patch-2.4.10 linux/arch/mips64/sgi-ip32/ip32-timer.c

• Lines: 48
• Date: Sun Sep 9 10:43:02 2001
• Orig file: v2.4.9/linux/arch/mips64/sgi-ip32/ip32-timer.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.9/linux/arch/mips64/sgi-ip32/ip32-timer.c linux/arch/mips64/sgi-ip32/ip32-timer.c
@@ -0,0 +1,47 @@
+/*
+ * IP32 timer calibration
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2001 Keith M Wesolowski
+ */
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <asm/mipsregs.h>
+#include <asm/param.h>
+#include <asm/ip32/crime.h>
+#include <asm/ip32/ip32_ints.h>
+
+extern u32 cc_interval;
+
+/* An arbitrary time; this can be decreased if reliability looks good */
+#define WAIT_MS 10
+#define PER_MHZ (1000000 / 2 / HZ)
+
+void __init ip32_timer_setup (struct irqaction *irq) {
+	u64 crime_time;
+	u32 cc_tick;
+
+	printk("Calibrating system timer... ");
+
+	crime_time = crime_read_64 (CRIME_TIME) & CRIME_TIME_MASK;
+	cc_tick = read_32bit_cp0_register (CP0_COUNT);
+
+	while ((crime_read_64 (CRIME_TIME) & CRIME_TIME_MASK) - crime_time 
+		< WAIT_MS * 1000000 / CRIME_NS_PER_TICK)
+		;
+	cc_tick = read_32bit_cp0_register (CP0_COUNT) - cc_tick;
+	cc_interval = cc_tick / HZ * (1000 / WAIT_MS);
+	/* The round-off seems unnecessary; in testing, the error of the
+	 * above procedure is < 100 ticks, which means it gets filtered
+	 * out by the HZ adjustment. 
+	 */
+	cc_interval = (cc_interval / PER_MHZ) * PER_MHZ;
+
+	printk("%d MHz CPU detected\n", (int) (cc_interval / PER_MHZ));
+
+	setup_irq (CLOCK_IRQ, irq);
+}