add handler for the timer interrupt

2013-11-27 22:50:19 +01:00 · 2013-11-27 22:50:19 +01:00 · ff0cf28a27
commit ff0cf28a27
parent 87801a1706
1 changed files with 111 additions and 0 deletions
--- a/arch/x86/kernel/timer.c
+++ b/arch/x86/kernel/timer.c
@ -0,0 +1,111 @@
+/*
+ * Copyright (c) 2010, Stefan Lankes, RWTH Aachen University
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *    * Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *    * Redistributions in binary form must reproduce the above copyright
+ *      notice, this list of conditions and the following disclaimer in the
+ *      documentation and/or other materials provided with the distribution.
+ *    * Neither the name of the University nor the names of its contributors
+ *      may be used to endorse or promote products derived from this
+ *      software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <eduos/stdio.h>
+#include <eduos/string.h>
+#include <eduos/tasks.h>
+#include <eduos/time.h>
+#include <eduos/errno.h>
+#include <asm/irq.h>
+#include <asm/irqflags.h>
+#include <asm/vga.h>
+#include <asm/io.h>
+
+/* 
+ * This will keep track of how many ticks the system
+ * has been running for 
+ */
+static volatile uint64_t timer_ticks = 0;
+
+uint64_t get_clock_tick(void)
+{
+	return timer_ticks;
+}
+
+/* 
+ * Handles the timer. In this case, it's very simple: We
+ * increment the 'timer_ticks' variable every time the
+ * timer fires. 
+ */
+static void timer_handler(struct state *s)
+{
+	/* Increment our 'tick counter' */
+	timer_ticks++;
+
+	/*
+	 * Every TIMER_FREQ clocks (approximately 1 second), we will
+	 * display a message on the screen
+	 */
+	/*if (timer_ticks % TIMER_FREQ == 0) {
+		vga_puts("One second has passed\n");
+	}*/
+}
+
+#define LATCH(f)	((CLOCK_TICK_RATE + f/2) / f)
+#define WAIT_SOME_TIME() do { uint64_t start = rdtsc(); \
+			      while(rdtsc() - start < 1000000) ; \
+			} while (0)
+
+/* 
+ * Sets up the system clock by installing the timer handler
+ * into IRQ0 
+ */
+int timer_init(void)
+{
+	/* 
+	 * Installs 'timer_handler' for the PIC and APIC timer,
+	 * only one handler will be later used.
+	 */
+	irq_install_handler(32, timer_handler);
+	irq_install_handler(123, timer_handler);
+
+	/*
+	 * Port 0x43 is for initializing the PIT:
+	 *
+	 * 0x34 means the following:
+	 * 0b...     (step-by-step binary representation)
+	 * ...  00  - channel 0
+	 * ...  11  - write two values to counter register:
+	 *            first low-, then high-byte
+	 * ... 010  - mode number 2: "rate generator" / frequency divider
+	 * ...   0  - binary counter (the alternative is BCD)
+	 */
+	outportb(0x43, 0x34);
+
+	WAIT_SOME_TIME();
+
+	/* Port 0x40 is for the counter register of channel 0 */
+
+	outportb(0x40, LATCH(TIMER_FREQ) & 0xFF);   /* low byte  */
+
+	WAIT_SOME_TIME();
+
+	outportb(0x40, LATCH(TIMER_FREQ) >> 8);     /* high byte */
+
+	return 0;
+}
+