Re: [RFC PATCH 02/14] drivers: thermal: introduce device tree parser

From: Eduardo Valentin
Date: Mon Sep 02 2013 - 12:29:58 EST

On 29-08-2013 19:19, Eduardo Valentin wrote:
> Mark, Pawel and Stephen,
>
>
> On 27-08-2013 14:17, Eduardo Valentin wrote:
>> On 27-08-2013 12:23, Mark Rutland wrote:
>>> On Tue, Aug 27, 2013 at 02:44:40PM +0100, Eduardo Valentin wrote:
>>>> Hello Mark,
>
> <cut>
>
> I believe now we need to align on thermal bindings, before I propose
> next version of this series. So, following the discussions on this
> thread, I believe a typical CPU thermal zone would look like the following:
> + #include <dt-bindings/thermal/thermal.h>
> +
> + cpu_thermal: cpu_thermal {
> + passive-delay = <250>; /* milliseconds */
> + polling-delay = <1000>; /* milliseconds */
> + /*
> + * sensor ID
> + */
> + sensors = <&bandgap0 0>;
> + /*
> + * cooling
> + * device Usage Trip lower
> bound upper bound
> + */
> + cooling-devices = <&cpu0 100 &cpu-alert
> THERMAL_NO_LIMITS THERMAL_NO_LIMITS>;
> + trips {
> + cpu-alert: cpu-alert {
> + temperature = <100000>; /* milliCelsius */
> + hysteresis = <2000>; /* milliCelsius */
> + type = <THERMAL_TRIP_PASSIVE>;
> + };
> + cpu-crit: cpu-crit {
> + temperature = <125000>; /* milliCelsius */
> + hysteresis = <2000>; /* milliCelsius */
> + type = <THERMAL_TRIP_CRITICAL>;
> + };
> + };
> + };
>
> *Note: THERMAL_NO_LIMIT means, it will be using the cooling device
> minimum and maximum limits.
>
> Couple of comments.
> 1. I am keeping the pooling intervals. A possible alternative way to
> describe that would be specifying the maximum dT/dt. Essentially because
> I am still convinced that this is part of hw specs.
>
> 2. The above follows your suggestion to use consumer pointing to
> producers. Although, I still need to figure out how this could be
> implemented for Linux. But I think that is another story, at least for
> now. We need to first align on the DT binding itself.
>
> 3. The link from cooling device specification to trip points, from my
> perspective, should be enough, and thus we shall not need the thermal
> cells and size for trip points, as you proposed. Let me know what you think.
>
> Below is another example, on a more complex scenario, board specific
> case (hypothetical, just for exemplification):
>
> + #include <dt-bindings/thermal/thermal.h>
> +
> + board_thermal: board_thermal {
> + passive-delay = <1000>; /* milliseconds */
> + polling-delay = <2500>; /* milliseconds */
> + /*
> + * sensor ID
> + */
> + sensors = <&adc-dummy 0>,
> + <&adc-dummy 1>,
> + <&adc-dymmy 2>;
> + /*
> + * cooling
> + * device Usage Trip lower upper
> + */
> + cooling-devices = <&cpu0 75 &cpu-trip 0 2>,
> + <&gpu0 40 &gpu-trip 0 2>;
> + <&lcd0 25 &lcd-trip 5 10>;
> + trips {
> + cpu-trip: cpu-trip {
> + temperature = <60000>; /* milliCelsius */
> + hysteresis = <2000>; /* milliCelsius */
> + type = <THERMAL_TRIP_PASSIVE>;
> + };
> + gpu-trip: gpu-trip {
> + temperature = <55000>; /* milliCelsius */
> + hysteresis = <2000>; /* milliCelsius */
> + type = <THERMAL_TRIP_PASSIVE>;
> + }
> + lcd-trip: lcp-trip {
> + temperature = <53000>; /* milliCelsius */
> + hysteresis = <2000>; /* milliCelsius */
> + type = <THERMAL_TRIP_PASSIVE>;
> + };
> + crit-trip: crit-trip {
> + temperature = <68000>; /* milliCelsius */
> + hysteresis = <2000>; /* milliCelsius */
> + type = <THERMAL_TRIP_CRITICAL>;
> + };
> + };
> + };
>
> Now writing the above example, one might want to have a way to say the
> sensor correlation equation.
>
> Another example:
> + #include <dt-bindings/thermal/thermal.h>
> +
> + dsp_thermal: dsp_thermal {
> + passive-delay = <250>; /* milliseconds */
> + polling-delay = <1000>; /* milliseconds */
> + /*
> + * sensor ID
> + */
> + sensors = <&bandgap0 1>;
> + /*
> + * cooling
> + * device Usage Trip lower
> bound upper bound
> + */
> + cooling-devices = <&dsp0 100 &dsp-alert
> THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
> + trips {
> + dsp-alert: dsp-alert {
> + temperature = <100000>; /* milliCelsius */
> + hysteresis = <2000>; /* milliCelsius */
> + type = <THERMAL_TRIP_PASSIVE>;
> + };
> + dsp-crit: cdsp-crit {
> + temperature = <125000>; /* milliCelsius */
> + hysteresis = <2000>; /* milliCelsius */
> + type = <THERMAL_TRIP_CRITICAL>;
> + };
> + };
> + };
> +
> + gpu_thermal: gpu_thermal {
> + passive-delay = <500>; /* milliseconds */
> + polling-delay = <1000>; /* milliseconds */
> + /*
> + * sensor ID
> + */
> + sensors = <&bandgap0 2>;
> + /*
> + * cooling
> + * device Usage Trip lower
> bound upper bound
> + */
> + cooling-devices = <&gpu0 100 &gpu-alert
> THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
> + trips {
> + gpu-alert: gpu-alert {
> + temperature = <100000>; /* milliCelsius */
> + hysteresis = <2000>; /* milliCelsius */
> + type = <THERMAL_TRIP_PASSIVE>;
> + };
> + gpu-crit: gpu-crit {
> + temperature = <125000>; /* milliCelsius */
> + hysteresis = <2000>; /* milliCelsius */
> + type = <THERMAL_TRIP_CRITICAL>;
> + };
> + };
> + };
>
>
> Wei, I think the above would cover for the IPs with multiple internal
> sensors cases you were looking for, right?
>
> Durga, please also check if I am missing something to cover for your
> plans to, in case you will be using DT to describe your HW.
>
> Anyways, Mark and Pawel, let me know if I missed something from our
> discussion. I believe the above bindings would look more like regular
> standard DT bindings. And also they should be now slim enough, without
> Linux implementation details and also without policies.

Any objections on the above binding proposal?

>
>>
>>
>
>


--
You have got to be excited about what you are doing. (L. Lamport)

Eduardo Valentin

Attachment: signature.asc
Description: OpenPGP digital signature