[PATCH v3 2/4] devicetree: bindings: let thermal-sensor point to other thermal zones

Javi Merino
2015-11-25T15:10:40Z

The thermal-sensor property of the thermal zone node accepts phandles to
thermal sensors. However, thermal zones can be created as an
aggregation of other thermal zones. Extend the thermal-sensors property
to allow phandles to other thermal zones. This patch also adds an
example that showcases how a board thermal zone can be created from the
aggregation of the cpu, gpu and lcd thermal zones.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Eduardo Valentin <edubezval@gmail.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Kumar Gala <galak@codeaurora.org>
Cc: devicetree@vger.kernel.org
Signed-off-by: Javi Merino <javi.merino@arm.com>
---

Notes:
Hi devicetree,

Is it ok to extend the definition of the thermal-sensors property like
this? IOW are phandles strongly typed?

.../devicetree/bindings/thermal/thermal.txt | 154 ++++++++++++++++++++-
1 file changed, 151 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/thermal/thermal.txt b/Documentation/devicetree/bindings/thermal/thermal.txt
index 41b817f7b670..52b7e9ae3b4d 100644
--- a/Documentation/devicetree/bindings/thermal/thermal.txt
+++ b/Documentation/devicetree/bindings/thermal/thermal.txt
@@ -145,9 +145,12 @@ Required properties:
Size: one cell

- thermal-sensors: A list of thermal sensor phandles and sensor specifier
- Type: list of used while monitoring the thermal zone.
- phandles + sensor
- specifier
+ Type: list of used while monitoring the thermal zone. The phandles
+ phandles + sensor can point to thermal sensors or other thermal zone
+ specifier nodes. If it points to other thermal zone
+ nodes you should omit the sensor specifier
+ and set #thermal-sensor-cells to 0 for the
+ thermal zone.

- trips: A sub-node which is a container of only trip point nodes
Type: sub-node required to describe the thermal zone.
@@ -603,3 +606,148 @@ thermal-zones {
The above example is a mix of previous examples, a sensor IP with several internal
sensors used to monitor different zones, one of them is composed by several sensors and
with different cooling devices.
+
+(e) Board thermal with stacked thermal zones
+
+Instead of setting up one thermal zone combining multiple thermal
+zones and multiple trip points for each cooling device, we can create
+a hierarchy of thermal zones.
+
+#include <dt-bindings/thermal/thermal.h>
+
+&i2c1 {
+ ...
+ /*
+ * An IC with several temperature sensor.
+ */
+ adc_dummy: sensor@0x50 {
+ ...
+ #thermal-sensor-cells = <1>; /* sensor internal ID */
+ };
+};
+
+thermal-zones {
+
+ cpu_thermal: cpu_thermal {
+ polling-delay-passive = <1000>; /* milliseconds */
+ polling-delay = <2500>; /* milliseconds */
+
+ sustainable-power = <2500>;
+
+ thermal-sensors = <&adc_dummy 0>
+
+ trips {
+ cpu_trip: cpu-trip {
+ temperature = <60000>; /* millicelsius */
+ hysteresis = <2000>; /* millicelsius */
+ type = "passive";
+ };
+ };
+
+ cooling-maps {
+ map0 {
+ trip = <&cpu_trip>;
+ cooling-device = <&cpu0 0 2>;
+ };
+ };
+ };
+
+ gpu_thermal: gpu_thermal {
+ polling-delay-passive = <1000>; /* milliseconds */
+ polling-delay = <2500>; /* milliseconds */
+
+ sustainable-power = <2500>;
+
+ thermal-sensors = <&adc_dummy 2>
+
+ trips {
+ gpu_trip: gpu-trip {
+ temperature = <55000>; /* millicelsius */
+ hysteresis = <2000>; /* millicelsius */
+ type = "passive";
+ }
+ };
+
+ cooling-maps {
+ map0 {
+ trip = <&gpu_trip>;
+ cooling-device = <&gpu0 0 2>;
+ };
+ };
+ };
+
+ lcd_thermal: lcd_thermal {
+ polling-delay-passive = <1000>; /* milliseconds */
+ polling-delay = <2500>; /* milliseconds */
+
+ sustainable-power = <2500>;
+
+ thermal-sensors = <&adc_dummy 1>
+
+ trips {
+ lcd_trip: lcp-trip {
+ temperature = <53000>; /* millicelsius */
+ hysteresis = <2000>; /* millicelsius */
+ type = "passive";
+ };
+ };
+
+ cooling-maps {
+ map0 {
+ trip = <&lcd_trip>;
+ cooling-device = <&lcd0 5 10>;
+ };
+ };
+ };
+
+ board_thermal: board-thermal {
+ polling-delay-passive = <1000>; /* milliseconds */
+ polling-delay = <2500>; /* milliseconds */
+
+ thermal-sensors = <&cpu_thermal &gpu_thermal &lcd_thermal>
+
+ sustainable-power = <2500>;
+
+ trips {
+ warm_trip: warm-trip {
+ temperature = <62000>; /* millicelsius */
+ hysteresis = <2000>; /* millicelsius */
+ type = "passive";
+ };
+ crit_trip: crit-trip {
+ temperature = <68000>; /* millicelsius */
+ hysteresis = <2000>; /* millicelsius */
+ type = "critical";
+ };
+ };
+
+ cooling-maps {
+ map0 {
+ trip = <&warm_trip>;
+ cooling-device = <&cpu0 2 2>;
+ contribution = <55>;
+ };
+ map1 {
+ trip = <&warm_trip>;
+ cooling-device = <&gpu0 2 2>;
+ contribution = <20>;
+ };
+ map2 {
+ trip = <&lcd_trip>;
+ cooling-device = <&lcd0 7 10>;
+ contribution = <15>;
+ };
+ };
+ };
+};
+
+The above example is a different take at example (d). We create one
+thermal zone per sensor: cpu_thermal, gpu_thermal and lcd_thermal.
+Each of which has its own trip point for each own cooling device. We
+then define a board_thermal thermal zone that is a combination of all
+the other thermal zones. If the board hits its warm_trip, then all
+cooling devices are throttled.
+
+This example illustrates how we can throttle each device individually
+if its too hot and at the same time have some control over the whole
+system.
--
1.9.1