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

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Message-ID: <CAMuHMdVPSzYkUumqMY78zxVcoQ6=W9Vfm_tyM_T3W8DFzCztVw@mail.gmail.com>
Date:	Fri, 16 May 2014 16:20:18 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Waldemar Brodkorb <wbx@...nadk.org>
Cc:	Linux MIPS Mailing List <linux-mips@...ux-mips.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Geert Uytterhoeven <geert+renesas@...ux-m68k.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: serial console on rb532 disabled on boot (linux 3.15rc5)

Hi Waldemar,

On Fri, May 16, 2014 at 3:49 PM, Waldemar Brodkorb <wbx@...nadk.org> wrote:
> 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.

Does this patch help? https://lkml.org/lkml/2014/5/10/9

I guess you're not using of_serial?
Your serial driver may need to set port.type too, if it doesn't already do so
and the type is PORT_UNKNOWN on re-registration.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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