On Wed, Apr 29, 2020 at 4:07 PM Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> wrote: > > Some devices are not able to cool down by reducing their voltage / > frequency because it could be not available or the system does not > allow voltage scaling. In this configuration, it is not possible to > use this strategy and the idle injection cooling device can be used > instead. > > One idle cooling device is now present for the CPU as implemented by > the combination of the idle injection framework belonging to the power > capping framework and the thermal cooling device. The missing part is > the DT binding providing a way to describe how the cooling device will > work on the system. > > A first iteration was done by making the cooling device to point to > the idle state. Unfortunately it does not make sense because it would > need to duplicate the idle state description for each CPU in order to > have a different phandle and make the thermal internal framework > happy. > > It was proposed to add an cooling-cells to <3>, unfortunately the > thermal framework is expecting a value of <2> as stated by the > documentation and it is not possible from the cooling device generic > code to loop this third value to the back end cooling device. > > Another proposal was to add a child 'thermal-idle' node as the SCMI > does. This approach allows to have a self-contained configuration for > the idle cooling device without colliding with the cpufreq cooling > device which is based on the CPU node. In addition, it allows to have > the cpufreq cooling device and the idle cooling device to co-exist > together as shown in the example. > > Reviewed-by: Rob Herring <robh@xxxxxxxxxx> > Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> Reviewed-by: Amit Kucheria <amit.kucheria@xxxxxxxxxx> > --- > - V4: > - Added Rob Herring reviewed-by > - V3: > - Removed extra line with tab inside > - V2: > - Fixed comment type > - Added dual license > - Fixed description s/begins to/should/ > - Changed name s/duration/duration-us/ > - Changed name s/latency/exit-latency-us/ > - Removed types for latency / duration > - Fixed s/idle-thermal/thermal-idle/ > --- > .../bindings/thermal/thermal-idle.yaml | 145 ++++++++++++++++++ > 1 file changed, 145 insertions(+) > create mode 100644 Documentation/devicetree/bindings/thermal/thermal-idle.yaml > > diff --git a/Documentation/devicetree/bindings/thermal/thermal-idle.yaml b/Documentation/devicetree/bindings/thermal/thermal-idle.yaml > new file mode 100644 > index 000000000000..7a922f540934 > --- /dev/null > +++ b/Documentation/devicetree/bindings/thermal/thermal-idle.yaml > @@ -0,0 +1,145 @@ > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) > +# Copyright 2020 Linaro Ltd. > +%YAML 1.2 > +--- > +$id: http://devicetree.org/schemas/thermal/thermal-idle.yaml# > +$schema: http://devicetree.org/meta-schemas/core.yaml# > + > +title: Thermal idle cooling device binding > + > +maintainers: > + - Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> > + > +description: | > + The thermal idle cooling device allows the system to passively > + mitigate the temperature on the device by injecting idle cycles, > + forcing it to cool down. > + > + This binding describes the thermal idle node. > + > +properties: > + $nodename: > + const: thermal-idle > + description: | > + A thermal-idle node describes the idle cooling device properties to > + cool down efficiently the attached thermal zone. > + > + '#cooling-cells': > + const: 2 > + 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. > + > + duration-us: > + description: | > + The idle duration in microsecond the device should cool down. > + > + exit-latency-us: > + description: | > + The exit latency constraint in microsecond for the injected > + idle state for the device. It is the latency constraint to > + apply when selecting an idle state from among all the present > + ones. > + > +required: > + - '#cooling-cells' > + > +examples: > + - | > + #include <dt-bindings/thermal/thermal.h> > + > + // Example: Combining idle cooling device on big CPUs with cpufreq cooling device > + cpus { > + #address-cells = <2>; > + #size-cells = <0>; > + > + /* ... */ > + > + cpu_b0: cpu@100 { > + device_type = "cpu"; > + compatible = "arm,cortex-a72"; > + reg = <0x0 0x100>; > + enable-method = "psci"; > + capacity-dmips-mhz = <1024>; > + dynamic-power-coefficient = <436>; > + #cooling-cells = <2>; /* min followed by max */ > + cpu-idle-states = <&CPU_SLEEP &CLUSTER_SLEEP>; > + thermal-idle { > + #cooling-cells = <2>; > + duration-us = <10000>; > + exit-latency-us = <500>; > + }; > + }; > + > + cpu_b1: cpu@101 { > + device_type = "cpu"; > + compatible = "arm,cortex-a72"; > + reg = <0x0 0x101>; > + enable-method = "psci"; > + capacity-dmips-mhz = <1024>; > + dynamic-power-coefficient = <436>; > + #cooling-cells = <2>; /* min followed by max */ > + cpu-idle-states = <&CPU_SLEEP &CLUSTER_SLEEP>; > + thermal-idle { > + #cooling-cells = <2>; > + duration-us = <10000>; > + exit-latency-us = <500>; > + }; > + }; > + > + /* ... */ > + > + }; > + > + /* ... */ > + > + thermal_zones { > + cpu_thermal: cpu { > + polling-delay-passive = <100>; > + polling-delay = <1000>; > + > + /* ... */ > + > + trips { > + cpu_alert0: cpu_alert0 { > + temperature = <65000>; > + hysteresis = <2000>; > + type = "passive"; > + }; > + > + cpu_alert1: cpu_alert1 { > + temperature = <70000>; > + hysteresis = <2000>; > + type = "passive"; > + }; > + > + cpu_alert2: cpu_alert2 { > + temperature = <75000>; > + hysteresis = <2000>; > + type = "passive"; > + }; > + > + cpu_crit: cpu_crit { > + temperature = <95000>; > + hysteresis = <2000>; > + type = "critical"; > + }; > + }; > + > + cooling-maps { > + map0 { > + trip = <&cpu_alert1>; > + cooling-device = <&{/cpus/cpu@100/thermal-idle} 0 15 >, > + <&{/cpus/cpu@101/thermal-idle} 0 15>; > + }; > + > + map1 { > + trip = <&cpu_alert2>; > + cooling-device = > + <&cpu_b0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>, > + <&cpu_b1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>; > + }; > + }; > + }; > + }; > -- > 2.17.1 >
