[PATCH 24/42] x86: Setup early console as early as possible in x86_start_kernel()

[Yinghai Lu <yinghai@kernel.org>]

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.

Use boot_params.hdr.version instead of adding another variable, Suggested by hpa.
Also need to apply this one after x86 memblock patchset.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
---
 arch/x86/include/asm/setup.h         |  2 ++
 arch/x86/kernel/head.c               | 26 ++++++++++++++++++++++++++
 arch/x86/kernel/head32.c             |  1 +
 arch/x86/kernel/head64.c             |  5 ++++-
 drivers/tty/serial/8250/8250_early.c | 17 +++++++++++++++++
 kernel/printk/printk.c               | 11 +++++++----
 6 files changed, 57 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
index 11af24e..3e5aa41 100644
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -40,6 +40,8 @@ static inline void vsmp_init(void) { }
 void setup_bios_corruption_check(void);
 
 extern unsigned long saved_video_mode;
+int setup_early_serial8250_console(char *cmdline);
+void setup_early_console(void);
 
 extern void reserve_standard_io_resources(void);
 extern void i386_reserve_resources(void);
diff --git a/arch/x86/kernel/head.c b/arch/x86/kernel/head.c
index 992f442..cc0cd83 100644
--- a/arch/x86/kernel/head.c
+++ b/arch/x86/kernel/head.c
@@ -69,3 +69,29 @@ void __init reserve_ebda_region(void)
 	/* reserve all memory between lowmem and the 1MB mark */
 	memblock_reserve(lowmem, 0x100000 - lowmem);
 }
+
+void __init setup_early_console(void)
+{
+#ifdef CONFIG_SERIAL_8250_CONSOLE
+	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 = strchrnul(p, ' ');
+	if ((q - p) >= sizeof(constr))
+		return;
+
+	memset(constr, 0, sizeof(constr));
+	memcpy(constr, p, q - p);
+
+	lockdep_init();
+
+	setup_early_serial8250_console(constr);
+#endif
+}
diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c
index 2911ef3..87ddca1 100644
--- a/arch/x86/kernel/head32.c
+++ b/arch/x86/kernel/head32.c
@@ -33,6 +33,7 @@ asmlinkage __visible void __init i386_start_kernel(void)
 {
 	cr4_init_shadow();
 	sanitize_boot_params(&boot_params);
+	setup_early_console();
 
 	/* Call the subarch specific early setup function */
 	switch (boot_params.hdr.hardware_subarch) {
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 5a46681..44dc63b 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -171,6 +171,7 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
 	load_idt((const struct desc_ptr *)&idt_descr);
 
 	copy_bootdata(__va(real_mode_data));
+	setup_early_console();
 
 	/*
 	 * Load microcode early on BSP.
@@ -189,8 +190,10 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
 void __init x86_64_start_reservations(char *real_mode_data)
 {
 	/* version is always not zero if it is copied */
-	if (!boot_params.hdr.version)
+	if (!boot_params.hdr.version) {
 		copy_bootdata(__va(real_mode_data));
+		setup_early_console();
+	}
 
 	reserve_ebda_region();
 
diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
index 771dda2..8a7fe75 100644
--- a/drivers/tty/serial/8250/8250_early.c
+++ b/drivers/tty/serial/8250/8250_early.c
@@ -152,3 +152,20 @@ int __init early_serial8250_setup(struct earlycon_device *device,
 }
 EARLYCON_DECLARE(uart8250, early_serial8250_setup);
 EARLYCON_DECLARE(uart, early_serial8250_setup);
+
+/* for x86 early early console */
+int __init setup_early_serial8250_console(char *cmdline)
+{
+	char *options;
+
+	options = strstr(cmdline, "uart8250,");
+	if (options)
+		return setup_earlycon(options);
+
+	options = strstr(cmdline, "uart,");
+	if (options)
+		return setup_earlycon(options);
+
+	return 0;
+}
+
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index cf8c242..f554c5f 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2454,11 +2454,14 @@ void register_console(struct console *newcon)
 	struct console_cmdline *c;
 
 	if (console_drivers)
-		for_each_console(bcon)
-			if (WARN(bcon == newcon,
-					"console '%s%d' already registered\n",
-					bcon->name, bcon->index))
+		for_each_console(bcon) {
+			/* not again */
+			if (bcon == newcon) {
+				printk(KERN_INFO "console '%s%d' already registered\n",
+					bcon->name, bcon->index);
 				return;
+			}
+	}
 
 	/*
 	 * before we register a new CON_BOOT console, make sure we don't
-- 
1.8.4.5