[PATCH V4 1/2] dt-bindings: thermal: add support for Broadcom's Northstar thermal

[Jon Mason]

On Sat, Apr 1, 2017 at 5:50 PM, Rafał Miłecki <zajec5 at gmail.com> wrote:
> On 04/01/2017 09:51 PM, Eduardo Valentin wrote:
>>
>> On Fri, Mar 31, 2017 at 10:11:23PM +0200, Rafał Miłecki wrote:
>>>
>>> From: Rafał Miłecki <rafal at milecki.pl>
>>>
>>> This commit documents binding for thermal used in Northstar family SoCs.
>>>
>>> Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
>>> ---
>>> V3: Add thermal-zones to the example
>>>     Rob: Because of this update, I didn't include Acked-by I got for V2
>>> ---
>>>  .../devicetree/bindings/thermal/brcm,ns-thermal    | 26
>>> ++++++++++++++++++++++
>>>  1 file changed, 26 insertions(+)
>>>  create mode 100644
>>> Documentation/devicetree/bindings/thermal/brcm,ns-thermal
>>>
>>> diff --git a/Documentation/devicetree/bindings/thermal/brcm,ns-thermal
>>> b/Documentation/devicetree/bindings/thermal/brcm,ns-thermal
>>> new file mode 100644
>>> index 000000000000..c561c7349f17
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/thermal/brcm,ns-thermal
>>> @@ -0,0 +1,26 @@
>>> +* Broadcom Northstar Thermal
>>> +
>>> +This binding describes thermal sensor that is part of Northstar's DMU
>>> (Device
>>> +Management Unit).
>>> +
>>> +Required properties:
>>> +- compatible : Must be "brcm,ns-thermal"
>>> +- reg : iomem address range of PVTMON registers
>>> +- #thermal-sensor-cells : Should be <0>
>>> +
>>> +Example:
>>> +
>>> +thermal: thermal at 1800c2c0 {
>>> +       compatible = "brcm,ns-thermal";
>>> +       reg = <0x1800c2c0 0x10>;
>>> +       #thermal-sensor-cells = <0>;
>>> +};
>>> +
>>> +thermal-zones {
>>> +       cpu_thermal: cpu-thermal {
>>> +               polling-delay-passive = <0>;
>>> +               polling-delay = <1000>;
>>> +               coefficients = <(-556) 418000>;
>>> +               thermal-sensors = <&thermal>;
>>
>>
>> You need to define trips and cooling devices here. Otherwise, makes
>> little sense to have this device in thermal subsystem. Here is an
>> example of minimal set:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/evalenti/linux-soc-thermal.git/commit/?h=linus&id=1e2ac9821de6a85d3e8358f238436708d1d46869
>>
>> The above has no passive action. It is just gonna shutdown the system if
>> temperature crosses a threshold.
>>
>> But, a typical cooling device would be CPU frequency throttling. Do you
>> have
>> that up and running in your routers?
>
>
> I don't have CPU freq throttling, so shutdown will be the only solution for
> critical temp right now.
>
> I know I should have at least a trip for critical temperature, but the
> problem
> is I don't know what value to use. There isn't any info about this in public
> datasheets. Broadcom's SDK doesn't mention it. Vendors share only the max
> environment temp, not the max CPU temp.
>
> So for now I only meant to provide user space access to reading current CPU
> temperature. I could do some stress tests and ask other users to do it as
> well.
>
> Or maybe I could just put in Documentation some round value that makes more
> or
> less sense and then work on a proper content of real DTS files?
>
> Unless we can get some hint from Broadcom people. Jon? Florian? Anyone?

I'll poke around and see if I can find a datasheet for NS/NSP.  Worst
case, I can ask one of the HW engineers for NSP, and we can use the
same value for NS.