermann writes:
The problem with the Jensen is twofold: First, it has the clock at a
different address. Secondly, it has a distinction beween "local" and
normal bus addresses. The local ones pertain to the hardware integrated
into the chipset, like serial/parallel ports and of course, the RTC.
Those need to be addressed differently. This is handled fine in the kernel,
and it's not a problem, since this usually gets totally optimized by the
compile. But the i/o routines of (g)libc lack this support so far.
The result of this is, that the old clock program worked only on the
Jensen when USE_DEV_PORT was defined, but not with the normal inb/outb
functions.
 */
int use_dev_port = 0;		/* 1 for Jensen */
int dev_port_fd;
unsigned short clock_ctl_addr = 0x70;	/* 0x170 for Jensen */
unsigned short clock_data_addr = 0x71; 	/* 0x171 for Jensen */


int century_byte = 0;		/* 0: don't access a century byte
				  50 (0x32): usual PC value
				  55 (0x37): PS/2 */

#ifdef __alpha__
int funkyTOY = 0;		/* 1 for PC164/LX164/SX164 type alpha */
#endif

#ifdef __alpha

static int
is_in_cpuinfo(char *fmt, char *str)
{
    FILE *cpuinfo;
    char field[256];
    char format[256];
    int found = 0;

    sprintf(format, "%s : %s", fmt, "%255s");

    if ((cpuinfo = fopen ("/proc/cpuinfo", "r")) != NULL) {
	while (!feof(cpuinfo)) {
	    if (fscanf (cpuinfo, format, field) == 1) {
		if (strncmp(field, str, strlen(str)) == 0)
		    found = 1;
		break;
	    }
	    fgets (field, 256, cpuinfo);
	}
	fclose(cpuinfo);
    }
    return found;
}

/* Set cmos_epoch, either from user options, or by asking the kernel,
   or by looking at /proc/cpu_info */
void
set_cmos_epoch(int ARCconsole, int SRM) {
  unsigned long epoch;

  /* Believe the user */
  if (epoch_option != -1) {
    cmos_epoch = epoch_option;
    return;
  }

  if (ARCconsole)
    cmos_epoch = 1980;

  if (ARCconsole || SRM)
    return;


  /* If we can ask the kernel, we don't need guessing from /proc/cpuinfo */
  if (get_epoch_rtc(&epoch, 1) == 0) {
     cmos_epoch = epoch;
     return;
  }

  /* The kernel source today says: read the year.
     If it is in 0-19 then the epoch is 2000.
     If it is in 20-47 then the epoch is 1980.
     If it is in 48-69 then the epoch is 1952.
     If it is in 70-99 then the epoch is 1928.
     Otherwise the epoch is 1900.
     Clearly, this must be changed before 2019. */

  /* See whether we are dealing with SRM or MILO, as they have
     different "epoch" ideas. */
  if (is_in_cpuinfo("system serial number", "MILO")) {
      ARCconsole = 1;
      if (debug) printf (_("booted from MILO\n"));
  }

  /* See whether we are dealing with a RUFFIAN aka Alpha PC-164 UX (or BX),
     as they have REALLY different TOY (TimeOfYear) format: BCD, and not
     an ARC-style epoch.
     BCD is detected dynamically, but we must NOT adjust like ARC. */
  if (ARCconsole && is_in_cpuinfo("system type", "Ruffian")) {
    ARCconsole = 0;
    if (debug) printf (_("Ruffian BCD clock\n"));
  }

  if (ARCconsole)
    cmos_epoch = 1980;
}

void
set_cmos_access(int Jensen, int funky_toy) {

  /* See whether we're dealing with a Jensen---it has a weird I/O
     system.  DEC was just learning how to build Alpha PCs.  */
  if (Jensen || is_in_cpuinfo("system type", "Jensen")) {
    use_dev_port = 1;
    clock_ctl_addr = 0x170;
    clock_data_addr = 0x171;
    if (debug) printf (_("clockport adjusted to 0x%x\n"), clock_ctl_addr);
  }

  /* see whether we are dealing with PC164/LX164/SX164, as they have a TOY
     that must be accessed differently to work correctly. */
  /* Nautilus stuff reported by Neoklis Kyriazis */
  if (funky_toy ||
      is_in_cpuinfo("system variation", "PC164") ||
      is_in_cpuinfo("system variation", "LX164") ||
      is_in_cpuinfo("system variation", "SX164") ||
      is_in_cpuinfo("system type", "Nautilus")) {
      funkyTOY = 1;
      if (debug) printf (_("funky TOY!\n"));
  }
}
#endif


#if __alpha__
/*
 * The Alpha doesn't allow user-level code to disable interrupts (for
 * good reasons).  Instead, we ensure atomic operation by performing
 * the operation and checking whether the high 32 bits of the cycle
 * counter changed.  If they did, a context switch must have occurred
 * and we redo the operation.  As long as the operation is reasonably
 * short, it will complete atomically, eventually.
 */

static unsigned long
atomic(const char *name, unsigned long (*op)(unsigned long),
       unsigned long arg)
{
  unsigned long ts1, ts2, n, v;

  for (n = 0; n < 1000; ++n) {
    asm volatile ("rpcc %0" : "r="(ts1));
    v = (*op)(arg);
    asm volatile ("rpcc %0" : "r="(ts2));

    if ((ts1 ^ ts2) >> 32 == 0) {
      return v;
    }
  }
  fprintf(stderr, _("%s: atomic %s failed for 1000 iterations!"), progname, name);
  exit(1);
}
#else

/*
 * Hmmh, this isn't very atomic.  Maybe we should force an error
 * instead?
 *
 * TODO: optimize the access to CMOS by mlockall(MCL_CURRENT)
 *       and SCHED_FIFO
 */
static unsigned long
atomic(const char *name, unsigned long (*op)(unsigned long),
       unsigned long arg)
{
    return (*op)(arg);
}

#endif


static inline
unsigned long cmos_read(unsigned long reg)
{
  if (use_dev_port) {
    unsigned char v = reg | 0x80;
    lseek(dev_port_fd, clock_ctl_addr, 0);
    if (write(dev_port_fd, &v, 1) == -1 && debug)
      printf(_("cmos_read(): write to control address %X failed: %s\n"), clock_ctl_addr, strerror(errno));
    lseek(dev_port_fd, clock_data_addr, 0);
    if (read(dev_port_fd, &v, 1) == -1 && debug)
      printf(_("cmos_read(): read data address %X failed: %s\n"), clock_data_addr, strerror(errno));
    return v;
  } else {
    /* We only want to read CMOS data, but unfortunately
       writing to bit 7 disables (1) or enables (0) NMI;
       since this bit is read-only we have to guess the old status.
       Various docs suggest that one should disable NMI while
       reading/writing CMOS data, and enable it again afterwards.
       This would yield the sequence
	  outb (reg | 0x80, 0x70);
	  val = inb(0x71);
	  outb (0x0d, 0x70);	// 0x0d: random read-only location
       Other docs state that "any write to 0x70 should be followed
       by an action to 0x71 or the RTC wil be left in an unknown state".
       Most docs say that it doesnt matter at all what one does.
     */
    /* bit 0x80: disable NMI while reading - should we?
       Let us follow the kernel and not disable.
       Called only with 0 <= reg < 128 */
    outb (reg, clock_ctl_addr);
    return inb (clock_data_addr);
  }
}

static inline
unsigned long cmos_write(unsigned long reg, unsigned long val)
{
  if (use_dev_port) {
    unsigned char v = reg | 0x80;
    lseek(dev_port_fd, clock_ctl_addr, 0);
    if (write(dev_port_fd, &v, 1) == -1 && debug)
      printf(_("cmos_write(): write to control address %X failed: %s\n"), clock_ctl_addr, strerror(errno));
    v = (val & 0xff);
    lseek(dev_port_fd, clock_data_addr, 0);
    if (write(dev_port_fd, &v, 1) == -1 && debug)
      printf(_("cmos_write(): write to data address %X failed: %s\n"), clock_data_addr, strerror(errno));
  } else {
    outb (reg, clock_ctl_addr);
    outb (val, clock_data_addr);
  }
  return 0;
}

static unsigned long cmos_set_time(unsigned long arg)
{
  unsigned char save_control, save_freq_select, pmbit = 0;
  struct tm tm = *(struct tm *) arg;
  unsigned int century;

/*
 * CMOS byte 10 (clock status register A) has 3 bitfields:
 * bit 7: 1 if data invalid, update in progress (read-only bit)
 *         (this is raised 224 us before the actual update starts)
 *  6-4    select base frequency
 *         010: 32768 Hz time base (default)
 *         111: reset
 *         all other combinations are manufacturer-dependent
 *         (e.g.: DS1287: 010 = start oscillator, anything else = stop)
 *  3-0    rate selection bits for interrupt
 *         0000 none (may stop RTC)
 *         0001, 0010 give same frequency as 1000, 1001
 *         0011 122 microseconds (minimum, 8192 Hz)
 *         .... each increase by 1 halves the frequency, doubles the period
 *         1111 500 milliseconds (maximum, 2 Hz)
 *         0110 976.562 microseconds (default 1024 Hz)
 */

  save_control = cmos_read (11);   /* tell the clock it's being set */
  cmos_write (11, (save_control | 0x80));
  save_freq_select = cmos_read (10);       /* stop and reset prescaler */
  cmos_write (10, (save_freq_select | 0x70));

  tm.tm_year += TM_EPOCH;
  century = tm.tm_year/100;
  tm.tm_year -= cmos_epoch;
  tm.tm_year %= 100;
  tm.tm_mon += 1;
  tm.tm_wday += 1;

  if (!(save_control & 0x02)) {	/* 12hr mode; the default is 24hr mode */
      if (tm.tm_hour == 0)
          tm.tm_hour = 24;
      if (tm.tm_hour > 12) {
	  tm.tm_hour -= 12;
	  pmbit = 0x80;
      }
  }

  if (!(save_control & 0x04)) { /* BCD mode - the default */
      BIN_TO_BCD(tm.tm_sec);
      BIN_TO_BCD(tm.tm_min);
      BIN_TO_BCD(tm.tm_hour);
      BIN_TO_BCD(tm.tm_wday);
      BIN_TO_BCD(tm.tm_mday);
      BIN_TO_BCD(tm.tm_mon);
      BIN_TO_BCD(tm.tm_year);
      BIN_TO_BCD(century);
  }

  cmos_write (0, tm.tm_sec);
  cmos_write (2, tm.tm_min);
  cmos_write (4, tm.tm_hour | pmbit);
  cmos_write (6, tm.tm_wday);
  cmos_write (7, tm.tm_mday);
  cmos_write (8, tm.tm_mon);
  cmos_write (9, tm.tm_year);
  if (century_byte)
	  cmos_write (century_byte, century);


    /* The kernel sources, linux/arch/i386/kernel/time.c, have the
       following comment:

       The following flags have to be released exactly in this order,
       otherwise the DS12887 (popular MC146818A clone with integrated
       battery and quartz) will not reset the oscillator and will not
       update precisely 500 ms later.  You won't find this mentioned
       in the Dallas Semiconductor data sheets, but who believes data
       sheets anyway ...  -- Markus Kuhn
    */

  cmos_write (11, save_control);
  cmos_write (10, save_freq_select);
  return 0;
}

static int
hclock_read(unsigned long reg) {
	return atomic("clock read", cmos_read, (reg));
}

static void
hclock_set_time(const struct tm *tm) {
	atomic("set time", cmos_set_time, (unsigned long)(tm));
}

static inline int
cmos_clock_busy(void) {
	return
#ifdef __alpha__
	                /* poll bit 4 (UF) of Control Register C */
	    funkyTOY ? (hclock_read(12) & 0x10) :
#endif
		        /* poll bit 7 (UIP) of Control Register A */
	    (hclock_read(10) & 0x80);
}


static int
synchronize_to_clock_tick_cmos(void) {
  int i;

  /* Wait for rise.  Should be within a second, but in case something
     weird happens, we have a limit on this loop to reduce the impact
     of this failure.
     */
  for (i = 0; !cmos_clock_busy(); i++)
	  if (i >= 10000000)
		  return 1;

  /* Wait for fall.  Should be within 2.228 ms. */
  for (i = 0; cmos_clock_busy(); i++)
	  if (i >= 1000000)
		  return 1;
  return 0;
}



static int
read_hardware_clock_cmos(struct tm *tm) {
/*----------------------------------------------------------------------------
  Read the hardware clock and return the current time via <tm> argument.
  Assume we have an ISA machine and read the clock directly with CPU I/O
  instructions.

  This function is not totally reliable.  It takes a finite and
  unpredictable amount of time to execute the code below.  During that
  time, the clock may change and we may even read an invalid value in
  the middle of an update.  We do a few checks to minimize this
  possibility, but only the kernel can actually read the clock
  properly, since it can execute code in a short and predictable
  amount of time (by turning of interrupts).

  In practice, the chance of this function returning the wrong time is
  extremely remote.

-----------------------------------------------------------------------------*/
  bool got_time = FALSE;
  unsigned char status, pmbit;

  status = pmbit = 0;		/* just for gcc */

  while (!got_time) {
    /* Bit 7 of Byte 10 of the Hardware Clock value is the Update In Progress
       (UIP) bit, which is on while and 244 uS before the Hardware Clock
       updates itself.  It updates the counters individually, so reading
       them during an update would produce garbage.  The update takes 2mS,
       so we could be spinning here that long waiting for this bit to turn
       off.

       Furthermore, it is pathologically possible for us to be in this
       code so long that even if the UIP bit is not on at first, the
       clock has changed while we were running.  We check for that too,
       and if it happens, we start over.
       */

    if (!cmos_clock_busy()) {
      /* No clock update in progress, go ahead and read */
      tm->tm_sec = hclock_read(0);
      tm->tm_min = hclock_read(2);
      tm->tm_hour = hclock_read(4);
      tm->tm_wday = hclock_read(6);
      tm->tm_mday = hclock_read(7);
      tm->tm_mon = hclock_read(8);
      tm->tm_year = hclock_read(9);
      status = hclock_read(11);
#if 0
      if (century_byte)
	  century = hclock_read(century_byte);
#endif

      /* Unless the clock changed while we were reading, consider this
         a good clock read .
       */
      if (tm->tm_sec == hclock_read (0))
	got_time = TRUE;
    }
    /* Yes, in theory we could have been running for 60 seconds and
       the above test wouldn't work!
       */
  }

  if (!(status & 0x04)) { /* BCD mode - the default */
      BCD_TO_BIN(tm->tm_sec);
      BCD_TO_BIN(tm->tm_min);
      pmbit = (tm->tm_hour & 0x80);
      tm->tm_hour &= 0x7f;
      BCD_TO_BIN(tm->tm_hour);
      BCD_TO_BIN(tm->tm_wday);
      BCD_TO_BIN(tm->tm_mday);
      BCD_TO_BIN(tm->tm_mon);
      BCD_TO_BIN(tm->tm_year);
#if 0
      BCD_TO_BIN(century);
#endif
  }

  /* We don't use the century byte of the Hardware Clock
     since we don't know its address (usually 50 or 55).
     Here, we follow the advice of the X/Open Base Working Group:
     "if century is not specified, then values in the range [69-99]
      refer to years in the twentieth century (1969 to 1999 inclusive),
      and values in the range [00-68] refer to years in the twenty-first
      century (2000 to 2068 inclusive)."
   */

  tm->tm_wday -= 1;
  tm->tm_mon -= 1;
  tm->tm_year += (cmos_epoch - TM_EPOCH);
  if (tm->tm_year < 69)
	  tm->tm_year += 100;
  if (pmbit) {
	  tm->tm_hour += 12;
	  if (tm->tm_hour == 24)
		  tm->tm_hour = 0;
  }

  tm->tm_isdst = -1;        /* don't know whether it's daylight */
  return 0;
}



static int
set_hardware_clock_cmos(const struct tm *new_broken_time) {

    hclock_set_time(new_broken_time);
    return 0;
}

static int
i386_iopl(const int level) {
#if defined(__i386__) || defined(__alpha__)
  extern int iopl(const int lvl);
  return iopl(level);
#else
  return -2;
#endif
}

static int
get_permissions_cmos(void) {
  int rc;

  if (use_dev_port) {
    if ((dev_port_fd = open("/dev/port", O_RDWR)) < 0) {
      int errsv = errno;
      fprintf(stderr, _("Cannot open /dev/port: %s"), strerror(errsv));
      rc = 1;
    } else
      rc = 0;
  } else {
    rc = i386_iopl(3);
    if (rc == -2) {
      fprintf(stderr, _("I failed to get permission because I didn't try.\n"));
    } else if (rc != 0) {
      rc = errno;
      fprintf(stderr, _("%s is unable to get I/O port access:  "
              "the iopl(3) call failed.\n"), progname);
      if(rc == EPERM && geteuid())
        fprintf(stderr, _("Probably you need root privileges.\n"));
    }
  }
  return rc ? 1 : 0;
}

static struct clock_ops cmos = {
	"direct I/O instructions to ISA clock",
	get_permissions_cmos,
	read_hardware_clock_cmos,
	set_hardware_clock_cmos,
	synchronize_to_clock_tick_cmos,
};


/* return &cmos if cmos clock present, NULL otherwise */
/* choose this construction to avoid gcc messages about unused variables */

struct clock_ops *
probe_for_cmos_clock(void){
    int have_cmos =
#if defined(__i386__) || defined(__alpha__)
	    TRUE;
#else
	    FALSE;
#endif
    return have_cmos ? &cmos : NULL;
}