ARM: Add an earlyprintk debug console
This patch allows an earlyprintk console if CONFIG_DEBUG_LL is enabled,
using the printch asm function.
The patch is based on the original work by Sascha Hauer.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Pavel Machek <pavel@ucw.cz>
diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index 1a6f70e..feb7b11 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -71,6 +71,14 @@
in the kernel. This is helpful if you are debugging code that
executes before the console is initialized.
+config EARLY_PRINTK
+ bool "Early printk"
+ depends on DEBUG_LL
+ help
+ Say Y here if you want to have an early console using the
+ kernel low-level debugging functions. Add earlyprintk to your
+ kernel parameters to enable this console.
+
config DEBUG_ICEDCC
bool "Kernel low-level debugging via EmbeddedICE DCC channel"
depends on DEBUG_LL
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 79087dd..d0e40b7 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -52,5 +52,6 @@
head-y := head$(MMUEXT).o
obj-$(CONFIG_DEBUG_LL) += debug.o
+obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
extra-y := $(head-y) init_task.o vmlinux.lds
diff --git a/arch/arm/kernel/early_printk.c b/arch/arm/kernel/early_printk.c
new file mode 100644
index 0000000..85aa2b2
--- /dev/null
+++ b/arch/arm/kernel/early_printk.c
@@ -0,0 +1,57 @@
+/*
+ * linux/arch/arm/kernel/early_printk.c
+ *
+ * Copyright (C) 2009 Sascha Hauer <s.hauer@pengutronix.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/console.h>
+#include <linux/init.h>
+
+extern void printch(int);
+
+static void early_write(const char *s, unsigned n)
+{
+ while (n-- > 0) {
+ if (*s == '\n')
+ printch('\r');
+ printch(*s);
+ s++;
+ }
+}
+
+static void early_console_write(struct console *con, const char *s, unsigned n)
+{
+ early_write(s, n);
+}
+
+static struct console early_console = {
+ .name = "earlycon",
+ .write = early_console_write,
+ .flags = CON_PRINTBUFFER | CON_BOOT,
+ .index = -1,
+};
+
+asmlinkage void early_printk(const char *fmt, ...)
+{
+ char buf[512];
+ int n;
+ va_list ap;
+
+ va_start(ap, fmt);
+ n = vscnprintf(buf, sizeof(buf), fmt, ap);
+ early_write(buf, n);
+ va_end(ap);
+}
+
+static int __init setup_early_printk(char *buf)
+{
+ register_console(&early_console);
+ return 0;
+}
+
+early_param("earlyprintk", setup_early_printk);