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

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

[Waldemar Brodkorb]

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@linux-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@linux-m68k.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

After reverting the change, everything is fine.

I can provide a .config and dmesg if needed.

Thanks in advance
 Waldemar

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

[Geert Uytterhoeven]

Hi Waldemar,

On Fri, May 16, 2014 at 3:49 PM, Waldemar Brodkorb <wbx@openadk.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@linux-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@linux-m68k.org>
>     Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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@linux-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

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

[Waldemar Brodkorb]

Hi Geert,
Geert Uytterhoeven wrote,

> Hi Waldemar,
> 
> On Fri, May 16, 2014 at 3:49 PM, Waldemar Brodkorb <wbx@openadk.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@linux-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@linux-m68k.org>
> >     Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> >
> > After reverting the change, everything is fine.
> 
> Does this patch help? https://lkml.org/lkml/2014/5/10/9

The second change in printk.c didn't help.
 
> I guess you're not using of_serial?

No, I am not.

> 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.

Tried following patch, but it didn't work:

diff -Nur linux-3.15-rc5.orig/arch/mips/rb532/serial.c
linux-3.15-rc5/arch/mips/rb532/serial.c
--- linux-3.15-rc5.orig/arch/mips/rb532/serial.c        2014-05-09
22:10:52.000000000 +0200
+++ linux-3.15-rc5/arch/mips/rb532/serial.c     2014-05-19
20:35:08.000000000 +0200
@@ -37,7 +37,7 @@
 extern unsigned int idt_cpu_freq;
 
 static struct uart_port rb532_uart = {
-       .flags = UPF_BOOT_AUTOCONF,
+       .type = PORT_16550A,
        .line = 0,
        .irq = UART0_IRQ,
        .iotype = UPIO_MEM,
diff -Nur linux-3.15-rc5.orig/kernel/printk/printk.c
linux-3.15-rc5/kernel/printk/printk.c
--- linux-3.15-rc5.orig/kernel/printk/printk.c  2014-05-09
22:10:52.000000000 +0200
+++ linux-3.15-rc5/kernel/printk/printk.c       2014-05-20
09:39:54.000000000 +0200
@@ -2413,6 +2413,7 @@
        if (console_drivers != NULL && console->flags & CON_CONSDEV)
                console_drivers->flags |= CON_CONSDEV;
 
+       console->flags &= ~CON_ENABLED;
        console_unlock();
        console_sysfs_notify();
        return res;


best regards
        Waldemar

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

[Geert Uytterhoeven]

Hi Waldemar,

On Tue, May 20, 2014 at 10:21 AM, Waldemar Brodkorb <wbx@openadk.org> wrote:
> Geert Uytterhoeven wrote,
>> On Fri, May 16, 2014 at 3:49 PM, Waldemar Brodkorb <wbx@openadk.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@linux-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@linux-m68k.org>
>> >     Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> >
>> > After reverting the change, everything is fine.
>>
>> Does this patch help? https://lkml.org/lkml/2014/5/10/9
>
> The second change in printk.c didn't help.

>> 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.
>
> Tried following patch, but it didn't work:
>
> diff -Nur linux-3.15-rc5.orig/arch/mips/rb532/serial.c
> linux-3.15-rc5/arch/mips/rb532/serial.c
> --- linux-3.15-rc5.orig/arch/mips/rb532/serial.c        2014-05-09
> 22:10:52.000000000 +0200
> +++ linux-3.15-rc5/arch/mips/rb532/serial.c     2014-05-19
> 20:35:08.000000000 +0200
> @@ -37,7 +37,7 @@
>  extern unsigned int idt_cpu_freq;
>
>  static struct uart_port rb532_uart = {
> -       .flags = UPF_BOOT_AUTOCONF,
> +       .type = PORT_16550A,

I'm afraid this is not gonna help. When the port is unregistered, its
type will be reset to PORT_UNKNOWN.
So before registering it again, its type must be set againin the actual
serial driver, cfr. the change to of_serial.c.

>         .line = 0,
>         .irq = UART0_IRQ,
>         .iotype = UPIO_MEM,
> diff -Nur linux-3.15-rc5.orig/kernel/printk/printk.c
> linux-3.15-rc5/kernel/printk/printk.c
> --- linux-3.15-rc5.orig/kernel/printk/printk.c  2014-05-09
> 22:10:52.000000000 +0200
> +++ linux-3.15-rc5/kernel/printk/printk.c       2014-05-20
> 09:39:54.000000000 +0200
> @@ -2413,6 +2413,7 @@
>         if (console_drivers != NULL && console->flags & CON_CONSDEV)
>                 console_drivers->flags |= CON_CONSDEV;
>
> +       console->flags &= ~CON_ENABLED;
>         console_unlock();
>         console_sysfs_notify();
>         return res;

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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