1 /* MN10300 RTC management
2 *
3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11 #include <linux/kernel.h>
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/mc146818rtc.h>
15 #include <linux/bcd.h>
16 #include <linux/timex.h>
17 #include <asm/rtc-regs.h>
18 #include <asm/rtc.h>
19
20 DEFINE_SPINLOCK(rtc_lock);
21 EXPORT_SYMBOL(rtc_lock);
22
23 /*
24 * Read the current RTC time
25 */
read_persistent_clock(struct timespec * ts)26 void read_persistent_clock(struct timespec *ts)
27 {
28 struct rtc_time tm;
29
30 get_rtc_time(&tm);
31
32 ts->tv_nsec = 0;
33 ts->tv_sec = mktime(tm.tm_year, tm.tm_mon, tm.tm_mday,
34 tm.tm_hour, tm.tm_min, tm.tm_sec);
35
36 /* if rtc is way off in the past, set something reasonable */
37 if (ts->tv_sec < 0)
38 ts->tv_sec = mktime(2009, 1, 1, 12, 0, 0);
39 }
40
41 /*
42 * In order to set the CMOS clock precisely, set_rtc_mmss has to be called 500
43 * ms after the second nowtime has started, because when nowtime is written
44 * into the registers of the CMOS clock, it will jump to the next second
45 * precisely 500 ms later. Check the Motorola MC146818A or Dallas DS12887 data
46 * sheet for details.
47 *
48 * BUG: This routine does not handle hour overflow properly; it just
49 * sets the minutes. Usually you'll only notice that after reboot!
50 */
set_rtc_mmss(unsigned long nowtime)51 static int set_rtc_mmss(unsigned long nowtime)
52 {
53 unsigned char save_control, save_freq_select;
54 int retval = 0;
55 int real_seconds, real_minutes, cmos_minutes;
56
57 /* gets recalled with irq locally disabled */
58 spin_lock(&rtc_lock);
59 save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being
60 * set */
61 CMOS_WRITE(save_control | RTC_SET, RTC_CONTROL);
62
63 save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset
64 * prescaler */
65 CMOS_WRITE(save_freq_select | RTC_DIV_RESET2, RTC_FREQ_SELECT);
66
67 cmos_minutes = CMOS_READ(RTC_MINUTES);
68 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
69 cmos_minutes = bcd2bin(cmos_minutes);
70
71 /*
72 * since we're only adjusting minutes and seconds,
73 * don't interfere with hour overflow. This avoids
74 * messing with unknown time zones but requires your
75 * RTC not to be off by more than 15 minutes
76 */
77 real_seconds = nowtime % 60;
78 real_minutes = nowtime / 60;
79 if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1)
80 /* correct for half hour time zone */
81 real_minutes += 30;
82 real_minutes %= 60;
83
84 if (abs(real_minutes - cmos_minutes) < 30) {
85 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
86 real_seconds = bin2bcd(real_seconds);
87 real_minutes = bin2bcd(real_minutes);
88 }
89 CMOS_WRITE(real_seconds, RTC_SECONDS);
90 CMOS_WRITE(real_minutes, RTC_MINUTES);
91 } else {
92 printk_once(KERN_NOTICE
93 "set_rtc_mmss: can't update from %d to %d\n",
94 cmos_minutes, real_minutes);
95 retval = -1;
96 }
97
98 /* The following flags have to be released exactly in this order,
99 * otherwise the DS12887 (popular MC146818A clone with integrated
100 * battery and quartz) will not reset the oscillator and will not
101 * update precisely 500 ms later. You won't find this mentioned in
102 * the Dallas Semiconductor data sheets, but who believes data
103 * sheets anyway ... -- Markus Kuhn
104 */
105 CMOS_WRITE(save_control, RTC_CONTROL);
106 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
107 spin_unlock(&rtc_lock);
108
109 return retval;
110 }
111
update_persistent_clock(struct timespec now)112 int update_persistent_clock(struct timespec now)
113 {
114 return set_rtc_mmss(now.tv_sec);
115 }
116
117 /*
118 * calibrate the TSC clock against the RTC
119 */
calibrate_clock(void)120 void __init calibrate_clock(void)
121 {
122 unsigned char status;
123
124 /* make sure the RTC is running and is set to operate in 24hr mode */
125 status = RTSRC;
126 RTCRB |= RTCRB_SET;
127 RTCRB |= RTCRB_TM_24HR;
128 RTCRB &= ~RTCRB_DM_BINARY;
129 RTCRA |= RTCRA_DVR;
130 RTCRA &= ~RTCRA_DVR;
131 RTCRB &= ~RTCRB_SET;
132 }
133