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 /* Ensure that the RTC is accessible. Bit 6 must be 0! */ 25 if (WARN_ON_ONCE((CMOS_READ(RTC_VALID) & 0x40) != 0)) { 26 spin_unlock_irqrestore(&rtc_lock, flags); 27 memset(time, 0xff, sizeof(*time)); 28 return 0; 29 } 30 31 /* 32 * Check whether there is an update in progress during which the 33 * readout is unspecified. The maximum update time is ~2ms. Poll 34 * every msec for completion. 35 * 36 * Store the second value before checking UIP so a long lasting NMI 37 * which happens to hit after the UIP check cannot make an update 38 * cycle invisible. 39 */ 40 time->tm_sec = CMOS_READ(RTC_SECONDS); 41 42 if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) { 43 spin_unlock_irqrestore(&rtc_lock, flags); 44 mdelay(1); 45 goto again; 46 } 47 48 /* Revalidate the above readout */ 49 if (time->tm_sec != CMOS_READ(RTC_SECONDS)) { 50 spin_unlock_irqrestore(&rtc_lock, flags); 51 goto again; 52 } 53 54 /* 55 * Only the values that we read from the RTC are set. We leave 56 * tm_wday, tm_yday and tm_isdst untouched. Even though the 57 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated 58 * by the RTC when initially set to a non-zero value. 59 */ 60 time->tm_min = CMOS_READ(RTC_MINUTES); 61 time->tm_hour = CMOS_READ(RTC_HOURS); 62 time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH); 63 time->tm_mon = CMOS_READ(RTC_MONTH); 64 time->tm_year = CMOS_READ(RTC_YEAR); 65 #ifdef CONFIG_MACH_DECSTATION 66 real_year = CMOS_READ(RTC_DEC_YEAR); 67 #endif 68 #ifdef CONFIG_ACPI 69 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 70 acpi_gbl_FADT.century) 71 century = CMOS_READ(acpi_gbl_FADT.century); 72 #endif 73 ctrl = CMOS_READ(RTC_CONTROL); 74 /* 75 * Check for the UIP bit again. If it is set now then 76 * the above values may contain garbage. 77 */ 78 retry = CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP; 79 /* 80 * A NMI might have interrupted the above sequence so check whether 81 * the seconds value has changed which indicates that the NMI took 82 * longer than the UIP bit was set. Unlikely, but possible and 83 * there is also virt... 84 */ 85 retry |= time->tm_sec != CMOS_READ(RTC_SECONDS); 86 87 spin_unlock_irqrestore(&rtc_lock, flags); 88 89 if (retry) 90 goto again; 91 92 if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD) 93 { 94 time->tm_sec = bcd2bin(time->tm_sec); 95 time->tm_min = bcd2bin(time->tm_min); 96 time->tm_hour = bcd2bin(time->tm_hour); 97 time->tm_mday = bcd2bin(time->tm_mday); 98 time->tm_mon = bcd2bin(time->tm_mon); 99 time->tm_year = bcd2bin(time->tm_year); 100 century = bcd2bin(century); 101 } 102 103 #ifdef CONFIG_MACH_DECSTATION 104 time->tm_year += real_year - 72; 105 #endif 106 107 if (century > 20) 108 time->tm_year += (century - 19) * 100; 109 110 /* 111 * Account for differences between how the RTC uses the values 112 * and how they are defined in a struct rtc_time; 113 */ 114 if (time->tm_year <= 69) 115 time->tm_year += 100; 116 117 time->tm_mon--; 118 119 return RTC_24H; 120 } 121 EXPORT_SYMBOL_GPL(mc146818_get_time); 122 123 /* Set the current date and time in the real time clock. */ 124 int mc146818_set_time(struct rtc_time *time) 125 { 126 unsigned long flags; 127 unsigned char mon, day, hrs, min, sec; 128 unsigned char save_control, save_freq_select; 129 unsigned int yrs; 130 #ifdef CONFIG_MACH_DECSTATION 131 unsigned int real_yrs, leap_yr; 132 #endif 133 unsigned char century = 0; 134 135 yrs = time->tm_year; 136 mon = time->tm_mon + 1; /* tm_mon starts at zero */ 137 day = time->tm_mday; 138 hrs = time->tm_hour; 139 min = time->tm_min; 140 sec = time->tm_sec; 141 142 if (yrs > 255) /* They are unsigned */ 143 return -EINVAL; 144 145 #ifdef CONFIG_MACH_DECSTATION 146 real_yrs = yrs; 147 leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) || 148 !((yrs + 1900) % 400)); 149 yrs = 72; 150 151 /* 152 * We want to keep the year set to 73 until March 153 * for non-leap years, so that Feb, 29th is handled 154 * correctly. 155 */ 156 if (!leap_yr && mon < 3) { 157 real_yrs--; 158 yrs = 73; 159 } 160 #endif 161 162 #ifdef CONFIG_ACPI 163 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 164 acpi_gbl_FADT.century) { 165 century = (yrs + 1900) / 100; 166 yrs %= 100; 167 } 168 #endif 169 170 /* These limits and adjustments are independent of 171 * whether the chip is in binary mode or not. 172 */ 173 if (yrs > 169) 174 return -EINVAL; 175 176 if (yrs >= 100) 177 yrs -= 100; 178 179 if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) 180 || RTC_ALWAYS_BCD) { 181 sec = bin2bcd(sec); 182 min = bin2bcd(min); 183 hrs = bin2bcd(hrs); 184 day = bin2bcd(day); 185 mon = bin2bcd(mon); 186 yrs = bin2bcd(yrs); 187 century = bin2bcd(century); 188 } 189 190 spin_lock_irqsave(&rtc_lock, flags); 191 save_control = CMOS_READ(RTC_CONTROL); 192 CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL); 193 save_freq_select = CMOS_READ(RTC_FREQ_SELECT); 194 CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT); 195 196 #ifdef CONFIG_MACH_DECSTATION 197 CMOS_WRITE(real_yrs, RTC_DEC_YEAR); 198 #endif 199 CMOS_WRITE(yrs, RTC_YEAR); 200 CMOS_WRITE(mon, RTC_MONTH); 201 CMOS_WRITE(day, RTC_DAY_OF_MONTH); 202 CMOS_WRITE(hrs, RTC_HOURS); 203 CMOS_WRITE(min, RTC_MINUTES); 204 CMOS_WRITE(sec, RTC_SECONDS); 205 #ifdef CONFIG_ACPI 206 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 207 acpi_gbl_FADT.century) 208 CMOS_WRITE(century, acpi_gbl_FADT.century); 209 #endif 210 211 CMOS_WRITE(save_control, RTC_CONTROL); 212 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT); 213 214 spin_unlock_irqrestore(&rtc_lock, flags); 215 216 return 0; 217 } 218 EXPORT_SYMBOL_GPL(mc146818_set_time); 219