Implement SC520 timers

Signed-off-by: Graeme Russ <graeme.russ at gmail.com>

1 files changed, 102 insertions, 0 deletions

diff --git a/lib_i386/pcat_timer.c b/lib_i386/pcat_timer.c
new file mode 100644
index 0000000..e282f64
--- /dev/null
+++ b/lib_i386/pcat_timer.c
@@ -0,0 +1,102 @@
+/*
+ * (C) Copyright 2002
+ * Daniel Engström, Omicron Ceti AB, daniel@omicron.se.
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <common.h>
+#include <asm/io.h>
+#include <asm/i8254.h>
+#include <asm/ibmpc.h>
+
+#define TIMER0_VALUE 0x04aa /* 1kHz 1.9318MHz / 1000 */
+#define TIMER2_VALUE 0x0a8e /* 440Hz */
+
+int timer_init(void)
+{
+	/* initialize timer 0 and 2
+	 *
+	 * Timer 0 is used to increment system_tick 1000 times/sec
+	 * Timer 1 was used for DRAM refresh in early PC's
+	 * Timer 2 is used to drive the speaker
+	 * (to stasrt a beep: write 3 to port 0x61,
+	 * to stop it again: write 0)
+	 */
+	outb (PIT_CMD_CTR0 | PIT_CMD_BOTH | PIT_CMD_MODE2,
+	      PIT_BASE + PIT_COMMAND);
+	outb (TIMER0_VALUE & 0xff, PIT_BASE + PIT_T0);
+	outb (TIMER0_VALUE >> 8, PIT_BASE + PIT_T0);
+
+	outb (PIT_CMD_CTR2 | PIT_CMD_BOTH | PIT_CMD_MODE3,
+	      PIT_BASE + PIT_COMMAND);
+	outb (TIMER2_VALUE & 0xff, PIT_BASE + PIT_T2);
+	outb (TIMER2_VALUE >> 8, PIT_BASE + PIT_T2);
+
+	irq_install_handler (0, timer_isr, NULL);
+	unmask_irq (0);
+
+	return 0;
+}
+
+static u16 read_pit(void)
+{
+	u8 low;
+
+	outb (PIT_CMD_LATCH, PIT_BASE + PIT_COMMAND);
+	low = inb (PIT_BASE + PIT_T0);
+
+	return ((inb (PIT_BASE + PIT_T0) << 8) | low);
+}
+
+/* this is not very exact */
+void udelay (unsigned long usec)
+{
+	int counter;
+	int wraps;
+
+	if (timer_init_done)
+	{
+		counter = read_pit ();
+		wraps = usec / 1000;
+		usec = usec % 1000;
+
+		usec *= 1194;
+		usec /= 1000;
+		usec += counter;
+
+		while (usec > 1194) {
+			usec -= 1194;
+			wraps++;
+		}
+
+		while (1) {
+			int new_count = read_pit ();
+
+			if (((new_count < usec) && !wraps) || wraps < 0)
+				break;
+
+			if (new_count > counter)
+				wraps--;
+
+			counter = new_count;
+		}
+	}
+
+}