The Linux Kernel Disabling HPET For Intel Coffee Lake

Written by Michael Larabel in Intel on 13 November 2019 at 07:46 AM EST. 31 Comments
Another Intel change being sent off for Linux 5.4 and to be back-ported to current stable series is disabling of HPET for Coffee Lake systems.

Due to bug reports going back at least a half-year and workarounds not panning out, kernel developers have decided to blacklist the High Precision Event Timer (HPET) on Coffee Lake systems.

Some Coffee Lake systems have a skewed HPET timer when entering the PC10 power state and that in turn marks the time stamp counter (TSC) as unstable.

Intel engineers have attributed the high precision event timer issue on Coffee Lake to being a firmware problem, but due to the problem being prevalent enough, the Linux kernel is force disabling HPET for all Coffee Lake systems (0x3ec4).

This isn't the first time the Linux kernel has resorted to force disabling HPET but previously they did so for Intel Bay Trail systems over accuracy issues with it halting in deep idle states.

The change is on its way to the mainline kernel and in turn the stable branches.
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