2 * RTC related functions
4 #include <linux/platform_device.h>
5 #include <linux/mc146818rtc.h>
6 #include <linux/acpi.h>
8 #include <linux/export.h>
12 #include <asm/vsyscall.h>
13 #include <asm/x86_init.h>
18 * This is a special lock that is owned by the CPU and holds the index
19 * register we are working with. It is required for NMI access to the
20 * CMOS/RTC registers. See include/asm-i386/mc146818rtc.h for details.
22 volatile unsigned long cmos_lock;
23 EXPORT_SYMBOL(cmos_lock);
24 #endif /* CONFIG_X86_32 */
26 /* For two digit years assume time is always after that */
27 #define CMOS_YEARS_OFFS 2000
29 DEFINE_SPINLOCK(rtc_lock);
30 EXPORT_SYMBOL(rtc_lock);
33 * In order to set the CMOS clock precisely, set_rtc_mmss has to be
34 * called 500 ms after the second nowtime has started, because when
35 * nowtime is written into the registers of the CMOS clock, it will
36 * jump to the next second precisely 500 ms later. Check the Motorola
37 * MC146818A or Dallas DS12887 data sheet for details.
39 * BUG: This routine does not handle hour overflow properly; it just
40 * sets the minutes. Usually you'll only notice that after reboot!
42 int mach_set_rtc_mmss(unsigned long nowtime)
44 int real_seconds, real_minutes, cmos_minutes;
45 unsigned char save_control, save_freq_select;
49 spin_lock_irqsave(&rtc_lock, flags);
51 /* tell the clock it's being set */
52 save_control = CMOS_READ(RTC_CONTROL);
53 CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
55 /* stop and reset prescaler */
56 save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
57 CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
59 cmos_minutes = CMOS_READ(RTC_MINUTES);
60 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
61 cmos_minutes = bcd2bin(cmos_minutes);
64 * since we're only adjusting minutes and seconds,
65 * don't interfere with hour overflow. This avoids
66 * messing with unknown time zones but requires your
67 * RTC not to be off by more than 15 minutes
69 real_seconds = nowtime % 60;
70 real_minutes = nowtime / 60;
71 /* correct for half hour time zone */
72 if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
76 if (abs(real_minutes - cmos_minutes) < 30) {
77 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
78 real_seconds = bin2bcd(real_seconds);
79 real_minutes = bin2bcd(real_minutes);
81 CMOS_WRITE(real_seconds, RTC_SECONDS);
82 CMOS_WRITE(real_minutes, RTC_MINUTES);
84 printk_once(KERN_NOTICE
85 "set_rtc_mmss: can't update from %d to %d\n",
86 cmos_minutes, real_minutes);
90 /* The following flags have to be released exactly in this order,
91 * otherwise the DS12887 (popular MC146818A clone with integrated
92 * battery and quartz) will not reset the oscillator and will not
93 * update precisely 500 ms later. You won't find this mentioned in
94 * the Dallas Semiconductor data sheets, but who believes data
95 * sheets anyway ... -- Markus Kuhn
97 CMOS_WRITE(save_control, RTC_CONTROL);
98 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
100 spin_unlock_irqrestore(&rtc_lock, flags);
105 unsigned long mach_get_cmos_time(void)
107 unsigned int status, year, mon, day, hour, min, sec, century = 0;
110 spin_lock_irqsave(&rtc_lock, flags);
113 * If UIP is clear, then we have >= 244 microseconds before
114 * RTC registers will be updated. Spec sheet says that this
115 * is the reliable way to read RTC - registers. If UIP is set
116 * then the register access might be invalid.
118 while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
121 sec = CMOS_READ(RTC_SECONDS);
122 min = CMOS_READ(RTC_MINUTES);
123 hour = CMOS_READ(RTC_HOURS);
124 day = CMOS_READ(RTC_DAY_OF_MONTH);
125 mon = CMOS_READ(RTC_MONTH);
126 year = CMOS_READ(RTC_YEAR);
129 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
130 acpi_gbl_FADT.century)
131 century = CMOS_READ(acpi_gbl_FADT.century);
134 status = CMOS_READ(RTC_CONTROL);
135 WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));
137 spin_unlock_irqrestore(&rtc_lock, flags);
139 if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) {
142 hour = bcd2bin(hour);
145 year = bcd2bin(year);
149 century = bcd2bin(century);
150 year += century * 100;
151 printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
153 year += CMOS_YEARS_OFFS;
155 return mktime(year, mon, day, hour, min, sec);
158 /* Routines for accessing the CMOS RAM/RTC. */
159 unsigned char rtc_cmos_read(unsigned char addr)
163 lock_cmos_prefix(addr);
164 outb(addr, RTC_PORT(0));
165 val = inb(RTC_PORT(1));
166 lock_cmos_suffix(addr);
170 EXPORT_SYMBOL(rtc_cmos_read);
172 void rtc_cmos_write(unsigned char val, unsigned char addr)
174 lock_cmos_prefix(addr);
175 outb(addr, RTC_PORT(0));
176 outb(val, RTC_PORT(1));
177 lock_cmos_suffix(addr);
179 EXPORT_SYMBOL(rtc_cmos_write);
181 int update_persistent_clock(struct timespec now)
183 return x86_platform.set_wallclock(now.tv_sec);
186 /* not static: needed by APM */
187 void read_persistent_clock(struct timespec *ts)
189 unsigned long retval;
191 retval = x86_platform.get_wallclock();
197 unsigned long long native_read_tsc(void)
199 return __native_read_tsc();
201 EXPORT_SYMBOL(native_read_tsc);
204 static struct resource rtc_resources[] = {
206 .start = RTC_PORT(0),
208 .flags = IORESOURCE_IO,
213 .flags = IORESOURCE_IRQ,
217 static struct platform_device rtc_device = {
220 .resource = rtc_resources,
221 .num_resources = ARRAY_SIZE(rtc_resources),
224 static __init int add_rtc_cmos(void)
227 static const char *ids[] __initconst =
228 { "PNP0b00", "PNP0b01", "PNP0b02", };
233 pnp_for_each_dev(dev) {
234 for (id = dev->id; id; id = id->next) {
235 for (i = 0; i < ARRAY_SIZE(ids); i++) {
236 if (compare_pnp_id(id, ids[i]) != 0)
242 if (of_have_populated_dt())
245 platform_device_register(&rtc_device);
246 dev_info(&rtc_device.dev,
247 "registered platform RTC device (no PNP device found)\n");
251 device_initcall(add_rtc_cmos);