Microsecond timers for Indy. From Keith Wesolowsky.

4 files changed, 115 insertions, 15 deletions

diff --git a/arch/mips/sgi/kernel/Makefile b/arch/mips/sgi/kernel/Makefile
index 760e9fe51..6eb3f1775 100644
--- a/arch/mips/sgi/kernel/Makefile
+++ b/arch/mips/sgi/kernel/Makefile
@@ -1,4 +1,4 @@
-# $Id: Makefile,v 1.7 1999/05/07 18:00:16 ulfc Exp $
+#
 # Makefile for the SGI specific kernel interface routines
 # under Linux.
 #
@@ -14,7 +14,7 @@
 	$(CC) $(CFLAGS) -c $< -o $*.o
 
 OBJS  = indy_mc.o indy_sc.o indy_hpc.o indy_int.o indy_rtc.o \
-        system.o indy_timer.o indyIRQ.o reset.o setup.o time.o
+        system.o indyIRQ.o reset.o setup.o time.o
 ifdef CONFIG_SGI_PROM_CONSOLE
 OBJS += promcon.o
 endif
diff --git a/arch/mips/sgi/kernel/indyIRQ.S b/arch/mips/sgi/kernel/indyIRQ.S
index fd8e2a1dd..14d20f044 100644
--- a/arch/mips/sgi/kernel/indyIRQ.S
+++ b/arch/mips/sgi/kernel/indyIRQ.S
@@ -1,4 +1,4 @@
-/* $Id: indyIRQ.S,v 1.3 1998/03/22 23:27:17 ralf Exp $
+/*
  * indyIRQ.S: Interrupt exception dispatch code for FullHouse and
  *            Guiness.
  *
@@ -67,7 +67,7 @@
 
 	/* Wheee, a timer interrupt. */
 	move	a0, sp
-	jal	indy_timer_interrupt
+	jal	indy_r4k_timer_interrupt
 	 nop				# delay slot
 
 	j	ret_from_irq
diff --git a/arch/mips/sgi/kernel/setup.c b/arch/mips/sgi/kernel/setup.c
index feefa10b2..afd52c343 100644
--- a/arch/mips/sgi/kernel/setup.c
+++ b/arch/mips/sgi/kernel/setup.c
@@ -1,5 +1,4 @@
-/* $Id: setup.c,v 1.29 2000/01/27 01:05:23 ralf Exp $
- *
+/*
  * setup.c: SGI specific setup, including init of the feature struct.
  *
  * Copyright (C) 1996 David S. Miller (dm@engr.sgi.com)
@@ -37,6 +36,8 @@ static int remote_debug = 0;
 extern void console_setup(char *);
 #endif
 
+extern unsigned long r4k_interval; /* Cycle counter ticks per 1/HZ seconds */
+
 extern struct rtc_ops indy_rtc_ops;
 void indy_reboot_setup(void);
 void sgi_volume_set(unsigned char);
@@ -136,6 +137,98 @@ int __init page_is_ram(unsigned long pagenr)
 	return 0;
 }
 
+void (*board_time_init)(struct irqaction *irq);
+
+static unsigned long dosample(volatile unsigned char *tcwp,
+                              volatile unsigned char *tc2p)
+{
+        unsigned long ct0, ct1;
+        unsigned char msb, lsb;
+
+        /* Start the counter. */
+        *tcwp = (SGINT_TCWORD_CNT2 | SGINT_TCWORD_CALL | SGINT_TCWORD_MRGEN);
+        *tc2p = (SGINT_TCSAMP_COUNTER & 0xff);
+        *tc2p = (SGINT_TCSAMP_COUNTER >> 8);
+
+        /* Get initial counter invariant */
+        ct0 = read_32bit_cp0_register(CP0_COUNT);
+
+        /* Latch and spin until top byte of counter2 is zero */
+        do {
+                *tcwp = (SGINT_TCWORD_CNT2 | SGINT_TCWORD_CLAT);
+                lsb = *tc2p;
+                msb = *tc2p;
+                ct1 = read_32bit_cp0_register(CP0_COUNT);
+        } while(msb);
+
+        /* Stop the counter. */
+        *tcwp = (SGINT_TCWORD_CNT2 | SGINT_TCWORD_CALL | SGINT_TCWORD_MSWST);
+
+        /* Return the difference, this is how far the r4k counter increments
+         * for every 1/HZ seconds. We round off the the nearest 1 MHz of
+	 * master clock (= 1000000 / 100 / 2 = 5000 count).
+         */
+        return ((ct1 - ct0) / 5000) * 5000;
+}
+
+#define ALLINTS (IE_IRQ0 | IE_IRQ1 | IE_IRQ2 | IE_IRQ3 | IE_IRQ4 | IE_IRQ5)
+
+void sgi_time_init (struct irqaction *irq) {
+	/* Here we need to calibrate the cycle counter to at least be close.
+	 * We don't need to actually register the irq handler because that's
+	 * all done in indyIRQ.S.
+	 */
+        struct sgi_ioc_timers *p;
+        volatile unsigned char *tcwp, *tc2p;
+	unsigned long r4k_ticks[3];
+	unsigned long r4k_next;
+
+        /* Figure out the r4k offset, the algorithm is very simple
+         * and works in _all_ cases as long as the 8254 counter
+         * register itself works ok (as an interrupt driving timer
+         * it does not because of bug, this is why we are using
+         * the onchip r4k counter/compare register to serve this
+         * purpose, but for r4k_offset calculation it will work
+         * ok for us).  There are other very complicated ways
+         * of performing this calculation but this one works just
+         * fine so I am not going to futz around. ;-)
+         */
+        p = ioc_timers;
+        tcwp = &p->tcword;
+        tc2p = &p->tcnt2;
+
+        printk("Calibrating system timer... ");
+        dosample(tcwp, tc2p);                   /* First sample. */
+        dosample(tcwp, tc2p);                   /* Eat one.     */
+        r4k_ticks[0] = dosample(tcwp, tc2p);      /* Second sample. */
+	dosample(tcwp, tc2p);			/* Eat another. */
+	r4k_ticks[1] += dosample (tcwp, tc2p);	/* Third sample. */
+
+	if (r4k_ticks[0] != r4k_ticks[1]) {
+		printk ("warning: timer counts differ, retrying...");
+		dosample (tcwp, tc2p);
+		r4k_ticks[2] = dosample (tcwp, tc2p);
+		if (r4k_ticks[2] == r4k_ticks[0] 
+		    || r4k_ticks[2] == r4k_ticks[1])
+			r4k_interval = r4k_ticks[2];
+		else {
+			printk ("disagreement, using average...");
+			r4k_interval = (r4k_ticks[0] + r4k_ticks[1] 
+					+ r4k_ticks[2]) / 3;
+		}
+	} else
+		r4k_interval = r4k_ticks[0];
+
+        printk("%d [%d.%02d MHz CPU]\n", (int) r4k_interval, 
+		(int) (r4k_interval / 5000), (int) (r4k_interval % 5000) / 50);
+
+	/* Set ourselves up for future interrupts */
+        r4k_next = (read_32bit_cp0_register(CP0_COUNT) + r4k_interval);
+        write_32bit_cp0_register(CP0_COMPARE, r4k_next);
+        set_cp0_status(ST0_IM, ALLINTS);
+	sti ();
+}
+
 void __init sgi_setup(void)
 {
 #ifdef CONFIG_SERIAL_CONSOLE
@@ -147,6 +240,7 @@ void __init sgi_setup(void)
 
 
 	irq_setup = sgi_irq_setup;
+	board_time_init = sgi_time_init;
 
 	/* Init the INDY HPC I/O controller.  Need to call this before
 	 * fucking with the memory controller because it needs to know the
diff --git a/arch/mips/sgi/kernel/time.c b/arch/mips/sgi/kernel/time.c
index 355f1c471..ea85b75db 100644
--- a/arch/mips/sgi/kernel/time.c
+++ b/arch/mips/sgi/kernel/time.c
@@ -1,15 +1,21 @@
-/* $Id: time.c,v 1.2 1998/04/05 11:24:00 ralf Exp $
- * time.c: Generic SGI time_init() code, this will dispatch to the
- *         appropriate per-architecture time/counter init code.
+/*
+ * time.c: Generic SGI handler for (spurious) 8254 interrupts
  *
  * Copyright (C) 1996 David S. Miller (dm@engr.sgi.com)
  */
-#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/kernel_stat.h>
+#include <asm/sgialib.h>
 
-extern void indy_timer_init(void);
-
-void __init time_init(void)
+void indy_8254timer_irq(void)
 {
-	/* XXX assume INDY for now XXX */
-	indy_timer_init();
+        int cpu = smp_processor_id();
+        int irq = 4;
+
+        irq_enter(cpu);
+        kstat.irqs[0][irq]++;
+        printk("indy_8254timer_irq: Whoops, should not have gotten this IRQ\n");
+        prom_getchar();
+        prom_imode();
+        irq_exit(cpu);
 }