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Commit 93fd03a8 authored by Catalin Marinas's avatar Catalin Marinas
Browse files

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: default avatarCatalin Marinas <catalin.marinas@arm.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: default avatarPavel Machek <pavel@ucw.cz>
parent 22763c5c

arch/arm/Kconfig.debug

+8 −0
Original line number Diff line number Diff line
@@ -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

arch/arm/kernel/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/arm/kernel/early_printk.c

0 → 100644
+57 −0
Original line number Diff line number Diff line 
/*

 *  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);