Hi,

The WDAT (Watchdog Action Table) is a special ACPI table introduced by
Microsoft [1] that abstracts the watchdog hardware from the OS. Windows
uses this table for its watchdog implementation instead of a native iTCO
driver.

Microsoft re-licensed the WDAT specification to be under Microsoft
Community Promise license [2] so it should be fine to use it in Linux.

This series brings WDAT table support to Linux.

When the driver is enabled and we find out that there is a WDAT table, the
driver will take over the native iTCO watchdog driver. Main advantage in
this is that we do not need to change the native iTCO driver whenever the
hardware changes. For example in Skylake iTCO moved to sit behind SMBus and
the NO_REBOOT bit was hidden behind P2SB (Primary to Sideband). In addition
we can expect this to be tested much better by OEMs who typically validate
that Windows works fine on their hardware/firmware.

Patch [1/4] adds ACPI enumeration support and the driver itself. It also
introduces acpi_has_watchdog() which can be used to check if we should use
ACPI watchdog or native one.

Patches [2-4/4] prevent creation of the native iTCO platform device if we
detect that the ACPI watchdog (WDAT) should be used instead.

The previous version of the series can be found in [3].

Changes from v1:
  * Moved wdat_wdt.c to live under drivers/watchdog
  * Added checks for timer_period, min_count and max_count
  * Use min_hw_heartbeat_ms and max_hw_heartbeat_ms instead of
    min/max_timeout
  * Instead of stopping the watchdog set WDOG_HW_RUNNING
  * Switched to use devm_watchdog_register_device() and dropped
    wdat_wdt_remove()
  * Do not ping watchdog in resume()
  * Added review tag from Guenter Roeck to patches [2-4/4].

[1] http://msdn.microsoft.com/en-us/windows/hardware/gg463320.aspx
[2] https://msdn.microsoft.com/en-us/openspecifications/dn646766.aspx
[3] http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1230607.html

Mika Westerberg (4):
  ACPI / watchdog: Add support for WDAT hardware watchdog
  mfd: lpc_ich: Do not create iTCO watchdog when WDAT table exists
  i2c: i801: Do not create iTCO watchdog when WDAT table exists
  platform/x86: intel_pmc_ipc: Do not create iTCO watchdog when WDAT
    table exists

 drivers/acpi/Kconfig                 |   3 +
 drivers/acpi/Makefile                |   1 +
 drivers/acpi/acpi_watchdog.c         | 123 ++++++++
 drivers/acpi/internal.h              |  10 +
 drivers/acpi/scan.c                  |   1 +
 drivers/i2c/busses/i2c-i801.c        |   4 +-
 drivers/mfd/lpc_ich.c                |   4 +
 drivers/platform/x86/intel_pmc_ipc.c |  12 +-
 drivers/watchdog/Kconfig             |  13 +
 drivers/watchdog/Makefile            |   1 +
 drivers/watchdog/wdat_wdt.c          | 525 +++++++++++++++++++++++++++++++++++
 include/linux/acpi.h                 |   6 +
 12 files changed, 698 insertions(+), 5 deletions(-)
 create mode 100644 drivers/acpi/acpi_watchdog.c
 create mode 100644 drivers/watchdog/wdat_wdt.c

-- 
2.9.3

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