[Bug 222079] [ichwd] New Intel TCO Watchdog Timer (Skylake/Sunrise Point and newer) is not supported

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=222079

--- Comment #5 from commit-hook at freebsd.org ---
A commit references this bug:

Author: avg
Date: Mon Oct 22 14:44:45 UTC 2018
New revision: 339591
URL: https://svnweb.freebsd.org/changeset/base/339591

Log:
  ichwd: add support for TCO watchdog timer in Lewisburg PCH (C620)

  The change is based on public documents listed below as well as Linux
  changes and the code developed by Kostik.

  The documents:
  - Intel? C620 Series Chipset Platform Controller Hub Datasheet
  - Intel? 100 Series and Intel? C230 Series Chipset Family Platform
    Controller Hub (PCH) Datasheet - Volume 2 of 2

  Interesting Linux commits:
  -
https://github.com/torvalds/linux/commit/9424693035a57961a8eb09e96aab315a7096535d
  -
https://github.com/torvalds/linux/commit/2a7a0e9bf7b32e838d873226808ab8a6c00148f7

  The peculiarity of the new chipsets is that the watchdog resources are
  configured in PCI registers of SMBus controller and Power Management
  function as opposed to the LPC bridge.  I took a simplistic approach of
  querying the resources from the respective PCI devices.  ichwd is still
  a device on isa bus.  The PCI devices are found by their slot and
  function defined in the datasheets as siblings of the upstream LPC
  bridge.

  There are some shortcuts and missing features.

  First of all, I have not implemented the functionality required to clear
  the no-reboot bit.  That would require writing to a special PCI
  configuration register of a hidden / invisible PCI device after which
  the device would start responding to accesses to other registers.  The
  no-reboot bit was not set on my test hardware, so I decided to leave its
  handling for the later time.

  Also, I did not try to handle the case where the watchdog resources are
  not configured by the hardware as well as the case where ACPI defined
  operational region conflicts with the watchdog resources.  My test
  system did not have either of those problem, so, again, I decided to
  leave those cases until later.
  See this Linux commit for some details of the ACPI problem:
 
https://github.com/torvalds/linux/commit/a7ae81952cdab56a1277bd2f9ed7284c0f575120

  Finally, I have added only the PCI ID found on my test system.  I think
  that more IDs can be added as the change gets tested.

  Tested on Dell PowerEdge R740.

  PR:           222079
  Reviewed by:  mav, kib
  MFC after:    3 weeks
  Relnotes:     maybe
  Sponsored by: Panzura
  Differential Revision: https://reviews.freebsd.org/D17585

Changes:
  head/sys/dev/ichwd/ichwd.c
  head/sys/dev/ichwd/ichwd.h

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