From 9e142daa83219e614fbc341ad6ec559ffe26f0fb Mon Sep 17 00:00:00 2001
From: Linus Nielsen Feltzing <linus@haxx.se>
Date: Sun, 5 May 2002 18:34:06 +0000
Subject: [PATCH] Added tick and interrupt level functions

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@449 a1c6a512-1295-4272-9138-f99709370657
---
 firmware/kernel.c | 129 ++++++++++++++++++++++++++++++++++++++++++++++
 firmware/kernel.h |   2 +
 2 files changed, 131 insertions(+)

diff --git a/firmware/kernel.c b/firmware/kernel.c
index f408c77bae..74393ce5bc 100644
--- a/firmware/kernel.c
+++ b/firmware/kernel.c
@@ -16,11 +16,25 @@
  * KIND, either express or implied.
  *
  ****************************************************************************/
+#include <stdlib.h>
 #include "kernel.h"
 #include "thread.h"
+#include "sh7034.h"
+#include "system.h"
+#include "panic.h"
 
 long current_tick = 0;
 
+static void tick_start(unsigned int interval_in_ms);
+
+/****************************************************************************
+ * Standard kernel stuff
+ ****************************************************************************/
+void kernel_init(void)
+{
+    tick_start(1);
+}
+
 void sleep(int ticks)
 {
     int timeout = current_tick + ticks;
@@ -36,6 +50,24 @@ void yield(void)
     switch_thread();
 }
 
+/****************************************************************************
+ * Interrupt level setting
+ * NOTE!!!!!!
+ * This one is not entirely safe. If an interrupt uses this function it
+ * MUST restore the old level before returning. Otherwise there is a small
+ * risk that set_irq_level returns the wrong level if interrupted after
+ * the stc instruction.
+ ****************************************************************************/
+int set_irq_level(int level)
+{
+    int i;
+
+    /* Read the old level and set the new one */
+    asm volatile ("stc sr, %0" : "=r" (i));
+    asm volatile ("ldc %0, sr" : : "r" (level<<4));
+    return (i >> 4) & 0x0f;
+}
+
 /****************************************************************************
  * Queue handling stuff
  ****************************************************************************/
@@ -62,3 +94,100 @@ void queue_post(struct event_queue *q, int id, void *data)
     q->events[wr].id = id;
     q->events[wr].data = data;
 }
+
+
+/****************************************************************************
+ * Timer tick
+ ****************************************************************************/
+#define NUM_TICK_TASKS 4
+void (*tick_funcs[NUM_TICK_TASKS])(void) = {NULL, NULL, NULL, NULL};
+
+static void tick_start(unsigned int interval_in_ms)
+{
+    unsigned int count;
+
+    count = FREQ / 1000 / 8 * interval_in_ms;
+
+    if(count > 0xffff)
+    {
+        panicf("Error! The tick interval is too long (%d ms)\n",
+               interval_in_ms);
+        return;
+    }
+    
+    /* We are using timer 0 */
+    
+    TSTR &= ~0x01; /* Stop the timer */
+    TSNC &= ~0x01; /* No synchronization */
+    TMDR &= ~0x01; /* Operate normally */
+
+    TCNT0 = 0;   /* Start counting at 0 */
+    GRA0 = count;
+    TCR0 = 0x23; /* Clear at GRA match, sysclock/8 */
+
+    /* Enable interrupt on level 1 */
+    IPRC = (IPRC & ~0x00f0) | 0x0010;
+    
+    TSR0 &= ~0x01;
+    TIER0 = 0xf9; /* Enable GRA match interrupt */
+
+    TSTR |= 0x01; /* Start timer 1 */
+}
+
+#pragma interrupt
+void IMIA0(void)
+{
+    int i;
+
+    /* Run through the list of tick tasks */
+    for(i = 0;i < NUM_TICK_TASKS;i++)
+    {
+        if(tick_funcs[i])
+        {
+            tick_funcs[i]();
+        }
+    }
+
+    current_tick++;
+
+    TSR0 &= ~0x01;
+}
+
+int tick_add_task(void (*f)(void))
+{
+    int i;
+    int oldlevel = set_irq_level(15);
+
+    /* Add a task if there is room */
+    for(i = 0;i < NUM_TICK_TASKS;i++)
+    {
+        if(tick_funcs[i] == NULL)
+        {
+            tick_funcs[i] = f;
+            set_irq_level(oldlevel);
+            return 0;
+        }
+    }
+    set_irq_level(oldlevel);
+    return -1;
+}
+
+int tick_remove_task(void (*f)(void))
+{
+    int i;
+    int oldlevel = set_irq_level(15);
+
+    /* Remove a task if it is there */
+    for(i = 0;i < NUM_TICK_TASKS;i++)
+    {
+        if(tick_funcs[i] == f)
+        {
+            tick_funcs[i] = NULL;
+            set_irq_level(oldlevel);
+            return 0;
+        }
+    }
+    
+    set_irq_level(oldlevel);
+    return -1;
+}
diff --git a/firmware/kernel.h b/firmware/kernel.h
index cef6cfe96a..b5a9ae3ff4 100644
--- a/firmware/kernel.h
+++ b/firmware/kernel.h
@@ -45,8 +45,10 @@ struct event_queue
 extern long current_tick;
 
 /* kernel functions */
+extern void kernel_init(void);
 extern void yield(void);
 extern void sleep(int ticks);
+int set_irq_level(int level);
 
 extern void queue_init(struct event_queue *q);
 extern struct event *queue_wait(struct event_queue *q);