Public bug reported:
On an iMac18,2 (2017) with a Broadcom BCM43602 [14e4:43ba] (subsystem
Apple [106b:016e]), Wi-Fi no longer connects since the installed system
moved to the 7.3 kernel. Booting with intel_iommu=off makes it work
again.
Wi-Fi worked in the Ubuntu 26.10 live session used to install the
machine (kernel 7.2.0-5, image of 2026-09-15). The installer then
upgraded to linux 7.3.0-5 and removed 7.2.0-5, and Wi-Fi has failed on
every boot since (7.3.0-5, 7.3.0-6 and 7.3.0-8, 13 boots in total). I
have no logs from the 7.2 live session, so I cannot tell whether the
IOMMU was enabled there.
What happens on a default boot:
1. brcmfmac loads, firmware starts, wlp3s0 appears, the initial scan
works (the access point is listed with a strong signal).
2. As soon as association starts, the IOMMU reports two faults for the Wi-Fi
device:
DMAR: DRHD: handling fault status reg 2
DMAR: [DMA Read NO_PASID] Request device [0000:03:00.0] fault addr 0xfffa3000
[fault reason 0x06] PTE Read access is not set
DMAR: [DMA Read NO_PASID] Request device [0000:03:00.0] fault addr 0xfffa5000
[fault reason 0x06] PTE Read access is not set
(the addresses vary between boots, e.g. 0xfff64000 / 0xfff65000)
3. The firmware stops answering:
ieee80211 phy0: brcmf_msgbuf_query_dcmd: Timeout on response for query command
ieee80211 phy0: brcmf_get_assoc_ies: could not get assoc info (-5)
4. After a few minutes the control ring fills up:
ieee80211 phy0: brcmf_msgbuf_tx_ioctl: Failed to reserve space in commonring
ieee80211 phy0: brcmf_run_escan: error (-12)
5. NetworkManager: "association took too long, failing activation",
reason 'ssid-not-found', retried forever.
WORKAROUND
Adding intel_iommu=off to the kernel command line. With it, on the same
kernel (7.3.0-8-generic): no DMAR fault, no firmware timeout,
association succeeds within seconds and traffic flows (IPv4 and IPv6).
The usual BCM43602 workarounds were already in place and did not help:
options brcmfmac feature_disable=0x82000 roamoff=1
options cfg80211 ieee80211_regdom=FR
SYSTEM
Release: Ubuntu 26.10 "Stonking Stingray" (development branch)
Kernel: 7.3.0-8-generic (7.3.0-8.8, based on 7.3.0-rc5); also 7.3.0-5.5 and
7.3.0-6.6
Machine: Apple iMac18,2
Wi-Fi: Broadcom BCM43602 802.11ac [14e4:43ba] rev 01, subsystem Apple
[106b:016e]
Driver: brcmfmac (in-tree), firmware brcm/brcmfmac43602-pcie
Firmware: BCM43602/1 wl0: Nov 10 2015 06:38:10 version 7.35.177.61 (r598657)
FWID 01-ea662a8c
linux-firmware: 20260915.git1522c78a
wpasupplicant: 2:2.11-2ubuntu2
Kernel config: CONFIG_INTEL_IOMMU_DEFAULT_ON=y,
CONFIG_INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON=y, IOMMU default domain type
"Translated", lazy TLB invalidation
Secure Boot: not supported on this machine
Note: a custom NVRAM file /lib/firmware/brcm/brcmfmac43602-pcie.txt was
added on 2026-09-20 while trying to fix this. The failure already
occurred on the boots before that file existed.
Note: the logs attached automatically by apport come from a boot with
intel_iommu=off (working). Kernel log excerpts from a failing boot
(default command line) are attached separately as dmesg-failing-
boot.txt.
ProblemType: Bug
DistroRelease: Ubuntu 26.10
Package: linux-image-7.3.0-8-generic 7.3.0-8.8
ProcVersionSignature: Ubuntu 7.3.0-8.8-generic 7.3.0-rc5
Uname: Linux 7.3.0-8-generic x86_64
ApportVersion: 2.36.0-0ubuntu1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: parents 18057 F.... wireplumber
/dev/snd/controlC1: parents 18057 F.... wireplumber
/dev/snd/seq: parents 18053 F.... pipewire
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Fri Oct 2 22:10:14 2026
InstallationDate: Installed on 2026-09-19 (13 days ago)
InstallationMedia: Ubuntu 26.10 "Stonking Stingray" - Daily amd64 (20260915)
MachineType: Apple Inc. iMac18,2
ProcEnviron:
LANG=fr_FR.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
ProcFB: 0 amdgpudrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.3.0-8-generic
root=UUID=449c41b8-da4d-4c34-ad74-1f7a5e150bb0 ro quiet splash intel_iommu=off
crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 04/11/2022
dmi.bios.release: 0.1
dmi.bios.vendor: Apple Inc.
dmi.bios.version: 451.140.1.0.0
dmi.board.name: Mac-77F17D7DA9285301
dmi.board.vendor: Apple Inc.
dmi.board.version: iMac18,2
dmi.chassis.type: 9
dmi.chassis.vendor: Apple Inc.
dmi.chassis.version: Mac-77F17D7DA9285301
dmi.modalias:
dmi:bvnAppleInc.:bvr451.140.1.0.0:bd04/11/2022:br0.1:svnAppleInc.:pniMac18,2:pvr1.0:rvnAppleInc.:rnMac-77F17D7DA9285301:rvriMac18,2:cvnAppleInc.:ct9:cvrMac-77F17D7DA9285301:sku:pfaiMac:
dmi.product.family: iMac
dmi.product.name: iMac18,2
dmi.product.version: 1.0
dmi.sys.vendor: Apple Inc.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug stonking wayland-session
** Attachment added: "dmesg-failing-boot.txt"
https://bugs.launchpad.net/bugs/2169339/+attachment/6005050/+files/dmesg-failing-boot.txt
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https://bugs.launchpad.net/bugs/2169339
Title:
[iMac18,2] BCM43602 Wi-Fi (brcmfmac) cannot associate on 7.3 kernels:
DMAR DMA Read faults, firmware hangs; works with intel_iommu=off
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