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
22void 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 */
68int 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
127void __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