patch-2.4.4 linux/arch/arm/mach-ebsa110/time.c

• Lines: 114
• Date: Thu Apr 12 12:20:31 2001
• Orig file: v2.4.3/linux/arch/arm/mach-ebsa110/time.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.3/linux/arch/arm/mach-ebsa110/time.c linux/arch/arm/mach-ebsa110/time.c
@@ -0,0 +1,113 @@
+/*
+ *  linux/arch/arm/mach-ebsa110/time.c
+ *
+ *  Copyright (C) 2001 Russell King
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/sched.h>
+#include <linux/init.h>
+
+#include <asm/io.h>
+
+#define PIT_CTRL		(PIT_BASE + 0x0d)
+#define PIT_T2			(PIT_BASE + 0x09)
+#define PIT_T1			(PIT_BASE + 0x05)
+#define PIT_T0			(PIT_BASE + 0x01)
+
+/*
+ * This is the rate at which your MCLK signal toggles (in Hz)
+ * This was measured on a 10 digit frequency counter sampling
+ * over 1 second.
+ */
+#define MCLK	47894000
+
+/*
+ * This is the rate at which the PIT timers get clocked
+ */
+#define CLKBY7	(MCLK / 7)
+
+/*
+ * If CLKBY7 is larger than this, then we must do software
+ * division of the timer interrupt.
+ */
+#if CLKBY7 > 6553500
+#define DIVISOR	2
+#else
+#define DIVISOR 1
+#endif
+
+/*
+ * This is the counter value
+ */
+#define COUNT	((CLKBY7 + (DIVISOR * HZ / 2)) / (DIVISOR * HZ))
+
+extern unsigned long (*gettimeoffset)(void);
+
+static unsigned long divisor;
+
+/*
+ * Get the time offset from the system PIT.  Note that if we have missed an
+ * interrupt, then the PIT counter will roll over (ie, be negative).
+ * This actually works out to be convenient.
+ */
+static unsigned long ebsa110_gettimeoffset(void)
+{
+	unsigned long offset, count;
+
+	__raw_writeb(0x40, PIT_CTRL);
+	count = __raw_readb(PIT_T1);
+	count |= __raw_readb(PIT_T1) << 8;
+
+	/*
+	 * If count > COUNT, make the number negative.
+	 */
+	if (count > COUNT)
+		count |= 0xffff0000;
+
+	offset = COUNT * (DIVISOR - divisor);
+	offset -= count;
+
+	/*
+	 * `offset' is in units of timer counts.  Convert
+	 * offset to units of microseconds.
+	 */
+	offset = offset * (1000000 / HZ) / (COUNT * DIVISOR);
+
+	return offset;
+}
+
+int ebsa110_reset_timer(void)
+{
+	u32 count;
+
+	/* latch and read timer 1 */
+	__raw_writeb(0x40, PIT_CTRL);
+	count = __raw_readb(PIT_T1);
+	count |= __raw_readb(PIT_T1) << 8;
+
+	count += COUNT;
+
+	__raw_writeb(count & 0xff, PIT_T1);
+	__raw_writeb(count >> 8, PIT_T1);
+
+	if (divisor == 0)
+		divisor = DIVISOR;
+	divisor -= 1;
+	return divisor;
+}
+
+void __init ebsa110_setup_timer(void)
+{
+	/*
+	 * Timer 1, mode 2, LSB/MSB
+	 */
+	__raw_writeb(0x70, PIT_CTRL);
+	__raw_writeb(COUNT & 0xff, PIT_T1);
+	__raw_writeb(COUNT >> 8, PIT_T1);
+	divisor = DIVISOR - 1;
+
+	gettimeoffset = ebsa110_gettimeoffset;
+}