initial commit

6 files changed, 407 insertions, 0 deletions

diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
new file mode 100644
index 0000000..18ccdd5
--- /dev/null
+++ b/kernel/sched/idle.c
@@ -0,0 +1,18 @@
+#include <avr/interrupt.h>
+#include <avr/sleep.h>
+#include <avr/power.h>
+#include "sched/idle.h"
+#include "tshield/tshield.h"
+
+void idle_entry(char args) {
+  while(1) {
+    tshield_led(TSHIELD_LED_IDLE,1);
+    set_sleep_mode(SLEEP_MODE_IDLE);
+    cli();
+    sleep_enable();
+    sei();
+    sleep_cpu();
+    sleep_disable();
+  };
+}
+
diff --git a/kernel/sched/include/sched/idle.h b/kernel/sched/include/sched/idle.h
new file mode 100644
index 0000000..3b6e40a
--- /dev/null
+++ b/kernel/sched/include/sched/idle.h
@@ -0,0 +1,6 @@
+#ifndef IDLE_H
+#define IDLE_H
+
+void idle_entry(char args);
+
+#endif
\ No newline at end of file
diff --git a/kernel/sched/include/sched/sched.h b/kernel/sched/include/sched/sched.h
new file mode 100644
index 0000000..d63b78c
--- /dev/null
+++ b/kernel/sched/include/sched/sched.h
@@ -0,0 +1,117 @@
+#ifndef SCHED_H
+#define SCHED_H
+
+#include "collection/list.h"
+#include "mcu/sched/context.h"
+
+/** Proposed default stack size, you may use this definition for declaring tasks. */
+#define STACK_SIZE 64
+
+/** Stack size to be allocated for the idle task. */
+#define IDLE_STACK_SIZE 64
+
+/**
+ * Task control block, contains runtime
+ * information of tasks.
+ */
+struct tcb_t {
+  /** Stack pointer of this task. (must be first in structure) */
+  char* volatile sp;
+
+  /** Lowest address of this task's memory (inclusive). */
+  char* mem_low;
+
+  /** Highest address of this task's memory (inclusive). */
+  char* mem_high;
+
+  /** Entry function of this task. */
+  void (*entry)(char);
+
+  /** Current wait queue that this task is in. */
+  struct list_head q;
+};
+
+/**
+ * Utility for declaring a task with statically allocated memory.
+ * Note: for a task to be scheduled, it must first be spawned (see spawn()).
+*/
+#define DECLARE_TASK(name, stack_size, entry_function) \
+  static char volatile declared_stack_##name[stack_size]; \
+  static struct tcb_t name = { \
+    .sp = 0, \
+    .mem_low = declared_stack_##name, \
+    .mem_high = declared_stack_##name + stack_size - 1, \
+    .entry = entry_function, \
+    .q = {} \
+  };
+
+/**
+ * Points to currently executing task. If no scheduling has been enabled,
+ * this points to NULL
+ */
+extern struct tcb_t* volatile current;
+
+/**
+ * Queue that contains all tasks that are ready to be run, awaiting their
+ * turn from the scheduler.
+ */
+extern struct list_head ready;
+
+/**
+ * Stack pointer for operations performed out of task context, including any
+ * calls made after SAVE_CONTEXT().
+ */
+extern char* volatile kstack;
+
+
+/** 
+ * Makes the current task sleep on a specific queue.
+ * This moves the current task to the given queue's tail.
+ */
+static inline void sleep_on(struct list_head* queue) {
+  list_move_tail(&current->q, queue);
+}
+
+/** 
+ * Wakes all tasks waiting in the given queue.
+ * This moves all tasks contained in the queue to the ready queue.
+ */
+static inline void wake_all(struct list_head* queue) {
+  list_splice_init(queue, ready.prev);
+}
+
+/**
+ * Initializes the scheduler by setting up kstack, initializing the idle task
+ * and selecting the first task to run.
+ */
+void sched_init();
+
+/**
+ * Ticks the scheduler.
+ */
+inline void sched_tick() {
+  schedule(); //in a round-robin scheduler, scheduling is called after every tick
+}
+
+/** 
+ * Enters the scheduler, setting current to the next runnable task.
+ */
+void schedule();
+
+/**
+ * Initializes a given task and adds it to the ready queue.
+ */
+void spawn(struct tcb_t* const tcb, char args);
+
+/**
+ * Voluntarily yields control of the CPU to the scheduler.
+ */
+void yield() __attribute__ ( ( naked ) );
+
+void freeze() __attribute__ ( ( naked ) );
+
+
+#define ENTER_CRITICAL() cli()
+#define EXIT_CRITICAL() sei()
+
+#endif
diff --git a/kernel/sched/mcu/atmega2560/context.c b/kernel/sched/mcu/atmega2560/context.c
new file mode 100644
index 0000000..7a88b33
--- /dev/null
+++ b/kernel/sched/mcu/atmega2560/context.c
@@ -0,0 +1,96 @@
+#include "mcu/sched/context.h"
+
+char* init_stack(const char* const mem_low, const char* const mem_high, void (*entry)(char), char args) {
+  char* sp = (char*) mem_high;
+  unsigned long address = (unsigned long) entry;
+  
+  
+  *sp = (char) 0x1;
+  sp--;
+  *sp = (char) 0x2;
+  sp--;
+  *sp = (char) 0x1;
+  sp--;
+  *sp = (char) 0x2;
+  sp--;
+  
+	*sp = (char) ( address & (unsigned short) 0x00ff );
+	sp--;
+
+	*sp = (char) ( (address >> 8) & ( unsigned short ) 0x00ff );
+	sp--;
+  
+  *sp = (char) ( (address >> 16) & ( unsigned short ) 0x00ff );
+	sp--;
+
+	*sp = (char) 0x00; //r0
+	sp--;
+	*sp = (char) 0x80; //SREG, enable interrupts when task starts
+	sp--;
+	*sp = ( char ) 0x00; //r1
+	sp--;
+	*sp = ( char ) 0x00; //r2
+	sp--;
+	*sp = ( char ) 0x00; //r3
+	sp--;
+	*sp = ( char ) 0x00; //r4
+	sp--;
+	*sp = ( char ) 0x00; //r5
+	sp--;
+	*sp = ( char ) 0x00; //r6
+	sp--;
+	*sp = ( char ) 0x00; //r7
+	sp--;
+	*sp = ( char ) 0x00; //r8
+	sp--;
+	*sp = ( char ) 0x00; //r9
+	sp--;
+	*sp = ( char ) 0x00; //r10
+	sp--;
+	*sp = ( char ) 0x00; //r11
+	sp--;
+	*sp = ( char ) 0x00; //r12
+	sp--;
+	*sp = ( char ) 0x00; //r13
+	sp--;
+	*sp = ( char ) 0x00; //r14
+	sp--;
+	*sp = ( char ) 0x00; //r15
+	sp--;
+	*sp = ( char ) 0x00; //r16
+	sp--;
+	*sp = ( char ) 0x00; //r17
+	sp--;
+	*sp = ( char ) 0x00; //r18
+	sp--;
+	*sp = ( char ) 0x00; //r19
+	sp--;
+	*sp = ( char ) 0x00; //r20
+	sp--;
+  *sp = ( char ) 0x00; //r21
+	sp--;
+  *sp = ( char ) 0x00; //r22
+	sp--;
+  *sp = ( char ) 0x00; //r23
+	sp--;
+  
+  *sp = (char) ( args ); //place first argument in register 24
+	sp--;
+  
+  *sp = ( char ) 0x00; //r25
+	sp--;
+  *sp = ( char ) 0x00; //r26
+	sp--;
+  *sp = ( char ) 0x00; //r27
+	sp--;
+  *sp = ( char ) 0x00; //r28
+	sp--;
+  *sp = ( char ) 0x00; //r29
+	sp--;
+  *sp = ( char ) 0x00; //r30
+	sp--;
+  *sp = ( char ) 0x00; //r31
+	sp--;
+  
+  return sp;
+}
diff --git a/kernel/sched/mcu/atmega2560/include/mcu/sched/context.h b/kernel/sched/mcu/atmega2560/include/mcu/sched/context.h
new file mode 100644
index 0000000..9ff8d42
--- /dev/null
+++ b/kernel/sched/mcu/atmega2560/include/mcu/sched/context.h
@@ -0,0 +1,116 @@
+#ifndef CONTEXT_H
+#define CONTEXT_H
+
+#include <avr/interrupt.h>
+
+#define SAVE_CONTEXT() \
+  asm volatile ( \
+    "push r0 \n\t" \
+    "in r0, __SREG__ \n\t" \
+    "cli \n\t" \
+    "push r0 \n\t" \
+    "push r1 \n\t" \
+    "clr r1 \n\t" \
+    "push r2 \n\t" \
+    "push r3 \n\t" \
+    "push r4 \n\t" \
+    "push r5 \n\t" \
+    "push r6 \n\t" \
+    "push r7 \n\t" \
+    "push r8 \n\t" \
+    "push r9 \n\t" \
+    "push r10 \n\t" \
+    "push r11 \n\t" \
+    "push r12 \n\t" \
+    "push r13 \n\t" \
+    "push r14 \n\t" \
+    "push r15 \n\t" \
+    "push r16 \n\t" \
+    "push r17 \n\t" \
+    "push r18 \n\t" \
+    "push r19 \n\t" \
+    "push r20 \n\t" \
+    "push r21 \n\t" \
+    "push r22 \n\t" \
+    "push r23 \n\t" \
+    "push r24 \n\t" \
+    "push r25 \n\t" \
+    "push r26 \n\t" \
+    "push r27 \n\t" \
+    "push r28 \n\t" \
+    "push r29 \n\t" \
+    "push r30 \n\t" \
+    "push r31 \n\t" \
+    "lds r26, current \n\t" \
+    "lds r27, current +1 \n\t" \
+    "in r0, __SP_L__ \n\t" \
+    "st x+, r0 	\n\t" \
+    "in r0, __SP_H__ \n\t" \
+    "st x+, r0 \n\t" \
+    "lds r26, kstack \n\t" \
+    "lds r27, kstack + 1 \n\t" \
+    "ld r28, x+ \n\t" \
+    "out __SP_L__, r28 \n\t" \
+    "ld r29, x+ \n\t" \
+    "out __SP_H__, r29 \n\t" \
+  )
+  
+#define RESTORE_CONTEXT() \
+  asm volatile ( \
+    "lds r26, kstack \n\t" \
+    "lds r27, kstack +1 \n\t" \
+    "in r0, __SP_L__ \n\t" \
+    "st x+, r0  \n\t" \
+    "in r0, __SP_H__ \n\t" \
+    "st x+, r0  \n\t" \
+    "lds r26, current \n\t" \
+    "lds r27, current + 1 \n\t" \
+    "ld r28, x+ \n\t" \
+    "out __SP_L__, r28 \n\t" \
+    "ld r29, x+ \n\t" \
+    "out __SP_H__, r29 \n\t" \
+    "pop r31 \n\t" \
+    "pop r30 \n\t" \
+    "pop r29 \n\t" \
+    "pop r28 \n\t" \
+    "pop r27 \n\t" \
+    "pop r26 \n\t" \
+    "pop r25 \n\t" \
+    "pop r24 \n\t" \
+    "pop r23 \n\t" \
+    "pop r22 \n\t" \
+    "pop r21 \n\t" \
+    "pop r20 \n\t" \
+    "pop r19 \n\t" \
+    "pop r18 \n\t" \
+    "pop r17 \n\t" \
+    "pop r16 \n\t" \
+    "pop r15 \n\t" \
+    "pop r14 \n\t" \
+    "pop r13 \n\t" \
+    "pop r12 \n\t" \
+    "pop r11 \n\t" \
+    "pop r10 \n\t" \
+    "pop r9 \n\t" \
+    "pop r8 \n\t" \
+    "pop r7 \n\t" \
+    "pop r6 \n\t" \
+    "pop r5 \n\t" \
+    "pop r4 \n\t" \
+    "pop r3 \n\t" \
+    "pop r2 \n\t" \
+    "pop r1 \n\t" \
+    "pop r0 \n\t" \
+    "out __SREG__, r0 \n\t" \
+    "pop r0 \n\t" \
+  )
+
+char* init_stack(const char* const mem_low, const char* const mem_high, void (*entry)(char), char args);
+
+static inline void init_kstack(char **kstack) {
+  *kstack = (char*) SP;
+}
+
+#define RETURN() asm volatile("ret");
+
+#endif
diff --git a/kernel/sched/sched.c b/kernel/sched/sched.c
new file mode 100644
index 0000000..8406b8d
--- /dev/null
+++ b/kernel/sched/sched.c
@@ -0,0 +1,54 @@
+#include "sched/sched.h"
+#include "sched/idle.h"
+#include "mcu/sched/context.h"
+
+struct tcb_t* volatile current = 0;
+DECLARE_TASK(idle, IDLE_STACK_SIZE, idle_entry);
+
+struct list_head ready = LIST_HEAD_INIT(ready);
+char* volatile kstack;
+
+static void init_idle() {
+  idle.sp = init_stack(idle.mem_low, idle.mem_high, idle.entry, 0);
+  INIT_LIST_HEAD(&idle.q);
+}
+
+void sched_init() {
+  init_kstack((char **) &kstack);
+  init_idle();
+  schedule();
+  sei();
+  RESTORE_CONTEXT();
+  RETURN();
+}
+
+void schedule() {
+  if(!list_empty(&ready)) {
+    current = list_entry(ready.next, struct tcb_t, q);
+    list_move_tail(&current->q, &ready);
+  } else {
+    current = &idle;
+  }
+}
+
+void spawn(struct tcb_t* const tcb, char args) {
+  tcb->sp = init_stack(tcb->mem_low, tcb->mem_high, tcb->entry, args);
+  INIT_LIST_HEAD(&tcb->q);
+  list_add_tail(&tcb->q, &ready);
+}
+
+void yield(void) {
+  SAVE_CONTEXT();
+  schedule();
+  RESTORE_CONTEXT();
+  asm volatile ( "ret" );
+}
+
+void freeze() {
+  SAVE_CONTEXT();
+  list_del_init(&current->q);
+  schedule();
+  RESTORE_CONTEXT();
+  asm volatile ( "ret" );
+}
+