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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3CB43C433EF for ; Tue, 22 Feb 2022 16:15:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233935AbiBVQQC (ORCPT ); Tue, 22 Feb 2022 11:16:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41302 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229530AbiBVQP5 (ORCPT ); Tue, 22 Feb 2022 11:15:57 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 73E151662D9; Tue, 22 Feb 2022 08:15:31 -0800 (PST) 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 3A3E61063; Tue, 22 Feb 2022 08:15:31 -0800 (PST) Received: from bogus (unknown [10.57.3.200]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D843B3F70D; Tue, 22 Feb 2022 08:15:29 -0800 (PST) Date: Tue, 22 Feb 2022 16:14:40 +0000 From: Sudeep Holla To: Krzysztof Kozlowski Cc: Oleksii Moisieiev , "robh+dt@kernel.org" , "devicetree@vger.kernel.org" , Sudeep Holla , Cristian Marussi , Stefano Stabellini , "linux-kernel@vger.kernel.org" Subject: Re: [RFC PATCH 0/1] dt-bindings: arm: Add scmi_devid paramter for Message-ID: <20220222161440.xadrgjftdyxenxgo@bogus> References: <2546477f-4190-e838-3095-f47b31802445@kernel.org> <20220221213932.GA164964@EPUAKYIW015D> <7f17ab8f-429f-d2e0-8f5f-bfa2dd19cc49@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7f17ab8f-429f-d2e0-8f5f-bfa2dd19cc49@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 22, 2022 at 09:06:25AM +0100, Krzysztof Kozlowski wrote: > On 21/02/2022 22:39, Oleksii Moisieiev wrote: > > Hi Krzysztof, > > > > On Mon, Feb 21, 2022 at 10:01:43PM +0100, Krzysztof Kozlowski wrote: > >> On 21/02/2022 18:26, Oleksii Moisieiev wrote: > >>> Introducing new parameter called scmi_devid to the device-tree bindings. > >>> This parameter should be set for the device nodes, which has > >>> clocks/power-domains/resets working through SCMI. > >>> Given parameter should set the device_id, needed to set device > >>> permissions in the Firmware. This feature will be extremely useful for > >>> the virtualized systems, which has more that one Guests running on the > >>> system at the same time or for the syestems, which require several > >>> agents with different permissions. Trusted agent will use scmi_devid to > >>> set the Device permissions for the Firmware (See Section 4.2.2.10 [0] > >>> for details). > >>> Agents concept is described in Section 4.2.1 [0]. > >>> > >>> scmi_devid in Device-tree node example: > >>> usb@e6590000 > >>> { > >>> scmi_devid = <19>; > >>> clocks = <&scmi_clock 3>, <&scmi_clock 2>; > >>> resets = <&scmi_reset 10>, <&scmi_reset 9>; > >>> power-domains = <&scmi_power 0>; > >>> }; > >> > >> And how do you prevent DT overlay adding such devid to any other node > >> thus allowing any other device to send requests with given devid? > >> > > Thank you for the quick response. > > scmi_devid value will be used only by Trusted Agent when the device > > permissions are set. Non-trusted agents, which in our case are > > represented as Guest OS are using scmi drivers, already present in linux > > kernel, ignores scmi_devid and uses scmi_clocks, scmi_power, scmi_reset > > nodes to access to SCMI protocol. > > Ah, ok. > > > > >> Plus few technicalities: > >> 1. Hyphen, not underscore in property name, so scmi-devid. > > > > Thanks for the tip, I will change that in v2. > > Few more thoughts: > 1. This looks specific to ARM SCMI, so you also need vendor prefix, so > something like: > arm,scmi-devid > arm,scmi-device-id > Keeping the other discussion separate, I wanted to comment on this. I agree with Krzysztof on having vendor specific prefix if we decide to add this device id thing. However, I prefer not to use "arm,scmi-" here. It can be "xen,scmi-" as we had plans to introduce some concepts in SCMI spec that may use looks like this device-id. I would just like to avoid conflicting with that in the future. It may happen to be same in the future (i.e. this xen device-id matches 100% with definition of device-id we might introduce in the spec, but I want to make assumption otherwise and leave scope for divergence however small/little it can be). No issues even if they converge and match 100% later in the far future. -- Regards, Sudeep