X-Git-Url: https://codewiz.org/gitweb?a=blobdiff_plain;f=kern%2Fswitch_avr.S;h=93892919ff483d5bdae0a915042c2fd799c00605;hb=3d3ba5cae20af3f5d1a75d7a3d727a2199160137;hp=266a77e4bd1ed08a39e27e00d99b028d0f26cb53;hpb=1cc167e20f21d2e81527ca47ccd4a21a6198f86f;p=bertos.git

diff --git a/kern/switch_avr.S b/kern/switch_avr.S
old mode 100755
new mode 100644
index 266a77e4..93892919
--- a/kern/switch_avr.S
+++ b/kern/switch_avr.S
@@ -3,7 +3,7 @@
  * <!--
  * Copyright 2004 Develer S.r.l. (http://www.develer.com/)
  * Copyright 1999,2000,2001 Bernardo Innocenti <bernie@develer.com>
- * All Rights Reserved.
+ * This file is part of DevLib - See devlib/README for information.
  * -->
  *
  * \brief AVR context switch
@@ -16,12 +16,25 @@
 
 #include <avr/io.h>
 
+/*
+ * NOTE: At each change of this function affecting proc.c
+ * (i.e. arguments, data stored in the stack) bump up version
+ * number in asm_switch_version().
+ */
+
 /* void asm_switch_context(void **new_sp, void **save_sp) */
 .globl asm_switch_context
 asm_switch_context:
 
-;	push	r0	caller-save
-;	push	r1	caller-save
+;	r0 is the TEMP REG and can be used freely.
+;	r1 is the ZERO REG and must always contain 0.
+;
+;	Stack frame is 19 byte, remember to update
+;	CPU_SAVED_REGS_CNT if you change pushed regs.
+
+	in	r0,SREG-__SFR_OFFSET
+	push	r0
+;	push	r1	;zero-reg
 	push	r2
 	push	r3
 	push	r4
@@ -38,48 +51,58 @@ asm_switch_context:
 	push	r15
 	push	r16
 	push	r17
-;	push	r18	caller-save
-;	push	r19	caller-save
-;	push	r20	caller-save
-;	push	r21	caller-save
-;	push	r22	caller-save
-;	push	r23	caller-save
-;	push	r24	caller-save
-;	push	r25	caller-save
-;	push	r26	caller-save
-;	push	r27	caller-save
+;	push	r18	;caller-save
+;	push	r19	;caller-save
+;	push	r20	;caller-save
+;	push	r21	;caller-save
+;	push	r22	;caller-save
+;	push	r23	;caller-save
+;	push	r24	;caller-save
+;	push	r25	;caller-save
+;	push	r26	;caller-save
+;	push	r27	;caller-save
 	push	r28
 	push	r29
-;	push	r30	caller-save
-;	push	r31	caller-save
+;	push	r30	;caller-save
+;	push	r31	;caller-save
 
-; First parameter (new_sp) is in r24:r25, second (save_sp) in r22:r23
+;	First parameter (new_sp) is in r24:r25, second (save_sp) in r22:r23
 
-	in	r0,SPL-__SFR_OFFSET	; r0:r1 = SP
-	in	r1,SPH-__SFR_OFFSET
+	in	r18,SPL-__SFR_OFFSET	; r18:r19 = SP
+	in	r19,SPH-__SFR_OFFSET
 	movw	r26,r22			; X = save_sp
-	st	X+,r0			; *save_sp = SP
-	st	X,r1
+	st	X+,r18			; *save_sp = SP
+	st	X,r19
 	movw	r26,r24			; X = new_sp
-	ld	r0,X+
-	ld	r1,X
-	out	SPL-__SFR_OFFSET,r0	; SP = *new_sp
-	out	SPH-__SFR_OFFSET,r1
+	ld	r18,X+
+	ld	r19,X
+
+; 	Set new stack pointer.
+;	AVR is an 8 bit processor so
+;	care must be taken when updating
+;	SP that is a 16 bit reg.
+;	Two instructions are required to update SP
+;	so an IRQ can sneak in between them.
+;	So IRQ *MUST* be disabled and then restored.
+	cli				; Disable interrupt
+	out	SPL-__SFR_OFFSET,r18	; SP = *new_sp
+	out	SPH-__SFR_OFFSET,r19
+	out	SREG-__SFR_OFFSET,r0	; Restore previous IRQ state
 
-;	pop	r31	caller-save
-;	pop	r30	caller-save
+;	pop	r31	;caller-save
+;	pop	r30	;caller-save
 	pop	r29
 	pop	r28
-;	pop	r27	caller-save
-;	pop	r26	caller-save
-;	pop	r25	caller-save
-;	pop	r24	caller-save
-;	pop	r23	caller-save
-;	pop	r22	caller-save
-;	pop	r21	caller-save
-;	pop	r20	caller-save
-;	pop	r19	caller-save
-;	pop	r18	caller-save
+;	pop	r27	;caller-save
+;	pop	r26	;caller-save
+;	pop	r25	;caller-save
+;	pop	r24	;caller-save
+;	pop	r23	;caller-save
+;	pop	r22	;caller-save
+;	pop	r21	;caller-save
+;	pop	r20	;caller-save
+;	pop	r19	;caller-save
+;	pop	r18	;caller-save
 	pop	r17
 	pop	r16
 	pop	r15
@@ -96,7 +119,17 @@ asm_switch_context:
 	pop	r4
 	pop	r3
 	pop	r2
-;	pop	r1	caller-save
-;	pop	r0	caller-save
+;	pop	r1	;zero-reg
+	pop	r0
+	out	SREG-__SFR_OFFSET,r0
 
 	ret
+
+
+/* int asm_switch_version(void) */
+.globl asm_switch_version
+asm_switch_version:
+	ldi r24,lo8(1)
+	ldi r25,hi8(1)
+	ret
+