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serial: convert early_uart to earlycon for 8250

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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>
This commit is contained in:
Yinghai Lu 2007-07-15 23:37:59 -07:00 • committed by Linus Torvalds
parent b1c931e393
commit 18a8bd949d
15 changed files with 138 additions and 101 deletions
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6
include/linux/serial.h
View file

@ -177,11 +177,5 @@ struct serial_icounter_struct {
#ifdef __KERNEL__
#include <linux/compiler.h>
/* Allow architectures to override entries in serial8250_ports[] at run time: */
struct uart_port; /* forward declaration */
extern int early_serial_setup(struct uart_port *port);
extern int early_serial_console_init(char *options);
extern int serial8250_start_console(struct uart_port *port, char *options);
#endif /* __KERNEL__ */
#endif /* _LINUX_SERIAL_H */