RE: [BUG] Suspend failure with nbcon + pm_debug_messages (Linux 6.18-rc4)

[Sherry Sun]

> -----Original Message-----
> From: John Ogness <john.ogness@xxxxxxxxxxxxx>
> Sent: Tuesday, November 4, 2025 4:29 PM
> To: Sherry Sun <sherry.sun@xxxxxxx>; esben@xxxxxxxxxx;
> pmladek@xxxxxxxx; senozhatsky@xxxxxxxxxxxx; tglx@xxxxxxxxxxxxx; Greg
> KH <gregkh@xxxxxxxxxxxxxxxxxxx>; Jiri Slaby <jirislaby@xxxxxxxxxx>; Shawn
> Guo <shawnguo@xxxxxxxxxx>; Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>;
> ryotkkr98@xxxxxxxxx; kkartik@xxxxxxxxxx; fj6611ie@xxxxxxxxxxxxxxxxx
> Cc: Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>; linux-serial
> <linux-serial@xxxxxxxxxxxxxxx>; imx@xxxxxxxxxxxxxxx; Pengutronix Kernel Team
> <kernel@xxxxxxxxxxxxxx>; linux-pm@xxxxxxxxxxxxxxx
> Subject: Re: [BUG] Suspend failure with nbcon + pm_debug_messages (Linux
> 6.18-rc4)
>
> Hi Sherry,
>
> On 2025-11-04, Sherry Sun <sherry.sun@xxxxxxx> 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
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>
> [1]
> https://github/.
> com%2FLinutronix%2Flinux%2Fcommit%2Fae173249d9028ef159fba040bdab
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