CVS commit: src/sys/dev/ic

["Michael van Elst" <mlelstv%netbsd.org@localhost>]

Module Name:    src
Committed By:   mlelstv
Date:           Sat Aug 20 06:47:28 UTC 2022

Modified Files:
        src/sys/dev/ic: hpet.c

Log Message:
It is possible to overflow the (low 32bit) HPET counter between hpet_attach
and TSC calibration if the boot is delayed for more than ~430 seconds (or
less, depending on HPET frequency). The result is a badly misconfigured
timecounter.

Change the measurement interval to ~1e6 HPET ticks (<100ms) during
the calibration to avoid the overflow. This introduces an error of
1ppm, compared to the previous unspecified but typical error of 0.1ppm.
But this is still much less than the guaranteed maximum frequency drift
of the HPET counter itself, which is 500ppm.


To generate a diff of this commit:
cvs rdiff -u -r1.17 -r1.18 src/sys/dev/ic/hpet.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.