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1da177e4 LT |
1 | /* |
2 | * include/asm-i386/mach-default/mach_time.h | |
3 | * | |
4 | * Machine specific set RTC function for generic. | |
5 | * Split out from time.c by Osamu Tomita <tomita@cinet.co.jp> | |
6 | */ | |
7 | #ifndef _MACH_TIME_H | |
8 | #define _MACH_TIME_H | |
9 | ||
10 | #include <linux/mc146818rtc.h> | |
11 | ||
12 | /* for check timing call set_rtc_mmss() 500ms */ | |
13 | /* used in arch/i386/time.c::do_timer_interrupt() */ | |
14 | #define USEC_AFTER 500000 | |
15 | #define USEC_BEFORE 500000 | |
16 | ||
17 | /* | |
18 | * In order to set the CMOS clock precisely, set_rtc_mmss has to be | |
19 | * called 500 ms after the second nowtime has started, because when | |
20 | * nowtime is written into the registers of the CMOS clock, it will | |
21 | * jump to the next second precisely 500 ms later. Check the Motorola | |
22 | * MC146818A or Dallas DS12887 data sheet for details. | |
23 | * | |
24 | * BUG: This routine does not handle hour overflow properly; it just | |
25 | * sets the minutes. Usually you'll only notice that after reboot! | |
26 | */ | |
27 | static inline int mach_set_rtc_mmss(unsigned long nowtime) | |
28 | { | |
29 | int retval = 0; | |
30 | int real_seconds, real_minutes, cmos_minutes; | |
31 | unsigned char save_control, save_freq_select; | |
32 | ||
33 | save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */ | |
34 | CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL); | |
35 | ||
36 | save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset prescaler */ | |
37 | CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT); | |
38 | ||
39 | cmos_minutes = CMOS_READ(RTC_MINUTES); | |
40 | if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) | |
41 | BCD_TO_BIN(cmos_minutes); | |
42 | ||
43 | /* | |
44 | * since we're only adjusting minutes and seconds, | |
45 | * don't interfere with hour overflow. This avoids | |
46 | * messing with unknown time zones but requires your | |
47 | * RTC not to be off by more than 15 minutes | |
48 | */ | |
49 | real_seconds = nowtime % 60; | |
50 | real_minutes = nowtime / 60; | |
51 | if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1) | |
52 | real_minutes += 30; /* correct for half hour time zone */ | |
53 | real_minutes %= 60; | |
54 | ||
55 | if (abs(real_minutes - cmos_minutes) < 30) { | |
56 | if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) { | |
57 | BIN_TO_BCD(real_seconds); | |
58 | BIN_TO_BCD(real_minutes); | |
59 | } | |
60 | CMOS_WRITE(real_seconds,RTC_SECONDS); | |
61 | CMOS_WRITE(real_minutes,RTC_MINUTES); | |
62 | } else { | |
63 | printk(KERN_WARNING | |
64 | "set_rtc_mmss: can't update from %d to %d\n", | |
65 | cmos_minutes, real_minutes); | |
66 | retval = -1; | |
67 | } | |
68 | ||
69 | /* The following flags have to be released exactly in this order, | |
70 | * otherwise the DS12887 (popular MC146818A clone with integrated | |
71 | * battery and quartz) will not reset the oscillator and will not | |
72 | * update precisely 500 ms later. You won't find this mentioned in | |
73 | * the Dallas Semiconductor data sheets, but who believes data | |
74 | * sheets anyway ... -- Markus Kuhn | |
75 | */ | |
76 | CMOS_WRITE(save_control, RTC_CONTROL); | |
77 | CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT); | |
78 | ||
79 | return retval; | |
80 | } | |
81 | ||
82 | static inline unsigned long mach_get_cmos_time(void) | |
83 | { | |
84 | unsigned int year, mon, day, hour, min, sec; | |
1da177e4 | 85 | |
63732c2f | 86 | do { |
1da177e4 LT |
87 | sec = CMOS_READ(RTC_SECONDS); |
88 | min = CMOS_READ(RTC_MINUTES); | |
89 | hour = CMOS_READ(RTC_HOURS); | |
90 | day = CMOS_READ(RTC_DAY_OF_MONTH); | |
91 | mon = CMOS_READ(RTC_MONTH); | |
92 | year = CMOS_READ(RTC_YEAR); | |
93 | } while (sec != CMOS_READ(RTC_SECONDS)); | |
63732c2f | 94 | |
41623b06 MM |
95 | if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) { |
96 | BCD_TO_BIN(sec); | |
97 | BCD_TO_BIN(min); | |
98 | BCD_TO_BIN(hour); | |
99 | BCD_TO_BIN(day); | |
100 | BCD_TO_BIN(mon); | |
101 | BCD_TO_BIN(year); | |
102 | } | |
103 | ||
104 | year += 1900; | |
105 | if (year < 1970) | |
1da177e4 LT |
106 | year += 100; |
107 | ||
108 | return mktime(year, mon, day, hour, min, sec); | |
109 | } | |
110 | ||
111 | #endif /* !_MACH_TIME_H */ |