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

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Message-ID:
 <DB9PR04MB842977523C92FDE8AF4B714A92C4A@DB9PR04MB8429.eurprd04.prod.outlook.com>
Date: Tue, 4 Nov 2025 09:46:30 +0000
From: Sherry Sun <sherry.sun@....com>
To: John Ogness <john.ogness@...utronix.de>, "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)



> -----Original Message-----
> From: John Ogness <john.ogness@...utronix.de>
> Sent: Tuesday, November 4, 2025 4:29 PM
> To: Sherry Sun <sherry.sun@....com>; esben@...nix.com;
> pmladek@...e.com; senozhatsky@...omium.org; 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; kkartik@...dia.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; Pengutronix Kernel Team
> <kernel@...gutronix.de>; 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:
> > Since the latest i.MX UART switch to nbcon console with commit
> > 70acca67bdd3 ("serial: imx: Switch to nbcon console"), I'm
> > encountering a suspend issue on an i.MX8MP EVK board while testing
> > with Linux 6.18-rc4.
> >
> > The system fails to suspend when both nbcon is enabled and
> > `pm_debug_messages` is turned on. When `pm_debug_messages` is
> > disabled, suspend works normally. Additionally, if I revert the patch
> > that adds nbcon support for the i.MX UART, suspend also works fine
> > even with `pm_debug_messages` enabled.
>
> 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?
>

Hi John,

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]?

Best Regards
Sherry

> [0]
> https://lore.ke/
> rnel.org%2Flkml%2F80b020fc-c18a-4da4-b222-
> 16da1cab2f4c%40nvidia.com&data=05%7C02%7Csherry.sun%40nxp.com%7C
> 223190eafeb045a646fb08de1b7c2741%7C686ea1d3bc2b4c6fa92cd99c5c3016
> 35%7C0%7C0%7C638978417234027264%7CUnknown%7CTWFpbGZsb3d8eyJ
> FbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiT
> WFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=PuIijva%2FcH8LBrPhAS
> PopGShQDJdoEBreIc8qGhR63E%3D&reserved=0
>
> [1]
> https://github/.
> com%2FLinutronix%2Flinux%2Fcommit%2Fae173249d9028ef159fba040bdab
> 260d80dda43f&data=05%7C02%7Csherry.sun%40nxp.com%7C223190eafeb0
> 45a646fb08de1b7c2741%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0
> %7C638978417234052653%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcG
> kiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIj
> oyfQ%3D%3D%7C0%7C%7C%7C&sdata=oyqo8zAnUA%2FuAc5RuTtOCVRJMZc
> k3IexrBNvI5NpjzQ%3D&reserved=0