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Posts: 31
Registered: ‎04-26-2018
Location: CA
Views: 15,326

FYI - Linux May Not Support Thunderbolt Native Mode



The T480s has a bug in the ACPI tables.


The bug causes heavy CPU usage on one thread due to frequent ACPI interrupts.


The symptoms are a slow system, and high CPU temperatures (idles at 65 Celsius).


The following circumstances trigger it:

-powering on the laptop

-waking from suspend (and possibly hibernate - untested)


The following actions prevent it:

-reboot the laptop (temporary fix)

-disable thunderbolt in the UEFI settings (permanent fix - as of UEFI v1.11)


The changelog for the UEFI update v1.11 makes explicit mention of this bug:


"<1.11> UEFI: 1.11 / ECP: 1.07

-(Fix) Fix an issue where system may become hot by system interrupts when Thundrebolt is disabled in ThinkPad Setup - Security - I/O Port Access."


Unfortunately, the bug still exists while thunderbolt is "enabled" in UEFI settings.


I believe I have found the specific code that is causing this bug, as well as the solution.


I would like to get in touch with a Lenovo engineer in order to help them resolve this issue.




Admin note; subject edited for relevancy

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