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
LINUX KERNEL --
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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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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