text: /*
   * RTC related functions
   */
  #include <linux/platform_device.h>
  #include <linux/mc146818rtc.h>
  #include <linux/acpi.h>
  #include <linux/bcd.h>
  #include <linux/export.h>
  #include <linux/pnp.h>
  #include <linux/of.h>
  
  #include <asm/vsyscall.h>
  #include <asm/x86_init.h>
  #include <asm/time.h>
  #include <asm/intel-mid.h>
  #include <asm/rtc.h>
  
  #ifdef CONFIG_X86_32
  /*
   * This is a special lock that is owned by the CPU and holds the index
   * register we are working with.  It is required for NMI access to the
   * CMOS/RTC registers.  See include/asm-i386/mc146818rtc.h for details.
   */
  volatile unsigned long cmos_lock;
  EXPORT_SYMBOL(cmos_lock);
  #endif /* CONFIG_X86_32 */
  
  /* For two digit years assume time is always after that */
  #define CMOS_YEARS_OFFS 2000
  
  DEFINE_SPINLOCK(rtc_lock);
  EXPORT_SYMBOL(rtc_lock);
  
  /*
   * In order to set the CMOS clock precisely, set_rtc_mmss has to be
   * called 500 ms after the second nowtime has started, because when
   * nowtime is written into the registers of the CMOS clock, it will
   * jump to the next second precisely 500 ms later. Check the Motorola
   * MC146818A or Dallas DS12887 data sheet for details.
   */
  int mach_set_rtc_mmss(const struct timespec *now)
  {
  	unsigned long nowtime = now->tv_sec;
  	struct rtc_time tm;
  	int retval = 0;
  
  	rtc_time_to_tm(nowtime, &tm);
  	if (!rtc_valid_tm(&tm)) {
  		retval = set_rtc_time(&tm);
  		if (retval)
  			printk(KERN_ERR "%s: RTC write failed with error %d\n",
  			       __func__, retval);
  	} else {
  		printk(KERN_ERR
  		       "%s: Invalid RTC value: write of %lx to RTC failed\n",
  			__func__, nowtime);
  		retval = -EINVAL;
  	}
  	return retval;
  }
  
  void mach_get_cmos_time(struct timespec *now)
  {
  	unsigned int status, year, mon, day, hour, min, sec, century = 0;
  	unsigned long flags;
  
  	spin_lock_irqsave(&rtc_lock, flags);
  
  	/*
  	 * If UIP is clear, then we have >= 244 microseconds before
  	 * RTC registers will be updated.  Spec sheet says that this
  	 * is the reliable way to read RTC - registers. If UIP is set
  	 * then the register access might be invalid.
  	 */
  	while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
  		cpu_relax();
  
  	sec = CMOS_READ(RTC_SECONDS);
  	min = CMOS_READ(RTC_MINUTES);
  	hour = CMOS_READ(RTC_HOURS);
  	day = CMOS_READ(RTC_DAY_OF_MONTH);
  	mon = CMOS_READ(RTC_MONTH);
  	year = CMOS_READ(RTC_YEAR);
  
  #ifdef CONFIG_ACPI
  	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
  	    acpi_gbl_FADT.century)
  		century = CMOS_READ(acpi_gbl_FADT.century);
  #endif
  
  	status = CMOS_READ(RTC_CONTROL);
  	WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));
  
  	spin_unlock_irqrestore(&rtc_lock, flags);
  
  	if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) {
  		sec = bcd2bin(sec);
  		min = bcd2bin(min);
  		hour = bcd2bin(hour);
  		day = bcd2bin(day);
  		mon = bcd2bin(mon);
  		year = bcd2bin(year);
  	}
  
  	if (century) {
  		century = bcd2bin(century);
  		year += century * 100;
  	} else
  		year += CMOS_YEARS_OFFS;
  
  	now->tv_sec = mktime(year, mon, day, hour, min, sec);
  	now->tv_nsec = 0;
  }
  
  /* Routines for accessing the CMOS RAM/RTC. */
  unsigned char rtc_cmos_read(unsigned char addr)
  {
  	unsigned char val;
  
  	lock_cmos_prefix(addr);
  	outb(addr, RTC_PORT(0));
  	val = inb(RTC_PORT(1));
  	lock_cmos_suffix(addr);
  
  	return val;
  }
  EXPORT_SYMBOL(rtc_cmos_read);
  
  void rtc_cmos_write(unsigned char val, unsigned char addr)
  {
  	lock_cmos_prefix(addr);
  	outb(addr, RTC_PORT(0));
  	outb(val, RTC_PORT(1));
  	lock_cmos_suffix(addr);
  }
  EXPORT_SYMBOL(rtc_cmos_write);
  
  int update_persistent_clock(struct timespec now)
  {
  	return x86_platform.set_wallclock(&now);
  }
  
  /* not static: needed by APM */
  void read_persistent_clock(struct timespec *ts)
  {
  	x86_platform.get_wallclock(ts);
  }
  
  
  static struct resource rtc_resources[] = {
  	[0] = {
  		.start	= RTC_PORT(0),
  		.end	= RTC_PORT(1),
  		.flags	= IORESOURCE_IO,
  	},
  	[1] = {
  		.start	= RTC_IRQ,
  		.end	= RTC_IRQ,
  		.flags	= IORESOURCE_IRQ,
  	}
  };
  
  static struct platform_device rtc_device = {
  	.name		= "rtc_cmos",
  	.id		= -1,
  	.resource	= rtc_resources,
  	.num_resources	= ARRAY_SIZE(rtc_resources),
  };
  
  static __init int add_rtc_cmos(void)
  {
  #ifdef CONFIG_PNP
  	static const char * const ids[] __initconst =
  	    { "PNP0b00", "PNP0b01", "PNP0b02", };
  	struct pnp_dev *dev;
  	struct pnp_id *id;
  	int i;
  
  	pnp_for_each_dev(dev) {
  		for (id = dev->id; id; id = id->next) {
  			for (i = 0; i < ARRAY_SIZE(ids); i++) {
  				if (compare_pnp_id(id, ids[i]) != 0)
  					return 0;
  			}
  		}
  	}
  #endif
  	if (of_have_populated_dt())
  		return 0;
  
  	/* Intel MID platforms don't have ioport rtc */
  	if (intel_mid_identify_cpu())
  		return -ENODEV;
  
  #ifdef CONFIG_ACPI
  	if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_CMOS_RTC) {
  		/* This warning can likely go away again in a year or two. */
  		pr_info("ACPI: not registering RTC platform device\n");
  		return -ENODEV;
  	}
  #endif
  
  	platform_device_register(&rtc_device);
  	dev_info(&rtc_device.dev,
  		 "registered platform RTC device (no PNP device found)\n");
  
  	return 0;
  }
  device_initcall(add_rtc_cmos);
  