** Attachment added: "dmesg-6.17.0-29-failing.txt" https://bugs.launchpad.net/ubuntu/+source/linux-hwe-6.17/+bug/2153170/+attachment/5971653/+files/dmesg-6.17.0-29-failing.txt
** Description changed: On 6.17.0-29.29~24.04.1, sustained writes to a CP2102N USB-UART adapter (Silicon Labs 10c4) lose bytes at all baud rates from 115200 to 921600, after a few hundred KB of contiguous output. The receiving device (ESP32-C3 over UART) reports its own RX-data timeout, which only fires if bytes are missing on the wire — the kernel does not log any disconnect or URB error. Booting 6.17.0-23.23~24.04.1 (same machine, same adapter, same cable, same target device) with no other change makes the problem disappear immediately. Flashing a ~3 MB firmware ZIP via shos flash completes in one shot on -23 and fails reliably on -29. Reproduction: Boot 6.17.0-29-generic. Plug a CP2102N USB-UART bridge into a USB-A port. Connect it to an ESP32-C3 (or any device that ACKs per-block at the application layer). Send sustained data >256 KB at e.g. 460800 baud. Expected: All bytes are received correctly. Actual: Bytes are dropped somewhere between host userspace and the device. + Observed A/B (single machine, all other variables held constant): + + 6.17.0-23.23~24.04.1 — 4/4 clean flashes of a 3 MB firmware, ~22 s each, zero retries. + 6.17.0-29.29~24.04.1 — 0/N clean flashes; every attempt failed mid-write at every baud rate from 921600 down to 115200, with the device reporting its own RX-data timeout. + + No kernel-side errors are logged during failure on -29 — dmesg shows the + CP2102N continuously attached. The bytes are apparently being lost + somewhere between host userspace and the device UART, but not by any + path the driver currently reports. + + Likely candidates include: + + changes to xHCI URB scheduling, + bulk transfer pacing on full-speed devices, + or cp210x flow-control handling differences between -23 and -29. + Hardware: HP DDAVIDENKO-LP xHCI controller Silicon Labs CP2102N (10c4:ea60) bcdDevice 1.00 Attached directly to xhci_hcd port 3-2 (no hub) Additional information: No kernel errors are logged during the failure — journalctl -k shows the device staying continuously attached. ProblemType: Bug DistroRelease: Ubuntu 24.04 Package: linux-image-6.17.0-29-generic 6.17.0-29.29~24.04.1 ProcVersionSignature: Ubuntu 6.17.0-23.23~24.04.1-generic 6.17.13 Uname: Linux 6.17.0-23-generic x86_64 ApportVersion: 2.28.1-0ubuntu3.8 Architecture: amd64 AudioDevicesInUse: - USER PID ACCESS COMMAND - /dev/snd/controlC0: dmytro-davidenko 2064 F.... pipewire - dmytro-davidenko 2068 F.... wireplumber - /dev/snd/seq: dmytro-davidenko 2064 F.... pipewire + USER PID ACCESS COMMAND + /dev/snd/controlC0: dmytro-davidenko 2064 F.... pipewire + dmytro-davidenko 2068 F.... wireplumber + /dev/snd/seq: dmytro-davidenko 2064 F.... pipewire CasperMD5CheckResult: pass CurrentDesktop: KDE Date: Tue May 19 18:16:00 2026 InstallationDate: Installed on 2025-06-10 (343 days ago) InstallationMedia: Ubuntu 24.04.1 LTS "Noble Numbat" - Release amd64 (20240827.1) MachineType: HP HP ProBook 450 15.6 inch G10 Notebook PC ProcFB: 0 i915drmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.17.0-23-generic root=UUID=f9672de6-3f28-4c9e-a017-ea091de86178 ro quiet splash vt.handoff=7 PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No PulseAudio daemon running, or not running as session daemon. RelatedPackageVersions: - linux-restricted-modules-6.17.0-23-generic N/A - linux-backports-modules-6.17.0-23-generic N/A - linux-firmware 20240318.git3b128b60-0ubuntu2.27 + linux-restricted-modules-6.17.0-23-generic N/A + linux-backports-modules-6.17.0-23-generic N/A + linux-firmware 20240318.git3b128b60-0ubuntu2.27 SourcePackage: linux-hwe-6.17 UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 12/09/2024 dmi.bios.release: 7.1 dmi.bios.vendor: HP dmi.bios.version: V72 Ver. 01.07.01 dmi.board.name: 8B7C dmi.board.vendor: HP dmi.board.version: KBC Version 52.39.00 dmi.chassis.type: 10 dmi.chassis.vendor: HP dmi.ec.firmware.release: 82.57 dmi.modalias: dmi:bvnHP:bvrV72Ver.01.07.01:bd12/09/2024:br7.1:efr82.57:svnHP:pnHPProBook45015.6inchG10NotebookPC:pvrSBKPF,SBKPFV2:rvnHP:rn8B7C:rvrKBCVersion52.39.00:cvnHP:ct10:cvr:sku969H2ET#ABB: dmi.product.family: 103C_5336AN HP ProBook dmi.product.name: HP ProBook 450 15.6 inch G10 Notebook PC dmi.product.sku: 969H2ET#ABB dmi.product.version: SBKPF,SBKPFV2 dmi.sys.vendor: HP -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2153170 Title: linux-image-6.17.0-29-generic: USB-serial (CP2102N) drops bytes on sustained writes; -23 works To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-hwe-6.17/+bug/2153170/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
