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

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Message-ID:
 <DB9PR04MB84295A352C49B093F4125A2F92C5A@DB9PR04MB8429.eurprd04.prod.outlook.com>
Date: Wed, 5 Nov 2025 03:43:16 +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: Wednesday, November 5, 2025 7:20 AM
> 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:
> >> 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.
> 

Hi John,

I tried to add "no_console_suspend loglevel=8 initcall_debug" boot arguments and enable pm_debug_messages, i.MX8MP suspend is still ok  with your patch [1].
And please note, i.MX8MP is ARM64 arch. 
I also tested the patch [1] with the same settings on i.MX6ULL(ARM32), same observation with i.MX8MP, suspend also works fine.
Seems the issue you observed here cannot be reproduced on i.MX UART as it doesn't use the irq_work, and at least per my testing, the fix should be addressed for both ARM64 and ARM32.

Best Regards
Sherry

> 
> >> [1]
> >> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit
> >>
> hub.com%2FLinutronix%2Flinux%2Fcommit%2Fae173249d9028ef159fba040b
> dab2
> >>
> 60d80dda43f&data=05%7C02%7Csherry.sun%40nxp.com%7C7988cfdc84f64e
> 9cd1d
> >>
> d08de1bf8ab21%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6389
> 789520
> >>
> 47428481%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYi
> OiIwLjAu
> >>
> MDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%
> 7C%7C
> >>
> &sdata=yPKOGyd5wAECK8HFz3bD09vLva6jCPAQyLZPNbnG%2Buk%3D&reserv
> ed=0