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

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Message-ID: <87qzuem7bo.fsf@jogness.linutronix.de>
Date: Tue, 04 Nov 2025 11:22:11 +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)

On 2025-11-04, Sherry Sun <sherry.sun@....com> wrote:
>> Thanks for reporting! I believe this is the same issue reported by NVIDIA [0]
>> when we tried to switch the 8250 UART driver to nbcon.
>>
>> We have been working with NVIDIA recently to address the issue. There is a
>> patch [1] we are currently testing that looks good so far. It is based on 6.17
>> but should work fine for 6.18-rc4 as well. Can you give it a spin?
>
> Thanks a lot for your quick reply, I just tried the patch [1] on my
> i.MX8MP EVK with L6.18-rc4, it does fix the suspend issue.  Now i.MX
> UART nbcon can enter suspend with `pm_debug_messages` is turned on.
> May I know what is the upstream plan for the patch [1]?

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.

Note that the patch still needs a formal review from the printk folks
once it hits LKML.

John Ogness

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