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
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 */
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
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
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