[Bug 260868] possible i386 regression after ce35a3bc852d25cb989bc1f3dc4ddb723d7d5117

From: <bugzilla-noreply_at_freebsd.org>
Date: Mon, 03 Jan 2022 18:02:26 UTC

--- Comment #13 from commit-hook@FreeBSD.org ---
A commit in branch main references this bug:


commit 0e494a9e3fd86ef54899dcbe0268866629096c1e
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2022-01-03 15:14:41 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2022-01-03 18:00:50 +0000

    x86: Skip late calibration if our reference timer has low quality

    Some AMD Geode-based systems end up using the 8254 PIT to calibrate the
    TSC during late calibration, which doesn't work because that
    timecounter's mask (65535) is much smaller than its frequency (1193182).
    Moreover, early calibration is done against the 8254 timer anyway.

    Work around the problem by simply using early calibration results if no
    high-quality timecounters exist.

    PR:             260868
    Fixes:          22875f88799e ("x86: Implement deferred TSC calibration")
    Reported and tested by: mike@sentex.net, Stefan Hegnauer
    Reviewed by:    imp, kib
    MFC after:      3 days
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D33730

 sys/x86/x86/tsc.c | 7 +++++++
 1 file changed, 7 insertions(+)

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