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>
19 * This is a special lock that is owned by the CPU and holds the index
20 * register we are working with. It is required for NMI access to the
21 * CMOS/RTC registers. See include/asm-i386/mc146818rtc.h for details.
23 volatile unsigned long cmos_lock;
24 EXPORT_SYMBOL(cmos_lock);
25 #endif /* CONFIG_X86_32 */
27 /* For two digit years assume time is always after that */
28 #define CMOS_YEARS_OFFS 2000
30 DEFINE_SPINLOCK(rtc_lock);
31 EXPORT_SYMBOL(rtc_lock);
33 #ifndef CONFIG_XEN_UNPRIVILEGED_GUEST
35 * In order to set the CMOS clock precisely, set_rtc_mmss has to be
36 * called 500 ms after the second nowtime has started, because when
37 * nowtime is written into the registers of the CMOS clock, it will
38 * jump to the next second precisely 500 ms later. Check the Motorola
39 * MC146818A or Dallas DS12887 data sheet for details.
41 * BUG: This routine does not handle hour overflow properly; it just
42 * sets the minutes. Usually you'll only notice that after reboot!
44 int mach_set_rtc_mmss(unsigned long nowtime)
46 int real_seconds, real_minutes, cmos_minutes;
47 unsigned char save_control, save_freq_select;
51 spin_lock_irqsave(&rtc_lock, flags);
53 /* tell the clock it's being set */
54 save_control = CMOS_READ(RTC_CONTROL);
55 CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
57 /* stop and reset prescaler */
58 save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
59 CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
61 cmos_minutes = CMOS_READ(RTC_MINUTES);
62 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
63 cmos_minutes = bcd2bin(cmos_minutes);
66 * since we're only adjusting minutes and seconds,
67 * don't interfere with hour overflow. This avoids
68 * messing with unknown time zones but requires your
69 * RTC not to be off by more than 15 minutes
71 real_seconds = nowtime % 60;
72 real_minutes = nowtime / 60;
73 /* correct for half hour time zone */
74 if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
78 if (abs(real_minutes - cmos_minutes) < 30) {
79 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
80 real_seconds = bin2bcd(real_seconds);
81 real_minutes = bin2bcd(real_minutes);
83 CMOS_WRITE(real_seconds, RTC_SECONDS);
84 CMOS_WRITE(real_minutes, RTC_MINUTES);
86 printk_once(KERN_NOTICE
87 "set_rtc_mmss: can't update from %d to %d\n",
88 cmos_minutes, real_minutes);
92 /* The following flags have to be released exactly in this order,
93 * otherwise the DS12887 (popular MC146818A clone with integrated
94 * battery and quartz) will not reset the oscillator and will not
95 * update precisely 500 ms later. You won't find this mentioned in
96 * the Dallas Semiconductor data sheets, but who believes data
97 * sheets anyway ... -- Markus Kuhn
99 CMOS_WRITE(save_control, RTC_CONTROL);
100 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
102 spin_unlock_irqrestore(&rtc_lock, flags);
107 unsigned long mach_get_cmos_time(void)
109 unsigned int status, year, mon, day, hour, min, sec, century = 0;
112 spin_lock_irqsave(&rtc_lock, flags);
115 * If UIP is clear, then we have >= 244 microseconds before
116 * RTC registers will be updated. Spec sheet says that this
117 * is the reliable way to read RTC - registers. If UIP is set
118 * then the register access might be invalid.
120 while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
123 sec = CMOS_READ(RTC_SECONDS);
124 min = CMOS_READ(RTC_MINUTES);
125 hour = CMOS_READ(RTC_HOURS);
126 day = CMOS_READ(RTC_DAY_OF_MONTH);
127 mon = CMOS_READ(RTC_MONTH);
128 year = CMOS_READ(RTC_YEAR);
131 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
132 acpi_gbl_FADT.century)
133 century = CMOS_READ(acpi_gbl_FADT.century);
136 status = CMOS_READ(RTC_CONTROL);
137 WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));
139 spin_unlock_irqrestore(&rtc_lock, flags);
141 if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) {
144 hour = bcd2bin(hour);
147 year = bcd2bin(year);
151 century = bcd2bin(century);
152 year += century * 100;
153 printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
155 year += CMOS_YEARS_OFFS;
157 return mktime(year, mon, day, hour, min, sec);
159 #endif /* CONFIG_XEN_UNPRIVILEGED_GUEST */
161 /* Routines for accessing the CMOS RAM/RTC. */
162 unsigned char rtc_cmos_read(unsigned char addr)
166 lock_cmos_prefix(addr);
167 outb(addr, RTC_PORT(0));
168 val = inb(RTC_PORT(1));
169 lock_cmos_suffix(addr);
173 EXPORT_SYMBOL(rtc_cmos_read);
175 void rtc_cmos_write(unsigned char val, unsigned char addr)
177 lock_cmos_prefix(addr);
178 outb(addr, RTC_PORT(0));
179 outb(val, RTC_PORT(1));
180 lock_cmos_suffix(addr);
182 EXPORT_SYMBOL(rtc_cmos_write);
184 int update_persistent_clock(struct timespec now)
186 return x86_platform.set_wallclock(now.tv_sec);
189 /* not static: needed by APM */
190 void read_persistent_clock(struct timespec *ts)
192 unsigned long retval;
194 retval = x86_platform.get_wallclock();
200 unsigned long long native_read_tsc(void)
202 return __native_read_tsc();
204 EXPORT_SYMBOL(native_read_tsc);
207 #ifndef CONFIG_XEN_UNPRIVILEGED_GUEST
208 static struct resource rtc_resources[] = {
210 .start = RTC_PORT(0),
212 .flags = IORESOURCE_IO,
217 .flags = IORESOURCE_IRQ,
221 static struct platform_device rtc_device = {
224 .resource = rtc_resources,
225 .num_resources = ARRAY_SIZE(rtc_resources),
228 static __init int add_rtc_cmos(void)
231 static const char *ids[] __initconst =
232 { "PNP0b00", "PNP0b01", "PNP0b02", };
237 pnp_for_each_dev(dev) {
238 for (id = dev->id; id; id = id->next) {
239 for (i = 0; i < ARRAY_SIZE(ids); i++) {
240 if (compare_pnp_id(id, ids[i]) != 0)
246 if (of_have_populated_dt())
249 /* Intel MID platforms don't have ioport rtc */
250 if (mrst_identify_cpu())
254 if (!is_initial_xendomain())
258 platform_device_register(&rtc_device);
259 dev_info(&rtc_device.dev,
260 "registered platform RTC device (no PNP device found)\n");
264 device_initcall(add_rtc_cmos);
265 #endif /* CONFIG_XEN_UNPRIVILEGED_GUEST */