From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CEB58C4742C for ; Mon, 16 Nov 2020 18:14:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 99D172227F for ; Mon, 16 Nov 2020 18:14:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731307AbgKPSOF (ORCPT ); Mon, 16 Nov 2020 13:14:05 -0500 Received: from foss.arm.com ([217.140.110.172]:44822 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730628AbgKPSOE (ORCPT ); Mon, 16 Nov 2020 13:14:04 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E1E7631B; Mon, 16 Nov 2020 10:14:03 -0800 (PST) Received: from usa.arm.com (e103737-lin.cambridge.arm.com [10.1.197.49]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id A170C3F719; Mon, 16 Nov 2020 10:14:02 -0800 (PST) From: Sudeep Holla To: linux-kernel@vger.kernel.org, devicetree@vger.kernel.org Cc: Sudeep Holla , Rob Herring , Manivannan Sadhasivam , Hector Yuan , Viresh Kumar , Bjorn Andersson , Rob Herring Subject: [PATCH v2] dt-bindings: dvfs: Add support for generic performance domains Date: Mon, 16 Nov 2020 18:13:56 +0000 Message-Id: <20201116181356.804590-1-sudeep.holla@arm.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The CLKSCREW attack [0] exposed security vulnerabilities in energy management implementations where untrusted software had direct access to clock and voltage hardware controls. In this attack, the malicious software was able to place the platform into unsafe overclocked or undervolted configurations. Such configurations then enabled the injection of predictable faults to reveal secrets. Many Arm-based systems used to or still use voltage regulator and clock frameworks in the kernel. These frameworks allow callers to independently manipulate frequency and voltage settings. Such implementations can render systems susceptible to this form of attack. Attacks such as CLKSCREW are now being mitigated by not having direct and independent control of clock and voltage in the kernel and moving that control to a trusted entity, such as the SCP firmware or secure world firmware/software which are to perform sanity checking on the requested performance levels, thereby preventing any attempted malicious programming. With the advent of such an abstraction, there is a need to replace the generic clock and regulator bindings used by such devices with a generic performance domains bindings. [0] https://www.usenix.org/conference/usenixsecurity17/technical-sessions/presentation/tang Cc: Rob Herring Signed-off-by: Sudeep Holla --- .../bindings/dvfs/performance-domain.yaml | 76 +++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100644 Documentation/devicetree/bindings/dvfs/performance-domain.yaml v1[1]->v2: - Changed to Dual License - Added select: true, enum for #performance-domain-cells and $ref for performance-domain - Changed the example to use real existing compatibles instead of made-up ones [1] https://lore.kernel.org/lkml/20201105173539.1426301-1-sudeep.holla@arm.com diff --git a/Documentation/devicetree/bindings/dvfs/performance-domain.yaml b/Documentation/devicetree/bindings/dvfs/performance-domain.yaml new file mode 100644 index 000000000000..29fb589a5192 --- /dev/null +++ b/Documentation/devicetree/bindings/dvfs/performance-domain.yaml @@ -0,0 +1,76 @@ +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/dvfs/performance-domain.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: Generic performance domains + +maintainers: + - Sudeep Holla + +description: |+ + This binding is intended for performance management of groups of devices or + CPUs that run in the same performance domain. Performance domains must not + be confused with power domains. A performance domain is defined by a set + of devices that always have to run at the same performance level. For a given + performance domain, there is a single point of control that affects all the + devices in the domain, making it impossible to set the performance level of + an individual device in the domain independently from other devices in + that domain. For example, a set of CPUs that share a voltage domain, and + have a common frequency control, is said to be in the same performance + domain. + + This device tree binding can be used to bind performance domain consumer + devices with their performance domains provided by performance domain + providers. A performance domain provider can be represented by any node in + the device tree and can provide one or more performance domains. A consumer + node can refer to the provider by a phandle and a set of phandle arguments + (so called performance domain specifiers) of length specified by the + \#performance-domain-cells property in the performance domain provider node. + +select: true + +properties: + "#performance-domain-cells": + description: + Number of cells in a performance domain specifier. Typically 0 for nodes + representing a single performance domain and 1 for nodes providing + multiple performance domains (e.g. performance controllers), but can be + any value as specified by device tree binding documentation of particular + provider. + enum: [ 0, 1 ] + + performance-domains: + $ref: '/schemas/types.yaml#/definitions/phandle-array' + description: + A phandle and performance domain specifier as defined by bindings of the + performance controller/provider specified by phandle. + +required: + - "#performance-domain-cells" + +additionalProperties: true + +examples: + - | + performance: performance-controller@12340000 { + compatible = "qcom,cpufreq-hw"; + reg = <0x12340000 0x1000>; + #performance-domain-cells = <1>; + }; + + // The node above defines a performance controller that is a performance + // domain provider and expects one cell as its phandle argument. + cpus { + #address-cells = <2>; + #size-cells = <0>; + + cpu@0 { + device_type = "cpu"; + compatible = "arm,cortex-a57"; + reg = <0x0 0x0>; + performance-domains = <&performance 1>; + }; + }; + -- 2.25.1