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Blackfin: add an early shadow console

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Add a memory based shadow console to keep a copy of the printk buffer in a
location which can be found externally.  This allows bootloaders to locate
and utilize the log buffer in case of silent (early/resume/etc...) crashes.

Signed-off-by: Robin Getz <robin.getz@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
This commit is contained in:
Robin Getz 2009-07-06 14:53:19 +00:00 committed by Mike Frysinger
parent 53e18df745
commit 3f871feaf3
4 changed files with 83 additions and 0 deletions
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2
arch/blackfin/include/asm/early_printk.h
View file

@ -23,6 +23,8 @@
#ifdef CONFIG_EARLY_PRINTK
extern int setup_early_printk(char *);
extern void enable_shadow_console(void);
#else
#define setup_early_printk(fmt) do { } while (0)
#define enable_shadow_console(fmt) do { } while (0)
#endif /* CONFIG_EARLY_PRINTK */

1
arch/blackfin/kernel/Makefile
View file

@ -26,6 +26,7 @@ obj-$(CONFIG_MODULES) += module.o
obj-$(CONFIG_KGDB) += kgdb.o
obj-$(CONFIG_KGDB_TESTS) += kgdb_test.o
obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
obj-$(CONFIG_EARLY_PRINTK) += shadow_console.o
obj-$(CONFIG_STACKTRACE) += stacktrace.o
# the kgdb test puts code into L2 and without linker

2
arch/blackfin/kernel/setup.c
View file

@ -810,6 +810,8 @@ void __init setup_arch(char **cmdline_p)
{
unsigned long sclk, cclk;
enable_shadow_console();
/* Check to make sure we are running on the right processor */
if (unlikely(CPUID != bfin_cpuid()))
printk(KERN_ERR "ERROR: Not running on ADSP-%s: unknown CPUID 0x%04x Rev 0.%d\n",

78
arch/blackfin/kernel/shadow_console.c Normal file
View file

@ -0,0 +1,78 @@
/*
* manage a small early shadow of the log buffer which we can pass between the
* bootloader so early crash messages are communicated properly and easily
*
* Copyright 2009 Analog Devices Inc.
*
* Enter bugs at http://blackfin.uclinux.org/
*
* Licensed under the GPL-2 or later.
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/string.h>
#include <asm/blackfin.h>
#include <asm/irq_handler.h>
#include <asm/early_printk.h>
#define SHADOW_CONSOLE_START (0x500)
#define SHADOW_CONSOLE_END (0x1000)
#define SHADOW_CONSOLE_MAGIC_LOC (0x4F0)
#define SHADOW_CONSOLE_MAGIC (0xDEADBEEF)
static __initdata char *shadow_console_buffer = (char *)SHADOW_CONSOLE_START;
static __init void early_shadow_write(struct console *con, const char *s,
unsigned int n)
{
/*
* save 2 bytes for the double null at the end
* once we fail on a long line, make sure we don't write a short line afterwards
*/
if ((shadow_console_buffer + n) <= (char *)(SHADOW_CONSOLE_END - 2)) {
memcpy(shadow_console_buffer, s, n);
shadow_console_buffer += n;
shadow_console_buffer[0] = 0;
shadow_console_buffer[1] = 0;
} else
shadow_console_buffer = (char *)SHADOW_CONSOLE_END;
}
static __initdata struct console early_shadow_console = {
.name = "early_shadow",
.write = early_shadow_write,
.flags = CON_BOOT | CON_PRINTBUFFER,
.index = -1,
.device = 0,
};
__init void enable_shadow_console(void)
{
int *loc = (int *)SHADOW_CONSOLE_MAGIC_LOC;
if (!(early_shadow_console.flags & CON_ENABLED)) {
register_console(&early_shadow_console);
/* for now, assume things are going to fail */
*loc = SHADOW_CONSOLE_MAGIC;
loc++;
*loc = SHADOW_CONSOLE_START;
}
}
static __init int disable_shadow_console(void)
{
/*
* by the time pure_initcall runs, the standard console is enabled,
* and the early_console is off, so unset the magic numbers
* unregistering the console is taken care of in common code (See
* ./kernel/printk:disable_boot_consoles() )
*/
int *loc = (int *)SHADOW_CONSOLE_MAGIC_LOC;
*loc = 0;
return 0;
}
pure_initcall(disable_shadow_console);