2 * linux/include/asm-arm/arch-ebsa285/time.h
4 * Copyright (C) 1998 Russell King.
5 * Copyright (C) 1998 Phil Blundell
7 * CATS has a real-time clock, though the evaluation board doesn't.
10 * 21-Mar-1998 RMK Created
11 * 27-Aug-1998 PJB CATS support
12 * 28-Dec-1998 APH Made leds optional
13 * 20-Jan-1999 RMK Started merge of EBSA285, CATS and NetWinder
14 * 16-Mar-1999 RMK More support for EBSA285-like machines with RTCs in
17 #define RTC_PORT(x) (rtc_base+(x))
18 #define RTC_ALWAYS_BCD 0
20 #include <linux/timex.h>
21 #include <linux/init.h>
22 #include <linux/sched.h>
23 #include <linux/mc146818rtc.h>
24 #include <linux/bcd.h>
26 #include <asm/hardware.h>
29 #include <asm/mach/time.h>
34 static unsigned long __init
get_isa_cmos_time(void)
36 unsigned int year
, mon
, day
, hour
, min
, sec
;
39 // check to see if the RTC makes sense.....
40 if ((CMOS_READ(RTC_VALID
) & RTC_VRT
) == 0)
41 return mktime(1970, 1, 1, 0, 0, 0);
43 /* The Linux interpretation of the CMOS clock register contents:
44 * When the Update-In-Progress (UIP) flag goes from 1 to 0, the
45 * RTC registers show the second which has precisely just started.
46 * Let's hope other operating systems interpret the RTC the same way.
48 /* read RTC exactly on falling edge of update flag */
49 for (i
= 0 ; i
< 1000000 ; i
++) /* may take up to 1 second... */
50 if (CMOS_READ(RTC_FREQ_SELECT
) & RTC_UIP
)
53 for (i
= 0 ; i
< 1000000 ; i
++) /* must try at least 2.228 ms */
54 if (!(CMOS_READ(RTC_FREQ_SELECT
) & RTC_UIP
))
57 do { /* Isn't this overkill ? UIP above should guarantee consistency */
58 sec
= CMOS_READ(RTC_SECONDS
);
59 min
= CMOS_READ(RTC_MINUTES
);
60 hour
= CMOS_READ(RTC_HOURS
);
61 day
= CMOS_READ(RTC_DAY_OF_MONTH
);
62 mon
= CMOS_READ(RTC_MONTH
);
63 year
= CMOS_READ(RTC_YEAR
);
64 } while (sec
!= CMOS_READ(RTC_SECONDS
));
66 if (!(CMOS_READ(RTC_CONTROL
) & RTC_DM_BINARY
) || RTC_ALWAYS_BCD
) {
74 if ((year
+= 1900) < 1970)
76 return mktime(year
, mon
, day
, hour
, min
, sec
);
79 static int set_isa_cmos_time(void)
82 int real_seconds
, real_minutes
, cmos_minutes
;
83 unsigned char save_control
, save_freq_select
;
84 unsigned long nowtime
= xtime
.tv_sec
;
86 save_control
= CMOS_READ(RTC_CONTROL
); /* tell the clock it's being set */
87 CMOS_WRITE((save_control
|RTC_SET
), RTC_CONTROL
);
89 save_freq_select
= CMOS_READ(RTC_FREQ_SELECT
); /* stop and reset prescaler */
90 CMOS_WRITE((save_freq_select
|RTC_DIV_RESET2
), RTC_FREQ_SELECT
);
92 cmos_minutes
= CMOS_READ(RTC_MINUTES
);
93 if (!(save_control
& RTC_DM_BINARY
) || RTC_ALWAYS_BCD
)
94 BCD_TO_BIN(cmos_minutes
);
97 * since we're only adjusting minutes and seconds,
98 * don't interfere with hour overflow. This avoids
99 * messing with unknown time zones but requires your
100 * RTC not to be off by more than 15 minutes
102 real_seconds
= nowtime
% 60;
103 real_minutes
= nowtime
/ 60;
104 if (((abs(real_minutes
- cmos_minutes
) + 15)/30) & 1)
105 real_minutes
+= 30; /* correct for half hour time zone */
108 if (abs(real_minutes
- cmos_minutes
) < 30) {
109 if (!(save_control
& RTC_DM_BINARY
) || RTC_ALWAYS_BCD
) {
110 BIN_TO_BCD(real_seconds
);
111 BIN_TO_BCD(real_minutes
);
113 CMOS_WRITE(real_seconds
,RTC_SECONDS
);
114 CMOS_WRITE(real_minutes
,RTC_MINUTES
);
118 /* The following flags have to be released exactly in this order,
119 * otherwise the DS12887 (popular MC146818A clone with integrated
120 * battery and quartz) will not reset the oscillator and will not
121 * update precisely 500 ms later. You won't find this mentioned in
122 * the Dallas Semiconductor data sheets, but who believes data
123 * sheets anyway ... -- Markus Kuhn
125 CMOS_WRITE(save_control
, RTC_CONTROL
);
126 CMOS_WRITE(save_freq_select
, RTC_FREQ_SELECT
);
131 void __init
isa_rtc_init(void)
133 if (machine_is_co285() ||
134 machine_is_personal_server())
136 * Add-in 21285s shouldn't access the RTC
148 reg_d
= CMOS_READ(RTC_REG_D
);
151 * make sure the divider is set
153 CMOS_WRITE(RTC_REF_CLCK_32KHZ
, RTC_REG_A
);
157 * (24 hour mode, update enabled)
159 reg_b
= CMOS_READ(RTC_REG_B
) & 0x7f;
161 CMOS_WRITE(reg_b
, RTC_REG_B
);
163 if ((CMOS_READ(RTC_REG_A
) & 0x7f) == RTC_REF_CLCK_32KHZ
&&
164 CMOS_READ(RTC_REG_B
) == reg_b
) {
168 * We have a RTC. Check the battery
170 if ((reg_d
& 0x80) == 0)
171 printk(KERN_WARNING
"RTC: *** warning: CMOS battery bad\n");
174 tv
.tv_sec
= get_isa_cmos_time();
175 do_settimeofday(&tv
);
176 set_rtc
= set_isa_cmos_time
;
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