linux-kernel - Re: [PATCH] serial: 8250: Default SERIAL_OF_PLATFORM to SERIAL

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Message-ID: <29E7A6C0-7829-4650-93C6-7220FECAA6EF@gmail.com>
Date:   Wed, 14 Nov 2018 19:56:47 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] serial: 8250: Default SERIAL_OF_PLATFORM to SERIAL_8250



On November 14, 2018 5:11:25 PM PST, Guenter Roeck <linux@...ck-us.net> wrote:
>On Thu, Nov 01, 2018 at 11:26:06AM -0700, Florian Fainelli wrote:
>> It is way too easy to miss enabling SERIAL_OF_PLATFORM which would
>> result in the inability for the kernel to have a valid console
>device,
>> which can be seen with:
>> 
>> Warning: unable to open an initial console.
>> 
>> and then:
>> 
>> Run /init as init process
>> Kernel panic - not syncing: Attempted to kill init!
>exitcode=0x00000100
>> 
>> Since SERIAL_OF_PLATFORM already depends on SERIAL_8250 && OF there
>> really is no drawback to defaulting this config to the value of
>> SERIAL_8250.
>> 
>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>
>This patch results in situations where CONFIG_SERIAL_OF_PLATFORM is now
>defined where it was not previously. Example mpc85xx_defconfig. This in
>turn results in boot failures for those configurations, with an error
>message of
>
>of_serial: probe of e0004500.serial failed with error -22
>
>which wasn't seen before.

Do you know which Device Tree is being used here? The most obvious thing that could be done is to add a !PPC condition but this might be missing other platforms doing their own 8250 registration yet being OF aware (sparc?).

>
>Not sure if replacing a potential problem with a real one is really an
>improvement.`

That comment is not particularly helpful though I have an appreciation for when a change breaks things in unexpected ways and how frustrating that can be.
-- 
Florian