serial: convert early_uart to earlycon for 8250

Beacuse SERIAL_PORT_DFNS is removed from include/asm-i386/serial.h and
include/asm-x86_64/serial.h.  the serial8250_ports need to be probed late in
serial initializing stage.  the console_init=>serial8250_console_init=>
register_console=>serial8250_console_setup will return -ENDEV, and console
ttyS0 can not be enabled at that time.  need to wait till uart_add_one_port in
drivers/serial/serial_core.c to call register_console to get console ttyS0.
that is too late.

Make early_uart to use early_param, so uart console can be used earlier.  Make
it to be bootconsole with CON_BOOT flag, so can use console handover feature.
and it will switch to corresponding normal serial console automatically.

new command line will be:
	console=uart8250,io,0x3f8,9600n8
	console=uart8250,mmio,0xff5e0000,115200n8
or
	earlycon=uart8250,io,0x3f8,9600n8
	earlycon=uart8250,mmio,0xff5e0000,115200n8

it will print in very early stage:
	Early serial console at I/O port 0x3f8 (options '9600n8')
	console [uart0] enabled
later for console it will print:
	console handover: boot [uart0] -> real [ttyS0]

Signed-off-by: <yinghai.lu@sun.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Gerd Hoffmann <kraxel@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 21 deletions

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index c84dab083a85..0b3ec38ae614 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -2514,12 +2514,18 @@ static int __init serial8250_console_setup(struct console *co, char *options)
         return uart_set_options(port, co, baud, parity, bits, flow);
 }
 
+static int __init serial8250_console_early_setup(void)
+{
+        return serial8250_find_port_for_earlycon();
+}
+
 static struct uart_driver serial8250_reg;
 static struct console serial8250_console = {
         .name           = "ttyS",
         .write          = serial8250_console_write,
         .device         = uart_console_device,
         .setup          = serial8250_console_setup,
+        .early_setup    = serial8250_console_early_setup,
         .flags          = CON_PRINTBUFFER,
         .index          = -1,
         .data           = &serial8250_reg,
@@ -2533,7 +2539,7 @@ static int __init serial8250_console_init(void)
 }
 console_initcall(serial8250_console_init);
 
-static int __init find_port(struct uart_port *p)
+int serial8250_find_port(struct uart_port *p)
 {
         int line;
         struct uart_port *port;
@@ -2546,26 +2552,6 @@ static int __init find_port(struct uart_port *p)
         return -ENODEV;
 }
 
-int __init serial8250_start_console(struct uart_port *port, char *options)
-{
-        int line;
-
-        line = find_port(port);
-        if (line < 0)
-                return -ENODEV;
-
-        add_preferred_console("ttyS", line, options);
-        printk("Adding console on ttyS%d at %s 0x%lx (options '%s')\n",
-                line, port->iotype == UPIO_MEM ? "MMIO" : "I/O port",
-                port->iotype == UPIO_MEM ? (unsigned long) port->mapbase :
-                    (unsigned long) port->iobase, options);
-        if (!(serial8250_console.flags & CON_ENABLED)) {
-                serial8250_console.flags &= ~CON_PRINTBUFFER;
-                register_console(&serial8250_console);
-        }
-        return line;
-}
-
 #define SERIAL8250_CONSOLE      &serial8250_console
 #else
 #define SERIAL8250_CONSOLE      NULL