1 // SPDX-License-Identifier: GPL-2.0-only
3 #include <linux/delay.h>
4 #include <linux/export.h>
5 #include <linux/mc146818rtc.h>
8 #include <linux/acpi.h>
12 * Returns true if a clock update is in progress
14 static inline unsigned char mc146818_is_updating(void)
19 spin_lock_irqsave(&rtc_lock, flags);
20 uip = (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
21 spin_unlock_irqrestore(&rtc_lock, flags);
25 unsigned int mc146818_get_time(struct rtc_time *time)
29 unsigned char century = 0;
31 #ifdef CONFIG_MACH_DECSTATION
32 unsigned int real_year;
36 * read RTC once any update in progress is done. The update
37 * can take just over 2ms. We wait 20ms. There is no need to
38 * to poll-wait (up to 1s - eeccch) for the falling edge of RTC_UIP.
39 * If you need to know *exactly* when a second has started, enable
40 * periodic update complete interrupts, (via ioctl) and then
41 * immediately read /dev/rtc which will block until you get the IRQ.
42 * Once the read clears, read the RTC time (again via ioctl). Easy.
44 if (mc146818_is_updating())
48 * Only the values that we read from the RTC are set. We leave
49 * tm_wday, tm_yday and tm_isdst untouched. Even though the
50 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
51 * by the RTC when initially set to a non-zero value.
53 spin_lock_irqsave(&rtc_lock, flags);
54 time->tm_sec = CMOS_READ(RTC_SECONDS);
55 time->tm_min = CMOS_READ(RTC_MINUTES);
56 time->tm_hour = CMOS_READ(RTC_HOURS);
57 time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
58 time->tm_mon = CMOS_READ(RTC_MONTH);
59 time->tm_year = CMOS_READ(RTC_YEAR);
60 #ifdef CONFIG_MACH_DECSTATION
61 real_year = CMOS_READ(RTC_DEC_YEAR);
64 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
65 acpi_gbl_FADT.century)
66 century = CMOS_READ(acpi_gbl_FADT.century);
68 ctrl = CMOS_READ(RTC_CONTROL);
69 spin_unlock_irqrestore(&rtc_lock, flags);
71 if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
73 time->tm_sec = bcd2bin(time->tm_sec);
74 time->tm_min = bcd2bin(time->tm_min);
75 time->tm_hour = bcd2bin(time->tm_hour);
76 time->tm_mday = bcd2bin(time->tm_mday);
77 time->tm_mon = bcd2bin(time->tm_mon);
78 time->tm_year = bcd2bin(time->tm_year);
79 century = bcd2bin(century);
82 #ifdef CONFIG_MACH_DECSTATION
83 time->tm_year += real_year - 72;
87 time->tm_year += (century - 19) * 100;
90 * Account for differences between how the RTC uses the values
91 * and how they are defined in a struct rtc_time;
93 if (time->tm_year <= 69)
100 EXPORT_SYMBOL_GPL(mc146818_get_time);
102 /* Set the current date and time in the real time clock. */
103 int mc146818_set_time(struct rtc_time *time)
106 unsigned char mon, day, hrs, min, sec;
107 unsigned char save_control, save_freq_select;
109 #ifdef CONFIG_MACH_DECSTATION
110 unsigned int real_yrs, leap_yr;
112 unsigned char century = 0;
115 mon = time->tm_mon + 1; /* tm_mon starts at zero */
121 if (yrs > 255) /* They are unsigned */
124 spin_lock_irqsave(&rtc_lock, flags);
125 #ifdef CONFIG_MACH_DECSTATION
127 leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) ||
128 !((yrs + 1900) % 400));
132 * We want to keep the year set to 73 until March
133 * for non-leap years, so that Feb, 29th is handled
136 if (!leap_yr && mon < 3) {
143 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
144 acpi_gbl_FADT.century) {
145 century = (yrs + 1900) / 100;
150 /* These limits and adjustments are independent of
151 * whether the chip is in binary mode or not.
154 spin_unlock_irqrestore(&rtc_lock, flags);
161 if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY)
169 century = bin2bcd(century);
172 save_control = CMOS_READ(RTC_CONTROL);
173 CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
174 save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
175 CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
177 #ifdef CONFIG_MACH_DECSTATION
178 CMOS_WRITE(real_yrs, RTC_DEC_YEAR);
180 CMOS_WRITE(yrs, RTC_YEAR);
181 CMOS_WRITE(mon, RTC_MONTH);
182 CMOS_WRITE(day, RTC_DAY_OF_MONTH);
183 CMOS_WRITE(hrs, RTC_HOURS);
184 CMOS_WRITE(min, RTC_MINUTES);
185 CMOS_WRITE(sec, RTC_SECONDS);
187 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
188 acpi_gbl_FADT.century)
189 CMOS_WRITE(century, acpi_gbl_FADT.century);
192 CMOS_WRITE(save_control, RTC_CONTROL);
193 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
195 spin_unlock_irqrestore(&rtc_lock, flags);
199 EXPORT_SYMBOL_GPL(mc146818_set_time);