[BUGREPORT] Issue with FM350_GL modem and suspend/resume on Linux kernel 6.1

[Vojtěch Maršál]

Hello Linux Kernel Mailing List,

I am writing to seek assistance regarding a persistent issue I have
been facing with modem functionality and the suspend/resume feature on
my Linux system running kernel version 6.1. I have already searched
through bug reports but have not found a resolution or response to a
similar issue. I would appreciate any guidance or insights you can
provide to help me resolve this problem.

Description of the issue: Whenever I set my notebook to deep sleep
mode, the system suspends successfully for the first time. However,
subsequent attempts to suspend the system result in an error related
to the modem. The error message in the kernel logs is as follows:

[ 375.151668] mtk_t7xx 0000:2c:00.0: [PM] Exiting suspend, modem in
invalid state
[ 375.151680] mtk_t7xx 0000:2c:00.0: PM: pci_pm_suspend():
t7xx_pci_pm_suspend+0x0/0x20 [mtk_t7xx] returns -14
 [ 375.151719] mtk_t7xx 0000:2c:00.0: PM: dpm_run_callback():
pci_pm_suspend+0x0/0x1b0 returns -14
[ 375.151736] mtk_t7xx 0000:2c:00.0: PM: failed to suspend async: error -14
[ 375.152120] PM: Some devices failed to suspend, or early wake event detected

Steps taken so far:

- Updated kernel and modem drivers to the latest available versions.
- Checked for BIOS updates for my notebook model, but none were available.
- Disabled power management for the modem by adding "options mtk_t7xx
power_save=0" to a configuration file, but the issue persisted.


I have also confirmed that there is an existing bug report related to
this issue in Bugzilla, but it has been unanswered for an extended
period.

https://bugzilla.kernel.org/show_bug.cgi?id=216523

https://bugzilla.kernel.org/show_bug.cgi?id=217590

Additional details:

Notebook model: ASUS Expertbook B2
Modem model: FM350_GL
Linux distribution: Ubuntu 20.04LTS
Kernel version: Linux 6.1

I kindly request your assistance in resolving this issue or providing
any further troubleshooting steps that may help. I am open to any
suggestions or insights you can offer. Please let me know if any
additional information is required.

Thank you for your attention and support.

Best regards, Vojtěch Maršál