[PATCH] x86: Setup early console as early as possible

[Yinghai Lu <yinghai.lu@oracle.com>]

Analyze "console=uart8250,io,0x3f8,115200n8" in i386_start_kernel/x86_64_start_kernel,
and call setup_early_serial8250_console() to init early serial console.

only can handle io port kind of 8250. because mmio need ioremap.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
---
 arch/x86/include/asm/setup.h |    1 +
 arch/x86/kernel/head.c       |   32 ++++++++++++++++++++++++++++++++
 arch/x86/kernel/head32.c     |    2 ++
 arch/x86/kernel/head64.c     |   11 +++++++++++
 kernel/printk.c              |    4 ++++
 5 files changed, 50 insertions(+)

Index: linux-2.6/arch/x86/include/asm/setup.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/setup.h
+++ linux-2.6/arch/x86/include/asm/setup.h
@@ -42,6 +42,7 @@ static inline void visws_early_detect(vo
 #endif
 
 extern unsigned long saved_video_mode;
+void setup_early_console(void);
 
 extern void reserve_standard_io_resources(void);
 extern void i386_reserve_resources(void);
Index: linux-2.6/arch/x86/kernel/head.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/head.c
+++ linux-2.6/arch/x86/kernel/head.c
@@ -53,3 +53,35 @@ void __init reserve_ebda_region(void)
 	/* reserve all memory between lowmem and the 1MB mark */
 	reserve_early_overlap_ok(lowmem, 0x100000, "BIOS reserved");
 }
+
+#ifdef CONFIG_SERIAL_8250_CONSOLE
+int setup_early_serial8250_console(char *cmdline);
+
+void __init setup_early_console(void)
+{
+	char constr[64], *p, *q;
+
+	/* Can not handle mmio type 8250 uart yet, too early */
+	p = strstr(boot_command_line, "console=uart8250,io,");
+	if (!p)
+		p = strstr(boot_command_line, "console=uart,io,");
+	if (!p)
+		return;
+
+	p += 8;	/* sizeof "console=" */
+	q = strchr(p, ' ');
+	if ((q - p) >= sizeof(constr))
+		return;
+
+	memset(constr, 0, sizeof(constr));
+	memcpy(constr, p, q - p);
+
+	lockdep_init();
+
+	setup_early_serial8250_console(constr);
+}
+#else
+void __init setup_early_console(void)
+{
+}
+#endif
Index: linux-2.6/arch/x86/kernel/head32.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/head32.c
+++ linux-2.6/arch/x86/kernel/head32.c
@@ -30,6 +30,8 @@ static void __init i386_default_early_se
 
 void __init i386_start_kernel(void)
 {
+	setup_early_console();
+
 #ifdef CONFIG_X86_TRAMPOLINE
 	/*
 	 * But first pinch a few for the stack/trampoline stuff
Index: linux-2.6/arch/x86/kernel/head64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/head64.c
+++ linux-2.6/arch/x86/kernel/head64.c
@@ -41,15 +41,21 @@ static void __init clear_bss(void)
 	       (unsigned long) __bss_stop - (unsigned long) __bss_start);
 }
 
+static int __initdata bootdata_copied;
 static void __init copy_bootdata(char *real_mode_data)
 {
 	char * command_line;
 
+	if (bootdata_copied)
+		return;
+
 	memcpy(&boot_params, real_mode_data, sizeof boot_params);
 	if (boot_params.hdr.cmd_line_ptr) {
 		command_line = __va(boot_params.hdr.cmd_line_ptr);
 		memcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
 	}
+
+	bootdata_copied = 1;
 }
 
 void __init x86_64_start_kernel(char * real_mode_data)
@@ -73,6 +79,10 @@ void __init x86_64_start_kernel(char * r
 	/* clear bss before set_intr_gate with early_idt_handler */
 	clear_bss();
 
+	/* boot_params is in bss */
+	copy_bootdata(__va(real_mode_data));
+	setup_early_console();
+
 	/* Make NULL pointers segfault */
 	zap_identity_mappings();
 
@@ -97,6 +107,7 @@ void __init x86_64_start_kernel(char * r
 void __init x86_64_start_reservations(char *real_mode_data)
 {
 	copy_bootdata(__va(real_mode_data));
+	setup_early_console();
 
 	reserve_early(__pa_symbol(&_text), __pa_symbol(&__bss_stop), "TEXT DATA BSS");
 
Index: linux-2.6/kernel/printk.c
===================================================================
--- linux-2.6.orig/kernel/printk.c
+++ linux-2.6/kernel/printk.c
@@ -1203,6 +1203,10 @@ void register_console(struct console *ne
 	if (console_drivers && newcon->flags & CON_BOOT) {
 		/* find the last or real console */
 		for_each_console(bcon) {
+			/* not again */
+			if (bcon == newcon)
+				return;
+
 			if (!(bcon->flags & CON_BOOT)) {
 				printk(KERN_INFO "Too late to register bootconsole %s%d\n",
 					newcon->name, newcon->index);