port-amd64/55694: "TSC time went backwards" spam on resume on amd64 (regression in -current)

[nia%pkgsrc.org@localhost]

>Number:         55694
>Category:       port-amd64
>Synopsis:       "TSC time went backwards" spam on resume on amd64 (regression in -current)
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    port-amd64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Oct 04 19:20:00 +0000 2020
>Originator:     nia
>Release:        NetBSD -current
>Organization:
>Environment:
NetBSD r 9.99.73 NetBSD 9.99.73 (GENERIC) #15: Sun Oct  4 20:17:57 CEST 2020  nia@r:/home/nia/src/sys/arch/amd64/compile/obj/GENERIC amd64
>Description:
After suspending, for several seconds after resume, the console gets spammed with "TSC time went backwards" on amd64. This is very agitating, clutters the console, and doesn't happen on netbsd-9. As a user, I have no idea what to do with this information other than tell the kernel to avoid using TSC.

I can observe this on several different amd64 laptops running -current.

https://i.imgur.com/adpeVld.jpg
>How-To-Repeat:
sysctl -w hw.acpi.sleep.state=3. Wake up. Watch for several seconds as the console is filled with TSC messages.
>Fix:
We should probably not be relying on TSC on anything that is capable of modern power management, since it's unreliable in this case.

Otherwise, the message should only be printed once.