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ARM: Add an earlyprintk debug console

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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>
This commit is contained in:
Catalin Marinas 2009-12-09 10:02:18 +00:00
parent 22763c5cf3
commit 93fd03a8c6
3 changed files with 66 additions and 0 deletions
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8
arch/arm/Kconfig.debug
View file

@ -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.
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

1
arch/arm/kernel/Makefile
View file

@ -52,5 +52,6 @@ endif
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

57
arch/arm/kernel/early_printk.c Normal file
View file

@ -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);