[Bug 2138308] Re: Ubuntu 25.10: 5GHz WiFi not detected with kernel 6.17/6.18 - Snapdragon X Elite

[Saikiran]

Hi,

This is a follow-up to my previous report and attached patch series.
After additional testing I can confirm that the commit 9eb6d6b ("Remove
broken frequency range filtering") is the critical change that restores
5GHz WiFi operation on the Lenovo Yoga Slim 7x (Snapdragon X Elite) with
kernel 6.19-rc5.

Attached in this archive are the individual patches (format-patch
output) for the following commits:

- 9eb6d6bb9eb01e9767b8ad70bf503c1631d64c71  (Remove broken frequency range filtering)  -- Primary fix
- 5946e4c0763755535f7f9f89761828b68a8019d1  (Improvements & cleanup)
- 26a6a6263f6c8919ade47f18814335e52384d474  (Improvements & cleanup)
- dae0671ab05a3a30cbba5e8b1f41e45a80c3900f  (Improvements & cleanup)
- 9126482be6353f03a2844f60be1a569bc14a6738  (Improvements & cleanup)

Notes about regressions observed:

- During testing I observed that two patches in the series (the
synchronous regulatory restore and the revert from faux_device to
platform_device) are associated with a reboot/shutdown stall on my
hardware: specifically, the sequence that included those changes caused
the system to hang during reboot at a user-space stop job
(NetworkManager.service) and required a hard-reset. Please treat this as
an important regression note. I am including the complete patches so
maintainers can test and review.

Tested on: Lenovo Yoga Slim 7x (Snapdragon X Elite), kernel 6.19-rc5
(local tree)

Happy to provide additional logs.


** Attachment added: "Patch series fixing ath12k 5GHz WiFi on Snapdragon X Elite (Lenovo Yoga Slim 7x)."
   https://bugs.launchpad.net/ubuntu-concept/+bug/2138308/+attachment/5940091/+files/5ghz_Wifi_Patches.tar.gz

** Patch removed: "Patch series (6 patches) fixing ath12k 5GHz WiFi on Snapdragon X Elite (Lenovo Yoga Slim 7x)."
   https://bugs.launchpad.net/ubuntu-concept/+bug/2138308/+attachment/5940008/+files/wifi-fixes.zip

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https://bugs.launchpad.net/bugs/2138308

Title:
  Ubuntu 25.10: 5GHz WiFi not detected with kernel 6.17/6.18 -
  Snapdragon X Elite

Status in ubuntu-concept:
  New

Bug description:
  This is a regression affecting ath12k on Qualcomm WCN7850 (Snapdragon
  X Elite laptops).

  Hardware:
  - Lenovo Yoga Slim 7x (Snapdragon X Elite)
  - Wi-Fi chipset: Qualcomm WCN7850 (ath12k_pci, hw2.0)

  Kernel versions tested:
  - 6.16.0-21-qcom-x1e → WORKING (5 GHz detected and usable)
  - 6.17.x → BROKEN (no 5 GHz BSS detected)
  - 6.18.0-9-qcom-x1e  → BROKEN (no 5 GHz BSS detected)

  Expected result:
  5 GHz networks should be detected and connectable, as on kernel 6.16.

  Actual result on 6.18:
  - No 5 GHz BSS entries appear at all
  - iw dev <iface> scan shows only 2.4 GHz channels (1–13)
  - This happens with:
    - ISP GPON router (non-DFS, channel 36, WPA2)
    - Samsung Galaxy S25+ hotspot forced to 5 GHz
  - NetworkManager never sees any 5 GHz SSIDs because the kernel scan does not report them.

  Debugging already performed:
  - ath12k firmware loads successfully
  - No firmware load failures
  - Regulatory domain correctly set (IN)
  - Disabled ath12k fw_stats polling (to fix earlier timeouts)
  - Disabled 802.11ax in cfg80211 (no effect)
  - Issue persists even after clean initramfs rebuild and reboot
  - No ath12k errors are logged on 6.18; 5 GHz frames appear to be
    dropped before BSS creation

  Additional evidence:
  - Same hardware, same firmware, same router
  - Only kernel version change causes regression

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