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 * Execute a function while the UIP (Update-in-progress) bit of the RTC is 13 * unset. 14 * 15 * Warning: callback may be executed more then once. 16 */ 17 bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param), 18 void *param) 19 { 20 int i; 21 unsigned long flags; 22 unsigned char seconds; 23 24 for (i = 0; i < 10; i++) { 25 spin_lock_irqsave(&rtc_lock, flags); 26 27 /* 28 * Check whether there is an update in progress during which the 29 * readout is unspecified. The maximum update time is ~2ms. Poll 30 * every msec for completion. 31 * 32 * Store the second value before checking UIP so a long lasting 33 * NMI which happens to hit after the UIP check cannot make 34 * an update cycle invisible. 35 */ 36 seconds = CMOS_READ(RTC_SECONDS); 37 38 if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) { 39 spin_unlock_irqrestore(&rtc_lock, flags); 40 mdelay(1); 41 continue; 42 } 43 44 /* Revalidate the above readout */ 45 if (seconds != CMOS_READ(RTC_SECONDS)) { 46 spin_unlock_irqrestore(&rtc_lock, flags); 47 continue; 48 } 49 50 if (callback) 51 callback(seconds, param); 52 53 /* 54 * Check for the UIP bit again. If it is set now then 55 * the above values may contain garbage. 56 */ 57 if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) { 58 spin_unlock_irqrestore(&rtc_lock, flags); 59 mdelay(1); 60 continue; 61 } 62 63 /* 64 * A NMI might have interrupted the above sequence so check 65 * whether the seconds value has changed which indicates that 66 * the NMI took longer than the UIP bit was set. Unlikely, but 67 * possible and there is also virt... 68 */ 69 if (seconds != CMOS_READ(RTC_SECONDS)) { 70 spin_unlock_irqrestore(&rtc_lock, flags); 71 continue; 72 } 73 spin_unlock_irqrestore(&rtc_lock, flags); 74 75 return true; 76 } 77 return false; 78 } 79 EXPORT_SYMBOL_GPL(mc146818_avoid_UIP); 80 81 /* 82 * If the UIP (Update-in-progress) bit of the RTC is set for more then 83 * 10ms, the RTC is apparently broken or not present. 84 */ 85 bool mc146818_does_rtc_work(void) 86 { 87 return mc146818_avoid_UIP(NULL, NULL); 88 } 89 EXPORT_SYMBOL_GPL(mc146818_does_rtc_work); 90 91 struct mc146818_get_time_callback_param { 92 struct rtc_time *time; 93 unsigned char ctrl; 94 #ifdef CONFIG_ACPI 95 unsigned char century; 96 #endif 97 #ifdef CONFIG_MACH_DECSTATION 98 unsigned int real_year; 99 #endif 100 }; 101 102 static void mc146818_get_time_callback(unsigned char seconds, void *param_in) 103 { 104 struct mc146818_get_time_callback_param *p = param_in; 105 106 /* 107 * Only the values that we read from the RTC are set. We leave 108 * tm_wday, tm_yday and tm_isdst untouched. Even though the 109 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated 110 * by the RTC when initially set to a non-zero value. 111 */ 112 p->time->tm_sec = seconds; 113 p->time->tm_min = CMOS_READ(RTC_MINUTES); 114 p->time->tm_hour = CMOS_READ(RTC_HOURS); 115 p->time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH); 116 p->time->tm_mon = CMOS_READ(RTC_MONTH); 117 p->time->tm_year = CMOS_READ(RTC_YEAR); 118 #ifdef CONFIG_MACH_DECSTATION 119 p->real_year = CMOS_READ(RTC_DEC_YEAR); 120 #endif 121 #ifdef CONFIG_ACPI 122 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 123 acpi_gbl_FADT.century) { 124 p->century = CMOS_READ(acpi_gbl_FADT.century); 125 } else { 126 p->century = 0; 127 } 128 #endif 129 130 p->ctrl = CMOS_READ(RTC_CONTROL); 131 } 132 133 int mc146818_get_time(struct rtc_time *time) 134 { 135 struct mc146818_get_time_callback_param p = { 136 .time = time 137 }; 138 139 if (!mc146818_avoid_UIP(mc146818_get_time_callback, &p)) { 140 memset(time, 0, sizeof(*time)); 141 return -EIO; 142 } 143 144 if (!(p.ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD) 145 { 146 time->tm_sec = bcd2bin(time->tm_sec); 147 time->tm_min = bcd2bin(time->tm_min); 148 time->tm_hour = bcd2bin(time->tm_hour); 149 time->tm_mday = bcd2bin(time->tm_mday); 150 time->tm_mon = bcd2bin(time->tm_mon); 151 time->tm_year = bcd2bin(time->tm_year); 152 #ifdef CONFIG_ACPI 153 p.century = bcd2bin(p.century); 154 #endif 155 } 156 157 #ifdef CONFIG_MACH_DECSTATION 158 time->tm_year += p.real_year - 72; 159 #endif 160 161 #ifdef CONFIG_ACPI 162 if (p.century > 19) 163 time->tm_year += (p.century - 19) * 100; 164 #endif 165 166 /* 167 * Account for differences between how the RTC uses the values 168 * and how they are defined in a struct rtc_time; 169 */ 170 if (time->tm_year <= 69) 171 time->tm_year += 100; 172 173 time->tm_mon--; 174 175 return 0; 176 } 177 EXPORT_SYMBOL_GPL(mc146818_get_time); 178 179 /* Set the current date and time in the real time clock. */ 180 int mc146818_set_time(struct rtc_time *time) 181 { 182 unsigned long flags; 183 unsigned char mon, day, hrs, min, sec; 184 unsigned char save_control, save_freq_select; 185 unsigned int yrs; 186 #ifdef CONFIG_MACH_DECSTATION 187 unsigned int real_yrs, leap_yr; 188 #endif 189 unsigned char century = 0; 190 191 yrs = time->tm_year; 192 mon = time->tm_mon + 1; /* tm_mon starts at zero */ 193 day = time->tm_mday; 194 hrs = time->tm_hour; 195 min = time->tm_min; 196 sec = time->tm_sec; 197 198 if (yrs > 255) /* They are unsigned */ 199 return -EINVAL; 200 201 #ifdef CONFIG_MACH_DECSTATION 202 real_yrs = yrs; 203 leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) || 204 !((yrs + 1900) % 400)); 205 yrs = 72; 206 207 /* 208 * We want to keep the year set to 73 until March 209 * for non-leap years, so that Feb, 29th is handled 210 * correctly. 211 */ 212 if (!leap_yr && mon < 3) { 213 real_yrs--; 214 yrs = 73; 215 } 216 #endif 217 218 #ifdef CONFIG_ACPI 219 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 220 acpi_gbl_FADT.century) { 221 century = (yrs + 1900) / 100; 222 yrs %= 100; 223 } 224 #endif 225 226 /* These limits and adjustments are independent of 227 * whether the chip is in binary mode or not. 228 */ 229 if (yrs > 169) 230 return -EINVAL; 231 232 if (yrs >= 100) 233 yrs -= 100; 234 235 if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) 236 || RTC_ALWAYS_BCD) { 237 sec = bin2bcd(sec); 238 min = bin2bcd(min); 239 hrs = bin2bcd(hrs); 240 day = bin2bcd(day); 241 mon = bin2bcd(mon); 242 yrs = bin2bcd(yrs); 243 century = bin2bcd(century); 244 } 245 246 spin_lock_irqsave(&rtc_lock, flags); 247 save_control = CMOS_READ(RTC_CONTROL); 248 CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL); 249 save_freq_select = CMOS_READ(RTC_FREQ_SELECT); 250 CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT); 251 252 #ifdef CONFIG_MACH_DECSTATION 253 CMOS_WRITE(real_yrs, RTC_DEC_YEAR); 254 #endif 255 CMOS_WRITE(yrs, RTC_YEAR); 256 CMOS_WRITE(mon, RTC_MONTH); 257 CMOS_WRITE(day, RTC_DAY_OF_MONTH); 258 CMOS_WRITE(hrs, RTC_HOURS); 259 CMOS_WRITE(min, RTC_MINUTES); 260 CMOS_WRITE(sec, RTC_SECONDS); 261 #ifdef CONFIG_ACPI 262 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 263 acpi_gbl_FADT.century) 264 CMOS_WRITE(century, acpi_gbl_FADT.century); 265 #endif 266 267 CMOS_WRITE(save_control, RTC_CONTROL); 268 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT); 269 270 spin_unlock_irqrestore(&rtc_lock, flags); 271 272 return 0; 273 } 274 EXPORT_SYMBOL_GPL(mc146818_set_time); 275