From 0b1797312b34ba2b8121f82605f8d2c419167737 Mon Sep 17 00:00:00 2001
From: Keith Packard <keithp@keithp.com>
Date: Sat, 27 Apr 2013 00:20:47 -0700
Subject: [PATCH] altos: Run self loader when application sets boot addr to 0

This causes the flash loader startup code to fall into the loader when
the application sets the boot address to zero.

Signed-off-by: Keith Packard <keithp@keithp.com>
---
 src/stm/ao_boot.h       | 3 ++-
 src/stm/ao_boot_chain.c | 7 +++++--
 src/stm/ao_interrupt.c  | 7 ++++---
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/src/stm/ao_boot.h b/src/stm/ao_boot.h
index 862e8755..e0ed4de7 100644
--- a/src/stm/ao_boot.h
+++ b/src/stm/ao_boot.h
@@ -24,7 +24,8 @@ ao_boot_chain(uint32_t *base);
 void
 ao_boot_check_pin(void);
 
-void
+/* Return true to switch to application (if present) */
+int
 ao_boot_check_chain(void);
 
 void
diff --git a/src/stm/ao_boot_chain.c b/src/stm/ao_boot_chain.c
index 668f6e6d..6a3864a7 100644
--- a/src/stm/ao_boot_chain.c
+++ b/src/stm/ao_boot_chain.c
@@ -26,7 +26,7 @@ ao_boot_chain(uint32_t *base)
 
 	sp = base[0];
 	pc = base[1];
-	if (0x08000100 <= pc && pc <= 0x08200000) {
+	if (0x08000100 <= pc && pc <= 0x08200000 && (pc & 1) == 1) {
 		asm ("mov sp, %0" : : "r" (sp));
 		asm ("mov lr, %0" : : "r" (pc));
 		asm ("bx lr");
@@ -44,14 +44,17 @@ struct ao_boot {
 
 static struct ao_boot __attribute__ ((section(".boot"))) ao_boot;
 	
-void
+int
 ao_boot_check_chain(void)
 {
 	if (ao_boot.signal == AO_BOOT_SIGNAL && ao_boot.check == AO_BOOT_CHECK) {
 		ao_boot.signal = 0;
 		ao_boot.check = 0;
+		if (ao_boot.base == 0)
+			return 0;
 		ao_boot_chain(ao_boot.base);
 	}
+	return 1;
 }
 
 void
diff --git a/src/stm/ao_interrupt.c b/src/stm/ao_interrupt.c
index 49156285..969e6a0f 100644
--- a/src/stm/ao_interrupt.c
+++ b/src/stm/ao_interrupt.c
@@ -42,10 +42,11 @@ const void *stm_interrupt_vector[];
 void start(void)
 {
 #ifdef AO_BOOT_CHAIN
-	ao_boot_check_chain();
-#endif
+	if (ao_boot_check_chain()) {
 #ifdef AO_BOOT_PIN
-	ao_boot_check_pin();
+		ao_boot_check_pin();
+#endif
+	}
 #endif
 	/* Set interrupt vector table offset */
 	stm_nvic.vto = (uint32_t) &stm_interrupt_vector;
-- 
2.30.2