arch/x86/kernel/rtc.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * RTC related functions
   4  */
   5 #include <linux/platform_device.h>
   6 #include <linux/mc146818rtc.h>
   7 #include <linux/acpi.h>
   8 #include <linux/bcd.h>
   9 #include <linux/export.h>
  10 #include <linux/pnp.h>
  11 #include <linux/of.h>
  12
  13 #include <asm/vsyscall.h>
  14 #include <asm/x86_init.h>
  15 #include <asm/time.h>
  16 #include <asm/intel-mid.h>
  17 #include <asm/setup.h>
  18
  19 #ifdef CONFIG_X86_32
  20 /*
  21  * This is a special lock that is owned by the CPU and holds the index
  22  * register we are working with.  It is required for NMI access to the
  23  * CMOS/RTC registers.  See include/asm-i386/mc146818rtc.h for details.
  24  */
  25 volatile unsigned long cmos_lock;
  26 EXPORT_SYMBOL(cmos_lock);
  27 #endif /* CONFIG_X86_32 */
  28
  29 /* For two digit years assume time is always after that */
  30 #define CMOS_YEARS_OFFS 2000
  31
  32 DEFINE_SPINLOCK(rtc_lock);
  33 EXPORT_SYMBOL(rtc_lock);
  34
  35 /*
  36  * In order to set the CMOS clock precisely, set_rtc_mmss has to be
  37  * called 500 ms after the second nowtime has started, because when
  38  * nowtime is written into the registers of the CMOS clock, it will
  39  * jump to the next second precisely 500 ms later. Check the Motorola
  40  * MC146818A or Dallas DS12887 data sheet for details.
  41  */
  42 int mach_set_rtc_mmss(const struct timespec *now)
  43 {
  44         unsigned long nowtime = now->tv_sec;
  45         struct rtc_time tm;
  46         int retval = 0;
  47
  48         rtc_time_to_tm(nowtime, &tm);
  49         if (!rtc_valid_tm(&tm)) {
  50                 retval = mc146818_set_time(&tm);
  51                 if (retval)
  52                         printk(KERN_ERR "%s: RTC write failed with error %d\n",
  53                                __func__, retval);
  54         } else {
  55                 printk(KERN_ERR
  56                        "%s: Invalid RTC value: write of %lx to RTC failed\n",
  57                         __func__, nowtime);
  58                 retval = -EINVAL;
  59         }
  60         return retval;
  61 }
  62
  63 void mach_get_cmos_time(struct timespec *now)
  64 {
  65         unsigned int status, year, mon, day, hour, min, sec, century = 0;
  66         unsigned long flags;
  67
  68         /*
  69          * If pm_trace abused the RTC as storage, set the timespec to 0,
  70          * which tells the caller that this RTC value is unusable.
  71          */
  72         if (!pm_trace_rtc_valid()) {
  73                 now->tv_sec = now->tv_nsec = 0;
  74                 return;
  75         }
  76
  77         spin_lock_irqsave(&rtc_lock, flags);
  78
  79         /*
  80          * If UIP is clear, then we have >= 244 microseconds before
  81          * RTC registers will be updated.  Spec sheet says that this
  82          * is the reliable way to read RTC - registers. If UIP is set
  83          * then the register access might be invalid.
  84          */
  85         while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
  86                 cpu_relax();
  87
  88         sec = CMOS_READ(RTC_SECONDS);
  89         min = CMOS_READ(RTC_MINUTES);
  90         hour = CMOS_READ(RTC_HOURS);
  91         day = CMOS_READ(RTC_DAY_OF_MONTH);
  92         mon = CMOS_READ(RTC_MONTH);
  93         year = CMOS_READ(RTC_YEAR);
  94
  95 #ifdef CONFIG_ACPI
  96         if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
  97             acpi_gbl_FADT.century)
  98                 century = CMOS_READ(acpi_gbl_FADT.century);
  99 #endif
 100
 101         status = CMOS_READ(RTC_CONTROL);
 102         WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));
 103
 104         spin_unlock_irqrestore(&rtc_lock, flags);
 105
 106         if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) {
 107                 sec = bcd2bin(sec);
 108                 min = bcd2bin(min);
 109                 hour = bcd2bin(hour);
 110                 day = bcd2bin(day);
 111                 mon = bcd2bin(mon);
 112                 year = bcd2bin(year);
 113         }
 114
 115         if (century) {
 116                 century = bcd2bin(century);
 117                 year += century * 100;
 118         } else
 119                 year += CMOS_YEARS_OFFS;
 120
 121         now->tv_sec = mktime(year, mon, day, hour, min, sec);
 122         now->tv_nsec = 0;
 123 }
 124
 125 /* Routines for accessing the CMOS RAM/RTC. */
 126 unsigned char rtc_cmos_read(unsigned char addr)
 127 {
 128         unsigned char val;
 129
 130         lock_cmos_prefix(addr);
 131         outb(addr, RTC_PORT(0));
 132         val = inb(RTC_PORT(1));
 133         lock_cmos_suffix(addr);
 134
 135         return val;
 136 }
 137 EXPORT_SYMBOL(rtc_cmos_read);
 138
 139 void rtc_cmos_write(unsigned char val, unsigned char addr)
 140 {
 141         lock_cmos_prefix(addr);
 142         outb(addr, RTC_PORT(0));
 143         outb(val, RTC_PORT(1));
 144         lock_cmos_suffix(addr);
 145 }
 146 EXPORT_SYMBOL(rtc_cmos_write);
 147
 148 int update_persistent_clock(struct timespec now)
 149 {
 150         return x86_platform.set_wallclock(&now);
 151 }
 152
 153 /* not static: needed by APM */
 154 void read_persistent_clock(struct timespec *ts)
 155 {
 156         x86_platform.get_wallclock(ts);
 157 }
 158
 159
 160 static struct resource rtc_resources[] = {
 161         [0] = {
 162                 .start  = RTC_PORT(0),
 163                 .end    = RTC_PORT(1),
 164                 .flags  = IORESOURCE_IO,
 165         },
 166         [1] = {
 167                 .start  = RTC_IRQ,
 168                 .end    = RTC_IRQ,
 169                 .flags  = IORESOURCE_IRQ,
 170         }
 171 };
 172
 173 static struct platform_device rtc_device = {
 174         .name           = "rtc_cmos",
 175         .id             = -1,
 176         .resource       = rtc_resources,
 177         .num_resources  = ARRAY_SIZE(rtc_resources),
 178 };
 179
 180 static __init int add_rtc_cmos(void)
 181 {
 182 #ifdef CONFIG_PNP
 183         static const char * const ids[] __initconst =
 184             { "PNP0b00", "PNP0b01", "PNP0b02", };
 185         struct pnp_dev *dev;
 186         struct pnp_id *id;
 187         int i;
 188
 189         pnp_for_each_dev(dev) {
 190                 for (id = dev->id; id; id = id->next) {
 191                         for (i = 0; i < ARRAY_SIZE(ids); i++) {
 192                                 if (compare_pnp_id(id, ids[i]) != 0)
 193                                         return 0;
 194                         }
 195                 }
 196         }
 197 #endif
 198         if (!x86_platform.legacy.rtc)
 199                 return -ENODEV;
 200
 201         platform_device_register(&rtc_device);
 202         dev_info(&rtc_device.dev,
 203                  "registered platform RTC device (no PNP device found)\n");
 204
 205         return 0;
 206 }
 207 device_initcall(add_rtc_cmos);