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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Date:   Fri, 8 Jan 2021 12:48:42 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Vineet Gupta <vgupta@...opsys.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        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 (21/01/07 09:58), Vineet Gupta wrote:
> On 1/7/21 9:04 AM, Petr Mladek wrote:
> > 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.
> 
> What happens in my case is console_on_rootfs() doesn't find /dev/console and
> switching to ttynull. /dev is not present because devtmpfs doesn't automount
> for initramfs.

I wonder if we'll move the nulltty fallback logic into printk code [1]
will it fix the problem?

[1] https://lore.kernel.org/lkml/X6x%2FAxD1qanC6evJ@jagdpanzerIV.localdomain/

	-ss