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Date: Thu, 12 Mar 2020 14:01:35 -0500
From: Rob Herring <robh@...nel.org>
To: Amit Kucheria <amit.kucheria@...aro.org>
Cc: linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
swboyd@...omium.org, mka@...omium.org, daniel.lezcano@...aro.org,
Amit Kucheria <amit.kucheria@...durent.com>,
Zhang Rui <rui.zhang@...el.com>, linux-pm@...r.kernel.org,
devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/3] dt-bindings: thermal: Add yaml bindings for
thermal cooling-devices
On Thu, Mar 05, 2020 at 06:26:42PM +0530, Amit Kucheria wrote:
> As part of moving the thermal bindings to YAML, split it up into 3
> bindings: thermal sensors, cooling devices and thermal zones.
>
> The property #cooling-cells is required in each device that acts as a
> cooling device - whether active or passive. So any device that can
> throttle its performance to passively reduce heat dissipation (e.g.
> cpus, gpus) and any device that can actively dissipate heat at different
> levels (e.g. fans) will contain this property.
>
> Signed-off-by: Amit Kucheria <amit.kucheria@...aro.org>
> ---
> .../thermal/thermal-cooling-devices.yaml | 114 ++++++++++++++++++
> 1 file changed, 114 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/thermal/thermal-cooling-devices.yaml
>
> diff --git a/Documentation/devicetree/bindings/thermal/thermal-cooling-devices.yaml b/Documentation/devicetree/bindings/thermal/thermal-cooling-devices.yaml
> new file mode 100644
> index 0000000000000..4745ea4b41ae7
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/thermal/thermal-cooling-devices.yaml
> @@ -0,0 +1,114 @@
> +# SPDX-License-Identifier: (GPL-2.0)
> +# Copyright 2020 Linaro Ltd.
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/thermal/thermal-cooling-devices.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Thermal cooling device binding
> +
> +maintainers:
> + - Amit Kucheria <amitk@...nel.org>
> +
> +description: |
> + Thermal management is achieved in devicetree by describing the sensor hardware
> + and the software abstraction of cooling devices and thermal zones required to
> + take appropriate action to mitigate thermal overload.
> +
> + The following node types are used to completely describe a thermal management
> + system in devicetree:
> + - thermal-sensor: device that measures temperature, has SoC-specific bindings
> + - cooling-device: device used to dissipate heat either passively or artively
> + - thermal-zones: a container of the following node types used to describe all
> + thermal data for the platform
> +
> + This binding describes the cooling devices.
> +
> + There are essentially two ways to provide control on power dissipation:
> + - Passive cooling: by means of regulating device performance. A typical
> + passive cooling mechanism is a CPU that has dynamic voltage and frequency
> + scaling (DVFS), and uses lower frequencies as cooling states.
> + - Active cooling: by means of activating devices in order to remove the
> + dissipated heat, e.g. regulating fan speeds.
> +
> + Any cooling device has a range of cooling states (i.e. different levels of
> + heat dissipation). They also have a way to determine the state of cooling in
> + which the device is. For example, a fan's cooling states correspond to the
> + different fan speeds possible. Cooling states are referred to by single
> + unsigned integers, where larger numbers mean greater heat dissipation. The
> + precise set of cooling states associated with a device should be defined in
> + a particular device's binding.
> +
This and patch 1 should have a 'select: true' so that this schema is
applied to all nodes (it does nothing if #cooling-cells is not present).
> +properties:
> + "#cooling-cells":
> + description:
> + Must be 2, in order to specify minimum and maximum cooling state used in
> + the cooling-maps reference. The first cell is the minimum cooling state
> + and the second cell is the maximum cooling state requested.
> + const: 2
> +
> +examples:
> + - |
> + #include <dt-bindings/interrupt-controller/arm-gic.h>
> + #include <dt-bindings/thermal/thermal.h>
> +
> + // Example 1: Cpufreq cooling device on CPU0
> + cpus {
> + #address-cells = <2>;
> + #size-cells = <0>;
> +
> + CPU0: cpu@0 {
> + device_type = "cpu";
> + compatible = "qcom,kryo385";
> + reg = <0x0 0x0>;
> + enable-method = "psci";
> + cpu-idle-states = <&LITTLE_CPU_SLEEP_0
> + &LITTLE_CPU_SLEEP_1
> + &CLUSTER_SLEEP_0>;
> + capacity-dmips-mhz = <607>;
> + dynamic-power-coefficient = <100>;
> + qcom,freq-domain = <&cpufreq_hw 0>;
> + #cooling-cells = <2>;
> + next-level-cache = <&L2_0>;
> + L2_0: l2-cache {
> + compatible = "cache";
> + next-level-cache = <&L3_0>;
> + L3_0: l3-cache {
> + compatible = "cache";
> + };
> + };
> + };
> +
> + /* ... */
> +
> + };
> +
> + /* ... */
> +
> + thermal-zones {
> + cpu0-thermal {
> + polling-delay-passive = <250>;
> + polling-delay = <1000>;
> +
> + thermal-sensors = <&tsens0 1>;
> +
> + trips {
> + cpu0_alert0: trip-point0 {
> + temperature = <90000>;
> + hysteresis = <2000>;
> + type = "passive";
> + };
> + };
> +
> + cooling-maps {
> + map0 {
> + trip = <&cpu0_alert0>;
> + cooling-device = <&CPU0 THERMAL_NO_LIMIT
> + THERMAL_NO_LIMIT>;
> + };
> + };
> + };
> +
> + /* ... */
> + };
> +...
> --
> 2.20.1
>
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