# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1453052982 -3600
# Node ID e75e6bb0021e132c0aa2012862219cbbc077254b
# Parent  5e7f7cb747e11daef4f9957d875037c668b66e33
Initialise registers so that the stage 2 payload may use interrupts.

diff -r 5e7f7cb747e1 -r e75e6bb0021e stage1/head1.S
--- a/stage1/head1.S	Sun Jan 17 18:48:13 2016 +0100
+++ b/stage1/head1.S	Sun Jan 17 18:49:42 2016 +0100
@@ -4,7 +4,7 @@
  * Copyright (C) 2009 Qi Hardware Inc.
  * Author: Wolfgang Spraul <wolfgang@sharism.cc>
  *
- * Copyright (C) 2015 Paul Boddie <paul@boddie.org.uk>
+ * Copyright (C) 2015, 2016 Paul Boddie <paul@boddie.org.uk>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -25,10 +25,15 @@
 .globl _start
 .set noreorder
 
+#define CP0_STATUS $12
+#define CP0_CAUSE $13
+
 _start:
 	b real_start
 	nop
-        // 8 words for firmware parameters (0x80002008), struct fw_args
+
+	/* 8 words for firmware parameters (0x80002008), struct fw_args */
+
 	.word 0x0
 	.word 0x0
 	.word 0x0
@@ -37,7 +42,19 @@
 	.word 0x0
 	.word 0x0
 	.word 0x0
+
 real_start:
+	/*
+	Reset various registers. Otherwise, interrupts do not apparently get
+	re-enabled properly later when requested.
+	*/
+
+	li $t0, 0x0040fc04 /* BEV=1, interrupts enabled, ERL=1 */
+	mtc0 $t0, CP0_STATUS
+
+        li $t0, 0x00800000 /* IV=1 */
+        mtc0 $t0, CP0_CAUSE 
+
 	/* Setup stack, jump to C code. */
 
 	la $sp, 0x80004000