linux-kernel - Re: [PATCH 5/6] tty/serial: Add Spreadtrum's serial earlycon

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Date:	Wed, 1 Oct 2014 08:55:39 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	zhang.lyra@...il.com, Catalin Marinas <catalin.marinas@....com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Jiri Slaby <jslaby@...e.cz>, Kumar Gala <galak@...eaurora.org>,
	Mark Brown <broonie@...aro.org>,
	Mark Rutland <mark.rutland@....com>,
	Murali Karicheri <m-karicheri2@...com>,
	Pawel Moll <pawel.moll@....com>, artagnon@...il.com,
	Robert Richter <rrichter@...ium.com>,
	Rob Herring <robh+dt@...nel.org>,
	Will Deacon <will.deacon@....com>, orsonzhai@...il.com,
	geng.ren@...eadtrum.com, zhizhou.zhang@...eadtrum.com,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"chunyan.zhang" <chunyan.zhang@...eadtrum.com>
Subject: Re: [PATCH 5/6] tty/serial: Add Spreadtrum's serial earlycon

On Mon, Sep 29, 2014 at 8:36 AM, Arnd Bergmann <arnd@...db.de> wrote:
> On Monday 29 September 2014 20:04:52 zhang.lyra@...il.com wrote:
>> From: "chunyan.zhang" <chunyan.zhang@...eadtrum.com>
>>
>> Adds earlycon support for the Spreadtrum's serial.
>>
>> Signed-off-by: chunyan.zhang <chunyan.zhang@...eadtrum.com>
>> ---
>>  drivers/tty/serial/Kconfig             |   12 ++++++
>>  drivers/tty/serial/Makefile            |    1 +
>>  drivers/tty/serial/serial_sprd_early.c |   64 ++++++++++++++++++++++++++++++++
>>  3 files changed, 77 insertions(+)
>>  create mode 100644 drivers/tty/serial/serial_sprd_early.c
>>
>> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
>> index 26cec64..ede16e6 100644
>> --- a/drivers/tty/serial/Kconfig
>> +++ b/drivers/tty/serial/Kconfig
>> @@ -85,6 +85,18 @@ config SERIAL_EARLYCON_ARM_SEMIHOST
>>         with "earlycon=smh" on the kernel command line. The console is
>>         enabled when early_param is processed.
>>
>> +config SERIAL_EARLYCON_SPRD
>> +     bool "Early console using SPRD serial"
>> +     depends on ARM64
>> +     select SERIAL_CORE
>> +     select SERIAL_CORE_CONSOLE
>> +     select SERIAL_EARLYCON
>> +     help
>
> I assume you will later want to have a proper device driver for
> this hardware, so it would be better to make the Kconfig symbol
> and the file name what you are going to use in the long run, but
> for now only have the earlycon support included.
>
>
>> +static int __init serial_sprd_early_console_setup(
>> +                             struct earlycon_device *device,
>> +                             const char *opt)
>> +{
>> +     if (!device->port.membase)
>> +             return -ENODEV;
>> +
>> +     device->con->write = serial_sprd_early_write;
>> +     return 0;
>> +}
>> +EARLYCON_DECLARE(serial_sprd, serial_sprd_early_console_setup);
>> +OF_EARLYCON_DECLARE(serial_sprd, "sprd,serial",
>> +                 serial_sprd_early_console_setup);
>>
>
> I think you should drop the EARLYCON_DECLARE() line, using
> OF_EARLYCON_DECLARE should be enough.

No, I've been telling people to put both in. The reason is you may
have a bootloader or boot files (e.g PXELINUX) that only allows
changing changing the command line or you want to override/extend the
command line in the kernel.

I'm thinking the declaration should be combined into one to do both
since I'm getting tired of making this comment.

Rob
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