2 * linux/arch/i386/kernel/time.c
4 * Copyright (C) 1991, 1992, 1995 Linus Torvalds
6 * Adapted for PowerPC (PreP) by Gary Thomas
7 * Modified by Cort Dougan (cort@cs.nmt.edu)
8 * copied and modified from intel version
11 #include <linux/errno.h>
12 #include <linux/sched.h>
13 #include <linux/kernel.h>
14 #include <linux/param.h>
15 #include <linux/string.h>
17 #include <linux/interrupt.h>
18 #include <linux/time.h>
19 #include <linux/timex.h>
20 #include <linux/kernel_stat.h>
21 #include <linux/mc146818rtc.h>
22 #include <linux/init.h>
24 #include <asm/segment.h>
26 #include <asm/processor.h>
27 #include <asm/nvram.h>
32 static int nvram_as1 = NVRAM_AS1;
33 static int nvram_as0 = NVRAM_AS0;
34 static int nvram_data = NVRAM_DATA;
36 long __init chrp_time_init(void)
38 struct device_node *rtcs;
41 rtcs = find_compatible_devices("rtc", "pnpPNP,b00");
42 if (rtcs == NULL || rtcs->addrs == NULL)
44 base = rtcs->addrs[0].address;
47 nvram_data = base + 1;
52 int __chrp chrp_cmos_clock_read(int addr)
55 outb(addr>>8, nvram_as1);
56 outb(addr, nvram_as0);
57 return (inb(nvram_data));
60 void __chrp chrp_cmos_clock_write(unsigned long val, int addr)
63 outb(addr>>8, nvram_as1);
64 outb(addr, nvram_as0);
65 outb(val, nvram_data);
70 * Set the hardware clock. -- Cort
72 int __chrp chrp_set_rtc_time(unsigned long nowtime)
74 unsigned char save_control, save_freq_select;
79 save_control = chrp_cmos_clock_read(RTC_CONTROL); /* tell the clock it's being set */
81 chrp_cmos_clock_write((save_control|RTC_SET), RTC_CONTROL);
83 save_freq_select = chrp_cmos_clock_read(RTC_FREQ_SELECT); /* stop and reset prescaler */
85 chrp_cmos_clock_write((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
88 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
89 BIN_TO_BCD(tm.tm_sec);
90 BIN_TO_BCD(tm.tm_min);
91 BIN_TO_BCD(tm.tm_hour);
92 BIN_TO_BCD(tm.tm_mon);
93 BIN_TO_BCD(tm.tm_mday);
94 BIN_TO_BCD(tm.tm_year);
96 chrp_cmos_clock_write(tm.tm_sec,RTC_SECONDS);
97 chrp_cmos_clock_write(tm.tm_min,RTC_MINUTES);
98 chrp_cmos_clock_write(tm.tm_hour,RTC_HOURS);
99 chrp_cmos_clock_write(tm.tm_mon,RTC_MONTH);
100 chrp_cmos_clock_write(tm.tm_mday,RTC_DAY_OF_MONTH);
101 chrp_cmos_clock_write(tm.tm_year,RTC_YEAR);
103 /* The following flags have to be released exactly in this order,
104 * otherwise the DS12887 (popular MC146818A clone with integrated
105 * battery and quartz) will not reset the oscillator and will not
106 * update precisely 500 ms later. You won't find this mentioned in
107 * the Dallas Semiconductor data sheets, but who believes data
108 * sheets anyway ... -- Markus Kuhn
110 chrp_cmos_clock_write(save_control, RTC_CONTROL);
111 chrp_cmos_clock_write(save_freq_select, RTC_FREQ_SELECT);
113 if ( (time_state == TIME_ERROR) || (time_state == TIME_BAD) )
114 time_state = TIME_OK;
118 unsigned long __chrp chrp_get_rtc_time(void)
120 unsigned int year, mon, day, hour, min, sec;
123 /* The Linux interpretation of the CMOS clock register contents:
124 * When the Update-In-Progress (UIP) flag goes from 1 to 0, the
125 * RTC registers show the second which has precisely just started.
126 * Let's hope other operating systems interpret the RTC the same way.
129 /* Since the UIP flag is set for about 2.2 ms and the clock
130 * is typically written with a precision of 1 jiffy, trying
131 * to obtain a precision better than a few milliseconds is
132 * an illusion. Only consistency is interesting, this also
133 * allows to use the routine for /dev/rtc without a potential
134 * 1 second kernel busy loop triggered by any reader of /dev/rtc.
137 for ( i = 0; i<1000000; i++) {
138 uip = chrp_cmos_clock_read(RTC_FREQ_SELECT);
139 sec = chrp_cmos_clock_read(RTC_SECONDS);
140 min = chrp_cmos_clock_read(RTC_MINUTES);
141 hour = chrp_cmos_clock_read(RTC_HOURS);
142 day = chrp_cmos_clock_read(RTC_DAY_OF_MONTH);
143 mon = chrp_cmos_clock_read(RTC_MONTH);
144 year = chrp_cmos_clock_read(RTC_YEAR);
145 uip |= chrp_cmos_clock_read(RTC_FREQ_SELECT);
146 if ((uip & RTC_UIP)==0) break;
149 if (!(chrp_cmos_clock_read(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
158 if ((year += 1900) < 1970)
160 return mktime(year, mon, day, hour, min, sec);
164 void __init chrp_calibrate_decr(void)
166 struct device_node *cpu;
167 unsigned int freq, *fp;
169 if (via_calibrate_decr())
173 * The cpu node should have a timebase-frequency property
174 * to tell us the rate at which the decrementer counts.
176 freq = 16666000; /* hardcoded default */
177 cpu = find_type_devices("cpu");
179 fp = (unsigned int *)
180 get_property(cpu, "timebase-frequency", NULL);
184 printk("time_init: decrementer frequency = %u.%.6u MHz\n",
185 freq/1000000, freq%1000000);
186 tb_ticks_per_jiffy = freq / HZ;
187 tb_to_us = mulhwu_scale_factor(freq, 1000000);