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

From: Vineet Gupta <vgupta@synopsys.com>
To: Petr Mladek <pmladek@suse.com>
Cc: linux-arch@vger.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	John Ogness <john.ogness@linutronix.de>,
	Shreyas Joshi <shreyas.joshi@biamp.com>,
	linux-kernel@vger.kernel.org,
	Steven Rostedt <rostedt@goodmis.org>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	buildroot@busybox.net, arcml <linux-snps-arc@lists.infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	shreyasjoshi15@gmail.com, Guenter Roeck <linux@roeck-us.net>
Subject: Re: ARC no console output (was Re: [PATCH 1/2] init/console: Use ttynull as a fallback when there is no console)
Date: Thu, 7 Jan 2021 09:58:05 -0800	[thread overview]
Message-ID: <466644f5-bed7-caef-9fcd-e66208f65545@synopsys.com> (raw)
In-Reply-To: <X/c/ONCYz2QQdvOP@alley>

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@synopsys.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.

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

I don't know if ttyS0 console should have registered already but even if 
it did - the /dev node missing would not have helped ?

> 
> 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
> 

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