patch-2.1.48 linux/arch/ppc/kernel/pmac_time.c

• Lines: 169
• Date: Thu Jul 31 13:09:17 1997
• Orig file: v2.1.47/linux/arch/ppc/kernel/pmac_time.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.1.47/linux/arch/ppc/kernel/pmac_time.c linux/arch/ppc/kernel/pmac_time.c
@@ -0,0 +1,168 @@
+/*
+ * Support for periodic interrupts (100 per second) and for getting
+ * the current time from the RTC on Power Macintoshes.
+ *
+ * At present, we use the decrementer register in the 601 CPU
+ * for our periodic interrupts.  This will probably have to be
+ * changed for other processors.
+ *
+ * Paul Mackerras	August 1996.
+ * Copyright (C) 1996 Paul Mackerras.
+ */
+#include <linux/errno.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/param.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <asm/cuda.h>
+#include <asm/prom.h>
+#include <asm/system.h>
+
+static int get_dec(void);
+static void set_dec(int);
+static unsigned long get_rtc_time(void);
+
+/* Apparently the RTC stores seconds since 1 Jan 1904 */
+#define RTC_OFFSET	2082844800
+
+/* Accessor functions for the decrementer register. */
+static inline int
+get_dec()
+{
+    int ret;
+
+    asm volatile("mfspr %0,22" : "=r" (ret) :);
+    return ret;
+}
+
+static inline void
+set_dec(int val)
+{
+    asm volatile("mtspr 22,%0" : : "r" (val));
+}
+
+/* The decrementer counts down by 128 every 128ns on a 601. */
+#define DECREMENTER_COUNT_601	(1000000000 / HZ)
+#define COUNT_PERIOD_NUM_601	1
+#define COUNT_PERIOD_DEN_601	1000
+
+unsigned decrementer_count;	/* count value for 1e6/HZ microseconds */
+unsigned count_period_num;	/* 1 decrementer count equals */
+unsigned count_period_den;	/* count_period_num / count_period_den us */
+
+/*
+ * This version of gettimeofday has microsecond resolution.
+ */
+void do_gettimeofday(struct timeval *tv)
+{
+	unsigned long flags;
+
+	save_flags(flags);
+	cli();
+	*tv = xtime;
+	tv->tv_usec += (decrementer_count - get_dec())
+	    * count_period_num / count_period_den;
+	if (tv->tv_usec >= 1000000) {
+		tv->tv_usec -= 1000000;
+		tv->tv_sec++;
+	}
+	restore_flags(flags);
+}
+
+void do_settimeofday(struct timeval *tv)
+{
+	unsigned long flags;
+	int frac_tick;
+
+	frac_tick = tv->tv_usec % (1000000 / HZ);
+	save_flags(flags);
+	cli();
+	xtime.tv_sec = tv->tv_sec;
+	xtime.tv_usec = tv->tv_usec - frac_tick;
+	set_dec(frac_tick * count_period_den / count_period_num);
+	restore_flags(flags);
+}
+
+/*
+ * timer_interrupt - gets called when the decrementer overflows,
+ * with interrupts disabled.
+ * We set it up to overflow again in 1/HZ seconds.
+ */
+void timer_interrupt(struct pt_regs * regs)
+{
+	int dval, d;
+
+	while ((dval = get_dec()) < 0) {
+		/*
+		 * Wait for the decrementer to change, then jump
+		 * in and add decrementer_count to its value
+		 * (quickly, before it changes again!)
+		 */
+		while ((d = get_dec()) == dval)
+			;
+		set_dec(d + decrementer_count);
+		do_timer(regs);
+	}
+
+}
+
+void
+time_init(void)
+{
+	struct device_node *cpu;
+	int freq, *fp, divisor;
+
+	if ((_get_PVR() >> 16) == 1) {
+		/* 601 processor: dec counts down by 128 every 128ns */
+		decrementer_count = DECREMENTER_COUNT_601;
+		count_period_num = COUNT_PERIOD_NUM_601;
+		count_period_den = COUNT_PERIOD_DEN_601;
+	} else {
+		/*
+		 * The cpu node should have a timebase-frequency property
+		 * to tell us the rate at which the decrementer counts.
+		 */
+		cpu = find_type_devices("cpu");
+		if (cpu == 0)
+			panic("can't find cpu node in time_init");
+		fp = (int *) get_property(cpu, "timebase-frequency", NULL);
+		if (fp == 0)
+			panic("can't get cpu timebase frequency");
+		freq = *fp * 60;	/* try to make freq/1e6 an integer */
+		divisor = 60;
+		printk("time_init: decrementer frequency = %d/%d\n",
+		       freq, divisor);
+		decrementer_count = freq / HZ / divisor;
+		count_period_num = divisor;
+		count_period_den = freq / 1000000;
+	}
+	set_dec(decrementer_count);
+}
+
+/*
+ * We can't do this in time_init, because via_cuda_init hasn't
+ * been called at that stage.
+ */
+void
+read_rtc_time(void)
+{
+	xtime.tv_sec = get_rtc_time();
+	xtime.tv_usec = 0;
+}
+
+static unsigned long
+get_rtc_time()
+{
+	struct cuda_request req;
+
+	/* Get the time from the RTC */
+	cuda_request(&req, NULL, 2, CUDA_PACKET, CUDA_GET_TIME);
+	while (!req.got_reply)
+		cuda_poll();
+	if (req.reply_len != 7)
+		panic("get_rtc_time: didn't expect %d byte reply",
+		      req.reply_len);
+	return (req.reply[3] << 24) + (req.reply[4] << 16)
+		+ (req.reply[5] << 8) + req.reply[6] - RTC_OFFSET;
+}