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

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Date:   Wed, 14 Nov 2018 21:38:36 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Florian Fainelli <f.fainelli@...il.com>
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 Wed, Nov 14, 2018 at 07:56:47PM -0800, Florian Fainelli wrote:
> 
> 
> 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.

Actally, never mind. I dropped the test cases. Sorry for the noise.

Guenter