Update with additional reproduction and recovery information.

System currently:

* Ubuntu 24.04.4 LTS
* Intel XMM7560 LTE Advanced Pro Modem [8086:7560]
* kernel driver: iosm
* ModemManager 1.23.4
* NetworkManager 1.46.0
* libmbim 1.31.2

The failure has now been characterized more clearly.

Before the failure escalates, the modem itself is still operational at
the radio/3GPP level. It can power on, register on the home network, use
LTE, and reach packet-service state "attached". The failure occurs when
establishing the actual data bearer.

Typical ModemManager output includes:

`port wwan0mbim0 timed out 2 consecutive times`

followed by:

`connection attempt failed: Transaction timed out`

and NetworkManager reports:

`failed to connect modem: MBIM core error: Transaction timed out`

Repeated attempts may eventually result in:

`port 'wwan0mbim0' no longer controllable, reprobing`

During a subsequent software recovery/rebind attempt, the failure
escalated into the iosm driver. The kernel reported repeated:

`iosm: msg timeout`

The WWAN ports were then disconnected. A new iosm probe failed with:

`invalid exec stage FFFFFFFF`
`failed to initialize mmio region`
`failed to init imem`
`probe ... failed with error -5`

At that point the PCI device was still present, but no driver was bound,
no `/dev/wwan*` ports existed, and ModemManager detected no modem.

A cold power-cycle of the computer restored the modem. After the cold
start, iosm bound normally again and the WWAN connection was
successfully established.

The system has subsequently been updated to kernel 6.8.0-138-generic. It
is currently operating normally with the XMM7560 connected through iosm.

I have not yet reproduced the failure on 6.8.0-138, so I cannot say
whether that kernel changes the behaviour. The important additional
observation is that ordinary software-level recovery was insufficient
once the modem/iosm state had degraded, while a cold power-cycle
recovered it.

The earlier relationship with service restarts also remains relevant:
the problem has previously been reproducible after the ModemManager
service is restarted as a consequence of a polkit restart.

If useful, I can collect additional sanitized ModemManager,
NetworkManager or iosm diagnostics if there is a preferred debug
procedure to run before performing another cold power-cycle.

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https://bugs.launchpad.net/bugs/2163470

Title:
  Intel XMM7560 WWAN fails to reconnect after ModemManager restart on
  Ubuntu 24.04

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