From dd828c8920cf7b43a89ece3cf10697963519d3e9 Mon Sep 17 00:00:00 2001
From: Kerogit <kr.git@kerogit.eu>
Date: Sat, 5 Apr 2025 23:41:54 +0200
Subject: [PATCH] arch/avr: fixed PC load on chips with more than 128kB program
 memory

The code used subi instruction to decrement the Y pointer but this
instruction only affects a byte, not a word. Fixed it by using
pre-decrement in the LD instruction instead.
---
 arch/avr/src/avr/excptmacros.h | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/avr/src/avr/excptmacros.h b/arch/avr/src/avr/excptmacros.h
index dcfa8c4e547..a6046abf873 100644
--- a/arch/avr/src/avr/excptmacros.h
+++ b/arch/avr/src/avr/excptmacros.h
@@ -465,7 +465,7 @@
 #if AVR_PC_SIZE <= 16
   adiw r28, REG_PC0
 #else
-  adiw r28, REG_PC2
+  adiw r28, (REG_PC2+1) /* Will pre-decrement this on use */
 #endif
 
   /* Fetch and set the new stack pointer */
@@ -490,14 +490,11 @@
   push r24 /* Push PC0 and PC1 on the stack (PC1 then PC0) */
   push r25
 #else
-  ld r25, y /* Load PC2 (r25) */
-  subi r28,1
+  ld r25, -y /* Load PC2 (r25) */
   push r25
-  ld r25, y /* Load PC1 (r25) */
-  subi r28,1
+  ld r25, -y /* Load PC1 (r25) */
   push r25
-  ld r25, y /* Load PC0 (r25) */
-  subi r28,1
+  ld r25, -y /* Load PC0 (r25) */
   push r25
 #endif