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 #define UIP_RECHECK_DELAY 100 /* usec */ 12 #define UIP_RECHECK_DELAY_MS (USEC_PER_MSEC / UIP_RECHECK_DELAY) 13 #define UIP_RECHECK_LOOPS_MS(x) (x / UIP_RECHECK_DELAY_MS) 14 15 /* 16 * Execute a function while the UIP (Update-in-progress) bit of the RTC is 17 * unset. The timeout is configurable by the caller in ms. 18 * 19 * Warning: callback may be executed more then once. 20 */ mc146818_avoid_UIP(void (* callback)(unsigned char seconds,void * param),int timeout,void * param)21 bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param), 22 int timeout, 23 void *param) 24 { 25 int i; 26 unsigned long flags; 27 unsigned char seconds; 28 29 for (i = 0; UIP_RECHECK_LOOPS_MS(i) < timeout; i++) { 30 spin_lock_irqsave(&rtc_lock, flags); 31 32 /* 33 * Check whether there is an update in progress during which the 34 * readout is unspecified. The maximum update time is ~2ms. Poll 35 * for completion. 36 * 37 * Store the second value before checking UIP so a long lasting 38 * NMI which happens to hit after the UIP check cannot make 39 * an update cycle invisible. 40 */ 41 seconds = CMOS_READ(RTC_SECONDS); 42 43 if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) { 44 spin_unlock_irqrestore(&rtc_lock, flags); 45 udelay(UIP_RECHECK_DELAY); 46 continue; 47 } 48 49 /* Revalidate the above readout */ 50 if (seconds != CMOS_READ(RTC_SECONDS)) { 51 spin_unlock_irqrestore(&rtc_lock, flags); 52 continue; 53 } 54 55 if (callback) 56 callback(seconds, param); 57 58 /* 59 * Check for the UIP bit again. If it is set now then 60 * the above values may contain garbage. 61 */ 62 if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) { 63 spin_unlock_irqrestore(&rtc_lock, flags); 64 udelay(UIP_RECHECK_DELAY); 65 continue; 66 } 67 68 /* 69 * A NMI might have interrupted the above sequence so check 70 * whether the seconds value has changed which indicates that 71 * the NMI took longer than the UIP bit was set. Unlikely, but 72 * possible and there is also virt... 73 */ 74 if (seconds != CMOS_READ(RTC_SECONDS)) { 75 spin_unlock_irqrestore(&rtc_lock, flags); 76 continue; 77 } 78 spin_unlock_irqrestore(&rtc_lock, flags); 79 80 if (UIP_RECHECK_LOOPS_MS(i) >= 100) 81 pr_warn("Reading current time from RTC took around %li ms\n", 82 UIP_RECHECK_LOOPS_MS(i)); 83 84 return true; 85 } 86 return false; 87 } 88 EXPORT_SYMBOL_GPL(mc146818_avoid_UIP); 89 90 /* 91 * If the UIP (Update-in-progress) bit of the RTC is set for more then 92 * 10ms, the RTC is apparently broken or not present. 93 */ mc146818_does_rtc_work(void)94 bool mc146818_does_rtc_work(void) 95 { 96 return mc146818_avoid_UIP(NULL, 1000, NULL); 97 } 98 EXPORT_SYMBOL_GPL(mc146818_does_rtc_work); 99 100 struct mc146818_get_time_callback_param { 101 struct rtc_time *time; 102 unsigned char ctrl; 103 #ifdef CONFIG_ACPI 104 unsigned char century; 105 #endif 106 #ifdef CONFIG_MACH_DECSTATION 107 unsigned int real_year; 108 #endif 109 }; 110 mc146818_get_time_callback(unsigned char seconds,void * param_in)111 static void mc146818_get_time_callback(unsigned char seconds, void *param_in) 112 { 113 struct mc146818_get_time_callback_param *p = param_in; 114 115 /* 116 * Only the values that we read from the RTC are set. We leave 117 * tm_wday, tm_yday and tm_isdst untouched. Even though the 118 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated 119 * by the RTC when initially set to a non-zero value. 120 */ 121 p->time->tm_sec = seconds; 122 p->time->tm_min = CMOS_READ(RTC_MINUTES); 123 p->time->tm_hour = CMOS_READ(RTC_HOURS); 124 p->time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH); 125 p->time->tm_mon = CMOS_READ(RTC_MONTH); 126 p->time->tm_year = CMOS_READ(RTC_YEAR); 127 #ifdef CONFIG_MACH_DECSTATION 128 p->real_year = CMOS_READ(RTC_DEC_YEAR); 129 #endif 130 #ifdef CONFIG_ACPI 131 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 132 acpi_gbl_FADT.century) { 133 p->century = CMOS_READ(acpi_gbl_FADT.century); 134 } else { 135 p->century = 0; 136 } 137 #endif 138 139 p->ctrl = CMOS_READ(RTC_CONTROL); 140 } 141 142 /** 143 * mc146818_get_time - Get the current time from the RTC 144 * @time: pointer to struct rtc_time to store the current time 145 * @timeout: timeout value in ms 146 * 147 * This function reads the current time from the RTC and stores it in the 148 * provided struct rtc_time. The timeout parameter specifies the maximum 149 * time to wait for the RTC to become ready. 150 * 151 * Return: 0 on success, -ETIMEDOUT if the RTC did not become ready within 152 * the specified timeout, or another error code if an error occurred. 153 */ mc146818_get_time(struct rtc_time * time,int timeout)154 int mc146818_get_time(struct rtc_time *time, int timeout) 155 { 156 struct mc146818_get_time_callback_param p = { 157 .time = time 158 }; 159 160 if (!mc146818_avoid_UIP(mc146818_get_time_callback, timeout, &p)) { 161 memset(time, 0, sizeof(*time)); 162 return -ETIMEDOUT; 163 } 164 165 if (!(p.ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD) 166 { 167 time->tm_sec = bcd2bin(time->tm_sec); 168 time->tm_min = bcd2bin(time->tm_min); 169 time->tm_hour = bcd2bin(time->tm_hour); 170 time->tm_mday = bcd2bin(time->tm_mday); 171 time->tm_mon = bcd2bin(time->tm_mon); 172 time->tm_year = bcd2bin(time->tm_year); 173 #ifdef CONFIG_ACPI 174 p.century = bcd2bin(p.century); 175 #endif 176 } 177 178 #ifdef CONFIG_MACH_DECSTATION 179 time->tm_year += p.real_year - 72; 180 #endif 181 182 #ifdef CONFIG_ACPI 183 if (p.century > 19) 184 time->tm_year += (p.century - 19) * 100; 185 #endif 186 187 /* 188 * Account for differences between how the RTC uses the values 189 * and how they are defined in a struct rtc_time; 190 */ 191 if (time->tm_year <= 69) 192 time->tm_year += 100; 193 194 time->tm_mon--; 195 196 return 0; 197 } 198 EXPORT_SYMBOL_GPL(mc146818_get_time); 199 200 /* AMD systems don't allow access to AltCentury with DV1 */ apply_amd_register_a_behavior(void)201 static bool apply_amd_register_a_behavior(void) 202 { 203 #ifdef CONFIG_X86 204 if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || 205 boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) 206 return true; 207 #endif 208 return false; 209 } 210 211 /* Set the current date and time in the real time clock. */ mc146818_set_time(struct rtc_time * time)212 int mc146818_set_time(struct rtc_time *time) 213 { 214 unsigned long flags; 215 unsigned char mon, day, hrs, min, sec; 216 unsigned char save_control, save_freq_select; 217 unsigned int yrs; 218 #ifdef CONFIG_MACH_DECSTATION 219 unsigned int real_yrs, leap_yr; 220 #endif 221 unsigned char century = 0; 222 223 yrs = time->tm_year; 224 mon = time->tm_mon + 1; /* tm_mon starts at zero */ 225 day = time->tm_mday; 226 hrs = time->tm_hour; 227 min = time->tm_min; 228 sec = time->tm_sec; 229 230 if (yrs > 255) /* They are unsigned */ 231 return -EINVAL; 232 233 #ifdef CONFIG_MACH_DECSTATION 234 real_yrs = yrs; 235 leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) || 236 !((yrs + 1900) % 400)); 237 yrs = 72; 238 239 /* 240 * We want to keep the year set to 73 until March 241 * for non-leap years, so that Feb, 29th is handled 242 * correctly. 243 */ 244 if (!leap_yr && mon < 3) { 245 real_yrs--; 246 yrs = 73; 247 } 248 #endif 249 250 #ifdef CONFIG_ACPI 251 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 252 acpi_gbl_FADT.century) { 253 century = (yrs + 1900) / 100; 254 yrs %= 100; 255 } 256 #endif 257 258 /* These limits and adjustments are independent of 259 * whether the chip is in binary mode or not. 260 */ 261 if (yrs > 169) 262 return -EINVAL; 263 264 if (yrs >= 100) 265 yrs -= 100; 266 267 spin_lock_irqsave(&rtc_lock, flags); 268 save_control = CMOS_READ(RTC_CONTROL); 269 spin_unlock_irqrestore(&rtc_lock, flags); 270 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) { 271 sec = bin2bcd(sec); 272 min = bin2bcd(min); 273 hrs = bin2bcd(hrs); 274 day = bin2bcd(day); 275 mon = bin2bcd(mon); 276 yrs = bin2bcd(yrs); 277 century = bin2bcd(century); 278 } 279 280 spin_lock_irqsave(&rtc_lock, flags); 281 save_control = CMOS_READ(RTC_CONTROL); 282 CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL); 283 save_freq_select = CMOS_READ(RTC_FREQ_SELECT); 284 if (apply_amd_register_a_behavior()) 285 CMOS_WRITE((save_freq_select & ~RTC_AMD_BANK_SELECT), RTC_FREQ_SELECT); 286 else 287 CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT); 288 289 #ifdef CONFIG_MACH_DECSTATION 290 CMOS_WRITE(real_yrs, RTC_DEC_YEAR); 291 #endif 292 CMOS_WRITE(yrs, RTC_YEAR); 293 CMOS_WRITE(mon, RTC_MONTH); 294 CMOS_WRITE(day, RTC_DAY_OF_MONTH); 295 CMOS_WRITE(hrs, RTC_HOURS); 296 CMOS_WRITE(min, RTC_MINUTES); 297 CMOS_WRITE(sec, RTC_SECONDS); 298 #ifdef CONFIG_ACPI 299 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID && 300 acpi_gbl_FADT.century) 301 CMOS_WRITE(century, acpi_gbl_FADT.century); 302 #endif 303 304 CMOS_WRITE(save_control, RTC_CONTROL); 305 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT); 306 307 spin_unlock_irqrestore(&rtc_lock, flags); 308 309 return 0; 310 } 311 EXPORT_SYMBOL_GPL(mc146818_set_time); 312