[Bug 2138308] [NEW] 5GHz WiFi not detected with kernel 6.17/6.18 - Snapdragon X Elite

[Saikiran]

Public bug reported:

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)
- 6.18.0-9-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

** Affects: ubuntu-concept
     Importance: Undecided
         Status: New


** Tags: wlan

** Attachment added: "I do not currently have logs from kernel 6.16, but 5 GHz works reliably on 6.16 and fails on 6.18 on the same hardware and router."
   https://bugs.launchpad.net/bugs/2138308/+attachment/5938975/+files/ath12k-wcn7850-regression-logs.tar.gz

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

Title:
  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)
  - 6.18.0-9-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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