From 7840f9c7dbbfcba9d7a56911a0d1c123415547b5 Mon Sep 17 00:00:00 2001
From: Martin Mares <mj@ucw.cz>
Date: Tue, 25 Feb 2020 20:57:36 +0100
Subject: [PATCH] Library: Compiler barrier, debug_flush()

---
 lib/dfu-bootloader.c | 3 +--
 lib/util-debug.c     | 8 ++++++++
 lib/util.h           | 8 ++++++++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/lib/dfu-bootloader.c b/lib/dfu-bootloader.c
index 1d7e02e..3df8351 100644
--- a/lib/dfu-bootloader.c
+++ b/lib/dfu-bootloader.c
@@ -451,8 +451,7 @@ restart: ;
 	DEBUG("DFU: Boot (sp=%08x pc=%08x)\n", (uint) sp, (uint) pc);
 
 #ifdef DEBUG_USART
-	while (!usart_get_flag(DEBUG_USART, USART_FLAG_TC))
-		;
+	debug_flush();
 #endif
 	debug_led(0);
 
diff --git a/lib/util-debug.c b/lib/util-debug.c
index 72a566e..d0914a6 100644
--- a/lib/util-debug.c
+++ b/lib/util-debug.c
@@ -80,6 +80,14 @@ void debug_putc(int c)
 #endif
 }
 
+void debug_flush(void)
+{
+#ifdef DEBUG_USART
+	while (!usart_get_flag(DEBUG_USART, USART_FLAG_TC))
+		;
+#endif
+}
+
 void debug_puts(const char *s)
 {
 	while (*s)
diff --git a/lib/util.h b/lib/util.h
index 6b9f4ba..18e3652 100644
--- a/lib/util.h
+++ b/lib/util.h
@@ -85,11 +85,19 @@ static inline void wait_for_interrupt(void)
 	asm volatile ("wfi");
 }
 
+// A compiler memory barrier
+
+static inline void barrier(void)
+{
+	asm volatile ("" : : : "memory");
+}
+
 // util-debug.c
 
 void debug_printf(const char *fmt, ...) __attribute__((format(printf,1,2)));
 void debug_puts(const char *s);
 void debug_putc(int c);
+void debug_flush(void);
 
 void debug_led(bool light);
 void debug_led_toggle(void);
-- 
2.39.2