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 < 100; 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 100 usec 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 udelay(100); 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 udelay(100); 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 /* AMD systems don't allow access to AltCentury with DV1 */ 180 static bool apply_amd_register_a_behavior(void) 181 { 182 #ifdef CONFIG_X86 183 if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || 184 boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) 185 return true; 186 #endif 187 return false; 188 } 189 190 /* Set the current date and time in the real time clock. */ 191 int mc146818_set_time(struct rtc_time *time) 192 { 193 unsigned long flags; 194 unsigned char mon, day, hrs, min, sec; 195 unsigned char save_control, save_freq_select; 196 unsigned int yrs; 197 #ifdef CONFIG_MACH_DECSTATION 198 unsigned int real_yrs, leap_yr; 199 #endif 200 unsigned char century = 0; 201 202 yrs = time->tm_year; 203 mon = time->tm_mon + 1; /* tm_mon starts at zero */ 204 day = time->tm_mday; 205 hrs = time->tm_hour; 206 min = time->tm_min; 207 sec = time->tm_sec; 208 209 if (yrs > 255) /* They are unsigned */ 210 return -EINVAL; 211 212 #ifdef CONFIG_MACH_DECSTATION 213 real_yrs = yrs; 214 leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) || 215 !((yrs + 1900) % 400)); 216 yrs = 72; 217 218 /* 219 * We want to keep the year set to 73 until March 220 * for non-leap years, so that Feb, 29th is handled 221 * correctly. 222 */ 223 if (!leap_yr && mon < 3) { 224 real_yrs--; 225 yrs = 73; 226 } 227 #endif 228 229 #ifdef CONFIG_ACPI 230 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 231 acpi_gbl_FADT.century) { 232 century = (yrs + 1900) / 100; 233 yrs %= 100; 234 } 235 #endif 236 237 /* These limits and adjustments are independent of 238 * whether the chip is in binary mode or not. 239 */ 240 if (yrs > 169) 241 return -EINVAL; 242 243 if (yrs >= 100) 244 yrs -= 100; 245 246 spin_lock_irqsave(&rtc_lock, flags); 247 save_control = CMOS_READ(RTC_CONTROL); 248 spin_unlock_irqrestore(&rtc_lock, flags); 249 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) { 250 sec = bin2bcd(sec); 251 min = bin2bcd(min); 252 hrs = bin2bcd(hrs); 253 day = bin2bcd(day); 254 mon = bin2bcd(mon); 255 yrs = bin2bcd(yrs); 256 century = bin2bcd(century); 257 } 258 259 spin_lock_irqsave(&rtc_lock, flags); 260 save_control = CMOS_READ(RTC_CONTROL); 261 CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL); 262 save_freq_select = CMOS_READ(RTC_FREQ_SELECT); 263 if (apply_amd_register_a_behavior()) 264 CMOS_WRITE((save_freq_select & ~RTC_AMD_BANK_SELECT), RTC_FREQ_SELECT); 265 else 266 CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT); 267 268 #ifdef CONFIG_MACH_DECSTATION 269 CMOS_WRITE(real_yrs, RTC_DEC_YEAR); 270 #endif 271 CMOS_WRITE(yrs, RTC_YEAR); 272 CMOS_WRITE(mon, RTC_MONTH); 273 CMOS_WRITE(day, RTC_DAY_OF_MONTH); 274 CMOS_WRITE(hrs, RTC_HOURS); 275 CMOS_WRITE(min, RTC_MINUTES); 276 CMOS_WRITE(sec, RTC_SECONDS); 277 #ifdef CONFIG_ACPI 278 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 279 acpi_gbl_FADT.century) 280 CMOS_WRITE(century, acpi_gbl_FADT.century); 281 #endif 282 283 CMOS_WRITE(save_control, RTC_CONTROL); 284 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT); 285 286 spin_unlock_irqrestore(&rtc_lock, flags); 287 288 return 0; 289 } 290 EXPORT_SYMBOL_GPL(mc146818_set_time); 291