linux-kernel - RE: [BUG] Suspend failure with nbcon + pm_debug

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Message-ID: <87bjlhz8pw.fsf@jogness.linutronix.de>
Date: Wed, 05 Nov 2025 00:25:55 +0106
From: John Ogness <john.ogness@...utronix.de>
To: Sherry Sun <sherry.sun@....com>, "esben@...nix.com" <esben@...nix.com>,
 "pmladek@...e.com" <pmladek@...e.com>, "senozhatsky@...omium.org"
 <senozhatsky@...omium.org>, "tglx@...utronix.de" <tglx@...utronix.de>,
 Greg KH <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>,
 Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>,
 "ryotkkr98@...il.com" <ryotkkr98@...il.com>, "kkartik@...dia.com"
 <kkartik@...dia.com>, "fj6611ie@...jp.fujitsu.com"
 <fj6611ie@...jp.fujitsu.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-serial
 <linux-serial@...r.kernel.org>, "imx@...ts.linux.dev"
 <imx@...ts.linux.dev>, Pengutronix Kernel Team <kernel@...gutronix.de>,
 "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: RE: [BUG] Suspend failure with nbcon + pm_debug_messages (Linux
 6.18-rc4)

Hi Sherry,

On 2025-11-04, Sherry Sun <sherry.sun@....com> wrote:
>> Thanks for confirming the fix. I will make an official post on LKML
>> with the patch today. Since the i.MX nbcon-driver is already
>> mainline, I will CC stable. I will CC you as well.
>
> I'll keep an eye on any fixes you send later and verify them if
> necessary. Hope this fix can be applied to the mainline and the stable
> tree ASAP.

Even with this patch [1] I am able to reproduce the problem on one of my
test boards. I am using the following extra boot arguments:

no_console_suspend loglevel=8 initcall_debug

And then:

# echo 1 > /sys/power/pm_debug_messages
# echo mem > /sys/power/state

This generates a lot of output and leads to the same suspend
failure. This may be due to the out-of-tree nbcon-8250 driver I am
using, which introduces extra irq_work usage within the driver. Could
you please try the above boot arguments with your i.MX board?

I am wondering if blocking the queueing of irq_work during suspend
should be generally implemented rather than just printk avoiding it. It
also seems to only be a problem for ARM32 so perhaps it needs to be
addressed at the architecture level.

John Ogness

>> [1] https://github.com/Linutronix/linux/commit/ae173249d9028ef159fba040bdab260d80dda43f