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=-13.1 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 3BB0BC43464 for ; Sat, 19 Sep 2020 00:23:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0B94321D43 for ; Sat, 19 Sep 2020 00:23:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726022AbgISAXv (ORCPT ); Fri, 18 Sep 2020 20:23:51 -0400 Received: from foss.arm.com ([217.140.110.172]:57762 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726009AbgISAXv (ORCPT ); Fri, 18 Sep 2020 20:23:51 -0400 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 168F01045; Fri, 18 Sep 2020 17:23:51 -0700 (PDT) Received: from [10.57.37.232] (unknown [10.57.37.232]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8BA433F718; Fri, 18 Sep 2020 17:23:48 -0700 (PDT) Subject: Re: [PATCH v2.1 1/3] perf: Add Arm CMN-600 DT binding To: Rob Herring Cc: Will Deacon , Mark Rutland , linux-arm-kernel , devicetree@vger.kernel.org, "Saidi, Ali" , tsahee@amazon.com, harb@amperecomputing.com, tuanphan@os.amperecomputing.com, james.yang@arm.com, patrik.berglund@arm.com References: <3647765303e8936d45a69fe7c1f92b8d1b45de4b.1600452762.git.robin.murphy@arm.com> From: Robin Murphy Message-ID: <152e2d42-9ace-f78b-145a-5882ce936c3e@arm.com> Date: Sat, 19 Sep 2020 01:23:45 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.2.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 2020-09-18 19:54, Rob Herring wrote: > On Fri, Sep 18, 2020 at 12:24 PM Robin Murphy wrote: >> >> Document the requirements for the CMN-600 DT binding. The internal >> topology is almost entirely discoverable by walking a tree of ID >> registers, but sadly both the starting point for that walk and the >> exact format of those registers are configuration-dependent and not >> discoverable from some sane fixed location. Oh well. >> >> Signed-off-by: Robin Murphy >> --- >> >> fix up $id as well, oops... >> >> .../devicetree/bindings/perf/arm,cmn.yaml | 57 +++++++++++++++++++ >> 1 file changed, 57 insertions(+) >> create mode 100644 Documentation/devicetree/bindings/perf/arm,cmn.yaml > > Do you expect this to cover more than cmn-600? If not, use the > compatible string for the file name. As far as I'm aware, future CMN products will maintain the same general PMU design, but with enough subtle differences to deserve their own compatible strings. >> diff --git a/Documentation/devicetree/bindings/perf/arm,cmn.yaml b/Documentation/devicetree/bindings/perf/arm,cmn.yaml >> new file mode 100644 >> index 000000000000..e4fcc0de25e2 >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/perf/arm,cmn.yaml >> @@ -0,0 +1,57 @@ >> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) >> +# Copyright 2020 Arm Ltd. >> +%YAML 1.2 >> +--- >> +$id: http://devicetree.org/schemas/perf/arm,cmn.yaml# >> +$schema: http://devicetree.org/meta-schemas/core.yaml# >> + >> +title: Arm CMN (Coherent Mesh Network) Performance Monitors >> + >> +maintainers: >> + - Robin Murphy >> + >> +properties: >> + compatible: >> + const: arm,cmn-600 >> + >> + reg: >> + items: >> + - description: Physical address of the base (PERIPHBASE) and >> + size (up to 64MB) of the configuration address space. >> + >> + interrupts: >> + minItems: 1 >> + maxItems: 4 >> + items: >> + - description: Overflow interrupt for DTC0 >> + - description: Overflow interrupt for DTC1 >> + - description: Overflow interrupt for DTC2 >> + - description: Overflow interrupt for DTC3 >> + description: One interrupt for each DTC domain implemented must >> + be specified, in order. DTC0 is always present. > > What's DTC? Debug and Trace Controller. I figure it's one of those situations where if someone knows enough about a CMN configuration to be able to write something to this binding, they're probably going to be familiar with the abbreviation. In CMN terminology, "DT" is all over the place meaning "Debug and Trace". Only now do I suddenly realise that discussing this in the context of Device Tree is pretty much the worst-case scenario for confusion :) >> + >> + arm,root-node: >> + $ref: /schemas/types.yaml#/definitions/uint32 >> + description: Offset from PERIPHBASE of the configuration >> + discovery node (see TRM definition of ROOTNODEBASE). > > You can enforce some alignment: > > multipleOf: 0x4000 That's one of the things that may vary in future, so I'm doubtful if it would really be worth the bother. There's only one correct value for a given configuration, and still hundreds of appropriately-aligned wrong ones, so ultimately either it's right and it works, or it's not and it won't (any sensible driver should do a bit of sanity-checking during discovery anyway). Robin. >> + >> +required: >> + - compatible >> + - reg >> + - interrupts >> + - arm,root-node >> + >> +additionalProperties: false >> + >> +examples: >> + - | >> + #include >> + #include >> + pmu@50000000 { >> + compatible = "arm,cmn-600"; >> + reg = <0x50000000 0x4000000>; >> + /* 4x2 mesh with one DTC, and CFG node at 0,1,1,0 */ >> + interrupts = ; >> + arm,root-node = <0x104000>; >> + }; >> +... >> -- >> 2.28.0.dirty