// SPDX-License-Identifier: GPL-2.0-only

  #include <linux/bcd.h>
  #include <linux/delay.h>
  #include <linux/export.h>
  #include <linux/mc146818rtc.h>
  
  #ifdef CONFIG_ACPI
  #include <linux/acpi.h>
  #endif
  
  /*
   * Returns true if a clock update is in progress
   */
  static inline unsigned char mc146818_is_updating(void)
  {
  	unsigned char uip;
  	unsigned long flags;
  
  	spin_lock_irqsave(&rtc_lock, flags);
  	uip = (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
  	spin_unlock_irqrestore(&rtc_lock, flags);
  	return uip;
  }
  
  unsigned int mc146818_get_time(struct rtc_time *time)
  {
  	unsigned char ctrl;
  	unsigned long flags;
  	unsigned char century = 0;
  
  #ifdef CONFIG_MACH_DECSTATION
  	unsigned int real_year;
  #endif
  
  	/*
  	 * read RTC once any update in progress is done. The update
  	 * can take just over 2ms. We wait 20ms. There is no need to
  	 * to poll-wait (up to 1s - eeccch) for the falling edge of RTC_UIP.
  	 * If you need to know *exactly* when a second has started, enable
  	 * periodic update complete interrupts, (via ioctl) and then
  	 * immediately read /dev/rtc which will block until you get the IRQ.
  	 * Once the read clears, read the RTC time (again via ioctl). Easy.
  	 */
  	if (mc146818_is_updating())
  		mdelay(20);
  
  	/*
  	 * Only the values that we read from the RTC are set. We leave
  	 * tm_wday, tm_yday and tm_isdst untouched. Even though the
  	 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
  	 * by the RTC when initially set to a non-zero value.
  	 */
  	spin_lock_irqsave(&rtc_lock, flags);
  	time->tm_sec = CMOS_READ(RTC_SECONDS);
  	time->tm_min = CMOS_READ(RTC_MINUTES);
  	time->tm_hour = CMOS_READ(RTC_HOURS);
  	time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
  	time->tm_mon = CMOS_READ(RTC_MONTH);
  	time->tm_year = CMOS_READ(RTC_YEAR);
  #ifdef CONFIG_MACH_DECSTATION
  	real_year = CMOS_READ(RTC_DEC_YEAR);
  #endif
  #ifdef CONFIG_ACPI
  	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
  	    acpi_gbl_FADT.century)
  		century = CMOS_READ(acpi_gbl_FADT.century);
  #endif
  	ctrl = CMOS_READ(RTC_CONTROL);
  	spin_unlock_irqrestore(&rtc_lock, flags);
  
  	if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  	{
  		time->tm_sec = bcd2bin(time->tm_sec);
  		time->tm_min = bcd2bin(time->tm_min);
  		time->tm_hour = bcd2bin(time->tm_hour);
  		time->tm_mday = bcd2bin(time->tm_mday);
  		time->tm_mon = bcd2bin(time->tm_mon);
  		time->tm_year = bcd2bin(time->tm_year);
  		century = bcd2bin(century);
  	}
  
  #ifdef CONFIG_MACH_DECSTATION
  	time->tm_year += real_year - 72;
  #endif

  	if (century > 20)

  		time->tm_year += (century - 19) * 100;
  
  	/*
  	 * Account for differences between how the RTC uses the values
  	 * and how they are defined in a struct rtc_time;
  	 */
  	if (time->tm_year <= 69)
  		time->tm_year += 100;
  
  	time->tm_mon--;
  
  	return RTC_24H;
  }
  EXPORT_SYMBOL_GPL(mc146818_get_time);
  
  /* Set the current date and time in the real time clock. */
  int mc146818_set_time(struct rtc_time *time)
  {
  	unsigned long flags;
  	unsigned char mon, day, hrs, min, sec;
  	unsigned char save_control, save_freq_select;
  	unsigned int yrs;
  #ifdef CONFIG_MACH_DECSTATION
  	unsigned int real_yrs, leap_yr;
  #endif
  	unsigned char century = 0;
  
  	yrs = time->tm_year;
  	mon = time->tm_mon + 1;   /* tm_mon starts at zero */
  	day = time->tm_mday;
  	hrs = time->tm_hour;
  	min = time->tm_min;
  	sec = time->tm_sec;
  
  	if (yrs > 255)	/* They are unsigned */
  		return -EINVAL;
  
  	spin_lock_irqsave(&rtc_lock, flags);
  #ifdef CONFIG_MACH_DECSTATION
  	real_yrs = yrs;
  	leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) ||
  			!((yrs + 1900) % 400));
  	yrs = 72;
  
  	/*
  	 * We want to keep the year set to 73 until March
  	 * for non-leap years, so that Feb, 29th is handled
  	 * correctly.
  	 */
  	if (!leap_yr && mon < 3) {
  		real_yrs--;
  		yrs = 73;
  	}
  #endif
  
  #ifdef CONFIG_ACPI
  	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
  	    acpi_gbl_FADT.century) {
  		century = (yrs + 1900) / 100;
  		yrs %= 100;
  	}
  #endif
  
  	/* These limits and adjustments are independent of
  	 * whether the chip is in binary mode or not.
  	 */
  	if (yrs > 169) {
  		spin_unlock_irqrestore(&rtc_lock, flags);
  		return -EINVAL;
  	}
  
  	if (yrs >= 100)
  		yrs -= 100;
  
  	if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY)
  	    || RTC_ALWAYS_BCD) {
  		sec = bin2bcd(sec);
  		min = bin2bcd(min);
  		hrs = bin2bcd(hrs);
  		day = bin2bcd(day);
  		mon = bin2bcd(mon);
  		yrs = bin2bcd(yrs);
  		century = bin2bcd(century);
  	}
  
  	save_control = CMOS_READ(RTC_CONTROL);
  	CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
  	save_freq_select = CMOS_READ(RTC_FREQ_SELECT);

  
  #ifdef CONFIG_X86
  	if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
  	     boot_cpu_data.x86 == 0x17) ||
  	     boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
  		CMOS_WRITE((save_freq_select & (~RTC_DIV_RESET2)),
  			RTC_FREQ_SELECT);
  		save_freq_select &= ~RTC_DIV_RESET2;
  	} else
  		CMOS_WRITE((save_freq_select | RTC_DIV_RESET2),
  			RTC_FREQ_SELECT);
  #else
  	CMOS_WRITE((save_freq_select | RTC_DIV_RESET2), RTC_FREQ_SELECT);
  #endif

  
  #ifdef CONFIG_MACH_DECSTATION
  	CMOS_WRITE(real_yrs, RTC_DEC_YEAR);
  #endif
  	CMOS_WRITE(yrs, RTC_YEAR);
  	CMOS_WRITE(mon, RTC_MONTH);
  	CMOS_WRITE(day, RTC_DAY_OF_MONTH);
  	CMOS_WRITE(hrs, RTC_HOURS);
  	CMOS_WRITE(min, RTC_MINUTES);
  	CMOS_WRITE(sec, RTC_SECONDS);
  #ifdef CONFIG_ACPI
  	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
  	    acpi_gbl_FADT.century)
  		CMOS_WRITE(century, acpi_gbl_FADT.century);
  #endif
  
  	CMOS_WRITE(save_control, RTC_CONTROL);
  	CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
  
  	spin_unlock_irqrestore(&rtc_lock, flags);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(mc146818_set_time);