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 (file)
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -71,6 +71,14 @@ config DEBUG_LL
          in the kernel.  This is helpful if you are debugging code that
          executes before the console is initialized.
 
          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
 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 (file)
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -52,5 +52,6 @@ endif
 
 head-y                 := head$(MMUEXT).o
 obj-$(CONFIG_DEBUG_LL) += debug.o
 
 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
 
 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 (file)
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);