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
20DEFINE_SPINLOCK(rtc_lock);
21EXPORT_SYMBOL(rtc_lock);
22
23/*
24 * Read the current RTC time
25 */
26void 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 */
51static 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
112int 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 */
120void __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