[Cbe-oss-dev] RFC: cbe-thermal: read default targets from the device tree

[Arnd Bergmann]

Currently, the Linux kernel hardcodes some default values that are
used for thermal throttling based on the digital thermal sensors
on the Cell Broadband Engine.
For new blades, we want to have the option to override these defaults
from the firmware. The proposal from our firmware team is to
add the following properties to the /be/pervasive device node:

"ppe-throttle-temp" property
            Specifies the minimum temperature the PPE is throttled.
            Temperature in °C, encoded as with encode-int.
            Default value is 100°C

"ppe-end-throttle-temp" property
            Specifies the temperature below the PPE throttling is exited.
            Temperature in °C, encoded as with encode-int.
            Default value is 90°C

"ppe-full-throttle-temp" property
            Specifies the minimum temperature the PPE is stopped.
            Temperature in °C, encoded as with encode-int.
            Default value is 120°C

"spe-throttle-temp" property
            Specifies the minimum temperature the SPEs are throttled.
            Temperature in °C, encoded as with encode-int.
            Default value is 100°C

"spe-end-throttle-temp" property
            Specifies the temperature below the SPEs throttling is exited.
            Temperature in °C, encoded as with encode-int.
            Default value is 90°C

"spe-full-throttle-temp" property
            Specifies the minimum temperature the PPE is stopped.
            Temperature in °C, encoded as with encode-int.
            Default value is 100°C

The user is then still able to override these values using sysfs in
Linux, but the defaults are taken from the device tree if present.

	Arnd <><