[v2,2/4] dt-bindings: thermal: Add the idle cooling device
diff mbox series

Message ID 20200414162634.1867-2-daniel.lezcano@linaro.org
State Superseded
Headers show
Series
  • [v2,1/4] powercap/drivers/idle_inject: Specify idle state max latency
Related show

Commit Message

Daniel Lezcano April 14, 2020, 4:26 p.m. UTC
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.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 - 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        | 146 ++++++++++++++++++
 1 file changed, 146 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/thermal/thermal-idle.yaml

Comments

Rob Herring April 14, 2020, 9:45 p.m. UTC | #1
On Tue, 14 Apr 2020 18:26:27 +0200, Daniel Lezcano 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.
> 
> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
> ---
>  - 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        | 146 ++++++++++++++++++
>  1 file changed, 146 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/thermal/thermal-idle.yaml
> 

My bot found errors running 'make dt_binding_check' on your patch:

Documentation/devicetree/bindings/thermal/thermal-idle.yaml:  while scanning a block scalar
  in "<unicode string>", line 39, column 20
found a tab character where an indentation space is expected
  in "<unicode string>", line 44, column 1
Documentation/devicetree/bindings/Makefile:12: recipe for target 'Documentation/devicetree/bindings/thermal/thermal-idle.example.dts' failed
make[1]: *** [Documentation/devicetree/bindings/thermal/thermal-idle.example.dts] Error 1
make[1]: *** Waiting for unfinished jobs....
warning: no schema found in file: Documentation/devicetree/bindings/thermal/thermal-idle.yaml
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/thermal/thermal-idle.yaml: ignoring, error parsing file
Makefile:1264: recipe for target 'dt_binding_check' failed
make: *** [dt_binding_check] Error 2

See https://patchwork.ozlabs.org/patch/1270492

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure dt-schema is up to date:

pip3 install git+https://github.com/devicetree-org/dt-schema.git@master --upgrade

Please check and re-submit.
Daniel Lezcano April 14, 2020, 9:49 p.m. UTC | #2
On 14/04/2020 23:45, Rob Herring wrote:
> On Tue, 14 Apr 2020 18:26:27 +0200, Daniel Lezcano wrote:

[ ... ]

> My bot found errors running 'make dt_binding_check' on your patch:
> 
> Documentation/devicetree/bindings/thermal/thermal-idle.yaml:  while scanning a block scalar
>   in "<unicode string>", line 39, column 20
> found a tab character where an indentation space is expected
>   in "<unicode string>", line 44, column 1
> Documentation/devicetree/bindings/Makefile:12: recipe for target 'Documentation/devicetree/bindings/thermal/thermal-idle.example.dts' failed
> make[1]: *** [Documentation/devicetree/bindings/thermal/thermal-idle.example.dts] Error 1
> make[1]: *** Waiting for unfinished jobs....
> warning: no schema found in file: Documentation/devicetree/bindings/thermal/thermal-idle.yaml
> /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/thermal/thermal-idle.yaml: ignoring, error parsing file
> Makefile:1264: recipe for target 'dt_binding_check' failed
> make: *** [dt_binding_check] Error 2
> 
> See https://patchwork.ozlabs.org/patch/1270492
> 
> If you already ran 'make dt_binding_check' and didn't see the above
> error(s), then make sure dt-schema is up to date:
> 
> pip3 install git+https://github.com/devicetree-org/dt-schema.git@master --upgrade
> 
> Please check and re-submit.

Sorry for that, I forgot to re-run the binding check and my editor is
automatically replacing spaces with tabs.

Patch
diff mbox series

diff --git a/Documentation/devicetree/bindings/thermal/thermal-idle.yaml b/Documentation/devicetree/bindings/thermal/thermal-idle.yaml
new file mode 100644
index 000000000000..760308fcd2fb
--- /dev/null
+++ b/Documentation/devicetree/bindings/thermal/thermal-idle.yaml
@@ -0,0 +1,146 @@ 
+# 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@linaro.org>
+
+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>;
+                       };
+                };
+          };
+    };