MIPS time code rewrite.

1 files changed, 519 insertions, 0 deletions

diff --git a/arch/mips/kernel/old-time.c b/arch/mips/kernel/old-time.c
new file mode 100644
index 000000000..d42ff610e
--- /dev/null
+++ b/arch/mips/kernel/old-time.c
@@ -0,0 +1,519 @@
+/*
+ * Copyright (C) 1991, 1992, 1995  Linus Torvalds
+ * Copyright (C) 1996 - 2000  Ralf Baechle
+ *
+ * This file contains the time handling details for PC-style clocks as
+ * found in some MIPS systems.
+ */
+/**************************************************************************
+ *  9 Nov, 2000.
+ *  Changed init_cycle_counter() routine, use the mips_cpu structure.
+ *
+ *  Kevin D. Kissell, kevink@mips.com and Carsten Langgaard, carstenl@mips
+ *  Copyright (C) 2000 MIPS Technologies, Inc.  All rights reserved.
+ *************************************************************************/
+
+#include <linux/config.h>
+#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 <linux/kernel_stat.h>
+
+#include <asm/bootinfo.h>
+#include <asm/cpu.h>
+#include <asm/mipsregs.h>
+#include <asm/io.h>
+#include <asm/irq.h>
+#include <asm/ddb5074.h>
+
+#include <linux/mc146818rtc.h>
+#include <linux/timex.h>
+
+extern volatile unsigned long wall_jiffies;
+unsigned long r4k_interval;
+extern rwlock_t xtime_lock;
+
+/*
+ * 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, timerlo;
+
+/*
+ * 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;
+	unsigned long quotient;
+
+	/*
+	 * Cached "1/(clocks per usec)*2^32" value.
+	 * It has to be recalculated once each jiffy.
+	 */
+	static unsigned long cached_quotient;
+
+	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;
+}
+
+/* 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;
+
+	static int count_p = LATCH;    /* for the first call after boot */
+	static unsigned long jiffies_p;
+
+	/*
+	 * cache volatile jiffies temporarily; we have IRQs turned off. 
+	 */
+	unsigned long jiffies_t;
+
+	/* timer count may underflow right here */
+	outb_p(0x00, 0x43);	/* latch the count ASAP */
+
+	count = inb_p(0x40);	/* read the latched count */
+
+	/*
+	 * We do this guaranteed double memory access instead of a _p 
+	 * postfix in the previous port access. Wheee, hackady hack
+	 */
+	jiffies_t = jiffies;
+
+	count |= inb_p(0x40) << 8;
+
+	/*
+	 * avoiding timer inconsistencies (they are rare, but they happen)...
+	 * there are two kinds of problems that must be avoided here:
+	 *  1. the timer counter underflows
+	 *  2. hardware problem with the timer, not giving us continuous time,
+	 *     the counter does small "jumps" upwards on some Pentium systems,
+	 *     (see c't 95/10 page 335 for Neptun bug.)
+	 */
+
+	if( jiffies_t == jiffies_p ) {
+		if( count > count_p ) {
+			/* the nutcase */
+
+			outb_p(0x0A, 0x20);
+
+			/* assumption about timer being IRQ1 */
+			if (inb(0x20) & 0x01) {
+				/*
+				 * We cannot detect lost timer interrupts ... 
+				 * well, that's why we call them lost, don't we? :)
+				 * [hmm, on the Pentium and Alpha we can ... sort of]
+				 */
+				count -= LATCH;
+			} else {
+				printk("do_slow_gettimeoffset(): hardware timer problem?\n");
+			}
+		}
+	} else
+		jiffies_p = jiffies_t;
+
+	count_p = count;
+
+	count = ((LATCH-1) - count) * TICK_SIZE;
+	count = (count + LATCH/2) / LATCH;
+
+	return 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;
+
+	read_lock_irqsave (&xtime_lock, flags);
+	*tv = xtime;
+	tv->tv_usec += do_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_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);
+}
+
+/*
+ * 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);
+	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 {
+		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;
+}
+
+/* last time the cmos clock got updated */
+static long last_rtc_update;
+
+/*
+ * 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)
+{
+#ifdef CONFIG_DDB5074
+	static unsigned cnt, period, dist;
+
+	if (cnt == 0 || cnt == dist)
+	    ddb5074_led_d2(1);
+	else if (cnt == 7 || cnt == dist+7)
+	    ddb5074_led_d2(0);
+	
+	if (++cnt > period) {
+	    cnt = 0;
+	    /* The hyperbolic function below modifies the heartbeat period
+	     * length in dependency of the current (5min) load. It goes
+	     * through the points f(0)=126, f(1)=86, f(5)=51,
+	     * f(inf)->30. */
+	     period = ((672<<FSHIFT)/(5*avenrun[0]+(7<<FSHIFT))) + 30;
+	     dist = period / 4;
+	}
+#endif
+	if(!user_mode(regs)) {
+		if (prof_buffer && current->pid) {
+			extern int _stext;
+			unsigned long pc = regs->cp0_epc;
+
+			pc -= (unsigned long) &_stext;
+			pc >>= prof_shift;
+			/*
+			 * Dont ignore out-of-bounds pc values silently,
+			 * put them into the last histogram slot, so if
+			 * present, they will show up as a sharp peak.
+			 */
+			if (pc > prof_len-1)
+				pc = prof_len-1;
+			atomic_inc((atomic_t *)&prof_buffer[pc]);
+		}
+	}
+	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.
+	 */
+	read_lock (&xtime_lock); 
+	if ((time_status & STA_UNSYNC) == 0 &&
+	    xtime.tv_sec > last_rtc_update + 660 &&
+	    xtime.tv_usec >= 500000 - ((unsigned) tick) / 2 &&
+	    xtime.tv_usec <= 500000 + ((unsigned) tick) / 2) {
+	  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); */
+	read_unlock (&xtime_lock); 
+}
+
+static inline 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;
+
+#ifdef CONFIG_SGI_IP22
+	/* Since we don't get anything but r4k timer interrupts, we need to
+	 * set this up so that we'll get one next time. Fortunately since we
+	 * have timerhi/timerlo, we don't care so much if we miss one. So
+	 * we need only ask for the next in r4k_interval counts. On other
+	 * archs we have a real timer, so we don't want this.
+	 */
+	write_32bit_cp0_register (CP0_COMPARE, 
+				  (unsigned long) (count + r4k_interval));
+        kstat.irqs[0][irq]++;
+#endif
+
+	timer_interrupt(irq, dev_id, regs);
+
+	if (!jiffies)
+	{
+		/*
+		 * If jiffies has overflowed in this timer_interrupt we must
+		 * update the timer[hi]/[lo] to make do_fast_gettimeoffset()
+		 * quotient calc still valid. -arca
+		 */
+		timerhi = timerlo = 0;
+	}
+}
+
+void indy_r4k_timer_interrupt (struct pt_regs *regs)
+{
+	static const int INDY_R4K_TIMER_IRQ = 7;
+	r4k_timer_interrupt (INDY_R4K_TIMER_IRQ, NULL, regs);
+}
+
+struct irqaction irq0  = { timer_interrupt, SA_INTERRUPT, 0,
+                                  "timer", NULL, NULL};
+
+
+void (*board_time_init)(struct irqaction *irq);
+
+void __init time_init(void)
+{
+	unsigned int epoch = 0, 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);
+	  }
+
+	/* Attempt to guess the epoch.  This is the same heuristic as in rtc.c so
+	   no stupid things will happen to timekeeping.  Who knows, maybe Ultrix
+  	   also uses 1952 as epoch ...  */
+	if (year > 10 && year < 44) {
+		epoch = 1980;
+	} else if (year < 96) {
+		epoch = 1952;
+	}
+	year += epoch;
+
+	write_lock_irq (&xtime_lock);
+	xtime.tv_sec = mktime(year, mon, day, hour, min, sec);
+	xtime.tv_usec = 0;
+	write_unlock_irq (&xtime_lock);
+
+	if (mips_cpu.options & MIPS_CPU_COUNTER) {
+		write_32bit_cp0_register(CP0_COUNT, 0);
+		do_gettimeoffset = do_fast_gettimeoffset;
+		irq0.handler = r4k_timer_interrupt;
+	}
+
+	board_time_init(&irq0);
+}