1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
|
/* MN10300 RTC management
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/mc146818rtc.h>
#include <linux/bcd.h>
#include <linux/timex.h>
#include <asm/rtc-regs.h>
#include <asm/rtc.h>
DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);
/* last time the RTC got updated */
static long last_rtc_update;
/* time for RTC to update itself in ioclks */
static unsigned long mn10300_rtc_update_period;
/*
* read the current RTC time
*/
unsigned long __init get_initial_rtc_time(void)
{
struct rtc_time tm;
get_rtc_time(&tm);
return mktime(tm.tm_year, tm.tm_mon, tm.tm_mday,
tm.tm_hour, tm.tm_min, tm.tm_sec);
}
/*
* In order to set the CMOS clock precisely, set_rtc_mmss has to be called 500
* ms after the second nowtime has started, because when nowtime is written
* into the registers of the CMOS clock, it will jump to the next second
* precisely 500 ms later. Check the Motorola MC146818A or Dallas DS12887 data
* sheet for details.
*
* BUG: This routine does not handle hour overflow properly; it just
* sets the minutes. Usually you'll only notice that after reboot!
*/
static int set_rtc_mmss(unsigned long nowtime)
{
unsigned char save_control, save_freq_select;
int retval = 0;
int real_seconds, real_minutes, cmos_minutes;
/* gets recalled with irq locally disabled */
spin_lock(&rtc_lock);
save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being
* set */
CMOS_WRITE(save_control | RTC_SET, RTC_CONTROL);
save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset
* prescaler */
CMOS_WRITE(save_freq_select | RTC_DIV_RESET2, RTC_FREQ_SELECT);
cmos_minutes = CMOS_READ(RTC_MINUTES);
if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
cmos_minutes = bcd2bin(cmos_minutes);
/*
* since we're only adjusting minutes and seconds,
* don't interfere with hour overflow. This avoids
* messing with unknown time zones but requires your
* RTC not to be off by more than 15 minutes
*/
real_seconds = nowtime % 60;
real_minutes = nowtime / 60;
if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1)
/* correct for half hour time zone */
real_minutes += 30;
real_minutes %= 60;
if (abs(real_minutes - cmos_minutes) < 30) {
if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
real_seconds = bin2bcd(real_seconds);
real_minutes = bin2bcd(real_minutes);
}
CMOS_WRITE(real_seconds, RTC_SECONDS);
CMOS_WRITE(real_minutes, RTC_MINUTES);
} else {
printk(KERN_WARNING
"set_rtc_mmss: can't update from %d to %d\n",
cmos_minutes, real_minutes);
retval = -1;
}
/* The following flags have to be released exactly in this order,
* otherwise the DS12887 (popular MC146818A clone with integrated
* battery and quartz) will not reset the oscillator and will not
* update precisely 500 ms later. You won't find this mentioned in
* the Dallas Semiconductor data sheets, but who believes data
* sheets anyway ... -- Markus Kuhn
*/
CMOS_WRITE(save_control, RTC_CONTROL);
CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
spin_unlock(&rtc_lock);
return retval;
}
void check_rtc_time(void)
{
/* the RTC clock just finished ticking over again this second
* - if we have an externally synchronized Linux clock, then update
* RTC clock accordingly every ~11 minutes. set_rtc_mmss() has to be
* called as close as possible to 500 ms before the new second starts.
*/
if ((time_status & STA_UNSYNC) == 0 &&
xtime.tv_sec > last_rtc_update + 660 &&
xtime.tv_nsec / 1000 >= 500000 - ((unsigned) TICK_SIZE) / 2 &&
xtime.tv_nsec / 1000 <= 500000 + ((unsigned) TICK_SIZE) / 2
) {
if (set_rtc_mmss(xtime.tv_sec) == 0)
last_rtc_update = xtime.tv_sec;
else
/* do it again in 60s */
last_rtc_update = xtime.tv_sec - 600;
}
}
/*
* calibrate the TSC clock against the RTC
*/
void __init calibrate_clock(void)
{
unsigned long count0, counth, count1;
unsigned char status;
/* make sure the RTC is running and is set to operate in 24hr mode */
status = RTSRC;
RTCRB |= RTCRB_SET;
RTCRB |= RTCRB_TM_24HR;
RTCRA |= RTCRA_DVR;
RTCRA &= ~RTCRA_DVR;
RTCRB &= ~RTCRB_SET;
/* work out the clock speed by counting clock cycles between ends of
* the RTC update cycle - track the RTC through one complete update
* cycle (1 second)
*/
startup_timestamp_counter();
while (!(RTCRA & RTCRA_UIP)) {}
while ((RTCRA & RTCRA_UIP)) {}
count0 = TMTSCBC;
while (!(RTCRA & RTCRA_UIP)) {}
counth = TMTSCBC;
while ((RTCRA & RTCRA_UIP)) {}
count1 = TMTSCBC;
shutdown_timestamp_counter();
MN10300_TSCCLK = count0 - count1; /* the timers count down */
mn10300_rtc_update_period = counth - count1;
MN10300_TSC_PER_HZ = MN10300_TSCCLK / HZ;
}
|
