Re: console vs earlycon ?
From: Masahiro Yamada
Date: Wed Oct 21 2015 - 05:09:45 EST
Hi Arnd,
2015-10-21 17:57 GMT+09:00 Arnd Bergmann <arnd@xxxxxxxx>:
> On Wednesday 21 October 2015 17:21:07 Masahiro Yamada wrote:
>> Hi.
>>
>>
>>
>>
>> I think there are three places where console could be enabled.
>>
>> [1] earlycon
>>
>> Each driver entry is declared with
>> EARLYCON_DECLARE() or OF_EARLYCON_DECLARE()
>>
>>
>>
>> [2] console_init()
>>
>> Each entry is declared with console_initcall()
>>
>>
>>
>> [3] when driver is probed
>> The console is usually enabled at this point
>> unless some special treatment is done.
>>
>>
>>
>>
>> My question is about [2].
>>
>> I am using 8250-ish UART device.
>>
>>
>> I noticed univ8250_console_match() and univ8250_console_setup()
>> always fail at the point of [2] unless early_serial_setup() has been
>> called in advance;
>> however, it looks like early_serial_setup() is only used for old platforms.
>>
>> So, console cannot be enabled at [2] for modern platforms.
>>
>>
>> My questions are:
>>
>> - Given that earlycon can be now available for major architectures such ARM,
>> [2] will be deprecated at some point in the future?
>>
>> - I am implementing earlycon for my own UART driver.
>> Is it meaningless to implement console_initcall() as well as earlycon?
>
> I would still do both. We don't enable earlycon by default at the moment,
> and I'd say things should remain working with just console_initcall().
>
> How closely related to 8250 is your hardware? If it's not all that different,
> you should probably reuse the existing driver.
Very close.
It is already in the mainline.
drivers/tty/serial/8250/8250_uniphier.c
The core parts are shared with 8250_core.c
I am trying to implement OF_EARLYCON_DECLARE() for that.
I was just wondering if console_initcall() should work as well.
As I said, I noticed the console_initcall() in 8250_core.c
only works on very limited platforms.
--
Best Regards
Masahiro Yamada
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