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Tue, 03 Nov 2026 07:23:35 -0800 (PST) Received: from [192.168.1.50] ([81.196.40.70]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4b2a9fafe08sm101068505e9.3.2026.11.03.07.23.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Nov 2026 07:23:35 -0800 (PST) Message-ID: <24567f1d-1ee8-4a1e-81dd-1225da9bcfd3@gmail.com> Date: Tue, 3 Nov 2026 17:23:32 +0200 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [REGRESSION] rtw88_8822bu: RTL8822BU unstable/disconnects on USB3 with newer kernels To: Tor-Arne Forsmo , "linux-wireless@vger.kernel.org" Cc: "regressions@lists.linux.dev" , "linux-kernel@vger.kernel.org" References: <1ZyN-kxUvoIDfNiCh2Ro6EooWLDGuN7Jwm8yKK8c1ZAeNrcmCia0aYwIDZs77lZtpppfBohrqEI6q4dwxAfcQRJa0JkjcQBO7mDZ7ACyAKM=@proton.me> Content-Language: en-US From: Bitterblue Smith In-Reply-To: <1ZyN-kxUvoIDfNiCh2Ro6EooWLDGuN7Jwm8yKK8c1ZAeNrcmCia0aYwIDZs77lZtpppfBohrqEI6q4dwxAfcQRJa0JkjcQBO7mDZ7ACyAKM=@proton.me> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 03/11/2026 13:10, Tor-Arne Forsmo wrote: > I've experienced new issues with a TP-Link Archer T4U. I've used this the past half a year without issues on a ubuntu server install, but recently I started experiencing disconnects on three different linux devices with two different Archer T4U (I bought a new one). The final fix was to revert back to a 6.18 kernel. I have never reported a bug before, I hope I'm writing to the correct e-mail addresses (I've gotten some help by AI). I've instructed ChatGPT to write a report of my findings, I hope this is helpful. > > From ChatGPT: > > > I believe I have encountered a regression affecting the rtw88_8822bu driver / RTL8822BU when operating over USB 3.0. > > The problem is reproducible on a Raspberry Pi 4 with a TP-Link Archer T4U v3 (USB ID 2357:0115). > > The important result is: > > 6.12.62+rpt-rpi-v8  - GOOD > 6.18.50+rpt-rpi-v8  - BAD > > These are Raspberry Pi OS kernels rather than vanilla upstream kernels, so I have not established the exact upstream regression range. > > Hardware: > > - Raspberry Pi 4 > > - TP-Link Archer T4U v3 > > - USB ID: 2357:0115 > > - Realtek RTL8822BU > > - Driver: rtw88_8822bu / rtw88_usb > > - Raspberry Pi OS / Debian 13 (trixie) > > - Adapter connected directly to a USB 3.0 port > > > With 6.18.50+rpt-rpi-v8, the adapter repeatedly disconnects and re-enumerates when used directly on USB 3.0. After reaching the SuperSpeed bus, it falls off USB again and this repeats approximately every few seconds. > > I observed the device numbers continuously increasing as it re-enumerated. The pattern was essentially: > > rtw88_8822bu: Firmware version 30.20.0, H2C version 14 > usb ...: USB disconnect > rtw88_8822bu: Firmware version 30.20.0, H2C version 14 > usb ...: USB disconnect > ... > > This continued for minutes. > > There are also -EPROTO (-71) errors associated with the USB2 -> USB3 transition. I understand that a single -71 during this transition may be expected for this device/driver. The problem I am reporting is not that initial message itself, but the subsequent repeated disconnect/re-enumeration loop after the adapter has reached SuperSpeed. > > The adapter works when limited to USB 2.0. > > I then installed 6.12.62+rpt-rpi-v8 on exactly the same Raspberry Pi without otherwise changing the system. > > With 6.12.62: > > $ uname -r > 6.12.62+rpt-rpi-v8 > > $ sudo modinfo rtw88_8822bu | grep -E 'filename|vermagic' > filename: /lib/modules/6.12.62+rpt-rpi-v8/kernel/drivers/net/wireless/realtek/rtw88/rtw88_8822bu.ko.xz > vermagic: 6.12.62+rpt-rpi-v8 SMP preempt mod_unload modversions aarch64 > > The same Archer T4U then enumerates successfully at SuperSpeed and remains there: > > $ lsusb > Bus 002 Device 005: ID 2357:0115 TP-Link Archer T4U ver.3 > > $ lsusb -t > /:  Bus 002.Port 001: Dev 001, Class=root_hub, Driver=xhci_hcd/4p, 5000M >     |__ Port 001: Dev 005, If 0, Class=Vendor Specific Class, Driver=rtw_8822bu, 5000M >     |__ Port 002: Dev 006, If 0, Class=Mass Storage, Driver=uas, 5000M > > The JMicron USB 3.0 disk dock shown above is simultaneously attached and operating at 5000M. > > I then connected the Wi-Fi network through the Archer rather than merely leaving the interface idle: > > $ nmcli device > DEVICE  TYPE  STATE         CONNECTION > wlan1   wifi  connected     netplan-wlan0-Rasktnedikanten > wlan0   wifi  disconnected  -- > > $ ip addr show wlan1 > wlan1: ... >     link/ether d8:44:89:03:3e:29 >     inet 192.168.10.71/24 ... > > The Pi is therefore actually carrying its network connection over the Archer at USB 3.0 speed under 6.12.62, rather than the adapter simply surviving enumeration. > > So far I have seen no USB errors or disconnects with 6.12.62. > > For comparison, under 6.18.50 the same adapter, Pi and direct USB 3.0 connection entered the disconnect/re-enumeration loop within seconds. > > I also have two physical Archer T4U v3 adapters. Both exhibited the direct-USB3 problem on the Pi with 6.18.50, so the Raspberry Pi result does not appear to be specific to one defective dongle. > > There are some additional observations from x86 systems which may or may not be related: > > - One older Archer T4U v3 has worked reliably for a long period on an x86 Debian machine in the past. > > - The same older adapter works on another current x86 Linux machine over USB 3.0. > > - On a different x86 Kubuntu machine with a newer kernel, the older adapter failed during/after USB3 enumeration with rtw88 errors including -71 and -110, register access failures, "failed to read hw feature report", "failed to setup chip efuse info", and a USB SuperSpeed reset. > > - A newer physical Archer T4U v3 works on that particular x86 machine. > > > Because of these additional results, there may also be some host/device sensitivity involved. However, the Raspberry Pi test is the controlled comparison I consider significant: same Pi, same adapter, same USB3 port, with 6.12.62 working and 6.18.50 failing very quickly. > > On the bad Raspberry Pi kernel, the relevant modules were: > > kernel: 6.18.50+rpt-rpi-v8 > > rtw88_8822bu: > srcversion: 594B4CB53E28BF8F6458E02 > vermagic: 6.18.50+rpt-rpi-v8 SMP preempt mod_unload modversions aarch64 > > rtw88_usb: > srcversion: C08071F92A5EA09279ABA16 > vermagic: 6.18.50+rpt-rpi-v8 SMP preempt mod_unload modversions aarch64 > > For reference, two Ubuntu x86 kernels I checked used: > > rtw88_8822bu srcversion: C04D1014EBE0F8F11E65854 > rtw88_usb    srcversion: B5E531378AC65924BDEA496 > > I have not bisected the regression or tested intermediate kernels. The Raspberry Pi is now being used as a working system, so I would prefer not to repeatedly change its kernel unless further testing is particularly important. > > I can provide the complete dmesg from the failing 6.18.50 test if useful. It contains the repeated disconnect/re-enumeration sequence. > > Please let me know if there is any other diagnostic information I can collect from the currently working 6.12.62 system without changing its kernel. > > > > Best regards, Tor-Arne Forsmo You could keep the 6.12.62 kernel and bisect only rtw88. It's not too difficult to compile it out of tree.