1 // SPDX-License-Identifier: GPL-2.0-only 2 #include <linux/bcd.h> 3 #include <linux/delay.h> 4 #include <linux/export.h> 5 #include <linux/mc146818rtc.h> 6 7 #ifdef CONFIG_ACPI 8 #include <linux/acpi.h> 9 #endif 10 11 /* 12 * Returns true if a clock update is in progress 13 */ 14 static inline unsigned char mc146818_is_updating(void) 15 { 16 unsigned char uip; 17 unsigned long flags; 18 19 spin_lock_irqsave(&rtc_lock, flags); 20 uip = (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP); 21 spin_unlock_irqrestore(&rtc_lock, flags); 22 return uip; 23 } 24 25 unsigned int mc146818_get_time(struct rtc_time *time) 26 { 27 unsigned char ctrl; 28 unsigned long flags; 29 unsigned char century = 0; 30 31 #ifdef CONFIG_MACH_DECSTATION 32 unsigned int real_year; 33 #endif 34 35 /* 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. 43 */ 44 if (mc146818_is_updating()) 45 mdelay(20); 46 47 /* 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. 52 */ 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); 62 #endif 63 #ifdef CONFIG_ACPI 64 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 65 acpi_gbl_FADT.century) 66 century = CMOS_READ(acpi_gbl_FADT.century); 67 #endif 68 ctrl = CMOS_READ(RTC_CONTROL); 69 spin_unlock_irqrestore(&rtc_lock, flags); 70 71 if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD) 72 { 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); 80 } 81 82 #ifdef CONFIG_MACH_DECSTATION 83 time->tm_year += real_year - 72; 84 #endif 85 86 if (century > 20) 87 time->tm_year += (century - 19) * 100; 88 89 /* 90 * Account for differences between how the RTC uses the values 91 * and how they are defined in a struct rtc_time; 92 */ 93 if (time->tm_year <= 69) 94 time->tm_year += 100; 95 96 time->tm_mon--; 97 98 return RTC_24H; 99 } 100 EXPORT_SYMBOL_GPL(mc146818_get_time); 101 102 /* Set the current date and time in the real time clock. */ 103 int mc146818_set_time(struct rtc_time *time) 104 { 105 unsigned long flags; 106 unsigned char mon, day, hrs, min, sec; 107 unsigned char save_control, save_freq_select; 108 unsigned int yrs; 109 #ifdef CONFIG_MACH_DECSTATION 110 unsigned int real_yrs, leap_yr; 111 #endif 112 unsigned char century = 0; 113 114 yrs = time->tm_year; 115 mon = time->tm_mon + 1; /* tm_mon starts at zero */ 116 day = time->tm_mday; 117 hrs = time->tm_hour; 118 min = time->tm_min; 119 sec = time->tm_sec; 120 121 if (yrs > 255) /* They are unsigned */ 122 return -EINVAL; 123 124 spin_lock_irqsave(&rtc_lock, flags); 125 #ifdef CONFIG_MACH_DECSTATION 126 real_yrs = yrs; 127 leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) || 128 !((yrs + 1900) % 400)); 129 yrs = 72; 130 131 /* 132 * We want to keep the year set to 73 until March 133 * for non-leap years, so that Feb, 29th is handled 134 * correctly. 135 */ 136 if (!leap_yr && mon < 3) { 137 real_yrs--; 138 yrs = 73; 139 } 140 #endif 141 142 #ifdef CONFIG_ACPI 143 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 144 acpi_gbl_FADT.century) { 145 century = (yrs + 1900) / 100; 146 yrs %= 100; 147 } 148 #endif 149 150 /* These limits and adjustments are independent of 151 * whether the chip is in binary mode or not. 152 */ 153 if (yrs > 169) { 154 spin_unlock_irqrestore(&rtc_lock, flags); 155 return -EINVAL; 156 } 157 158 if (yrs >= 100) 159 yrs -= 100; 160 161 if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) 162 || RTC_ALWAYS_BCD) { 163 sec = bin2bcd(sec); 164 min = bin2bcd(min); 165 hrs = bin2bcd(hrs); 166 day = bin2bcd(day); 167 mon = bin2bcd(mon); 168 yrs = bin2bcd(yrs); 169 century = bin2bcd(century); 170 } 171 172 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); 176 177 #ifdef CONFIG_MACH_DECSTATION 178 CMOS_WRITE(real_yrs, RTC_DEC_YEAR); 179 #endif 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); 186 #ifdef CONFIG_ACPI 187 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 188 acpi_gbl_FADT.century) 189 CMOS_WRITE(century, acpi_gbl_FADT.century); 190 #endif 191 192 CMOS_WRITE(save_control, RTC_CONTROL); 193 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT); 194 195 spin_unlock_irqrestore(&rtc_lock, flags); 196 197 return 0; 198 } 199 EXPORT_SYMBOL_GPL(mc146818_set_time); 200