* [REGRESSION] BCM4355 Wi-Fi fails with Intel IOMMU on 7.3.0-2-t2-noble @ 2026-10-20 11:32 Peter Kiddier 2026-10-20 11:49 ` Peter Kiddier 0 siblings, 1 reply; 3+ messages in thread From: Peter Kiddier @ 2026-10-20 11:32 UTC (permalink / raw) To: linux-wireless; +Cc: brcm80211, iommu, arend.vanspriel, regressions Hello, I am reporting a Wi-Fi regression on a 2018 Apple MacBook Air with a T2 chip, running Linux Mint Zena based on Ubuntu 24.04. The Broadcom BCM4355 Wi-Fi device works with kernel 7.2.11-3-t2-noble but fails with 7.3.0-2-t2-noble. Disabling the Intel IOMMU using intel_iommu=off restores Wi-Fi on 7.3.0-2. Hardware: - Apple MacBook Air 2018 (MacBookAir8,1) - Wi-Fi: Broadcom BCM4355 802.11ac Wireless LAN SoC - PCI ID: 14e4:43dc (subsystem 106b:0843) - Driver: brcmfmac - Interface: wlp2s0 Test results: - 7.2.11-3-t2-noble, default kernel command line: Wi-Fi works. - 7.3.0-2-t2-noble, default kernel command line: Wi-Fi fails. - 7.3.0-2-t2-noble with intel_iommu=off: Wi-Fi works. - Reloading brcmfmac on the failing configuration does not restore Wi-Fi. On the failing 7.3.0-2 boot, the driver detects the device, loads its firmware and creates wlp2s0: brcmfmac 0000:02:00.0: enabling device (0000 -> 0002) brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac4355c1-pcie for chip BCM4355/12 brcmfmac: brcmf_c_process_txcap_blob: TxCap blob found, loading brcmfmac: brcmf_c_preinit_dcmds: Firmware: BCM4355/12 wl0: Jul 8 2023 17:49:51 version 9.30.503.0.32.5.87 FWID 01-e74b9cb0 brcmfmac 0000:02:00.0 wlp2s0: renamed from wlan0 However, Wi-Fi subsequently stops responding. The kernel log reports errors including: brcmf_msgbuf_query_dcmd: Timeout on response for query command brcmf_cfg80211_scan: scan error (-5) brcmf_run_escan: error (-5) brcmf_msgbuf_tx_ioctl: Failed to reserve space in commonring brcmf_cfg80211_get_channel: chanspec failed (-5) There is also an error creating the P2P interface: brcmf_cfg80211_add_iface: add iface p2p-dev-wlp2s0 type 10 failed: err=-52 I tried reloading the driver using: sudo modprobe -r brcmfmac_wcc sudo modprobe -r brcmfmac sudo modprobe brcmfmac The driver and firmware loaded again, but Wi-Fi remained unusable. The firmware files are present under /lib/firmware/brcm/, and the firmware version reported by the driver is the same on the working and failing kernels. The brcmfmac module metadata differs between the kernels: Working kernel 7.2.11-3-t2-noble: srcversion: 3B6176FDB720DDE8E7C596B Failing kernel 7.3.0-2-t2-noble: srcversion: 3DCA38D52402541701276CF I did not find obvious PCIe AER or fatal errors in the failing boot's kernel log. It has been suggested testing intel_iommu=off after reloading brcmfmac. The driver reload did not help, but booting with intel_iommu=off restored Wi-Fi. This strongly suggests an interaction between Intel IOMMU handling and the BCM4355/brcmfmac driver in the 7.3.0-2-t2-noble kernel. I have not tested a vanilla upstream kernel, so I cannot yet confirm whether this reproduces outside the T2 kernel packages. Unfortunately, I have limited time available for further testing, so I may not be able to investigate additional requests promptly. I wanted to report the reproducible behaviour and the intel_iommu=off workaround in case it helps identify the regression. Could you advise on further diagnostics, or whether this should be investigated as an IOMMU or brcmfmac regression? Thank you. ^ permalink raw reply [flat|nested] 3+ messages in thread
* [REGRESSION] BCM4355 Wi-Fi fails with Intel IOMMU on 7.3.0-2-t2-noble 2026-10-20 11:32 [REGRESSION] BCM4355 Wi-Fi fails with Intel IOMMU on 7.3.0-2-t2-noble Peter Kiddier @ 2026-10-20 11:49 ` Peter Kiddier 2026-10-20 12:08 ` Aditya Garg 0 siblings, 1 reply; 3+ messages in thread From: Peter Kiddier @ 2026-10-20 11:49 UTC (permalink / raw) To: linux-wireless Cc: brcm80211, iommu, arend.vanspriel, regressions, jgg, kevin.tian, joro, will, robin.murphy, dwmw2, baolu.lu, linux-kernel Adding the IOMMU maintainers and linux-kernel. The original report and test results are below for context. I haven't tested a vanilla upstream kernel, and may have limited time for further testing, but wanted to share the findings in case they're useful. Thank you. On Tue, 20 Oct 2026 at 22:32, Peter Kiddier <peter@kiddier.org> wrote: > > Hello, > > I am reporting a Wi-Fi regression on a 2018 Apple MacBook Air with a > T2 chip, running Linux Mint Zena based on Ubuntu 24.04. > > The Broadcom BCM4355 Wi-Fi device works with kernel 7.2.11-3-t2-noble > but fails with 7.3.0-2-t2-noble. Disabling the Intel IOMMU using > intel_iommu=off restores Wi-Fi on 7.3.0-2. > > Hardware: > - Apple MacBook Air 2018 (MacBookAir8,1) > - Wi-Fi: Broadcom BCM4355 802.11ac Wireless LAN SoC > - PCI ID: 14e4:43dc (subsystem 106b:0843) > - Driver: brcmfmac > - Interface: wlp2s0 > > Test results: > > - 7.2.11-3-t2-noble, default kernel command line: Wi-Fi works. > - 7.3.0-2-t2-noble, default kernel command line: Wi-Fi fails. > - 7.3.0-2-t2-noble with intel_iommu=off: Wi-Fi works. > - Reloading brcmfmac on the failing configuration does not restore Wi-Fi. > > On the failing 7.3.0-2 boot, the driver detects the device, loads its > firmware and creates wlp2s0: > > brcmfmac 0000:02:00.0: enabling device (0000 -> 0002) > brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac4355c1-pcie for > chip BCM4355/12 > brcmfmac: brcmf_c_process_txcap_blob: TxCap blob found, loading > brcmfmac: brcmf_c_preinit_dcmds: Firmware: BCM4355/12 wl0: Jul 8 2023 > 17:49:51 version 9.30.503.0.32.5.87 FWID 01-e74b9cb0 > brcmfmac 0000:02:00.0 wlp2s0: renamed from wlan0 > > However, Wi-Fi subsequently stops responding. The kernel log reports > errors including: > > brcmf_msgbuf_query_dcmd: Timeout on response for query command > brcmf_cfg80211_scan: scan error (-5) > brcmf_run_escan: error (-5) > brcmf_msgbuf_tx_ioctl: Failed to reserve space in commonring > brcmf_cfg80211_get_channel: chanspec failed (-5) > > There is also an error creating the P2P interface: > > brcmf_cfg80211_add_iface: add iface p2p-dev-wlp2s0 type 10 failed: err=-52 > > I tried reloading the driver using: > > sudo modprobe -r brcmfmac_wcc > sudo modprobe -r brcmfmac > sudo modprobe brcmfmac > > The driver and firmware loaded again, but Wi-Fi remained unusable. > > The firmware files are present under /lib/firmware/brcm/, and the > firmware version reported by the driver is the same on the working and > failing kernels. > > The brcmfmac module metadata differs between the kernels: > > Working kernel 7.2.11-3-t2-noble: > srcversion: 3B6176FDB720DDE8E7C596B > > Failing kernel 7.3.0-2-t2-noble: > srcversion: 3DCA38D52402541701276CF > > I did not find obvious PCIe AER or fatal errors in the failing boot's > kernel log. > > It has been suggested testing intel_iommu=off after reloading > brcmfmac. The driver reload did not help, but booting with > intel_iommu=off restored Wi-Fi. > > This strongly suggests an interaction between Intel IOMMU handling and > the BCM4355/brcmfmac driver in the 7.3.0-2-t2-noble kernel. > > I have not tested a vanilla upstream kernel, so I cannot yet confirm > whether this reproduces outside the T2 kernel packages. Unfortunately, > I have limited time available for further testing, so I may not be > able to investigate additional requests promptly. I wanted to report > the reproducible behaviour and the intel_iommu=off workaround in case > it helps identify the regression. > > Could you advise on further diagnostics, or whether this should be > investigated as an IOMMU or brcmfmac regression? > > Thank you. ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [REGRESSION] BCM4355 Wi-Fi fails with Intel IOMMU on 7.3.0-2-t2-noble 2026-10-20 11:49 ` Peter Kiddier @ 2026-10-20 12:08 ` Aditya Garg 0 siblings, 0 replies; 3+ messages in thread From: Aditya Garg @ 2026-10-20 12:08 UTC (permalink / raw) To: Peter Kiddier, linux-wireless Cc: brcm80211, iommu, arend.vanspriel, regressions, jgg, kevin.tian, joro, will, robin.murphy, dwmw2, baolu.lu, linux-kernel On 20/10/26 5:19 pm, Peter Kiddier wrote: > Adding the IOMMU maintainers and linux-kernel. > > The original report and test results are below for context. > > I haven't tested a vanilla upstream kernel, and may have limited time > for further testing, but wanted to share the findings in case they're > useful. > > Thank you. https://www.mail-archive.com/ubuntu-bugs@lists.ubuntu.com/info.html Similar issue is present in older non T2 Macs, so definitely not a T2 patches issue. Also, T2 patches do not touch IOMMU or brcmfmac > > > On Tue, 20 Oct 2026 at 22:32, Peter Kiddier <peter@kiddier.org> wrote: >> >> Hello, >> >> I am reporting a Wi-Fi regression on a 2018 Apple MacBook Air with a >> T2 chip, running Linux Mint Zena based on Ubuntu 24.04. >> >> The Broadcom BCM4355 Wi-Fi device works with kernel 7.2.11-3-t2-noble >> but fails with 7.3.0-2-t2-noble. Disabling the Intel IOMMU using >> intel_iommu=off restores Wi-Fi on 7.3.0-2. >> >> Hardware: >> - Apple MacBook Air 2018 (MacBookAir8,1) >> - Wi-Fi: Broadcom BCM4355 802.11ac Wireless LAN SoC >> - PCI ID: 14e4:43dc (subsystem 106b:0843) >> - Driver: brcmfmac >> - Interface: wlp2s0 >> >> Test results: >> >> - 7.2.11-3-t2-noble, default kernel command line: Wi-Fi works. >> - 7.3.0-2-t2-noble, default kernel command line: Wi-Fi fails. >> - 7.3.0-2-t2-noble with intel_iommu=off: Wi-Fi works. >> - Reloading brcmfmac on the failing configuration does not restore Wi-Fi. >> >> On the failing 7.3.0-2 boot, the driver detects the device, loads its >> firmware and creates wlp2s0: >> >> brcmfmac 0000:02:00.0: enabling device (0000 -> 0002) >> brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac4355c1-pcie for >> chip BCM4355/12 >> brcmfmac: brcmf_c_process_txcap_blob: TxCap blob found, loading >> brcmfmac: brcmf_c_preinit_dcmds: Firmware: BCM4355/12 wl0: Jul 8 2023 >> 17:49:51 version 9.30.503.0.32.5.87 FWID 01-e74b9cb0 >> brcmfmac 0000:02:00.0 wlp2s0: renamed from wlan0 >> >> However, Wi-Fi subsequently stops responding. The kernel log reports >> errors including: >> >> brcmf_msgbuf_query_dcmd: Timeout on response for query command >> brcmf_cfg80211_scan: scan error (-5) >> brcmf_run_escan: error (-5) >> brcmf_msgbuf_tx_ioctl: Failed to reserve space in commonring >> brcmf_cfg80211_get_channel: chanspec failed (-5) >> >> There is also an error creating the P2P interface: >> >> brcmf_cfg80211_add_iface: add iface p2p-dev-wlp2s0 type 10 failed: err=-52 >> >> I tried reloading the driver using: >> >> sudo modprobe -r brcmfmac_wcc >> sudo modprobe -r brcmfmac >> sudo modprobe brcmfmac >> >> The driver and firmware loaded again, but Wi-Fi remained unusable. >> >> The firmware files are present under /lib/firmware/brcm/, and the >> firmware version reported by the driver is the same on the working and >> failing kernels. >> >> The brcmfmac module metadata differs between the kernels: >> >> Working kernel 7.2.11-3-t2-noble: >> srcversion: 3B6176FDB720DDE8E7C596B >> >> Failing kernel 7.3.0-2-t2-noble: >> srcversion: 3DCA38D52402541701276CF >> >> I did not find obvious PCIe AER or fatal errors in the failing boot's >> kernel log. >> >> It has been suggested testing intel_iommu=off after reloading >> brcmfmac. The driver reload did not help, but booting with >> intel_iommu=off restored Wi-Fi. >> >> This strongly suggests an interaction between Intel IOMMU handling and >> the BCM4355/brcmfmac driver in the 7.3.0-2-t2-noble kernel. >> >> I have not tested a vanilla upstream kernel, so I cannot yet confirm >> whether this reproduces outside the T2 kernel packages. Unfortunately, >> I have limited time available for further testing, so I may not be >> able to investigate additional requests promptly. I wanted to report >> the reproducible behaviour and the intel_iommu=off workaround in case >> it helps identify the regression. >> >> Could you advise on further diagnostics, or whether this should be >> investigated as an IOMMU or brcmfmac regression? >> >> Thank you. ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2026-10-20 12:08 UTC | newest] Thread overview: 3+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2026-10-20 11:32 [REGRESSION] BCM4355 Wi-Fi fails with Intel IOMMU on 7.3.0-2-t2-noble Peter Kiddier 2026-10-20 11:49 ` Peter Kiddier 2026-10-20 12:08 ` Aditya Garg
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox