xref: /openbmc/linux/arch/x86/kernel/rtc.c (revision 643d1f7f)
1 /*
2  * RTC related functions
3  */
4 #include <linux/acpi.h>
5 #include <linux/bcd.h>
6 #include <linux/mc146818rtc.h>
7 
8 #include <asm/time.h>
9 #include <asm/vsyscall.h>
10 
11 #ifdef CONFIG_X86_32
12 # define CMOS_YEARS_OFFS 1900
13 /*
14  * This is a special lock that is owned by the CPU and holds the index
15  * register we are working with.  It is required for NMI access to the
16  * CMOS/RTC registers.  See include/asm-i386/mc146818rtc.h for details.
17  */
18 volatile unsigned long cmos_lock = 0;
19 EXPORT_SYMBOL(cmos_lock);
20 #else
21 /*
22  * x86-64 systems only exists since 2002.
23  * This will work up to Dec 31, 2100
24  */
25 # define CMOS_YEARS_OFFS 2000
26 #endif
27 
28 DEFINE_SPINLOCK(rtc_lock);
29 EXPORT_SYMBOL(rtc_lock);
30 
31 /*
32  * In order to set the CMOS clock precisely, set_rtc_mmss has to be
33  * called 500 ms after the second nowtime has started, because when
34  * nowtime is written into the registers of the CMOS clock, it will
35  * jump to the next second precisely 500 ms later. Check the Motorola
36  * MC146818A or Dallas DS12887 data sheet for details.
37  *
38  * BUG: This routine does not handle hour overflow properly; it just
39  *      sets the minutes. Usually you'll only notice that after reboot!
40  */
41 int mach_set_rtc_mmss(unsigned long nowtime)
42 {
43 	int retval = 0;
44 	int real_seconds, real_minutes, cmos_minutes;
45 	unsigned char save_control, save_freq_select;
46 
47 	 /* tell the clock it's being set */
48 	save_control = CMOS_READ(RTC_CONTROL);
49 	CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
50 
51 	/* stop and reset prescaler */
52 	save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
53 	CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
54 
55 	cmos_minutes = CMOS_READ(RTC_MINUTES);
56 	if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
57 		BCD_TO_BIN(cmos_minutes);
58 
59 	/*
60 	 * since we're only adjusting minutes and seconds,
61 	 * don't interfere with hour overflow. This avoids
62 	 * messing with unknown time zones but requires your
63 	 * RTC not to be off by more than 15 minutes
64 	 */
65 	real_seconds = nowtime % 60;
66 	real_minutes = nowtime / 60;
67 	/* correct for half hour time zone */
68 	if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
69 		real_minutes += 30;
70 	real_minutes %= 60;
71 
72 	if (abs(real_minutes - cmos_minutes) < 30) {
73 		if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
74 			BIN_TO_BCD(real_seconds);
75 			BIN_TO_BCD(real_minutes);
76 		}
77 		CMOS_WRITE(real_seconds,RTC_SECONDS);
78 		CMOS_WRITE(real_minutes,RTC_MINUTES);
79 	} else {
80 		printk(KERN_WARNING
81 		       "set_rtc_mmss: can't update from %d to %d\n",
82 		       cmos_minutes, real_minutes);
83 		retval = -1;
84 	}
85 
86 	/* The following flags have to be released exactly in this order,
87 	 * otherwise the DS12887 (popular MC146818A clone with integrated
88 	 * battery and quartz) will not reset the oscillator and will not
89 	 * update precisely 500 ms later. You won't find this mentioned in
90 	 * the Dallas Semiconductor data sheets, but who believes data
91 	 * sheets anyway ...                           -- Markus Kuhn
92 	 */
93 	CMOS_WRITE(save_control, RTC_CONTROL);
94 	CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
95 
96 	return retval;
97 }
98 
99 unsigned long mach_get_cmos_time(void)
100 {
101 	unsigned int year, mon, day, hour, min, sec, century = 0;
102 
103 	/*
104 	 * If UIP is clear, then we have >= 244 microseconds before
105 	 * RTC registers will be updated.  Spec sheet says that this
106 	 * is the reliable way to read RTC - registers. If UIP is set
107 	 * then the register access might be invalid.
108 	 */
109 	while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
110 		cpu_relax();
111 
112 	sec = CMOS_READ(RTC_SECONDS);
113 	min = CMOS_READ(RTC_MINUTES);
114 	hour = CMOS_READ(RTC_HOURS);
115 	day = CMOS_READ(RTC_DAY_OF_MONTH);
116 	mon = CMOS_READ(RTC_MONTH);
117 	year = CMOS_READ(RTC_YEAR);
118 
119 #if defined(CONFIG_ACPI) && defined(CONFIG_X86_64)
120 	/* CHECKME: Is this really 64bit only ??? */
121 	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
122 	    acpi_gbl_FADT.century)
123 		century = CMOS_READ(acpi_gbl_FADT.century);
124 #endif
125 
126 	if (RTC_ALWAYS_BCD || !(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY)) {
127 		BCD_TO_BIN(sec);
128 		BCD_TO_BIN(min);
129 		BCD_TO_BIN(hour);
130 		BCD_TO_BIN(day);
131 		BCD_TO_BIN(mon);
132 		BCD_TO_BIN(year);
133 	}
134 
135 	if (century) {
136 		BCD_TO_BIN(century);
137 		year += century * 100;
138 		printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
139 	} else {
140 		year += CMOS_YEARS_OFFS;
141 		if (year < 1970)
142 			year += 100;
143 	}
144 
145 	return mktime(year, mon, day, hour, min, sec);
146 }
147 
148 /* Routines for accessing the CMOS RAM/RTC. */
149 unsigned char rtc_cmos_read(unsigned char addr)
150 {
151 	unsigned char val;
152 
153 	lock_cmos_prefix(addr);
154 	outb_p(addr, RTC_PORT(0));
155 	val = inb_p(RTC_PORT(1));
156 	lock_cmos_suffix(addr);
157 	return val;
158 }
159 EXPORT_SYMBOL(rtc_cmos_read);
160 
161 void rtc_cmos_write(unsigned char val, unsigned char addr)
162 {
163 	lock_cmos_prefix(addr);
164 	outb_p(addr, RTC_PORT(0));
165 	outb_p(val, RTC_PORT(1));
166 	lock_cmos_suffix(addr);
167 }
168 EXPORT_SYMBOL(rtc_cmos_write);
169 
170 static int set_rtc_mmss(unsigned long nowtime)
171 {
172 	int retval;
173 	unsigned long flags;
174 
175 	spin_lock_irqsave(&rtc_lock, flags);
176 	retval = set_wallclock(nowtime);
177 	spin_unlock_irqrestore(&rtc_lock, flags);
178 
179 	return retval;
180 }
181 
182 /* not static: needed by APM */
183 unsigned long read_persistent_clock(void)
184 {
185 	unsigned long retval, flags;
186 
187 	spin_lock_irqsave(&rtc_lock, flags);
188 	retval = get_wallclock();
189 	spin_unlock_irqrestore(&rtc_lock, flags);
190 
191 	return retval;
192 }
193 
194 int update_persistent_clock(struct timespec now)
195 {
196 	return set_rtc_mmss(now.tv_sec);
197 }
198 
199 unsigned long long native_read_tsc(void)
200 {
201 	return __native_read_tsc();
202 }
203 EXPORT_SYMBOL(native_read_tsc);
204 
205