Which is better to specify console, "console= " or "stdout-path" ?

[Masahiro Yamada]

Hi Peter.

2015-10-21 21:46 GMT+09:00 Peter Hurley <peter at hurleysoftware.com>:
> On 10/21/2015 04:58 AM, Sudeep Holla wrote:
>> On 21/10/15 06:09, Masahiro Yamada wrote:
>>> I think there exist two ways to specify the console port and baudrate.
>>>
>>>
>>> [1] Specify console in bootargs
>>>
>>>    chosen {
>>>          bootargs = "console=ttyS0,115200";
>>>    };
>>>
>>>
>>> [2] Specify stdout-path
>>>
>>>     chosen {
>>>           stdout-path = "serial0:115200n8";
>>
>> This will work for even early/boot console, so this is better than
>> option [1]
>
> Be aware that options specified via /chosen/stdout-path are
> currently ignored by earlycon. There were some hiccups getting the
> initial support upstream; when 4.4 hits mainline, I'll resubmit
> my series that implements the of_serial i/o properties and
> options passthrough to earlycon setup.


As I said in another thread ("serial: earlycon: allow to specify
uartclk in earlycon kernel-parameter"),
stdout-path can pass dev->baud, but not port->uartclk.

It is usually specified "clocks" phandle, but
clk is not ready at the point of earlycon.

It seems impossible to set up the baudrate even if the options are passed.


-- 
Best Regards
Masahiro Yamada