linux-kernel - Re: [PATCH v3] console: use first console if stdout-path device doesn't appear

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Date:   Mon, 7 Nov 2016 09:18:06 +0000
From:   Paul Burton <paul.burton@...tec.com>
To:     Michael Ellerman <mpe@...erman.id.au>
CC:     Larry Finger <Larry.Finger@...inger.net>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Andreas Schwab <schwab@...ux-m68k.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Borislav Petkov <bp@...e.de>, Petr Mladek <pmladek@...e.com>,
        Tejun Heo <tj@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH v3] console: use first console if stdout-path device doesn't appear

On Monday, 7 November 2016 19:27:32 GMT Michael Ellerman wrote:
> Paul Burton <paul.burton@...tec.com> writes:
> > If a device tree specified a preferred device for kernel console output
> > via the stdout-path or linux,stdout-path chosen node properties there's
> > no guarantee that it will have specified a device for which we have a
> > driver. It may also be the case that we do have a driver but it doesn't
> > call of_console_check() to register as a preferred console (eg. offb
> > driver as used on powermac systems).
> > 
> > In these cases try to ensure that we provide some console output by
> > enabling the first usable registered console, which we keep track of
> > with the of_fallback_console variable. Affected systems will enable
> > their console later than they did prior to commit 05fd007e4629
> > ("console: don't prefer first registered if DT specifies stdout-path")
> > but should otherwise produce the same output.
> > 
> > Tested in QEMU with a PowerPC pseries_defconfig kernel.
> 
> Hi Paul,
> 
> This does "work", as in it boots and I get a console. But the delay in
> getting output on the VGA is not workable. I get pretty much no output
> until the machine is booted entirely to userspace, meaning any crash
> prior to that will be undebuggable.
> 
> I also note Andreas reports it doesn't work at all on PowerMac.
> 
> Please send a revert and we can try again next cycle.
> 
> cheers

Hi Michael,

A revert was already submitted by Hans de Goede & is being discussed over 
here:

https://marc.info/?l=linux-kernel&m=147826151427455&w=2

Thanks,
    Paul
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