1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
4  *  Copyright (C) 2000, 2003  Maciej W. Rozycki
5  *
6  * This file contains the time handling details for PC-style clocks as
7  * found in some MIPS systems.
8  *
9  */
10 #include <linux/bcd.h>
11 #include <linux/init.h>
12 #include <linux/mc146818rtc.h>
13 #include <linux/param.h>
14 
15 #include <asm/cpu-features.h>
16 #include <asm/ds1287.h>
17 #include <asm/time.h>
18 #include <asm/dec/interrupts.h>
19 #include <asm/dec/ioasic.h>
20 #include <asm/dec/machtype.h>
21 
read_persistent_clock64(struct timespec64 * ts)22 void read_persistent_clock64(struct timespec64 *ts)
23 {
24 	unsigned int year, mon, day, hour, min, sec, real_year;
25 	unsigned long flags;
26 
27 	spin_lock_irqsave(&rtc_lock, flags);
28 
29 	do {
30 		sec = CMOS_READ(RTC_SECONDS);
31 		min = CMOS_READ(RTC_MINUTES);
32 		hour = CMOS_READ(RTC_HOURS);
33 		day = CMOS_READ(RTC_DAY_OF_MONTH);
34 		mon = CMOS_READ(RTC_MONTH);
35 		year = CMOS_READ(RTC_YEAR);
36 		/*
37 		 * The PROM will reset the year to either '72 or '73.
38 		 * Therefore we store the real year separately, in one
39 		 * of unused BBU RAM locations.
40 		 */
41 		real_year = CMOS_READ(RTC_DEC_YEAR);
42 	} while (sec != CMOS_READ(RTC_SECONDS));
43 
44 	spin_unlock_irqrestore(&rtc_lock, flags);
45 
46 	if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
47 		sec = bcd2bin(sec);
48 		min = bcd2bin(min);
49 		hour = bcd2bin(hour);
50 		day = bcd2bin(day);
51 		mon = bcd2bin(mon);
52 		year = bcd2bin(year);
53 	}
54 
55 	year += real_year - 72 + 2000;
56 
57 	ts->tv_sec = mktime64(year, mon, day, hour, min, sec);
58 	ts->tv_nsec = 0;
59 }
60 
61 /*
62  * In order to set the CMOS clock precisely, update_persistent_clock64 has to
63  * be called 500 ms after the second nowtime has started, because when
64  * nowtime is written into the registers of the CMOS clock, it will
65  * jump to the next second precisely 500 ms later.  Check the Dallas
66  * DS1287 data sheet for details.
67  */
update_persistent_clock64(struct timespec64 now)68 int update_persistent_clock64(struct timespec64 now)
69 {
70 	time64_t nowtime = now.tv_sec;
71 	int retval = 0;
72 	int real_seconds, real_minutes, cmos_minutes;
73 	unsigned char save_control, save_freq_select;
74 
75 	/* irq are locally disabled here */
76 	spin_lock(&rtc_lock);
77 	/* tell the clock it's being set */
78 	save_control = CMOS_READ(RTC_CONTROL);
79 	CMOS_WRITE((save_control | RTC_SET), RTC_CONTROL);
80 
81 	/* stop and reset prescaler */
82 	save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
83 	CMOS_WRITE((save_freq_select | RTC_DIV_RESET2), RTC_FREQ_SELECT);
84 
85 	cmos_minutes = CMOS_READ(RTC_MINUTES);
86 	if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
87 		cmos_minutes = bcd2bin(cmos_minutes);
88 
89 	/*
90 	 * since we're only adjusting minutes and seconds,
91 	 * don't interfere with hour overflow. This avoids
92 	 * messing with unknown time zones but requires your
93 	 * RTC not to be off by more than 15 minutes
94 	 */
95 	real_minutes = div_s64_rem(nowtime, 60, &real_seconds);
96 	if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1)
97 		real_minutes += 30;	/* correct for half hour time zone */
98 	real_minutes %= 60;
99 
100 	if (abs(real_minutes - cmos_minutes) < 30) {
101 		if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
102 			real_seconds = bin2bcd(real_seconds);
103 			real_minutes = bin2bcd(real_minutes);
104 		}
105 		CMOS_WRITE(real_seconds, RTC_SECONDS);
106 		CMOS_WRITE(real_minutes, RTC_MINUTES);
107 	} else {
108 		printk_once(KERN_NOTICE
109 		       "set_rtc_mmss: can't update from %d to %d\n",
110 		       cmos_minutes, real_minutes);
111 		retval = -1;
112 	}
113 
114 	/* The following flags have to be released exactly in this order,
115 	 * otherwise the DS1287 will not reset the oscillator and will not
116 	 * update precisely 500 ms later.  You won't find this mentioned
117 	 * in the Dallas Semiconductor data sheets, but who believes data
118 	 * sheets anyway ...                           -- Markus Kuhn
119 	 */
120 	CMOS_WRITE(save_control, RTC_CONTROL);
121 	CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
122 	spin_unlock(&rtc_lock);
123 
124 	return retval;
125 }
126 
plat_time_init(void)127 void __init plat_time_init(void)
128 {
129 	int ioasic_clock = 0;
130 	u32 start, end;
131 	int i = HZ / 8;
132 
133 	/* Set up the rate of periodic DS1287 interrupts. */
134 	ds1287_set_base_clock(HZ);
135 
136 	/* On some I/O ASIC systems we have the I/O ASIC's counter.  */
137 	if (IOASIC)
138 		ioasic_clock = dec_ioasic_clocksource_init() == 0;
139 	if (cpu_has_counter) {
140 		ds1287_timer_state();
141 		while (!ds1287_timer_state())
142 			;
143 
144 		start = read_c0_count();
145 
146 		while (i--)
147 			while (!ds1287_timer_state())
148 				;
149 
150 		end = read_c0_count();
151 
152 		mips_hpt_frequency = (end - start) * 8;
153 		printk(KERN_INFO "MIPS counter frequency %dHz\n",
154 			mips_hpt_frequency);
155 
156 		/*
157 		 * All R4k DECstations suffer from the CP0 Count erratum,
158 		 * so we can't use the timer as a clock source, and a clock
159 		 * event both at a time.  An accurate wall clock is more
160 		 * important than a high-precision interval timer so only
161 		 * use the timer as a clock source, and not a clock event
162 		 * if there's no I/O ASIC counter available to serve as a
163 		 * clock source.
164 		 */
165 		if (!ioasic_clock) {
166 			init_r4k_clocksource();
167 			mips_hpt_frequency = 0;
168 		}
169 	}
170 
171 	ds1287_clockevent_init(dec_interrupt[DEC_IRQ_RTC]);
172 }
173