rp2040

commit c49d611c72bb8695818395f8fde47c1dbd5dbaa7
parent 8a347c5c0da05100a62c21f461cd4cc4e0e343ab
Author: Matsuda Kenji <info@mtkn.jp>
Date:   Mon, 18 Mar 2024 13:02:55 +0900

contex switch, wip

Diffstat:
M
ex3/main.c
 | 
35
++++++++++++++++-------------------
M
ex3/proc.s
 | 
8
+++++---

2 files changed, 21 insertions(+), 22 deletions(-)
diff --git a/ex3/main.c b/ex3/main.c
@@ -63,24 +63,9 @@ main(void) {
 	p1.r[15] = 0x20000101; // pc
 	p1.next = NULL;
 
-	for (;;) {
-		wfi();
-		for (int i = 0; i < 17; i++) {
-			printh(ptab.head->r[i]);
-			puts("");
-		}
-	}
-	return 0;
-}
+	proc0();
 
-// Save_context saves the context starting at sp to the current proc struct.
-void
-save_context(unsigned int r[17])
-{
-	int i;
-	for (i = 0; i < 17; i++) {
-		ptab.head->r[i] = r[i];
-	}
+	return 0;
 }
 
 void
@@ -88,15 +73,27 @@ scheduler(void) {
 	puts("scheduler called");
 }
 
-void
-switch_context(void) {
+// Switch_context saves registers r to the currently executing proc struct
+// and then move it to the tail of task queue.
+// It returns the next PC of the next task in the queue
+unsigned int
+switch_context(unsigned int r[17]) {
 	proc *p;
+
+	// save context
+	int i;
+	for (i = 0; i < 17; i++) {
+		ptab.head->r[i] = r[i];
+	}
+	// update task queue
 	p = ptab.head;
 	ptab.head = ptab.head->next;
 	ptab.tail->next = p;
 	ptab.tail = p;
 	ptab.tail->next = NULL;
 	restore_context(ptab.head->r);
+
+	return ptab.head->r[15];
 }
 
 void
diff --git a/ex3/proc.s b/ex3/proc.s
@@ -4,6 +4,7 @@
 proc0:
 	ldr r0, =msg0
 	bl puts
+	wfi
 	b proc0
 
 	.align 2
@@ -16,6 +17,7 @@ msg0:
 proc1:
 	ldr r0, =msg1
 	bl puts
+	wfi
 	b proc1
 
 	.align 2
@@ -99,8 +101,6 @@ isr_alarm:
 	add r3, r3, #4
 	ldr r0, [r1, r2]
 	str r0, [r1, r3] // ReturnAddress(ExceptionType): The next pc at interrupt.
-	ldr r0, =0x20000101 // The entry point of proc1
-	str r0, [r1, r2]
 
 	add r2, r2, #4
 	add r3, r3, #4
@@ -108,7 +108,9 @@ isr_alarm:
 	str r0, [r1, r3]
 
 	mov r0, r1
-	bl save_context
+	bl switch_context
+	sub r2, r2, #4
+	str r0, [r1, r2]
 
 	add sp, sp, #(17*4)
 	ldr r0, =(1000 * 1000)