cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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time.c (4945B)


      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}