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 unsigned int mc146818_get_time(struct rtc_time *time) 12 { 13 unsigned char ctrl; 14 unsigned long flags; 15 unsigned char century = 0; 16 bool retry; 17 18 #ifdef CONFIG_MACH_DECSTATION 19 unsigned int real_year; 20 #endif 21 22 again: 23 spin_lock_irqsave(&rtc_lock, flags); 24 /* 25 * Check whether there is an update in progress during which the 26 * readout is unspecified. The maximum update time is ~2ms. Poll 27 * every msec for completion. 28 * 29 * Store the second value before checking UIP so a long lasting NMI 30 * which happens to hit after the UIP check cannot make an update 31 * cycle invisible. 32 */ 33 time->tm_sec = CMOS_READ(RTC_SECONDS); 34 35 if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) { 36 spin_unlock_irqrestore(&rtc_lock, flags); 37 mdelay(1); 38 goto again; 39 } 40 41 /* Revalidate the above readout */ 42 if (time->tm_sec != CMOS_READ(RTC_SECONDS)) { 43 spin_unlock_irqrestore(&rtc_lock, flags); 44 goto again; 45 } 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 time->tm_min = CMOS_READ(RTC_MINUTES); 54 time->tm_hour = CMOS_READ(RTC_HOURS); 55 time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH); 56 time->tm_mon = CMOS_READ(RTC_MONTH); 57 time->tm_year = CMOS_READ(RTC_YEAR); 58 #ifdef CONFIG_MACH_DECSTATION 59 real_year = CMOS_READ(RTC_DEC_YEAR); 60 #endif 61 #ifdef CONFIG_ACPI 62 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 63 acpi_gbl_FADT.century) 64 century = CMOS_READ(acpi_gbl_FADT.century); 65 #endif 66 ctrl = CMOS_READ(RTC_CONTROL); 67 /* 68 * Check for the UIP bit again. If it is set now then 69 * the above values may contain garbage. 70 */ 71 retry = CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP; 72 /* 73 * A NMI might have interrupted the above sequence so check whether 74 * the seconds value has changed which indicates that the NMI took 75 * longer than the UIP bit was set. Unlikely, but possible and 76 * there is also virt... 77 */ 78 retry |= time->tm_sec != CMOS_READ(RTC_SECONDS); 79 80 spin_unlock_irqrestore(&rtc_lock, flags); 81 82 if (retry) 83 goto again; 84 85 if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD) 86 { 87 time->tm_sec = bcd2bin(time->tm_sec); 88 time->tm_min = bcd2bin(time->tm_min); 89 time->tm_hour = bcd2bin(time->tm_hour); 90 time->tm_mday = bcd2bin(time->tm_mday); 91 time->tm_mon = bcd2bin(time->tm_mon); 92 time->tm_year = bcd2bin(time->tm_year); 93 century = bcd2bin(century); 94 } 95 96 #ifdef CONFIG_MACH_DECSTATION 97 time->tm_year += real_year - 72; 98 #endif 99 100 if (century > 20) 101 time->tm_year += (century - 19) * 100; 102 103 /* 104 * Account for differences between how the RTC uses the values 105 * and how they are defined in a struct rtc_time; 106 */ 107 if (time->tm_year <= 69) 108 time->tm_year += 100; 109 110 time->tm_mon--; 111 112 return RTC_24H; 113 } 114 EXPORT_SYMBOL_GPL(mc146818_get_time); 115 116 /* Set the current date and time in the real time clock. */ 117 int mc146818_set_time(struct rtc_time *time) 118 { 119 unsigned long flags; 120 unsigned char mon, day, hrs, min, sec; 121 unsigned char save_control, save_freq_select; 122 unsigned int yrs; 123 #ifdef CONFIG_MACH_DECSTATION 124 unsigned int real_yrs, leap_yr; 125 #endif 126 unsigned char century = 0; 127 128 yrs = time->tm_year; 129 mon = time->tm_mon + 1; /* tm_mon starts at zero */ 130 day = time->tm_mday; 131 hrs = time->tm_hour; 132 min = time->tm_min; 133 sec = time->tm_sec; 134 135 if (yrs > 255) /* They are unsigned */ 136 return -EINVAL; 137 138 #ifdef CONFIG_MACH_DECSTATION 139 real_yrs = yrs; 140 leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) || 141 !((yrs + 1900) % 400)); 142 yrs = 72; 143 144 /* 145 * We want to keep the year set to 73 until March 146 * for non-leap years, so that Feb, 29th is handled 147 * correctly. 148 */ 149 if (!leap_yr && mon < 3) { 150 real_yrs--; 151 yrs = 73; 152 } 153 #endif 154 155 #ifdef CONFIG_ACPI 156 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 157 acpi_gbl_FADT.century) { 158 century = (yrs + 1900) / 100; 159 yrs %= 100; 160 } 161 #endif 162 163 /* These limits and adjustments are independent of 164 * whether the chip is in binary mode or not. 165 */ 166 if (yrs > 169) 167 return -EINVAL; 168 169 if (yrs >= 100) 170 yrs -= 100; 171 172 if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) 173 || RTC_ALWAYS_BCD) { 174 sec = bin2bcd(sec); 175 min = bin2bcd(min); 176 hrs = bin2bcd(hrs); 177 day = bin2bcd(day); 178 mon = bin2bcd(mon); 179 yrs = bin2bcd(yrs); 180 century = bin2bcd(century); 181 } 182 183 spin_lock_irqsave(&rtc_lock, flags); 184 save_control = CMOS_READ(RTC_CONTROL); 185 CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL); 186 save_freq_select = CMOS_READ(RTC_FREQ_SELECT); 187 CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT); 188 189 #ifdef CONFIG_MACH_DECSTATION 190 CMOS_WRITE(real_yrs, RTC_DEC_YEAR); 191 #endif 192 CMOS_WRITE(yrs, RTC_YEAR); 193 CMOS_WRITE(mon, RTC_MONTH); 194 CMOS_WRITE(day, RTC_DAY_OF_MONTH); 195 CMOS_WRITE(hrs, RTC_HOURS); 196 CMOS_WRITE(min, RTC_MINUTES); 197 CMOS_WRITE(sec, RTC_SECONDS); 198 #ifdef CONFIG_ACPI 199 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 200 acpi_gbl_FADT.century) 201 CMOS_WRITE(century, acpi_gbl_FADT.century); 202 #endif 203 204 CMOS_WRITE(save_control, RTC_CONTROL); 205 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT); 206 207 spin_unlock_irqrestore(&rtc_lock, flags); 208 209 return 0; 210 } 211 EXPORT_SYMBOL_GPL(mc146818_set_time); 212