Re: [PATCH] ARM: shmobile: alt dts: Drop console= bootargs parameter

[Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>]

Hello.

On 01/31/2015 07:17 AM, Simon Horman wrote:

>>> Alt is booted from DT, so chosen/stdout-path is
>>> always used, and we can drop the "console=" parameter from chosen/bootargs.

>>> This change has a side-effect of changing the console speed from 38400
>>> to 115200. This is intentional as 115200 is consistently used on
>>> all other shmobile boards.

>>     I'd say it's not very practical to change the console's baud rate from
>> U-Boot's default

> It is consistent with the handling of all other boards with
> renesas SoCs that are present in mainline.

    Well, not quite: Henninger/Porter is still using 38400.

>> (AFAIR changing baud rate in U-Boot didn't work)...

    That was a recollection from the other board though, I haven't yet tried 
to do it on the SILK board (and I'm unable to currently as the power supply 
seems dead).

> Perhaps that relates to the version of built of uboot.
> On the board I have access to I see:

> ver=U-Boot 2013.01.01-g5df9446 (Oct 01 2014 - 14:59:23)

U-Boot 2013.01.01 (Oct 17 2014 - 20:59:18)

> And the following setting altered the baud rate of u-boot (IIRC).

> baudrate=115200

    I was going to try that but the board just didn't power up.

>>> Cc: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
>>> Cc: Geert Uytterhoeven <geert+renesas@glider.be>
>>> Cc: devicetree@vger.kernel.org
>>> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
>>> ---
>>>   arch/arm/boot/dts/r8a7794-alt.dts | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)

>>> diff --git a/arch/arm/boot/dts/r8a7794-alt.dts b/arch/arm/boot/dts/r8a7794-alt.dts
>>> index 8aec512..f2cf757 100644
>>> --- a/arch/arm/boot/dts/r8a7794-alt.dts
>>> +++ b/arch/arm/boot/dts/r8a7794-alt.dts
>>> @@ -20,7 +20,7 @@
>>>   	};
>>>
>>>   	chosen {
>>> -		bootargs = "console=ttySC0,38400 ignore_loglevel rw root=/dev/nfs ip=dhcp";
>>> +		bootargs = "ignore_loglevel rw root=/dev/nfs ip=dhcp";

>>     Hm, does this even work as intended? I've tried to boot another R8A7794
>> based board and I couldn't get any output with alike command line. Booting
>> with 'earlyprintk=serial' has shown that tty0 was enabled as a console which
>> is not what we wanted.

> If you are backporting this change then I believe it has some dependencies
> that I can follow up on if it is useful to you.

    Contrariwise, I'm forward-porting.

> If you are using mainline (e.g. next or renesas-next) then yes,
> it works. I have tested it numerous times since the patch was merged.

    I'm traditionally using the 'renesas-devel-*' tags.

WBR, Sergei