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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 221D9C432BE for ; Wed, 25 Aug 2021 18:49:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 07330610C9 for ; Wed, 25 Aug 2021 18:49:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242435AbhHYSuM (ORCPT ); Wed, 25 Aug 2021 14:50:12 -0400 Received: from foss.arm.com ([217.140.110.172]:57966 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240322AbhHYSuK (ORCPT ); Wed, 25 Aug 2021 14:50:10 -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 A4EC431B; Wed, 25 Aug 2021 11:49:24 -0700 (PDT) Received: from e120937-lin (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EB3B03F66F; Wed, 25 Aug 2021 11:49:22 -0700 (PDT) Date: Wed, 25 Aug 2021 19:49:15 +0100 From: Cristian Marussi To: Jim Quinlan Cc: Florian Fainelli , open list , "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" , Sudeep Holla , Jonathan Cameron , etienne.carriere@linaro.org, Vincent Guittot , Souvik Chakravarty Subject: Re: [PATCH v4 11/12] [RFC] firmware: arm_scmi: Add sync_cmds_atomic_replies transport flag Message-ID: <20210825184915.GI13160@e120937-lin> References: <20210824135941.38656-1-cristian.marussi@arm.com> <20210824135941.38656-12-cristian.marussi@arm.com> <7a2f972d-fdd0-d0f7-cac2-1989980ed872@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 25, 2021 at 01:17:47PM -0400, Jim Quinlan wrote: > On Wed, Aug 25, 2021 at 12:38 PM Florian Fainelli wrote: > > > > > > Hi Florian and Jim, > > On 8/24/2021 3:59 PM, Cristian Marussi wrote: > > > A flag is added to let the transport signal the core that its handling of > > > synchronous command messages implies that, after .send_message has returned > > > successfully, the requested command can be assumed to be fully and > > > completely executed on SCMI platform side so that any possible response > > > value is already immediately available to be retrieved by a .fetch_reponse: > > > in other words the polling phase can be skipped in such a case and the > > > response values accessed straight away. > > > > > > Note that all of the above applies only when polling mode of operation was > > > selected by the core: if instead a completion IRQ was found to be available > > > the normal response processing path based on completions will still be > > > followed. > > > > This might actually have to be settable on a per-message basis ideally > > since we may be transporting short lived SCMI messages for which the > > completion can be done at SMC time, and long lived SCMI messages (e.g.: > > involving a voltage change) for which we would prefer a completion > > interrupt. Jim, what do you think? > Even if the SCMI main driver could be configured this way in an > elegant manner, I'm not sure that there is a clean way of specifying > this attribute on a per-message basis. Certainly we could do this > with our own protocols, but many of our "long lived" messages are the > Perf protocol's set_level command. At any rate, let me give it some > thought. > The new flag .sync_cmds_atomic_replies applies only when polling mode has been selected for a specific cmd transaction, which means when no completion IRQ was found available OR if xfer.poll_completion was excplicitly set for a specific command. At the moment in this series (unknown bugs apart :D), if you have a channel configured with a completion IRQ and the .sync_cmds_atomic_replies set for the transport, this latter flag would be generally ignored and a wait_for_completion() will be normally used upon reception of the completionIRQ, UNLESS you specify that one specific command has to be polled using the per message xfer.poll_completion flag: so you should be already able to selectively use a polling which immediately returns after the smc by setting xfer.poll_completion for that specific short lived message (since sync_cmds_atomic_replies is set and applies to pollmode). On the other side any other LONG lived message will be naturally handled via completionIRQ + wait_for_completion. (at least that was the aim..) !!! NOTE that you'll have also to drop [PATCH v4 10/12] [RFC] firmware: arm_scmi: Make smc transport atomic from this series for the wait_completion to happen as you wish. As said I'm not sure that this whole mixing of polling and IRQs on the same channel on a regular won't cause any issues: any feedback on this from your setup is much appreciated. (maybe it's fine for SMC transport, but it led to a bit of hell in the past with mboxes AFAIK...) Thanks a lot again for your feedback, I'll have to chat with Sudeep about the various issues/configs possibility that we discussed and I'll keep you in the loop. Thanks, Cristian P.S.: I'll be off for a few weeks, so even though I'll keep an eye on the mail, I cannot guarantee any responsiveness :D