thermal: da9062/61: Thermal junction temperature monitoring driver

thermal: da9062/61: Thermal junction temperature monitoring driver

Add junction temperature monitoring supervisor device driver, compatible
with the DA9062 and DA9061 PMICs. A MODULE_DEVICE_TABLE() macro is added.

If the PMIC's internal junction temperature rises above T_WARN (125 degC)
an interrupt is issued. This T_WARN level is defined as the
THERMAL_TRIP_HOT trip-wire inside the device driver.

The thermal triggering mechanism is interrupt based and happens when the
temperature rises above a given threshold level. The component cannot
return an exact temperature, it only has knowledge if the temperature is
above or below a given threshold value. A status bit must be polled to
detect when the temperature falls below that threshold level again. A
kernel work queue is configured to repeatedly poll and detect when the
temperature falls below this trip-wire, between 1 and 10 second intervals
(defaulting at 3 seconds).

This scheme is provided as an example. It would be expected that any
final implementation will also include a notify() function and any of these
settings could be altered to match the application where appropriate.

When over-temperature is reached, the interrupt from the DA9061/2 will be
repeatedly triggered. The IRQ is therefore disabled when the first
over-temperature event happens and the status bit is polled using a
work-queue until it becomes false.

This strategy is designed to allow the periodic transmission of uevents
(HOT trip point) as the first level of temperature supervision method. It
is intended for non-invasive temperature control, where the necessary
measures for cooling the system down are left to the host software. Once
the temperature falls again, the IRQ is re-enabled so a new critical
over-temperature event can be detected.

Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Steve Twiss <stwiss.opensource@diasemi.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>