mlxsw: core: Add the hottest thermal zone detection

mlxsw: core: Add the hottest thermal zone detection

When multiple sensors are mapped to the same cooling device, the
cooling device should be set according the worst sensor from the
sensors associated with this cooling device.

Provide the hottest thermal zone detection and enforce cooling device
to follow the temperature trends of the hottest zone only.
Prevent competition for the cooling device control from others zones,
by "stable trend" indication. A cooling device will not perform any
actions associated with a zone with a "stable trend".

When other thermal zone is detected as a hottest, a cooling device is
to be switched to following temperature trends of new hottest zone.

Thermal zone score is represented by 32 bits unsigned integer and
calculated according to the next formula:
For T < TZ<t><i>, where t from {normal trip = 0, high trip = 1, hot
trip = 2, critical = 3}:
TZ<i> score = (T + (TZ<t><i> - T) / 2) / (TZ<t><i> - T) * 256 ** j;
Highest thermal zone score s is set as MAX(TZ<i>score);
Following this formula, if TZ<i> is in trip point higher than TZ<k>,
the higher score is to be always assigned to TZ<i>.

For two thermal zones located at the same kind of trip point, the higher
score will be assigned to the zone which is closer to the next trip
point. Thus, the highest score will always be assigned objectively to
the hottest thermal zone.

All the thermal zones initially are to be configured with mode
"enabled" with the "step_wise" governor.

Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>