mirror of
https://github.com/torvalds/linux.git
synced 2026-07-28 10:09:10 +02:00
Linux kernel source tree
USB transport adds significant latency to H2C/C2H round-trips used by RF calibration. The existing timeout values were designed for PCIe and are too tight for USB, causing "failed to wait RF DACK", "failed to wait RF TSSI" and similar errors on USB adapters. Apply a 4x timeout multiplier when the device uses USB transport. The multiplier is applied in rtw89_phy_rfk_report_wait() so all calibrations benefit without changing any call sites or PCIe timeout values. The 4x multiplier was chosen based on measured data from two independent testers (RTL8922AU, 6GHz MLO and 2.4/5GHz): Calibration PCIe timeout Max measured (USB) 4x timeout PRE_NTFY 5ms 1ms 20ms DACK 58ms 72ms 232ms RX_DCK 128ms 374ms 512ms TSSI normal 20ms 24ms 80ms TSSI scan 6ms 14ms 24ms TXGAPK 54ms 18ms 216ms IQK 84ms 53ms 336ms DPK 34ms 30ms 136ms Tested with RTL8922AU on 6GHz MLO (5GHz + 6GHz simultaneous): 25 connect/disconnect cycles with zero failures. The 4x multiplier was also verified under adverse host conditions on 5GHz. 5 cycles per scenario, stress-ng as the load generator, max observed time per calibration: Calibration PCIe 4x Baseline CPU stress Mem stress Combined PRE_NTFY 5 20 0 0 0 1 DACK 58 232 71 (!) 71 (!) 71 (!) 71 (!) RX_DCK 128 512 23 22 22 23 IQK 84 336 53 53 53 53 DPK 34 136 23 23 26 23 TSSI 20 80 6 9 14 9 TXGAPK 54 216 16 16 16 16 Legend: (!) = exceeds PCIe budget but within 4x budget. Two observations from that matrix: 1. DACK exceeds the stock PCIe budget (58ms) in baseline on 5GHz on this hardware. Without the 4x multiplier, DACK fails -ETIMEDOUT deterministically on every connect, no stress needed. This is the condition the patch addresses. 2. Calibration times appear dominated by USB transport round-trip latency rather than host load, though hardware and external component factors may also contribute. DACK stays at 71ms across all four scenarios. Host-side stress has essentially zero effect on observed calibration duration. Bumping the multiplier above 4x would not address a failure mode that this stress matrix produces. Reported-by: Devin Wittmayer <lucid_duck@justthetip.ca> Link: https://github.com/Lucid-Duck/rtw89-usb3-gap/tree/main/evidence/crash-2026-04-11 Signed-off-by: Louis Kotze <loukot@gmail.com> Tested-by: Devin Wittmayer <lucid_duck@justthetip.ca> # RTL8922AU (BrosTrend BE6500) Tested-by: Devin Wittmayer <lucid_duck@justthetip.ca> # RTL8852AU (D-Link DWA-X1850 A1) Tested-by: Devin Wittmayer <lucid_duck@justthetip.ca> # RTL8852AU (D-Link DWA-X1850 B1) Tested-by: Devin Wittmayer <lucid_duck@justthetip.ca> # RTL8852BU (BrosTrend AX4L) Tested-by: Devin Wittmayer <lucid_duck@justthetip.ca> # RTL8852CU (EDUP AX5400) Acked-by: Ping-Ke Shih <pkshih@realtek.com> Signed-off-by: Ping-Ke Shih <pkshih@realtek.com> Link: https://patch.msgid.link/20260416045536.817930-1-loukot@gmail.com |
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .pylintrc | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer - Getting started with kernel development * Academic Researcher - Studying kernel internals and architecture * Security Expert - Hardening and vulnerability analysis * Backport/Maintenance Engineer - Maintaining stable kernels * System Administrator - Configuring and troubleshooting * Maintainer - Leading subsystems and reviewing patches * Hardware Vendor - Writing drivers for new hardware * Distribution Maintainer - Packaging kernels for distros * AI Coding Assistant - LLMs and AI-powered development tools For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst