linux-kernel - serial console on rb532 disabled on boot (linux 3.15rc5)

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Message-ID: <20140516134904.GW618@waldemar-brodkorb.de>
Date:	Fri, 16 May 2014 15:49:04 +0200
From:	Waldemar Brodkorb <wbx@...nadk.org>
To:	linux-mips@...ux-mips.org
Cc:	linux-kernel@...r.kernel.org,
	Geert Uytterhoeven <geert+renesas@...ux-m68k.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: serial console on rb532 disabled on boot (linux 3.15rc5)

Hi Linux hackers,

I am trying to bootup my Mikrotik RB532 board with the latest
kernel, but my serial console is disabled after boot:
..
Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
serial8250: ttyS0 at MMIO 0x0 (irq = 104, base_baud = 12499875) is a
16550A
console [ttyS0] enabled
console [ttyS0] disabled

I used git bisect to find the problematic commit:
commit 5f5c9ae56c38942623f69c3e6dc6ec78e4da2076
Author: Geert Uytterhoeven <geert+renesas@...ux-m68k.org>
Date:   Fri Feb 28 14:21:32 2014 +0100

    serial_core: Unregister console in uart_remove_one_port()
    
    If the serial port being removed is used as a console, it must
also be
    unregistered from the console subsystem using
unregister_console().
    
    uart_ops.release_port() will release resources (e.g. iounmap()
the serial
    port registers), causing a crash on subsequent kernel output if
the console
    is still registered.
    
    Signed-off-by: Geert Uytterhoeven <geert+renesas@...ux-m68k.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

After reverting the change, everything is fine.

I can provide a .config and dmesg if needed.

Thanks in advance
 Waldemar

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