2 * linux/arch/sh/kernel/rtc-mpc1211.c -- MPC-1211 on-chip RTC support
4 * Copyright (C) 2002 Saito.K & Jeanne
8 #include <linux/init.h>
9 #include <linux/kernel.h>
10 #include <linux/sched.h>
11 #include <linux/time.h>
12 #include <linux/bcd.h>
13 #include <linux/mc146818rtc.h>
15 unsigned long get_cmos_time(void)
17 unsigned int year
, mon
, day
, hour
, min
, sec
;
22 sec
= CMOS_READ(RTC_SECONDS
);
23 min
= CMOS_READ(RTC_MINUTES
);
24 hour
= CMOS_READ(RTC_HOURS
);
25 day
= CMOS_READ(RTC_DAY_OF_MONTH
);
26 mon
= CMOS_READ(RTC_MONTH
);
27 year
= CMOS_READ(RTC_YEAR
);
28 } while (sec
!= CMOS_READ(RTC_SECONDS
));
30 if (!(CMOS_READ(RTC_CONTROL
) & RTC_DM_BINARY
) || RTC_ALWAYS_BCD
) {
39 spin_unlock(&rtc_lock
);
45 return mktime(year
, mon
, day
, hour
, min
, sec
);
48 void mpc1211_rtc_gettimeofday(struct timeval
*tv
)
51 tv
->tv_sec
= get_cmos_time();
55 /* arc/i386/kernel/time.c */
57 * In order to set the CMOS clock precisely, set_rtc_mmss has to be
58 * called 500 ms after the second nowtime has started, because when
59 * nowtime is written into the registers of the CMOS clock, it will
60 * jump to the next second precisely 500 ms later. Check the Motorola
61 * MC146818A or Dallas DS12887 data sheet for details.
63 * BUG: This routine does not handle hour overflow properly; it just
64 * sets the minutes. Usually you'll only notice that after reboot!
66 static int set_rtc_mmss(unsigned long nowtime
)
69 int real_seconds
, real_minutes
, cmos_minutes
;
70 unsigned char save_control
, save_freq_select
;
72 /* gets recalled with irq locally disabled */
74 save_control
= CMOS_READ(RTC_CONTROL
); /* tell the clock it's being set */
75 CMOS_WRITE((save_control
|RTC_SET
), RTC_CONTROL
);
77 save_freq_select
= CMOS_READ(RTC_FREQ_SELECT
); /* stop and reset prescaler */
78 CMOS_WRITE((save_freq_select
|RTC_DIV_RESET2
), RTC_FREQ_SELECT
);
80 cmos_minutes
= CMOS_READ(RTC_MINUTES
);
81 if (!(save_control
& RTC_DM_BINARY
) || RTC_ALWAYS_BCD
)
82 BCD_TO_BIN(cmos_minutes
);
85 * since we're only adjusting minutes and seconds,
86 * don't interfere with hour overflow. This avoids
87 * messing with unknown time zones but requires your
88 * RTC not to be off by more than 15 minutes
90 real_seconds
= nowtime
% 60;
91 real_minutes
= nowtime
/ 60;
92 if (((abs(real_minutes
- cmos_minutes
) + 15)/30) & 1)
93 real_minutes
+= 30; /* correct for half hour time zone */
96 if (abs(real_minutes
- cmos_minutes
) < 30) {
97 if (!(save_control
& RTC_DM_BINARY
) || RTC_ALWAYS_BCD
) {
98 BIN_TO_BCD(real_seconds
);
99 BIN_TO_BCD(real_minutes
);
101 CMOS_WRITE(real_seconds
,RTC_SECONDS
);
102 CMOS_WRITE(real_minutes
,RTC_MINUTES
);
105 "set_rtc_mmss: can't update from %d to %d\n",
106 cmos_minutes
, real_minutes
);
110 /* The following flags have to be released exactly in this order,
111 * otherwise the DS12887 (popular MC146818A clone with integrated
112 * battery and quartz) will not reset the oscillator and will not
113 * update precisely 500 ms later. You won't find this mentioned in
114 * the Dallas Semiconductor data sheets, but who believes data
115 * sheets anyway ... -- Markus Kuhn
117 CMOS_WRITE(save_control
, RTC_CONTROL
);
118 CMOS_WRITE(save_freq_select
, RTC_FREQ_SELECT
);
119 spin_unlock(&rtc_lock
);
124 int mpc1211_rtc_settimeofday(const struct timeval
*tv
)
126 unsigned long nowtime
= tv
->tv_sec
;
128 return set_rtc_mmss(nowtime
);
131 void mpc1211_time_init(void)
133 rtc_get_time
= mpc1211_rtc_gettimeofday
;
134 rtc_set_time
= mpc1211_rtc_settimeofday
;