• Yinghai Lu's avatar
    serial: convert early_uart to earlycon for 8250 · 18a8bd94
    Yinghai Lu authored
    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: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    18a8bd94
serial.h 5 KB