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Diffstat (limited to 'arch/mips/kernel/time.c')
| -rw-r--r-- | arch/mips/kernel/time.c | 292 |
1 files changed, 292 insertions, 0 deletions
diff --git a/arch/mips/kernel/time.c b/arch/mips/kernel/time.c new file mode 100644 index 000000000..2dd1d54ee --- /dev/null +++ b/arch/mips/kernel/time.c @@ -0,0 +1,292 @@ +/* + * linux/arch/mips/kernel/time.c + * + * Copyright (C) 1991, 1992, 1995 Linus Torvalds + * + * This file contains the time handling details for PC-style clocks as + * found in some MIPS systems. + */ +#include <linux/errno.h> +#include <linux/sched.h> +#include <linux/kernel.h> +#include <linux/param.h> +#include <linux/string.h> +#include <linux/mm.h> +#include <linux/interrupt.h> + +#include <asm/bootinfo.h> +#include <asm/uaccess.h> +#include <asm/io.h> +#include <asm/irq.h> + +#include <linux/mc146818rtc.h> +#include <linux/timex.h> + +/* This function must be called with interrupts disabled + * It was inspired by Steve McCanne's microtime-i386 for BSD. -- jrs + * + * However, the pc-audio speaker driver changes the divisor so that + * it gets interrupted rather more often - it loads 64 into the + * counter rather than 11932! This has an adverse impact on + * do_gettimeoffset() -- it stops working! What is also not + * good is that the interval that our timer function gets called + * is no longer 10.0002 ms, but 9.9767 ms. To get around this + * would require using a different timing source. Maybe someone + * could use the RTC - I know that this can interrupt at frequencies + * ranging from 8192Hz to 2Hz. If I had the energy, I'd somehow fix + * it so that at startup, the timer code in sched.c would select + * using either the RTC or the 8253 timer. The decision would be + * based on whether there was any other device around that needed + * to trample on the 8253. I'd set up the RTC to interrupt at 1024 Hz, + * and then do some jiggery to have a version of do_timer that + * advanced the clock by 1/1024 s. Every time that reached over 1/100 + * of a second, then do all the old code. If the time was kept correct + * then do_gettimeoffset could just return 0 - there is no low order + * divider that can be accessed. + * + * Ideally, you would be able to use the RTC for the speaker driver, + * but it appears that the speaker driver really needs interrupt more + * often than every 120 us or so. + * + * Anyway, this needs more thought.... pjsg (1993-08-28) + * + * If you are really that interested, you should be reading + * comp.protocols.time.ntp! + */ + +#define TICK_SIZE tick + +static unsigned long do_slow_gettimeoffset(void) +{ + int count; + unsigned long offset = 0; + + /* timer count may underflow right here */ + outb_p(0x00, 0x43); /* latch the count ASAP */ + count = inb_p(0x40); /* read the latched count */ + count |= inb(0x40) << 8; + /* we know probability of underflow is always MUCH less than 1% */ + if (count > (LATCH - LATCH/100)) { + /* check for pending timer interrupt */ + outb_p(0x0a, 0x20); + if (inb(0x20) & 1) + offset = TICK_SIZE; + } + count = ((LATCH-1) - count) * TICK_SIZE; + count = (count + LATCH/2) / LATCH; + return offset + count; +} + +static unsigned long (*do_gettimeoffset)(void) = do_slow_gettimeoffset; + +/* + * This version of gettimeofday has near microsecond resolution. + */ +void do_gettimeofday(struct timeval *tv) +{ + unsigned long flags; + + save_flags(flags); + cli(); + *tv = xtime; + tv->tv_usec += do_gettimeoffset(); + if (tv->tv_usec >= 1000000) { + tv->tv_usec -= 1000000; + tv->tv_sec++; + } + restore_flags(flags); +} + +void do_settimeofday(struct timeval *tv) +{ + cli(); + /* This is revolting. We need to set the xtime.tv_usec + * correctly. However, the value in this location is + * is value at the last tick. + * Discover what correction gettimeofday + * would have done, and then undo it! + */ + tv->tv_usec -= do_gettimeoffset(); + + if (tv->tv_usec < 0) { + tv->tv_usec += 1000000; + tv->tv_sec--; + } + + xtime = *tv; + time_state = TIME_BAD; + time_maxerror = MAXPHASE; + time_esterror = MAXPHASE; + sti(); +} + +/* + * In order to set the CMOS clock precisely, set_rtc_mmss has to be + * called 500 ms after the second nowtime has started, because when + * nowtime is written into the registers of the CMOS clock, it will + * jump to the next second precisely 500 ms later. Check the Motorola + * MC146818A or Dallas DS12887 data sheet for details. + */ +static int set_rtc_mmss(unsigned long nowtime) +{ + int retval = 0; + int real_seconds, real_minutes, cmos_minutes; + unsigned char save_control, save_freq_select; + + save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */ + CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL); + + save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset prescaler */ + CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT); + + cmos_minutes = CMOS_READ(RTC_MINUTES); + if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) + BCD_TO_BIN(cmos_minutes); + + /* + * since we're only adjusting minutes and seconds, + * don't interfere with hour overflow. This avoids + * messing with unknown time zones but requires your + * RTC not to be off by more than 15 minutes + */ + real_seconds = nowtime % 60; + real_minutes = nowtime / 60; + if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1) + real_minutes += 30; /* correct for half hour time zone */ + real_minutes %= 60; + + if (abs(real_minutes - cmos_minutes) < 30) { + if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) { + BIN_TO_BCD(real_seconds); + BIN_TO_BCD(real_minutes); + } + CMOS_WRITE(real_seconds,RTC_SECONDS); + CMOS_WRITE(real_minutes,RTC_MINUTES); + } else + retval = -1; + + /* The following flags have to be released exactly in this order, + * otherwise the DS12887 (popular MC146818A clone with integrated + * battery and crystal) will not reset the oscillator and will not + * update precisely 500 ms later. You won't find this mentioned in + * the Dallas Semiconductor data sheets, but who believes data + * sheets anyway ... -- Markus Kuhn + */ + CMOS_WRITE(save_control, RTC_CONTROL); + CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT); + + return retval; +} + +/* last time the cmos clock got updated */ +static long last_rtc_update = 0; + +/* + * timer_interrupt() needs to keep up the real-time clock, + * as well as call the "do_timer()" routine every clocktick + */ +static void timer_interrupt(int irq, void *dev_id, struct pt_regs * regs) +{ + do_timer(regs); + + /* + * If we have an externally synchronized Linux clock, then update + * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be + * called as close as possible to 500 ms before the new second starts. + */ + if (time_state != TIME_BAD && xtime.tv_sec > last_rtc_update + 660 && + xtime.tv_usec > 500000 - (tick >> 1) && + xtime.tv_usec < 500000 + (tick >> 1)) + if (set_rtc_mmss(xtime.tv_sec) == 0) + last_rtc_update = xtime.tv_sec; + else + last_rtc_update = xtime.tv_sec - 600; /* do it again in 60 s */ + /* As we return to user mode fire off the other CPU schedulers.. this is + basically because we don't yet share IRQ's around. This message is + rigged to be safe on the 386 - basically it's a hack, so don't look + closely for now.. */ + smp_message_pass(MSG_ALL_BUT_SELF, MSG_RESCHEDULE, 0L, 0); +} + +/* Converts Gregorian date to seconds since 1970-01-01 00:00:00. + * Assumes input in normal date format, i.e. 1980-12-31 23:59:59 + * => year=1980, mon=12, day=31, hour=23, min=59, sec=59. + * + * [For the Julian calendar (which was used in Russia before 1917, + * Britain & colonies before 1752, anywhere else before 1582, + * and is still in use by some communities) leave out the + * -year/100+year/400 terms, and add 10.] + * + * This algorithm was first published by Gauss (I think). + * + * WARNING: this function will overflow on 2106-02-07 06:28:16 on + * machines were long is 32-bit! (However, as time_t is signed, we + * will already get problems at other places on 2038-01-19 03:14:08) + */ +static inline unsigned long mktime(unsigned int year, unsigned int mon, + unsigned int day, unsigned int hour, + unsigned int min, unsigned int sec) +{ + if (0 >= (int) (mon -= 2)) { /* 1..12 -> 11,12,1..10 */ + mon += 12; /* Puts Feb last since it has leap day */ + year -= 1; + } + return ((( + (unsigned long)(year/4 - year/100 + year/400 + 367*mon/12 + day) + + year*365 - 719499 + )*24 + hour /* now have hours */ + )*60 + min /* now have minutes */ + )*60 + sec; /* finally seconds */ +} + +static struct irqaction irq0 = { timer_interrupt, 0, 0, "timer", NULL, NULL}; + +void (*board_time_init)(struct irqaction *irq); + +void time_init(void) +{ + unsigned int year, mon, day, hour, min, sec; + int i; + + /* The Linux interpretation of the CMOS clock register contents: + * When the Update-In-Progress (UIP) flag goes from 1 to 0, the + * RTC registers show the second which has precisely just started. + * Let's hope other operating systems interpret the RTC the same way. + */ + /* read RTC exactly on falling edge of update flag */ + for (i = 0 ; i < 1000000 ; i++) /* may take up to 1 second... */ + if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) + break; + for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */ + if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)) + break; + do { /* Isn't this overkill ? UIP above should guarantee consistency */ + sec = CMOS_READ(RTC_SECONDS); + min = CMOS_READ(RTC_MINUTES); + hour = CMOS_READ(RTC_HOURS); + day = CMOS_READ(RTC_DAY_OF_MONTH); + mon = CMOS_READ(RTC_MONTH); + year = CMOS_READ(RTC_YEAR); + } while (sec != CMOS_READ(RTC_SECONDS)); + if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) + { + BCD_TO_BIN(sec); + BCD_TO_BIN(min); + BCD_TO_BIN(hour); + BCD_TO_BIN(day); + BCD_TO_BIN(mon); + BCD_TO_BIN(year); + } +#if 0 /* the IBM way */ + if ((year += 1900) < 1970) + year += 100; +#else + /* true for all MIPS machines? */ + year += 1980; +#endif + xtime.tv_sec = mktime(year, mon, day, hour, min, sec); + xtime.tv_usec = 0; + + /* FIXME: If we have the CPU hardware time counters, use them */ + board_time_init(&irq0); +} |