Blackfin: add os log functions

Part of the mini Blackfin ABI with operating systems is that they can use
0x4f0-0x4f8 to pass log buffers to/from bootloaders.  So add support to
U-Boot for reading the log buffer.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

cpu/blackfin/Makefile

@@ -17,7 +17,7 @@ EXTRA    :=
 CEXTRA   := initcode.o
 SEXTRA   := start.o
 SOBJS    := interrupt.o cache.o
-COBJS-y  := cpu.o traps.o interrupts.o reset.o serial.o watchdog.o
+COBJS-y  := cpu.o traps.o interrupts.o os_log.o reset.o serial.o watchdog.o
 COBJS-$(CONFIG_JTAG_CONSOLE) += jtag-console.o
 
 ifeq ($(CONFIG_BFIN_BOOT_MODE),BFIN_BOOT_BYPASS)

cpu/blackfin/os_log.c

@@ -0,0 +1,30 @@
+/*
+ * functions for handling OS log buffer
+ *
+ * Copyright (c) 2009 Analog Devices Inc.
+ *
+ * Licensed under the 2-clause BSD.
+ */
+
+#include <common.h>
+
+#define OS_LOG_MAGIC       0xDEADBEEF
+#define OS_LOG_MAGIC_ADDR  ((unsigned long *)0x4f0)
+#define OS_LOG_PTR_ADDR    ((char **)0x4f4)
+
+bool bfin_os_log_check(void)
+{
+	if (*OS_LOG_MAGIC_ADDR != OS_LOG_MAGIC)
+		return false;
+	*OS_LOG_MAGIC_ADDR = 0;
+	return true;
+}
+
+void bfin_os_log_dump(void)
+{
+	char *log = *OS_LOG_PTR_ADDR;
+	while (*log) {
+		puts(log);
+		log += strlen(log) + 1;
+	}
+}