2 * RTC related functions
4 #include <linux/acpi.h>
6 #include <linux/mc146818rtc.h>
9 #include <asm/vsyscall.h>
13 * This is a special lock that is owned by the CPU and holds the index
14 * register we are working with. It is required for NMI access to the
15 * CMOS/RTC registers. See include/asm-i386/mc146818rtc.h for details.
17 volatile unsigned long cmos_lock
= 0;
18 EXPORT_SYMBOL(cmos_lock
);
21 /* For two digit years assume time is always after that */
22 #define CMOS_YEARS_OFFS 2000
24 DEFINE_SPINLOCK(rtc_lock
);
25 EXPORT_SYMBOL(rtc_lock
);
28 * In order to set the CMOS clock precisely, set_rtc_mmss has to be
29 * called 500 ms after the second nowtime has started, because when
30 * nowtime is written into the registers of the CMOS clock, it will
31 * jump to the next second precisely 500 ms later. Check the Motorola
32 * MC146818A or Dallas DS12887 data sheet for details.
34 * BUG: This routine does not handle hour overflow properly; it just
35 * sets the minutes. Usually you'll only notice that after reboot!
37 int mach_set_rtc_mmss(unsigned long nowtime
)
40 int real_seconds
, real_minutes
, cmos_minutes
;
41 unsigned char save_control
, save_freq_select
;
43 /* tell the clock it's being set */
44 save_control
= CMOS_READ(RTC_CONTROL
);
45 CMOS_WRITE((save_control
|RTC_SET
), RTC_CONTROL
);
47 /* stop and reset prescaler */
48 save_freq_select
= CMOS_READ(RTC_FREQ_SELECT
);
49 CMOS_WRITE((save_freq_select
|RTC_DIV_RESET2
), RTC_FREQ_SELECT
);
51 cmos_minutes
= CMOS_READ(RTC_MINUTES
);
52 if (!(save_control
& RTC_DM_BINARY
) || RTC_ALWAYS_BCD
)
53 BCD_TO_BIN(cmos_minutes
);
56 * since we're only adjusting minutes and seconds,
57 * don't interfere with hour overflow. This avoids
58 * messing with unknown time zones but requires your
59 * RTC not to be off by more than 15 minutes
61 real_seconds
= nowtime
% 60;
62 real_minutes
= nowtime
/ 60;
63 /* correct for half hour time zone */
64 if (((abs(real_minutes
- cmos_minutes
) + 15)/30) & 1)
68 if (abs(real_minutes
- cmos_minutes
) < 30) {
69 if (!(save_control
& RTC_DM_BINARY
) || RTC_ALWAYS_BCD
) {
70 BIN_TO_BCD(real_seconds
);
71 BIN_TO_BCD(real_minutes
);
73 CMOS_WRITE(real_seconds
,RTC_SECONDS
);
74 CMOS_WRITE(real_minutes
,RTC_MINUTES
);
77 "set_rtc_mmss: can't update from %d to %d\n",
78 cmos_minutes
, real_minutes
);
82 /* The following flags have to be released exactly in this order,
83 * otherwise the DS12887 (popular MC146818A clone with integrated
84 * battery and quartz) will not reset the oscillator and will not
85 * update precisely 500 ms later. You won't find this mentioned in
86 * the Dallas Semiconductor data sheets, but who believes data
87 * sheets anyway ... -- Markus Kuhn
89 CMOS_WRITE(save_control
, RTC_CONTROL
);
90 CMOS_WRITE(save_freq_select
, RTC_FREQ_SELECT
);
95 unsigned long mach_get_cmos_time(void)
97 unsigned int status
, year
, mon
, day
, hour
, min
, sec
, century
= 0;
100 * If UIP is clear, then we have >= 244 microseconds before
101 * RTC registers will be updated. Spec sheet says that this
102 * is the reliable way to read RTC - registers. If UIP is set
103 * then the register access might be invalid.
105 while ((CMOS_READ(RTC_FREQ_SELECT
) & RTC_UIP
))
108 sec
= CMOS_READ(RTC_SECONDS
);
109 min
= CMOS_READ(RTC_MINUTES
);
110 hour
= CMOS_READ(RTC_HOURS
);
111 day
= CMOS_READ(RTC_DAY_OF_MONTH
);
112 mon
= CMOS_READ(RTC_MONTH
);
113 year
= CMOS_READ(RTC_YEAR
);
116 if (acpi_gbl_FADT
.header
.revision
>= FADT2_REVISION_ID
&&
117 acpi_gbl_FADT
.century
)
118 century
= CMOS_READ(acpi_gbl_FADT
.century
);
121 status
= CMOS_READ(RTC_CONTROL
);
122 WARN_ON_ONCE(RTC_ALWAYS_BCD
&& (status
& RTC_DM_BINARY
));
124 if (RTC_ALWAYS_BCD
|| !(status
& RTC_DM_BINARY
)) {
135 year
+= century
* 100;
136 printk(KERN_INFO
"Extended CMOS year: %d\n", century
* 100);
138 year
+= CMOS_YEARS_OFFS
;
140 return mktime(year
, mon
, day
, hour
, min
, sec
);
143 /* Routines for accessing the CMOS RAM/RTC. */
144 unsigned char rtc_cmos_read(unsigned char addr
)
148 lock_cmos_prefix(addr
);
149 outb_p(addr
, RTC_PORT(0));
150 val
= inb_p(RTC_PORT(1));
151 lock_cmos_suffix(addr
);
154 EXPORT_SYMBOL(rtc_cmos_read
);
156 void rtc_cmos_write(unsigned char val
, unsigned char addr
)
158 lock_cmos_prefix(addr
);
159 outb_p(addr
, RTC_PORT(0));
160 outb_p(val
, RTC_PORT(1));
161 lock_cmos_suffix(addr
);
163 EXPORT_SYMBOL(rtc_cmos_write
);
165 static int set_rtc_mmss(unsigned long nowtime
)
170 spin_lock_irqsave(&rtc_lock
, flags
);
171 retval
= set_wallclock(nowtime
);
172 spin_unlock_irqrestore(&rtc_lock
, flags
);
177 /* not static: needed by APM */
178 unsigned long read_persistent_clock(void)
180 unsigned long retval
, flags
;
182 spin_lock_irqsave(&rtc_lock
, flags
);
183 retval
= get_wallclock();
184 spin_unlock_irqrestore(&rtc_lock
, flags
);
189 int update_persistent_clock(struct timespec now
)
191 return set_rtc_mmss(now
.tv_sec
);
194 unsigned long long native_read_tsc(void)
196 return __native_read_tsc();
198 EXPORT_SYMBOL(native_read_tsc
);