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Date: Mon, 14 Sep 2009 16:07:31 -0400
From: Mike Frysinger <vapier@...too.org>
To: linux-kernel@...r.kernel.org
Cc: uclinux-dist-devel@...ckfin.uclinux.org,
Robin Getz <robin.getz@...log.com>
Subject: [PATCH 27/72] Blackfin: add an early shadow console
From: Robin Getz <robin.getz@...log.com>
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@...log.com>
Signed-off-by: Mike Frysinger <vapier@...too.org>
---
arch/blackfin/include/asm/early_printk.h | 2 +
arch/blackfin/kernel/Makefile | 1 +
arch/blackfin/kernel/setup.c | 2 +
arch/blackfin/kernel/shadow_console.c | 78 ++++++++++++++++++++++++++++++
4 files changed, 83 insertions(+), 0 deletions(-)
create mode 100644 arch/blackfin/kernel/shadow_console.c
diff --git a/arch/blackfin/include/asm/early_printk.h b/arch/blackfin/include/asm/early_printk.h
index 110f1c1..f5b6b7d 100644
--- a/arch/blackfin/include/asm/early_printk.h
+++ b/arch/blackfin/include/asm/early_printk.h
@@ -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 */
diff --git a/arch/blackfin/kernel/Makefile b/arch/blackfin/kernel/Makefile
index 141d928..a8ddbc8 100644
--- a/arch/blackfin/kernel/Makefile
+++ b/arch/blackfin/kernel/Makefile
@@ -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
diff --git a/arch/blackfin/kernel/setup.c b/arch/blackfin/kernel/setup.c
index 6dbf219..3974764 100644
--- a/arch/blackfin/kernel/setup.c
+++ b/arch/blackfin/kernel/setup.c
@@ -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",
diff --git a/arch/blackfin/kernel/shadow_console.c b/arch/blackfin/kernel/shadow_console.c
new file mode 100644
index 0000000..15819ff
--- /dev/null
+++ b/arch/blackfin/kernel/shadow_console.c
@@ -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);
--
1.6.4.2
--
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