In the merge window of Linux 6.17, the PCIe subsystem has undergone a new round of updates. Although this update is not the most talked-about in recent years, it still introduces several noteworthy enhancements, including support for new platform controllers, improvements in driver quality, and optimizations in resource management.
Overview of Key Updates
1. Update of Intel VMD Host Bridge Driver
Support has been added for the Intel Panther Lake H / P / U series platforms. This change only requires the addition of new PCI device IDs, allowing the <span>vmd</span> driver to correctly identify and initialize the PCIe root ports of these platforms, ensuring that storage devices and others can be enumerated and accessed properly.
2. Enhanced Support for Qualcomm PCIe Controllers
- • The Qualcomm PCIe controller driver has added support for the Snapdragon SA8255p automotive-grade SoC.
- • In the DeviceTree binding, definitions for the PCIe controller nodes of QC5615 and QCS8300 SoCs have been added, providing necessary hardware descriptions for PCIe bus initialization on these platforms.
3. Support for Sophgo SG2044 Controller
New PCIe controller driver and DeviceTree binding for the Sophgo SG2044 SoC have been added, supporting initialization and operation of this platform in both Root Complex (RC) and Endpoint (EP) modes.
4. Improvements in Rockchip PCIe Driver Quality
Stability of PCIe link training for the RK3399 platform has been optimized. Developer Geraldo Nascimento stated:
“During 30 days of debugging, fixes were made for certain devices with compatibility issues, allowing the PCIe link to retrain at the Gen2 (5.0 GT/s) rate with maximum probability across all 4 lanes. Compared to the old kernel version, this improvement is expected to achieve higher link rates in actual deployments.”
5. Built-in Driver Support for Asynchronous Probe
Previously, the <span>async_probe</span> mechanism was only applicable to modular drivers. This update extends it to built-in drivers, thereby reducing initialization delays caused by PCI bus scanning during kernel startup.
6. Support for Dynamic Resizing of VF BAR / IOV Resources
New support has been added for dynamic resizing of BAR registers and IOV-related resources for SR-IOV Virtual Functions. This will enhance the flexibility of resource allocation and improve compatibility in multi-VF device environments.
Conclusion
The PCI/PCIe updates in Linux 6.17, while not revolutionary, lay a foundation for improved hardware compatibility and performance through support for multiple platforms, enhancements in driver quality, and optimizations in resource management. For developers involved in embedded platforms, automotive SoCs, and virtualization I/O, these changes may yield direct benefits.
For more details, refer to the patch notes in the Linux 6.17 PCI/PCIe Pull Request.