USB Changes For Linux 5.17: Overdue Xen pvUSB To DWC3 Multi-Stream Transfer

Written by Michael Larabel in Linux Kernel on 14 January 2022 at 12:00 AM EST. 2 Comments
Landing this week as part of the various subsystems overseen by Linux's second-in-command Greg Kroah-Hartman were the USB changes for Linux 5.17.

There were many USB (and Thunderbolt) changes for Linux 5.17 such as Synopsys' DWC3 "Multi-Stream Transfer" feature, Xen pvUSB making its debut after being out-of-tree since its start in ~2008, various power management changes, and more. Some of the USB subsystem highlights for 5.17 include:

- Multi-Stream Transfer (MST; not to be confused with DisplayPort's MST - Multi-Stream Transport) for the Synopsys DesignWare Core SuperSpeed USB 3.0 controller. Synopsys added Multi-Stream Transfer to improve bulk streams performance for SuperSpeed and SuperSpeed Plus with their DWC3 controller with this latest Linux kernel driver code. Synopsys has found this Multi-Stream Transfer mode for DWC3 can lead to a "significant performance improvement" for UASP transfers.

- Improved thermal/power management for Intel's Titan Ridge Thunderbolt controller. Titan Ridge is the codename for the JHL7440 / JHL7540 / JHL7340 Thunderbolt 3 controllers.

- The Xen pvUSB driver is being mainlined more than a decade after it was first started. This allows for USB device support for Xen para-virtualized use-cases with guest systems able to access USB devices passed from Dom0 for generic USB device support.

- Adding a 20ms delay for SuperSpeed hubs resume for letting links transit to U0 state for more reliable remote wakeup handling.

- ASpeed AST2600 UHCI support.

- Suspend/resume support for the USB Xilinx UDC driver code.

See this pull request for the full list of USB feature changes for Linux 5.17.
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