patch-2.4.4 linux/arch/mips/ite-boards/generic/time.c

• Lines: 379
• Date: Fri Apr 13 20:26:07 2001
• Orig file: v2.4.3/linux/arch/mips/ite-boards/generic/time.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.3/linux/arch/mips/ite-boards/generic/time.c linux/arch/mips/ite-boards/generic/time.c
@@ -0,0 +1,378 @@
+/*
+ * Carsten Langgaard, carstenl@mips.com
+ * Copyright (C) 1999,2000 MIPS Technologies, Inc.  All rights reserved.
+ *
+ * ########################################################################
+ *
+ *  This program is free software; you can distribute it and/or modify it
+ *  under the terms of the GNU General Public License (Version 2) as
+ *  published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope it will be useful, but WITHOUT
+ *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ *  for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
+ *
+ * ########################################################################
+ *
+ * Setting up the clock on the MIPS boards.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/kernel_stat.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+
+#include <asm/mipsregs.h>
+#include <asm/ptrace.h>
+#include <asm/it8172/it8172_int.h>
+
+#include <linux/mc146818rtc.h>
+#include <linux/timex.h>
+
+extern void enable_cpu_timer(void);
+extern volatile unsigned long wall_jiffies;
+extern rwlock_t xtime_lock;
+
+unsigned long missed_heart_beats = 0;
+static long last_rtc_update = 0;
+static unsigned long r4k_offset; /* Amount to increment compare reg each time */
+static unsigned long r4k_cur;    /* What counter should be at next timer irq */
+static unsigned int timer_tick_count=0;
+
+static inline void ack_r4ktimer(unsigned long newval)
+{
+	write_32bit_cp0_register(CP0_COMPARE, newval);
+}
+
+
+/*
+ * 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.
+ *
+ * BUG: This routine does not handle hour overflow properly; it just
+ *      sets the minutes. Usually you won't notice until after reboot!
+ */
+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);
+
+	/*
+	 * 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) {
+		CMOS_WRITE(real_seconds,RTC_SECONDS);
+		CMOS_WRITE(real_minutes,RTC_MINUTES);
+	} else {
+		printk(KERN_WARNING
+		       "set_rtc_mmss: can't update from %d to %d\n",
+		       cmos_minutes, real_minutes);
+ 		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;
+}
+
+
+/*
+ * There are a lot of conceptually broken versions of the MIPS timer interrupt
+ * handler floating around.  This one is rather different, but the algorithm
+ * is provably more robust.
+ */
+void mips_timer_interrupt(struct pt_regs *regs)
+{
+	if (r4k_offset == 0)
+		goto null;
+
+	do {
+		kstat.irqs[0][MIPS_CPU_TIMER_IRQ]++;
+		do_timer(regs);
+
+		/* Historical comment/code:
+ 		 * RTC time of day s updated approx. every 11 
+ 		 * minutes.  Because of how the numbers work out 
+ 		 * we need to make absolutely sure we do this update
+ 		 * within 500ms before the * next second starts, 
+ 		 * thus the following code.
+ 		 */
+		read_lock(&xtime_lock);
+		if ((time_status & STA_UNSYNC) == 0 
+		    && 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 {
+				/* do it again in 60 s */
+	    			last_rtc_update = xtime.tv_sec - 600; 
+			}
+		read_unlock(&xtime_lock);
+
+		r4k_cur += r4k_offset;
+		ack_r4ktimer(r4k_cur);
+
+	} while (((unsigned long)read_32bit_cp0_register(CP0_COUNT)
+	         - r4k_cur) < 0x7fffffff);
+
+	return;
+
+null:
+	ack_r4ktimer(0);
+}
+
+/* 
+ * Figure out the r4k offset, the amount to increment the compare
+ * register for each time tick. 
+ * Use the RTC to calculate offset.
+ */
+static unsigned long __init cal_r4koff(void)
+{
+	unsigned long count;
+	unsigned int flags;
+
+	__save_and_cli(flags);
+
+	/* Start counter exactly on falling edge of update flag */
+	while (CMOS_READ(RTC_REG_A) & RTC_UIP);
+	while (!(CMOS_READ(RTC_REG_A) & RTC_UIP));
+
+	/* Start r4k counter. */
+	write_32bit_cp0_register(CP0_COUNT, 0);
+
+	/* Read counter exactly on falling edge of update flag */
+	while (CMOS_READ(RTC_REG_A) & RTC_UIP);
+	while (!(CMOS_READ(RTC_REG_A) & RTC_UIP));
+
+	count = read_32bit_cp0_register(CP0_COUNT);
+
+	/* restore interrupts */
+	__restore_flags(flags);
+		
+	return (count / HZ);
+}
+
+static unsigned long __init get_mips_time(void)
+{
+	unsigned int year, mon, day, hour, min, sec;
+	unsigned char save_control;
+
+	save_control = CMOS_READ(RTC_CONTROL);
+
+	/* Freeze it. */
+	CMOS_WRITE(save_control | RTC_SET, RTC_CONTROL);
+
+	/* Read regs. */
+	sec = CMOS_READ(RTC_SECONDS);
+	min = CMOS_READ(RTC_MINUTES);
+	hour = CMOS_READ(RTC_HOURS);
+
+	if (!(save_control & RTC_24H))
+	{
+		if ((hour & 0xf) == 0xc)
+		        hour &= 0x80;
+	        if (hour & 0x80)
+		        hour = (hour & 0xf) + 12;     
+	}
+	day = CMOS_READ(RTC_DAY_OF_MONTH);
+	mon = CMOS_READ(RTC_MONTH);
+	year = CMOS_READ(RTC_YEAR);
+
+	/* Unfreeze clock. */
+	CMOS_WRITE(save_control, RTC_CONTROL);
+
+	if ((year += 1900) < 1970)
+	        year += 100;
+
+	return mktime(year, mon, day, hour, min, sec);
+}
+
+void __init time_init(void)
+{
+        unsigned int est_freq, flags;
+
+        /* Set Data mode - binary. */ 
+        CMOS_WRITE(CMOS_READ(RTC_CONTROL) | RTC_DM_BINARY, RTC_CONTROL);
+
+	printk("calculating r4koff... ");
+	r4k_offset = cal_r4koff();
+	printk("%08lx(%d)\n", r4k_offset, (int) r4k_offset);
+
+	est_freq = 2*r4k_offset*HZ;	
+	est_freq += 5000;    /* round */
+	est_freq -= est_freq%10000;
+	printk("CPU frequency %d.%02d MHz\n", est_freq/1000000, 
+	       (est_freq%1000000)*100/1000000);
+	r4k_cur = (read_32bit_cp0_register(CP0_COUNT) + r4k_offset);
+
+	write_32bit_cp0_register(CP0_COMPARE, r4k_cur);
+
+	enable_cpu_timer();
+
+	/* Read time from the RTC chipset. */
+	write_lock_irqsave (&xtime_lock, flags);
+	xtime.tv_sec = get_mips_time();
+	xtime.tv_usec = 0;
+	write_unlock_irqrestore(&xtime_lock, flags);
+}
+
+/* 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;
+
+/*
+ * 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 (tmp && 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;
+
+	__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;
+}
+
+void do_gettimeofday(struct timeval *tv)
+{
+	unsigned int flags;
+
+	read_lock_irqsave (&xtime_lock, flags);
+	*tv = xtime;
+	tv->tv_usec += do_fast_gettimeoffset();
+
+	/*
+	 * xtime is atomically updated in timer_bh. jiffies - wall_jiffies
+	 * is nonzero if the timer bottom half hasnt executed yet.
+	 */
+	if (jiffies - wall_jiffies)
+		tv->tv_usec += USECS_PER_JIFFY;
+
+	read_unlock_irqrestore (&xtime_lock, flags);
+
+	if (tv->tv_usec >= 1000000) {
+		tv->tv_usec -= 1000000;
+		tv->tv_sec++;
+	}
+}
+
+void do_settimeofday(struct timeval *tv)
+{
+	write_lock_irq (&xtime_lock);
+
+	/* 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_fast_gettimeoffset();
+
+	if (tv->tv_usec < 0) {
+		tv->tv_usec += 1000000;
+		tv->tv_sec--;
+	}
+
+	xtime = *tv;
+	time_adjust = 0;		/* stop active adjtime() */
+	time_status |= STA_UNSYNC;
+	time_maxerror = NTP_PHASE_LIMIT;
+	time_esterror = NTP_PHASE_LIMIT;
+
+	write_unlock_irq (&xtime_lock);
+}