Public bug reported:
[Impact]
The MediaTek MT7925 WiFi 7 chip (14c3:7925, mt7925e driver) is soldered into a
wide range of 2024–2026 laptops (e.g. ThinkPad P16s Gen 4 AMD, T14 Gen 6 and
many others). The in-tree driver up to and including kernel 7.0 does not
support following AP channel switch announcements (CSA) in station mode.
mac80211 logs:
wlp194s0: driver doesn't support chan-switch with channel contexts
and tears the connection down every time the AP performs a channel
switch (e.g. a DFS radar evacuation, which the AP is legally required to
perform). Each event costs a full deauth + reauth + DHCP cycle: 15–75 s
of outage in the common case. In the worst case the interrupted WPA
handshake is misclassified by wpa_supplicant as WRONG_KEY,
NetworkManager enters need-auth, and connectivity is not restored
without manual user action (observed: 6.5 minutes, ended only by
manually re-selecting the network).
Windows clients and Intel-based Linux clients on the same AP follow the
same channel switches seamlessly, i.e. this is purely a driver
capability gap. I have two days of 15-second-interval monitoring data
showing 8 such disconnects across all times of day, including one that
dropped an ongoing video call while an Intel BE201 laptop on the same 5
GHz BSSID was unaffected.
This cannot be solved by waiting for newer kernels on LTS: the fix is a
feature and will not flow into 7.0 via stable updates, and the 24.04 HWE
stack terminates at 7.0.
[Fix]
Upstream in mainline as of v7.1:
7900da40e315 wifi: mt76: mt7925: introduce CSA support in non-MLO mode
plus the follow-up fix (post-7.1, headed for 7.2/stable), which should be
included to avoid a known crash in the new CSA beacon path:
351dd7d2c80d wifi: mt76: mt7921/mt7925: fix NULL dereference in CSA
beacon
Canonical has already validated exactly this backport on both affected bases:
it shipped as "NVIDIA: SAUCE: wifi: mt76: mt7925: introduce CSA support in
non-MLO mode" in linux-nvidia-6.14 (6.14.0-1013.13) and linux-nvidia-6.17
(6.17.0-1004.4) via LP: #2129209, with SRU verification completed on noble
(2025-11-04). This request is to carry the same patch in the generic, OEM and
HWE flavors so that non-NVIDIA-platform users get it too.
[Test Plan]
1. Laptop with MT7925, connected to a 5 GHz BSS on a DFS channel (52–144,
common default on ISP routers).
2. Trigger or await an AP channel switch (radar evacuation or manual channel
change on the AP).
3. Unpatched: dmesg shows "driver doesn't support chan-switch with channel
contexts"; wpa_supplicant logs CTRL-EVENT-DISCONNECTED reason=4
locally_generated=1; connectivity drops for 15+ seconds.
4. Patched: the station follows the CSA; no deauthentication, no visible
interruption. Regression check: normal connect/disconnect/suspend cycles and
2.4 GHz operation unaffected.
[Where problems could occur]
The changes are confined to the mt7925/mt792x driver. The main risk is
the new CSA handling path itself, which is why the follow-up NULL-
dereference fix (351dd7d2c80d) should be picked together with the
feature commit. The identical feature backport has been shipping in the
linux-nvidia kernels since 2025-11/12 without reported regressions.
[Additional information]
Affected hardware here: ThinkPad P16s Gen 4 AMD, MEDIATEK 14c3:7925, kernel
6.17.0-1030-oem (Linux Mint 22.3 on the noble/24.04 base).
Example event (client side):
kernel: wlp194s0: driver doesn't support chan-switch with channel contexts
wpa_supplicant: CTRL-EVENT-DISCONNECTED bssid=3c:2d:9e:cd:8c:50 reason=4
locally_generated=1
** Affects: linux-oem-6.17 (Ubuntu)
Importance: Undecided
Status: New
** Attachment added: "dmesg and journalctl log excerpts"
https://bugs.launchpad.net/bugs/2162014/+attachment/5987458/+files/lp-mt7925-csa-evidence.txt
--
You received this bug notification because you are a member of Ubuntu
Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/2162014
Title:
Backport mt7925 CSA support to oem-6.17 and 7.0 kernels (already
shipped in linux-nvidia via LP#2129209)
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux-oem-6.17/+bug/2162014/+subscriptions
--
ubuntu-bugs mailing list
[email protected]
https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
