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

[John Ogness <john.ogness@linutronix.de>]

Hi Sherry,

On 2025-11-04, Sherry Sun <sherry.sun@nxp.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?

John Ogness

[0] https://lore.kernel.org/lkml/80b020fc-c18a-4da4-b222-16da1cab2f4c@nvidia.com

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