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

["Rafał Miłecki" <rafal@milecki.pl>]

On 04/03/2017 04:54 PM, Jon Mason wrote:
> On Sun, Apr 2, 2017 at 11:07 PM, Jon Mason <jon.mason@broadcom.com> wrote:
>> On Sat, Apr 1, 2017 at 5:50 PM, Rafał Miłecki <zajec5@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@milecki.pl>
>>>>>
>>>>> This commit documents binding for thermal used in Northstar family SoCs.
>>>>>
>>>>> Signed-off-by: Rafał Miłecki <rafal@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@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.
>
> In the NS documentation, under "Absolute Maximum Ratings":
>
> The "Maximum Junction Temperature" is 125 C
> The "Commercial Ambient Temperature (Operating)" range is 0 to 75 C
> The "Industrial  Ambient Temperature (Operating)" range is -40 to 85 C
> The "Storage Temperature" range is -40 to 125 C
>
> In the NSP documentation, under "Absolute Maximum Ratings":
>
> The "Maximum Junction Temperature" is 110 C
> The "Commercial Ambient Temperature (Operating)" range is 0 to 75 C
> The "Industrial  Ambient Temperature (Operating)" range is -40 to 85 C
> The "Storage Temperature" range is -40 to 125 C
>
> I believe the first one is the number you are looking for.

Thanks a lot for this valuable info! I'll send next version today.

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