ARM: enable raw_printk() over serial debug channel

arch/arm/kernel/Makefile

@@ -88,6 +88,7 @@ obj-$(CONFIG_PARAVIRT)	+= paravirt.o
 head-y			:= head$(MMUEXT).o
 obj-$(CONFIG_DEBUG_LL)	+= debug.o
 obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o
+obj-$(CONFIG_RAW_PRINTK)	+= raw_printk.o
 obj-$(CONFIG_IPIPE)	+= ipipe.o
 obj-$(CONFIG_IPIPE_ARM_KUSER_TSC) += ipipe_tsc.o ipipe_tsc_asm.o
 

arch/arm/kernel/raw_printk.c

+#include <linux/kernel.h>
+#include <linux/console.h>
+#include <linux/init.h>
+
+void __weak printascii(const char *s)
+{
+	/*
+	 * Allow building if CONFIG_DEBUG_LL is off but keep silent on
+	 * raw_printk().
+	 */
+}
+
+static void raw_console_write(struct console *co,
+			      const char *s, unsigned count)
+{
+	printascii(s);
+}
+
+static struct console raw_console = {
+	.name		= "rawcon",
+	.write_raw	= raw_console_write,
+	.flags		= CON_PRINTBUFFER | CON_RAW | CON_ENABLED,
+	.index		= -1,
+};
+
+static int __init raw_console_init(void)
+{
+	register_console(&raw_console);
+
+	return 0;
+}
+
+console_initcall(raw_console_init);