linux-kernel - Re: ARC no console output (was Re: [PATCH 1/2] init/console: Use ttynull as a fallback when there is no console)

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Message-ID: <X/c/ONCYz2QQdvOP@alley>
Date:   Thu, 7 Jan 2021 18:04:56 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Vineet Gupta <vgupta@...opsys.com>
Cc:     John Ogness <john.ogness@...utronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Shreyas Joshi <shreyas.joshi@...mp.com>,
        shreyasjoshi15@...il.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        linux-kernel@...r.kernel.org, buildroot@...ybox.net,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        linux-arch@...r.kernel.org,
        arcml <linux-snps-arc@...ts.infradead.org>
Subject: Re: ARC no console output (was Re: [PATCH 1/2] init/console: Use
 ttynull as a fallback when there is no console)

On Thu 2021-01-07 08:43:16, Vineet Gupta wrote:
> Hi John,
> 
> On 1/7/21 1:02 AM, John Ogness wrote:
> > Hi Vineet,
> > 
> > On 2021-01-06, Vineet Gupta <vgupta@...opsys.com> wrote:
> > > This breaks ARC booting (no output on console).
> > 
> > Could you provide the kernel boot arguments that you use? This series is
> > partly about addressing users that have used boot arguments that are
> > technically incorrect (even if had worked). Seeing the boot arguments of
> > users that are not experiencing problems may help to reveal some of the
> > unusual console usages until now.
> 
> 
> Kernel command line: earlycon=uart8250,mmio32,0xf0005000,115200n8
> console=ttyS0,115200n8 debug print-fatal-signals=1

This is strange, the problematic patch should use ttynull
only as a fallback. It should not be used when a particular console
is defined on the command line.

The only explanation would be that ttyS0 gets registered too late
and ttynull is added as a fallback in the meantime.

Anyway, I propose the revert the problematic patch for 5.11-rc3,
see
https://lore.kernel.org/lkml/20210107164400.17904-2-pmladek@suse.com/
This mystery is a good reason to avoid bigger changes at this stage.

Best Regards,
Petr