rp2040

commit 7223002cb9a28c1cc45943ea980d2367b840c544
parent c49d611c72bb8695818395f8fde47c1dbd5dbaa7
Author: Matsuda Kenji <info@mtkn.jp>
Date:   Tue, 19 Mar 2024 10:02:54 +0900

try to implement context switch

Diffstat:
M
ex3/main.c
 | 
15
+++++++--------
M
ex3/proc.s
 | 
32
+++++++++++++++++++++++++++-----

2 files changed, 34 insertions(+), 13 deletions(-)
diff --git a/ex3/main.c b/ex3/main.c
@@ -39,11 +39,11 @@ typedef struct proc_tab {
 } proc_tab;
 
 proc_tab ptab;
+proc p0, p1;
 
 int
 main(void) {
 	init();
-	proc p0, p1;
 
 	memcpy((void *)0x20000000, &proc0_start, (long) &proc0_size);
 	memcpy((void *)0x20000100, &proc1_start, (long) &proc1_size);
@@ -53,18 +53,18 @@ main(void) {
 
 	p0.id = 0;
 	p0.r[13] = 0x20000100; // sp
-	p0.r[14] = (unsigned int) main; // lr
+	p0.r[14] = (unsigned int) halt; // lr
 	p0.r[15] = 0x20000001; // pc
+	p0.r[16] = 0;
 	p0.next = &p1;
 
 	p1.id = 1;
 	p1.r[13] = 0x20000200; // sp
-	p1.r[14] = (unsigned int) main; // lr
+	p1.r[14] = (unsigned int) halt; // lr
 	p1.r[15] = 0x20000101; // pc
+	p1.r[16] = 0;
 	p1.next = NULL;
 
-	proc0();
-
 	return 0;
 }
 
@@ -76,7 +76,7 @@ scheduler(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
+unsigned int *
 switch_context(unsigned int r[17]) {
 	proc *p;
 
@@ -91,9 +91,8 @@ switch_context(unsigned int r[17]) {
 	ptab.tail->next = p;
 	ptab.tail = p;
 	ptab.tail->next = NULL;
-	restore_context(ptab.head->r);
 
-	return ptab.head->r[15];
+	return ptab.head->r;
 }
 
 void
diff --git a/ex3/proc.s b/ex3/proc.s
@@ -108,15 +108,37 @@ isr_alarm:
 	str r0, [r1, r3]
 
 	mov r0, r1
-	bl switch_context
-	sub r2, r2, #4
-	str r0, [r1, r2]
-
+	bl switch_context // r0 is the r[17] of the next task.
 	add sp, sp, #(17*4)
+	add r2, sp, #4 // for the popped lr
+
+	ldr r1, [r0, #(0 * 4)] // r0
+	str r1, [r2, #0]
+	ldr r1, [r0, #(1 * 4)] // r1
+	str r1, [r2, #0x4]
+	ldr r1, [r0, #(2 * 4)] // r2
+	str r1, [r2, #0x8]
+	ldr r1, [r0, #(3 * 4)] // r3
+	str r1, [r2, #0xc]
+	ldr r1, [r0, #(12 * 4)] // r12
+	str r1, [r2, #0x10]
+	ldr r1, [r0, #(14 * 4)] // lr
+	str r1, [r2, #0x14]
+	ldr r1, [r0, #(15 * 4)] // ReturnAddress
+	str r1, [r2, #0x18]
+	ldr r1, [r0, #(16 * 4)] // xpsr
+	str r1, [r2, #0x1c]
+	mov r4, r0
+
 	ldr r0, =(1000 * 1000)
 	bl set_alarm
 
-	pop {pc}
+	pop {r5}
+
+	ldr r0, [r4, #(13 * 4)] // sp
+	mov sp, r0
+
+	bx r5
 
 	.align 2
 alarm_msg: