2 * RTC related functions
4 #include <linux/platform_device.h>
5 #include <linux/mc146818rtc.h>
6 #include <linux/acpi.h>
11 #include <asm/vsyscall.h>
12 #include <asm/x86_init.h>
17 * This is a special lock that is owned by the CPU and holds the index
18 * register we are working with. It is required for NMI access to the
19 * CMOS/RTC registers. See include/asm-i386/mc146818rtc.h for details.
21 volatile unsigned long cmos_lock;
22 EXPORT_SYMBOL(cmos_lock);
23 #endif /* CONFIG_X86_32 */
25 /* For two digit years assume time is always after that */
26 #define CMOS_YEARS_OFFS 2000
28 DEFINE_SPINLOCK(rtc_lock);
29 EXPORT_SYMBOL(rtc_lock);
32 * In order to set the CMOS clock precisely, set_rtc_mmss has to be
33 * called 500 ms after the second nowtime has started, because when
34 * nowtime is written into the registers of the CMOS clock, it will
35 * jump to the next second precisely 500 ms later. Check the Motorola
36 * MC146818A or Dallas DS12887 data sheet for details.
38 * BUG: This routine does not handle hour overflow properly; it just
39 * sets the minutes. Usually you'll only notice that after reboot!
41 int mach_set_rtc_mmss(unsigned long nowtime)
43 int real_seconds, real_minutes, cmos_minutes;
44 unsigned char save_control, save_freq_select;
48 spin_lock_irqsave(&rtc_lock, flags);
50 /* tell the clock it's being set */
51 save_control = CMOS_READ(RTC_CONTROL);
52 CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
54 /* stop and reset prescaler */
55 save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
56 CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
58 cmos_minutes = CMOS_READ(RTC_MINUTES);
59 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
60 cmos_minutes = bcd2bin(cmos_minutes);
63 * since we're only adjusting minutes and seconds,
64 * don't interfere with hour overflow. This avoids
65 * messing with unknown time zones but requires your
66 * RTC not to be off by more than 15 minutes
68 real_seconds = nowtime % 60;
69 real_minutes = nowtime / 60;
70 /* correct for half hour time zone */
71 if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
75 if (abs(real_minutes - cmos_minutes) < 30) {
76 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
77 real_seconds = bin2bcd(real_seconds);
78 real_minutes = bin2bcd(real_minutes);
80 CMOS_WRITE(real_seconds, RTC_SECONDS);
81 CMOS_WRITE(real_minutes, RTC_MINUTES);
83 printk_once(KERN_NOTICE
84 "set_rtc_mmss: can't update from %d to %d\n",
85 cmos_minutes, real_minutes);
89 /* The following flags have to be released exactly in this order,
90 * otherwise the DS12887 (popular MC146818A clone with integrated
91 * battery and quartz) will not reset the oscillator and will not
92 * update precisely 500 ms later. You won't find this mentioned in
93 * the Dallas Semiconductor data sheets, but who believes data
94 * sheets anyway ... -- Markus Kuhn
96 CMOS_WRITE(save_control, RTC_CONTROL);
97 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
99 spin_unlock_irqrestore(&rtc_lock, flags);
104 unsigned long mach_get_cmos_time(void)
106 unsigned int status, year, mon, day, hour, min, sec, century = 0;
109 spin_lock_irqsave(&rtc_lock, flags);
112 * If UIP is clear, then we have >= 244 microseconds before
113 * RTC registers will be updated. Spec sheet says that this
114 * is the reliable way to read RTC - registers. If UIP is set
115 * then the register access might be invalid.
117 while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
120 sec = CMOS_READ(RTC_SECONDS);
121 min = CMOS_READ(RTC_MINUTES);
122 hour = CMOS_READ(RTC_HOURS);
123 day = CMOS_READ(RTC_DAY_OF_MONTH);
124 mon = CMOS_READ(RTC_MONTH);
125 year = CMOS_READ(RTC_YEAR);
128 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
129 acpi_gbl_FADT.century)
130 century = CMOS_READ(acpi_gbl_FADT.century);
133 status = CMOS_READ(RTC_CONTROL);
134 WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));
136 spin_unlock_irqrestore(&rtc_lock, flags);
138 if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) {
141 hour = bcd2bin(hour);
144 year = bcd2bin(year);
148 century = bcd2bin(century);
149 year += century * 100;
150 printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
152 year += CMOS_YEARS_OFFS;
154 return mktime(year, mon, day, hour, min, sec);
157 /* Routines for accessing the CMOS RAM/RTC. */
158 unsigned char rtc_cmos_read(unsigned char addr)
162 lock_cmos_prefix(addr);
163 outb(addr, RTC_PORT(0));
164 val = inb(RTC_PORT(1));
165 lock_cmos_suffix(addr);
169 EXPORT_SYMBOL(rtc_cmos_read);
171 void rtc_cmos_write(unsigned char val, unsigned char addr)
173 lock_cmos_prefix(addr);
174 outb(addr, RTC_PORT(0));
175 outb(val, RTC_PORT(1));
176 lock_cmos_suffix(addr);
178 EXPORT_SYMBOL(rtc_cmos_write);
180 int update_persistent_clock(struct timespec now)
182 return x86_platform.set_wallclock(now.tv_sec);
185 /* not static: needed by APM */
186 void read_persistent_clock(struct timespec *ts)
188 unsigned long retval;
190 retval = x86_platform.get_wallclock();
196 unsigned long long native_read_tsc(void)
198 return __native_read_tsc();
200 EXPORT_SYMBOL(native_read_tsc);
203 static struct resource rtc_resources[] = {
205 .start = RTC_PORT(0),
207 .flags = IORESOURCE_IO,
212 .flags = IORESOURCE_IRQ,
216 static struct platform_device rtc_device = {
219 .resource = rtc_resources,
220 .num_resources = ARRAY_SIZE(rtc_resources),
223 static __init int add_rtc_cmos(void)
226 static const char *ids[] __initconst =
227 { "PNP0b00", "PNP0b01", "PNP0b02", };
232 pnp_for_each_dev(dev) {
233 for (id = dev->id; id; id = id->next) {
234 for (i = 0; i < ARRAY_SIZE(ids); i++) {
235 if (compare_pnp_id(id, ids[i]) != 0)
241 if (of_have_populated_dt())
244 platform_device_register(&rtc_device);
245 dev_info(&rtc_device.dev,
246 "registered platform RTC device (no PNP device found)\n");
250 device_initcall(add_rtc_cmos);