linux-kernel - [PATCH 1/2] DT: bindings: Add cooling cells for idle states

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Date:   Thu, 19 Dec 2019 23:19:27 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     daniel.lezcano@...aro.org
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Amit Kucheria <amit.kucheria@...aro.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        devicetree@...r.kernel.org (open list:OPEN FIRMWARE AND FLATTENED
        DEVICE TREE BINDINGS), linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 1/2] DT: bindings: Add cooling cells for idle states

Add DT documentation to add an idle state as a cooling device. The CPU
is actually the cooling device but the definition is already used by
frequency capping. As we need to make cpufreq capping and idle
injection to co-exist together on the system in order to mitigate at
different trip points, the CPU can not be used as the cooling device
for idle injection. The idle state can be seen as an hardware feature
and therefore as a component for the passive mitigation.

Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
---
 Documentation/devicetree/bindings/arm/idle-states.txt | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Documentation/devicetree/bindings/arm/idle-states.txt b/Documentation/devicetree/bindings/arm/idle-states.txt
index 771f5d20ae18..702a19b6b0b2 100644
--- a/Documentation/devicetree/bindings/arm/idle-states.txt
+++ b/Documentation/devicetree/bindings/arm/idle-states.txt
@@ -346,6 +346,17 @@ follows:
 	idle-states node. Please refer to the entry-method bindings
 	documentation for properties definitions.
 
+	When the idle state is used as a cooling device, the #cooling-cells
+	must be added in order to allow registering it.
+
+	- #cooling-cells:
+		Usage: Optional
+		Type: unsigned
+		Size: one cell
+		Definition: A cooling device specific information. At least
+			    must be two. Refer to the thermal DT bindings for
+			    more details.
+
 ===========================================
 4 - Examples
 ===========================================
-- 
2.17.1