The Linux Kernel Disabling HPET For More Platforms - Including Ice Lake
Written by Michael Larabel in Intel on 29 November 2019 at 08:18 AM EST. 6 Comments
INTEL --
Reported on earlier this month is the decision by Linux kernel developers to disable HPET for Intel Coffee Lake systems. The High Precision Event Timer was being disabled since on some Coffee Lake systems at least this timer skews when entering the PC10 power state and that makes the time-stamp counter unstable.

This is believed to be a firmware issue rather than a hardware problem, but the best course of action was just disabling HPET for Coffee Lake systems to avoid the problem. Fortunately, the Linux kernel has other supported clock sources besides HPET and in fact TSC is preferred over it due to lower overhead.

In any case, kernel developers have determined this HPET blacklisting needs to be expanded. Coffee Lake H is also now black-listed over seeing the same behavior of a skewed timer when hitting the PC10 power state.

But beyond Coffee Lake, it turns out HPET is even being disabled for the new Intel Ice Lake platform over the same problem.

As this does appear to be a firmware issue, hopefully a proper software solution will end up being worked out in due course but for now the kernel is blacklisting affected platforms.
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