Improved thermal / power management for Intel Thunderbolt “Titan Ridge” on Linux

For those with systems using an Intel “Titan Ridge” Thunderbolt 3 controller, an improvement in the Linux kernel driver en route to the mainline should generate thermal / power benefits.

Intel’s Titan Ridge are the JHL7440 / JHL7540 / JHL7340 controllers providing Thunderbolt 3 in some desktop motherboards. Titan Ridge was released in 2018 and has been supported in the main Linux kernel since that point.

Intel continues to improve support for Linux Thunderbolt (and USB4) drivers.

While support for the Intel Titan Ridge driver is in place with Linux Thunderbolt code, it turns out that low power link states were not enabled for it. But a new patch from Intel now enables low power “CL0s” mode for Titan Ridge. CL0s is the simplest of the various CLx low power link states.

Intel Titan Ridge Controller Specifications.

Intel had already implemented low power link states for the new USB4 support, while for Titan Ridge, CL0s are being implemented for the Titan Ridge Peripheral Router to enable better thermal / thermal management. food. This allows the power of the transmitter and receiver to be reduced when a high speed channel is inactive. It’s unfortunate that such important power management features haven’t been hardwired since Titan Ridge began, but at least it’s better now than ever.

This CL0s support for Titan Ridge was taken over in Thunderbolt development tree. Is also added an option of “clx_enabled” as a new module parameter to easily disable CLx low power link states if hardware problems are discovered by users after the kernel starts putting the Thunderbolt hardware into the CL0s state. These Thunderbolt changes have yet to be sent as part of the USB changes for the next kernel, but given the timeline, they will likely still do so for Linux 5.17.

Alan A. Seibert