linux-kernel - [PATCH v4 4/8] dt-bindings: firmware: arm,scmi: Add atomic-threshold-us optional property

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Date:   Sun, 13 Feb 2022 19:58:28 +0000
From:   Cristian Marussi <cristian.marussi@....com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     sudeep.holla@....com, james.quinlan@...adcom.com,
        Jonathan.Cameron@...wei.com, f.fainelli@...il.com,
        etienne.carriere@...aro.org, vincent.guittot@...aro.org,
        souvik.chakravarty@....com, peter.hilber@...nsynergy.com,
        igor.skalkin@...nsynergy.com, cristian.marussi@....com,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org
Subject: [PATCH v4 4/8] dt-bindings: firmware: arm,scmi: Add atomic-threshold-us optional property

SCMI protocols in the platform can optionally signal to the OSPM agent
the expected execution latency for a specific resource/operation pair.

Introduce an SCMI system wide optional property to describe a global time
threshold which can be configured on a per-platform base to determine the
opportunity, or not, for an SCMI command advertised to have a higher
latency than the threshold, to be considered for atomic operations:
high-latency SCMI synchronous commands should be preferably issued in the
usual non-atomic mode.

Cc: Rob Herring <robh+dt@...nel.org>
Cc: devicetree@...r.kernel.org
Signed-off-by: Cristian Marussi <cristian.marussi@....com>
---
v3 --> v4
- renamed property to atomic-threshold-us
v1 --> v2
- rephrased the property description
---
 .../devicetree/bindings/firmware/arm,scmi.yaml        | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
index eae15df36eef..3ffa669b91af 100644
--- a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
+++ b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
@@ -81,6 +81,15 @@ properties:
   '#size-cells':
     const: 0
 
+  atomic-threshold-us:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      An optional time value, expressed in microseconds, representing, on this
+      platform, the threshold above which any SCMI command, advertised to have
+      an higher-than-threshold execution latency, should not be considered for
+      atomic mode of operation, even if requested.
+      If left unconfigured defaults to zero.
+
   arm,smc-id:
     $ref: /schemas/types.yaml#/definitions/uint32
     description:
@@ -264,6 +273,8 @@ examples:
             #address-cells = <1>;
             #size-cells = <0>;
 
+            atomic_threshold = <10000>;
+
             scmi_devpd: protocol@11 {
                 reg = <0x11>;
                 #power-domain-cells = <1>;
-- 
2.17.1