1 files changed, 420 insertions, 0 deletions

diff --git a/sys-utils/hwclock-cmos.c b/sys-utils/hwclock-cmos.c
new file mode 100644
index 0000000..a11f676
--- /dev/null
+++ b/sys-utils/hwclock-cmos.c
@@ -0,0 +1,420 @@
+/*
+ * 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 <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "c.h"
+#include "nls.h"
+#include "pathnames.h"
+
+/* for inb, outb */
+#if defined(__i386__) || defined(__x86_64__)
+# ifdef HAVE_SYS_IO_H
+#  include <sys/io.h>
+# elif defined(HAVE_ASM_IO_H)
+#  include <asm/io.h>
+# else
+#  undef __i386__
+#  undef __x86_64__
+#  warning "disable cmos access - no sys/io.h or asm/io.h"
+static void outb(int a __attribute__((__unused__)),
+		 int b __attribute__((__unused__)))
+{
+}
+
+static int inb(int c __attribute__((__unused__)))
+{
+	return 0;
+}
+# endif				/* __i386__ __x86_64__ */
+#else
+# warning "disable cmos access - not i386 or x86_64"
+static void outb(int a __attribute__((__unused__)),
+		 int b __attribute__((__unused__)))
+{
+}
+
+static int inb(int c __attribute__((__unused__)))
+{
+	return 0;
+}
+#endif				/* for inb, outb */
+
+#include "hwclock.h"
+
+#define BCD_TO_BIN(val) ((val)=((val)&15) + ((val)>>4)*10)
+#define BIN_TO_BCD(val) ((val)=(((val)/10)<<4) + (val)%10)
+
+#define IOPL_NOT_IMPLEMENTED -2
+
+/*
+ * POSIX uses 1900 as epoch for a struct tm, and 1970 for a time_t.
+ */
+#define TM_EPOCH 1900
+
+static unsigned short clock_ctl_addr = 0x70;
+static unsigned short clock_data_addr = 0x71;
+
+/*
+ * 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(unsigned long (*op) (unsigned long),
+			    unsigned long arg)
+{
+	return (*op) (arg);
+}
+
+/*
+ * 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 will be left in an unknown state". Most
+ * docs say that it doesn't 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
+ */
+
+static inline unsigned long cmos_read(unsigned long reg)
+{
+	outb(reg, clock_ctl_addr);
+	return inb(clock_data_addr);
+}
+
+static inline unsigned long cmos_write(unsigned long reg, unsigned long val)
+{
+	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;
+
+/*
+ * 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 %= 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);
+	}
+
+	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);
+
+	/*
+	 * 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(cmos_read, reg);
+}
+
+static void hclock_set_time(const struct tm *tm)
+{
+	atomic(cmos_set_time, (unsigned long)(tm));
+}
+
+static inline int cmos_clock_busy(void)
+{
+	return
+	    /* poll bit 7 (UIP) of Control Register A */
+	    (hclock_read(10) & 0x80);
+}
+
+static int synchronize_to_clock_tick_cmos(const struct hwclock_control *ctl
+					  __attribute__((__unused__)))
+{
+	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;
+}
+
+/*
+ * 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.
+ */
+static int read_hardware_clock_cmos(const struct hwclock_control *ctl
+				    __attribute__((__unused__)), struct tm *tm)
+{
+	unsigned char status = 0, pmbit = 0;
+
+	while (1) {
+		/*
+		 * 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);
+			/*
+			 * Unless the clock changed while we were reading,
+			 * consider this a good clock read .
+			 */
+			if (tm->tm_sec == hclock_read(0))
+				break;
+		}
+		/*
+		 * 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);
+	}
+
+	/*
+	 * 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;
+	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 hwclock_control *ctl
+				   __attribute__((__unused__)),
+				   const struct tm *new_broken_time)
+{
+	hclock_set_time(new_broken_time);
+	return 0;
+}
+
+#if defined(__i386__) || defined(__x86_64__)
+# if defined(HAVE_IOPL)
+static int i386_iopl(const int level)
+{
+	return iopl(level);
+}
+# else
+static int i386_iopl(const int level __attribute__ ((__unused__)))
+{
+	extern int ioperm(unsigned long from, unsigned long num, int turn_on);
+	return ioperm(clock_ctl_addr, 2, 1);
+}
+# endif
+#else
+static int i386_iopl(const int level __attribute__ ((__unused__)))
+{
+	return IOPL_NOT_IMPLEMENTED;
+}
+#endif
+
+static int get_permissions_cmos(void)
+{
+	int rc;
+
+	rc = i386_iopl(3);
+	if (rc == IOPL_NOT_IMPLEMENTED) {
+		warnx(_("ISA port access is not implemented"));
+	} else if (rc != 0) {
+		warn(_("iopl() port access failed"));
+	}
+	return rc;
+}
+
+static const char *get_device_path(void)
+{
+	return NULL;
+}
+
+static struct clock_ops cmos_interface = {
+	N_("Using direct ISA access to the clock"),
+	get_permissions_cmos,
+	read_hardware_clock_cmos,
+	set_hardware_clock_cmos,
+	synchronize_to_clock_tick_cmos,
+	get_device_path,
+};
+
+/*
+ * return &cmos if cmos clock present, NULL otherwise.
+ */
+struct clock_ops *probe_for_cmos_clock(void)
+{
+#if defined(__i386__) || defined(__x86_64__)
+	return &cmos_interface;
+#else
+	return NULL;
+#endif
+}