patch-2.3.9 linux/arch/mips/dec/time.c

• Lines: 440
• Date: Fri Jun 25 17:40:12 1999
• Orig file: v2.3.8/linux/arch/mips/dec/time.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.3.8/linux/arch/mips/dec/time.c linux/arch/mips/dec/time.c
@@ -0,0 +1,439 @@
+
+/*
+ *  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/init.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/mipsregs.h>
+#include <asm/io.h>
+#include <asm/irq.h>
+
+#include <linux/mc146818rtc.h>
+#include <linux/timex.h>
+
+extern volatile unsigned long lost_ticks;
+
+/*
+ * Change this if you have some constant time drift
+ */
+/* This is the value for the PC-style PICs. */
+/* #define USECS_PER_JIFFY (1000020/HZ) */
+
+/* This is for machines which generate the exact clock. */
+#define USECS_PER_JIFFY (1000000/HZ)
+
+/* Cycle counter value at the previous timer interrupt.. */
+
+static unsigned int timerhi = 0, timerlo = 0;
+
+/*
+ * On MIPS only R4000 and better have a cycle counter.
+ *
+ * FIXME: Does playing with the RP bit in c0_status interfere with this code?
+ */
+static unsigned long do_fast_gettimeoffset(void)
+{
+    u32 count;
+    unsigned long res, tmp;
+
+    /* Last jiffy when do_fast_gettimeoffset() was called. */
+    static unsigned long last_jiffies = 0;
+    unsigned long quotient;
+
+    /*
+     * Cached "1/(clocks per usec)*2^32" value.
+     * It has to be recalculated once each jiffy.
+     */
+    static unsigned long cached_quotient = 0;
+
+    tmp = jiffies;
+
+    quotient = cached_quotient;
+
+    if (last_jiffies != tmp) {
+	last_jiffies = tmp;
+	__asm__(".set\tnoreorder\n\t"
+		".set\tnoat\n\t"
+		".set\tmips3\n\t"
+		"lwu\t%0,%2\n\t"
+		"dsll32\t$1,%1,0\n\t"
+		"or\t$1,$1,%0\n\t"
+		"ddivu\t$0,$1,%3\n\t"
+		"mflo\t$1\n\t"
+		"dsll32\t%0,%4,0\n\t"
+		"nop\n\t"
+		"ddivu\t$0,%0,$1\n\t"
+		"mflo\t%0\n\t"
+		".set\tmips0\n\t"
+		".set\tat\n\t"
+		".set\treorder"
+      :	"=&r"(quotient)
+      :	"r"(timerhi),
+		"m"(timerlo),
+		"r"(tmp),
+		"r"(USECS_PER_JIFFY)
+      :	"$1");
+	cached_quotient = quotient;
+    }
+    /* Get last timer tick in absolute kernel time */
+    count = read_32bit_cp0_register(CP0_COUNT);
+
+    /* .. relative to previous jiffy (32 bits is enough) */
+    count -= timerlo;
+//printk("count: %08lx, %08lx:%08lx\n", count, timerhi, timerlo);
+
+    __asm__("multu\t%1,%2\n\t"
+	    "mfhi\t%0"
+  :	    "=r"(res)
+  :	    "r"(count),
+	    "r"(quotient));
+
+    /*
+     * Due to possible jiffies inconsistencies, we need to check 
+     * the result so that we'll get a timer that is monotonic.
+     */
+    if (res >= USECS_PER_JIFFY)
+	res = USECS_PER_JIFFY - 1;
+
+    return res;
+}
+
+/* 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)
+{
+    /*
+     * This is a kludge until I find a way for the
+     * DECstations without bus cycle counter. HK
+     */
+    return 0;
+}
+
+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_and_cli(flags);
+    *tv = xtime;
+    tv->tv_usec += do_gettimeoffset();
+
+    /*
+     * xtime is atomically updated in timer_bh. lost_ticks is
+     * nonzero if the timer bottom half hasnt executed yet.
+     */
+    if (lost_ticks)
+	tv->tv_usec += USECS_PER_JIFFY;
+
+    restore_flags(flags);
+
+    if (tv->tv_usec >= 1000000) {
+	tv->tv_usec -= 1000000;
+	tv->tv_sec++;
+    }
+}
+
+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 quartz) 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 inline
+ timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+{
+    volatile unsigned char dummy;
+
+    dummy = CMOS_READ(RTC_REG_C);	/* ACK RTC Interrupt */
+    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 */
+}
+
+static void r4k_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+{
+    unsigned int count;
+
+    /*
+     * The cycle counter is only 32 bit which is good for about
+     * a minute at current count rates of upto 150MHz or so.
+     */
+    count = read_32bit_cp0_register(CP0_COUNT);
+    timerhi += (count < timerlo);	/* Wrap around */
+    timerlo = count;
+
+    timer_interrupt(irq, dev_id, regs);
+}
+
+/* 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 */
+}
+
+char cyclecounter_available;
+
+static inline void init_cycle_counter(void)
+{
+    switch (mips_cputype) {
+    case CPU_UNKNOWN:
+    case CPU_R2000:
+    case CPU_R3000:
+    case CPU_R3000A:
+    case CPU_R3041:
+    case CPU_R3051:
+    case CPU_R3052:
+    case CPU_R3081:
+    case CPU_R3081E:
+    case CPU_R6000:
+    case CPU_R6000A:
+    case CPU_R8000:		/* Not shure about that one, play safe */
+	cyclecounter_available = 0;
+	break;
+    case CPU_R4000PC:
+    case CPU_R4000SC:
+    case CPU_R4000MC:
+    case CPU_R4200:
+    case CPU_R4400PC:
+    case CPU_R4400SC:
+    case CPU_R4400MC:
+    case CPU_R4600:
+    case CPU_R10000:
+    case CPU_R4300:
+    case CPU_R4650:
+    case CPU_R4700:
+    case CPU_R5000:
+    case CPU_R5000A:
+    case CPU_R4640:
+    case CPU_NEVADA:
+	cyclecounter_available = 1;
+	break;
+    }
+}
+
+struct irqaction irq0 =
+{timer_interrupt, SA_INTERRUPT, 0,
+ "timer", NULL, NULL};
+
+
+void (*board_time_init) (struct irqaction * irq);
+
+__initfunc(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);
+    }
+    /*
+     * The DECstation RTC is used as a TOY (Time Of Year).
+     * The PROM will reset the year to either '70, '71 or '72.
+     * This hack will only work until Dec 31 2001.
+     */
+    year += 1927;
+
+    xtime.tv_sec = mktime(year, mon, day, hour, min, sec);
+    xtime.tv_usec = 0;
+
+    init_cycle_counter();
+
+    if (cyclecounter_available) {
+	write_32bit_cp0_register(CP0_COUNT, 0);
+	do_gettimeoffset = do_fast_gettimeoffset;
+	irq0.handler = r4k_timer_interrupt;
+    }
+    board_time_init(&irq0);
+}