Blackfin arch: Initial patch to add earlyprintk support

This allows debugging of problems which happen eary in the kernel
boot process (after bootargs are parsed, but before serial subsystem
is fully initialized)

Signed-off-by: Robin Getz <robin.getz@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

3 files changed, 176 insertions, 0 deletions

diff --git a/arch/blackfin/Kconfig b/arch/blackfin/Kconfig
index 26ebb0e8c431..cc789b988f3a 100644
--- a/arch/blackfin/Kconfig
+++ b/arch/blackfin/Kconfig
@@ -1164,6 +1164,20 @@ config DEBUG_BFIN_NO_KERN_HWTRACE
 	  Say Y here to disable hardware tracing in some known "jumpy" pieces
 	  of code so that the trace buffer will extend further back.
 
+config EARLY_PRINTK
+	bool "Early printk" 
+	default n
+	help
+	  This option enables special console drivers which allow the kernel
+	  to print messages very early in the bootup process.
+
+	  This is useful for kernel debugging when your machine crashes very
+	  early before the console code is initialized. After enabling this
+	  feature, you must add "earlyprintk=serial,uart0,57600" to the
+	  command line (bootargs). It is safe to say Y here in all cases, as
+	  all of this lives in the init section and is thrown away after the
+	  kernel boots completely.
+
 config DUAL_CORE_TEST_MODULE
 	tristate "Dual Core Test Module"
 	depends on (BF561)
diff --git a/arch/blackfin/kernel/Makefile b/arch/blackfin/kernel/Makefile
index 243883ec6de1..8aeb6066b19b 100644
--- a/arch/blackfin/kernel/Makefile
+++ b/arch/blackfin/kernel/Makefile
@@ -13,3 +13,4 @@ obj-$(CONFIG_MODULES)                += module.o
 obj-$(CONFIG_BFIN_DMA_5XX)           += bfin_dma_5xx.o
 obj-$(CONFIG_DUAL_CORE_TEST_MODULE)  += dualcore_test.o
 obj-$(CONFIG_KGDB)                   += kgdb.o
+obj-$(CONFIG_EARLY_PRINTK)           += early_printk.o
diff --git a/arch/blackfin/kernel/early_printk.c b/arch/blackfin/kernel/early_printk.c
new file mode 100644
index 000000000000..9bf61706694f
--- /dev/null
+++ b/arch/blackfin/kernel/early_printk.c
@@ -0,0 +1,161 @@
+/*
+ * File:         arch/blackfin/kernel/early_printk.c
+ * Based on:     arch/x86_64/kernel/early_printk.c
+ * Author:       Robin Getz <rgetz@blackfin.uclinux.org
+ *
+ * Created:      14Aug2007
+ * Description:  allow a console to be used for early printk
+ *
+ * Modified:
+ *               Copyright 2004-2007 Analog Devices Inc.
+ *
+ * Bugs:         Enter bugs at http://blackfin.uclinux.org/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/serial_core.h>
+#include <linux/console.h>
+#include <linux/string.h>
+#include <asm/blackfin.h>
+#include <asm/irq_handler.h>
+#include <asm/early_printk.h>
+
+#ifdef CONFIG_SERIAL_BFIN
+extern struct console *bfin_earlyserial_init(unsigned int port,
+						unsigned int cflag);
+#endif
+
+static struct console *early_console;
+
+/* Default console
+ * Port n == ttyBFn
+ * cflags == UART output modes
+ */
+#define DEFAULT_PORT 0
+#define DEFAULT_CFLAG CS8|B57600
+
+#ifdef CONFIG_SERIAL_CORE
+/* What should get here is "0,57600" */
+static struct console * __init earlyserial_init(char *buf)
+{
+	int baud, bit;
+	char parity;
+	unsigned int serial_port = DEFAULT_PORT;
+	unsigned int cflag = DEFAULT_CFLAG;
+
+	serial_port = simple_strtoul(buf, &buf, 10);
+	buf++;
+
+	cflag = 0;
+	baud = simple_strtoul(buf, &buf, 10);
+	switch (baud) {
+	case 1200:
+		cflag |= B1200;
+		break;
+	case 2400:
+		cflag |= B2400;
+		break;
+	case 4800:
+		cflag |= B4800;
+		break;
+	case 9600:
+		cflag |= B9600;
+		break;
+	case 19200:
+		cflag |= B19200;
+		break;
+	case 38400:
+		cflag |= B38400;
+		break;
+	case 115200:
+		cflag |= B115200;
+		break;
+	default:
+		cflag |= B57600;
+	}
+
+	parity = buf[0];
+	buf++;
+	switch (parity) {
+	case 'e':
+		cflag |= PARENB;
+		break;
+	case 'o':
+		cflag |= PARODD;
+		break;
+	}
+
+	bit = simple_strtoul(buf, &buf, 10);
+	switch (bit) {
+	case 5:
+		cflag |= CS5;
+		break;
+	case 6:
+		cflag |= CS5;
+		break;
+	case 7:
+		cflag |= CS5;
+		break;
+	default:
+		cflag |= CS8;
+	}
+
+#ifdef CONFIG_SERIAL_BFIN
+	return bfin_earlyserial_init(serial_port, cflag);
+#else
+	return NULL;
+#endif
+
+}
+#endif
+
+int __init setup_early_printk(char *buf)
+{
+
+	/* Crashing in here would be really bad, so check both the var
+	   and the pointer before we start using it
+	 */
+	if (!buf)
+		return 0;
+
+	if (!*buf)
+		return 0;
+
+	if (early_console != NULL)
+		return 0;
+
+#ifdef CONFIG_SERIAL_BFIN
+	/* Check for Blackfin Serial */
+	if (!strncmp(buf, "serial,uart", 11)) {
+		buf += 11;
+		early_console = earlyserial_init(buf);
+	}
+#endif
+#ifdef CONFIG_FB
+		/* TODO: add framebuffer console support */
+#endif
+
+	if (likely(early_console)) {
+		early_console->flags |= CON_BOOT;
+
+		register_console(early_console);
+		printk(KERN_INFO "early printk enabled on %s%d\n",
+			early_console->name,
+			early_console->index);
+	}
+
+	return 0;
+}
+
+early_param("earlyprintk", setup_early_printk);