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 A14ADC83F22 for ; Wed, 30 Aug 2023 19:22:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243087AbjH3TUt (ORCPT ); Wed, 30 Aug 2023 15:20:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36296 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242670AbjH3JOi (ORCPT ); Wed, 30 Aug 2023 05:14:38 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 0212FD2; Wed, 30 Aug 2023 02:14:36 -0700 (PDT) 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 303B92F4; Wed, 30 Aug 2023 02:15:15 -0700 (PDT) Received: from bogus (unknown [10.57.36.157]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 689003F64C; Wed, 30 Aug 2023 02:14:34 -0700 (PDT) Date: Wed, 30 Aug 2023 10:13:37 +0100 From: Sudeep Holla To: Pawandeep Oza Cc: "Pawandeep Oza (QUIC)" , "rafael@kernel.org" , Sudeep Holla , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-acpi@vger.kernel.org" Subject: Re: ACPI binding with SCMI Message-ID: <20230830091337.4rsik2tza6hqa22r@bogus> References: <20230807154834.888328-1-quic_poza@quicinc.com> <20230818091931.iqh6bxiifk4wyc32@bogus> <20230829091912.xefuenspdbazvqlh@bogus> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 29, 2023 at 03:10:34PM +0000, Pawandeep Oza wrote: > I am looking for scmi binding to ACPI. Basically, SCMI based perf control. > We have ACPI based system, so I am looking for where I can describe (some > way to describe doorbell and share memory in ACPI), and then scmi perf can > bind to it via some sort of transport (perhaps fastchannels ? ) OK, the Section 5.2 ACPI-based Transport in the SCMI spec can be more clearer IMO. It does state: " SCMI FastChannels can be represented as ACPI System Memory and used in the Continuous Performance Control (CPC) object when using ACPI Collaborative Processor Performance Control (CPPC)." It doesn't cover the fact that CPPC is compatible only with SCMI fastchannels without doorbells. Just a plain MMIO register to set the perf. The normal PCC mailbox works fine if the CPPC Desired Perf Register is a PCC address space based GAS. However the command is not 1:1 compatible with SCMI perf. This is one of the reason why the protocols 0x0-0xF was reserved in SCMI to be compatible with the ACPI CPPC way of using PCC for perf. Hope this helps and I didn't make it more complicated for you. -- Regards, Sudeep