iTCO_wdt: all versions count down twice

The ICH9 is listed as having TCO v2, and indeed the behavior in the
datasheet corresponds to v2 (for example the NO_REBOOT flag is
accessible via the 16KiB-aligned Root Complex Base Address).

However, the TCO counts twice just like in v1; the documentation
of the SECOND_TO_STS bit says: "ICH9 sets this bit to 1 to indicate
that the TIMEOUT bit had been (or is currently) set and a second
timeout occurred before the TCO_RLD register was written. If this
bit is set and the NO_REBOOT config bit is 0, then the ICH9 will
reboot the system after the second timeout.  The same can be found
in the BayTrail (Atom E3800) datasheet, and even HOWTOs around
the Internet say that it will reboot after _twice_ the specified
heartbeat.

I did not find the Apollo Lake datasheet, but because v4/v5 has
a SECOND_TO_STS bit just like the previous version I'm enabling
this for Apollo Lake as well.

Cc: linux-watchdog@vger.kernel.org
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

0 files changed, 0 insertions, 0 deletions