linux-kernel - [RFC PATCH 1/2] dt-bindings: arm: Add secure-clocks binding description

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Date:   Thu, 23 Apr 2020 08:48:07 +0200
From:   Etienne Carriere <etienne.carriere@...aro.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        robh+dt@...nel.org, Etienne Carriere <etienne.carriere@...aro.org>
Subject: [RFC PATCH 1/2] dt-bindings: arm: Add secure-clocks binding description

Describe how clocks property can leverage secure- property prefix
for clocks handled exclusively or shared by secure and non-secure
worlds.

Signed-off-by: Etienne Carriere <etienne.carriere@...aro.org>
---
 .../devicetree/bindings/arm/secure.txt        | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/Documentation/devicetree/bindings/arm/secure.txt b/Documentation/devicetree/bindings/arm/secure.txt
index f27bbff2c780..9bc94921f2a6 100644
--- a/Documentation/devicetree/bindings/arm/secure.txt
+++ b/Documentation/devicetree/bindings/arm/secure.txt
@@ -53,6 +53,25 @@ Valid Secure world properties
    status = "disabled";                             /* disabled in both */
    status = "disabled"; secure-status = "disabled"; /* disabled in both */
 
+- secure-clocks : specifies the Phandle list secure world shall use
+  for the related clocks whereas property "clocks" specifies the
+  clock Phandle list non-secure shall use for the that clocks.
+  This configuration can apply for example when a hardware clock is
+  shared by the 2 worlds and the hardware implements a specific interface
+  for each world, i.e.:
+
+  clocks = <&clk DMA_NS>;	/* NS relies on clock handle DMA_NS */
+  secure-clocks = <&clk DMA_S>;	/* S relies on clock handle DMA_S */
+
+  Another example where use of "clocks" and "secure-clocks" can apply
+  is when hardware implements a clock that secure and non-secure must
+  share, as a shared GPIO bank clock, and secure world relies on clock
+  device driver whereas non-secure world relies on a software service
+  exposed by secure world as SCMI clock device. I.e.:
+
+  clocks = <&scmi_clk 2>;	/* NS relies on SCMI resources */
+  secure-clocks= <&clk 5>;	/* S accesses the SoC reset interfaces */
+
 The secure-chosen node
 ----------------------
 
-- 
2.17.1