[Bug 2146536] Re: [REGRESSION] Intel XMM7360 (Fibocom L850) modem not detected / SIM missing on Ubuntu 25.04+

** Tags added: kernel-daily-bug

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https://bugs.launchpad.net/bugs/2146536

Title:
[REGRESSION] Intel XMM7360 (Fibocom L850) modem not detected / SIM
missing on Ubuntu 25.04+

Status in linux package in Ubuntu:
New

Bug description:
Hardware:

Laptop: HP EliteBook 830 G8
Modem: Intel XMM7360 (Fibocom L850 LTE)
PCI ID: 8086:7360
Firmware: HP OEM (whitelisted firmware, not generic, BIOS-restricted)

Summary of the problem:
This appears to be a regression in the in-kernel iosm driver affecting Intel XMM7360-based modems with OEM HP firmware.

The modem worked correctly on Ubuntu 24.10 with the stock kernel and iosm driver.
Starting from Ubuntu 25.04, the SIM is no longer detected.
Starting from Ubuntu 25.10, the modem is not properly initialized and becomes unusable.

The issue is reproducible and persists across reboots.

Regression range:

Last known working: Ubuntu 24.10
First broken (SIM not detected): Ubuntu 25.04
Further regression (modem unusable): Ubuntu 25.10

Detailed description:
On affected systems, the modem is detected on the PCI bus, but fails during initialization when handled by the iosm driver.

ModemManager reports:

state: failed
failed reason: sim-missing

AT command interface is partially functional, but SIM access is
broken:

AT responds correctly
AT+CFUN works
AT+CPIN? returns ERROR
AT+CREG reports not registered (0,0)

Additionally:

No /dev/cdc-wdm device is created
ModemManager cannot fully manage the modem
The device does not transition into an operational state

This suggests that the iosm driver fails to properly initialize the
modem or establish the control channel required for SIM access.

Workaround:
The modem becomes operational when using an out-of-tree driver:

https://github.com/xmm7360/xmm7360-pci

Steps:
make
sudo insmod xmm7360.ko

With this driver:

The modem initializes correctly
AT interface works
The device reports readiness:
[ 4694.634478] xmm7360 0000:55:00.0: modem is ready

This strongly indicates that the hardware and firmware are functional,
and that the regression is specific to the iosm driver or related
kernel components.

Steps to reproduce:

Boot Ubuntu 25.04 or 25.10
Ensure iosm driver is used (default kernel behavior)
Run:
mmcli -L
mmcli -m 0 --enable

Observed result:

Modem enters failed state
SIM is reported as missing
Device remains unusable

Expected result:

Modem should initialize correctly
SIM should be detected
ModemManager should be able to control the modem
Network registration should be possible
ModemManager output:
/org/freedesktop/ModemManager1/Modem/0 [Fibocom] L850 LTE Module

Status | state: failed
| failed reason: sim-missing

Full mmcli output:

/org/freedesktop/ModemManager1/Modem/0 [Fibocom] L850 LTE Module
-----------------------------
General | path: /org/freedesktop/ModemManager1/Modem/0
| device id: 5c8833d8b4341b0bf13dc1c1d4268cb19c62be1f
-----------------------------
Hardware | manufacturer: Fibocom
| model: L850 LTE Module
| firmware revision: 18500.5001.00.05.27.30
| supported: gsm-umts, lte
| current: gsm-umts, lte
| equipment id: 863989052417938
-----------------------------
System | device: /sys/devices/pci0000:00/0000:00:1c.0/0000:55:00.0
| drivers: xmm7360
| plugin: generic
| primary port: ttyXMM2
| ports: ttyXMM1 (at), ttyXMM2 (at), wwan0 (net)
-----------------------------
Status | state: failed
| failed reason: sim-missing
| power state: on


AT interaction:

AT
OK

AT+CFUN=1
OK

AT+CPIN?
ERROR

AT+CPIN=?
OK

AT+CREG?
+CREG: 0,0


Direct serial access test (picocom):

sudo picocom -b 115200 /dev/ttyXMM1

AT+CFUN=4
OK
AT+CFUN=1
OK
AT+CPIN?
ERROR


dmesg (relevant part):

[ 4694.634478] xmm7360 0000:55:00.0: modem is ready


Also no MBIM control device present:

ls /dev/cdc-wdm*
ls: cannot access '/dev/cdc-wdm*': No such file or directory


PCI device detection:

lspci -nn | grep -i xmm
55:00.0 Wireless controller [0d40]: Intel Corporation XMM7360 LTE Advanced Modem [8086:7360] (rev 01)


RF state:

rfkill list
0: hci0: Bluetooth
Soft blocked: no
Hard blocked: no
1: phy0: Wireless LAN
Soft blocked: no
Hard blocked: no


System information:

uname -a
Linux elitebook-hp 6.17.0-19-generic #19-Ubuntu SMP x86_64 GNU/Linux

lsb_release -a
Distributor ID: Ubuntu
Description: Ubuntu 25.10
Release: 25.10
Codename: unknown


Additional notes:

This device uses HP OEM firmware and is BIOS-whitelisted
Replacing firmware or modem is not possible due to platform restrictions
The issue is not hardware-related (confirmed by working alternative driver)
Likely root cause: regression in iosm driver or related subsystem between kernel versions used in Ubuntu 24.10 and 25.04+

Additional testing with alternative driver forks:
An attempt was made to use alternative forks of the xmm7360 out-of-tree driver.
However, they did not provide a complete solution for this platform.

Reason:

HP OEM firmware differs from generic firmware expected by these drivers
The modem does not expose a standard MBIM control interface (/dev/cdc-wdm)
Some forks rely on assumptions about firmware behavior that do not hold for HP-whitelisted devices

As a result:

Partial initialization may occur
SIM access and full modem functionality remain unreliable or broken

Therefore, using out-of-tree drivers is not a viable long-term
solution.

Primary goal:
Restore full functionality using the in-kernel iosm driver.

Request:
Please investigate regression in iosm driver affecting Intel XMM7360 (Fibocom L850) with OEM firmware.


With regards,
Stanislav

ProblemType: Bug
DistroRelease: Ubuntu 25.10
Package: linux-image-6.17.0-19-generic 6.17.0-19.19
ProcVersionSignature: Ubuntu 6.17.0-19.19-generic 6.17.13
Uname: Linux 6.17.0-19-generic x86_64
ApportVersion: 2.33.1-0ubuntu3
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Fri Mar 27 12:29:40 2026
InstallationDate: Installed on 2025-09-28 (180 days ago)
InstallationMedia: Ubuntu 25.04 "Plucky Puffin" - Release amd64 (20250415.3)
MachineType: HP HP ELITEBOOK 830 G8
ProcEnviron:
LANG=ru_RU.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.17.0-19-generic root=UUID=6a23b845-81bc-47b1-81af-ca4c9a7bd9c8 ro quiet splash resume=/dev/nvme0n1p5 crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M vt.handoff=7
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
firmware-sof N/A
linux-firmware 20250901.git993ff19b-0ubuntu1.9
SourcePackage: linux
UpgradeStatus: Upgraded to questing on 2025-10-10 (168 days ago)
dmi.bios.date: 11/06/2025
dmi.bios.release: 23.0
dmi.bios.vendor: HP
dmi.bios.version: T76 Ver. 01.23.00
dmi.board.name: 880D
dmi.board.vendor: HP
dmi.board.version: KBC Version 30.57.00
dmi.chassis.type: 10
dmi.chassis.vendor: HP
dmi.ec.firmware.release: 48.87
dmi.modalias: dmi:bvnHP:bvrT76Ver.01.23.00:bd11/06/2025:br23.0:efr48.87:svnHP:pnHPELITEBOOK830G8:pvrSBKPFV3:rvnHP:rn880D:rvrKBCVersion30.57.00:cvnHP:ct10:cvr:sku2Y2R9EA#ACB:
dmi.product.family: 103C_5336AN HP EliteBook
dmi.product.name: HP ELITEBOOK 830 G8
dmi.product.sku: 2Y2R9EA#ACB
dmi.product.version: SBKPFV3
dmi.sys.vendor: HP

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