Linux-PM Archive on lore.kernel.org
 help / color / Atom feed
From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: rafael@kernel.org, robh@kernel.org
Cc: daniel.lezcano@linaro.org, Zhang Rui <rui.zhang@intel.com>,
	Amit Kucheria <amit.kucheria@verdurent.com>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	linux-pm@vger.kernel.org (open list:THERMAL),
	devicetree@vger.kernel.org (open list:OPEN FIRMWARE AND
	FLATTENED DEVICE TREE BINDINGS),
	linux-kernel@vger.kernel.org (open list)
Subject: [PATCH 2/4] dt-bindings: thermal: Add the idle cooling device
Date: Mon, 30 Mar 2020 00:03:18 +0200
Message-ID: <20200329220324.8785-2-daniel.lezcano@linaro.org> (raw)
In-Reply-To: <20200329220324.8785-1-daniel.lezcano@linaro.org>

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 showed in the example.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 .../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..f9f59cfa3c36
--- /dev/null
+++ b/Documentation/devicetree/bindings/thermal/thermal-idle.yaml
@@ -0,0 +1,145 @@
+# SPDX-License-Identifier: (GPL-2.0)
+# 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:
+      $ref: /schemas/types.yaml#/definitions/uint32
+      description: |
+         The idle duration in microsecond the device begins to cool down.
+
+   latency:
+      $ref: /schemas/types.yaml#/definitions/uint32
+      description: |
+         The exit latency constraint in microsecond for the injected
+         idle state for the device.
+
+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>;
+                         idle-thermal {
+                                 #cooling-cells = <2>;
+                                 duration = <10000>;
+                                 latency = <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>;
+                        idle-thermal {
+                                #cooling-cells = <2>;
+                                duration = <10000>;
+                                latency = <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/idle-thermal} 0 15 >,
+                                              <&{/cpus/cpu@101/idle-thermal} 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


  reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-29 22:03 [PATCH V2 1/4] powercap/drivers/idle_inject: Specify idle state max latency Daniel Lezcano
2020-03-29 22:03 ` Daniel Lezcano [this message]
2020-04-07 13:36   ` [PATCH 2/4] dt-bindings: thermal: Add the idle cooling device Daniel Lezcano
2020-04-07 14:09   ` Amit Kucheria
2020-04-10 16:59   ` Rob Herring
2020-04-12 18:08     ` Daniel Lezcano
2020-03-29 22:03 ` [PATCH 3/4] thermal/drivers/cpuidle_cooling: Change the registration function Daniel Lezcano
2020-03-30  9:58   ` Viresh Kumar
2020-03-29 22:03 ` [PATCH 4/4] thermal: cpuidle: Register cpuidle cooling device Daniel Lezcano
2020-04-03  9:38 ` [PATCH V2 1/4] powercap/drivers/idle_inject: Specify idle state max latency Rafael J. Wysocki
2020-04-03 11:09   ` Daniel Lezcano

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200329220324.8785-2-daniel.lezcano@linaro.org \
    --to=daniel.lezcano@linaro.org \
    --cc=amit.kucheria@verdurent.com \
    --cc=devicetree@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pm@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=rafael@kernel.org \
    --cc=robh+dt@kernel.org \
    --cc=robh@kernel.org \
    --cc=rui.zhang@intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-PM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-pm/0 linux-pm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-pm linux-pm/ https://lore.kernel.org/linux-pm \
		linux-pm@vger.kernel.org
	public-inbox-index linux-pm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-pm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git