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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A96BFCCF9EE for ; Thu, 30 Oct 2025 00:53:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:References:Cc:To:From:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=IniilaBss4ARvgvSKGFl6OJKKn5eXDeB1rP41HTysu0=; b=hwKSFVPRfm32TvnbG8OMLsNgau 59bKWbyj9UWuf3JoMvjtZTS1tNKi3wVfXaGEsIsf5+Iv5hbpmeUU7vgT1i5Wfh3g8fqlvIy1RdfLT oswpcNaIDrTCaugz6VY6CyseqO7To8a4zR0cBGzd/RLKQd6sSV91lvmZlqUHjKuw+sbws+ME4+M6V AEJDhWGNMug0sZaof6GA9oT8ruzjDyH4ZA/gau9pjXJioAzundh0tgl6Pz+oVOwUU86NmFlm05KPQ 7JZZ6W6V10ZT+PohFxmu6jlsDWUvbgb6hH76vlOAToUdoKa2ZHHQr0F0V+m3GjwFlcj8i2aAZHL3M RYv+ce/Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vEGuP-00000003JAT-17gm; Thu, 30 Oct 2025 00:52:57 +0000 Received: from mout-p-103.mailbox.org ([80.241.56.161]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vEGuM-00000003J9X-3PKA for linux-arm-kernel@lists.infradead.org; Thu, 30 Oct 2025 00:52:56 +0000 Received: from smtp202.mailbox.org (smtp202.mailbox.org [IPv6:2001:67c:2050:b231:465::202]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-103.mailbox.org (Postfix) with ESMTPS id 4cxlvd0Hprz9scQ; Thu, 30 Oct 2025 01:52:45 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mailbox.org; s=mail20150812; t=1761785565; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=IniilaBss4ARvgvSKGFl6OJKKn5eXDeB1rP41HTysu0=; b=kEI1bBYyyLEhaTuVznkOU9OUJQPU6XXU4pjIJhf1QXSwTb0uh2uh2IwGh28dDJeCZjZzTK DtWIbPfSDMmnGNqf1+YWJqqZeWEcZiw6GJak0wTW7SOilU4bBoAODKKLw4OuH2siLnewHc vVKjAh5Yx0CmtFQjNUloAi/e1ZGGDf8ndvO4weaCG2vTllk3hP7GMeX8wHj5znHHbqpz8C ZvJ0fw3lOsDOjphHR3xXI3ejXu1sPH/4j3yAZxtBW6XALi4JYUa8KISnK1VxFIss5DJq9f ywYnWWdRIP28CQnxUsDhpthZSRUxygTaR+Oc06o1xnwkitIQX/kBy0va5NcnUA== Message-ID: <5ae0a793-d3e7-45d1-bf5c-3c46593d1824@mailbox.org> Date: Thu, 30 Oct 2025 01:52:42 +0100 MIME-Version: 1.0 Subject: Re: [PATCH 1/2] dt-bindings: firmware: arm,scmi: Document arm,poll-transport property From: Marek Vasut To: Cristian Marussi Cc: arm-scmi@vger.kernel.org, Conor Dooley , Florian Fainelli , Krzysztof Kozlowski , Rob Herring , Sudeep Holla , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-renesas-soc@vger.kernel.org References: <20251023123644.8730-1-marek.vasut+renesas@mailbox.org> <70554674-7020-4582-a4e7-dbee34907096@mailbox.org> Content-Language: en-US In-Reply-To: <70554674-7020-4582-a4e7-dbee34907096@mailbox.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-MBO-RS-META: meqz3wrctz4xpsm9cpmk745gwhfgm5x4 X-MBO-RS-ID: 1b87ccad0ed6c2ee2ee X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251029_175255_193341_F0001660 X-CRM114-Status: GOOD ( 17.05 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 10/23/25 4:00 PM, Marek Vasut wrote: Hello again, >> On Thu, Oct 23, 2025 at 02:35:57PM +0200, Marek Vasut wrote: >>> Document new property arm,poll-transport, which sets all SCMI >>> operation into >>> poll mode. This is meant to work around uncooperative SCP >>> implementations, >>> which do not generate completion interrupts. This applies primarily >>> on mbox >>> based implementations, but does also cover SMC and VirtIO ones. >> >> Hi, >> >> ..indeed I was thinking a while ago about exposing the existing force- >> polling >> switch but in my case it was purely a testing-scenario configuration, >> so a >> no-no for the DT, things are different if you have to describe an HW >> that has >> no completion IRQ also on the a2p channel... > > Correct, at least until the SCP on this hardware is updated. > >> ...having said that, though, usually polling-mode is reserved to a few >> selected commands in a few chosen scenarios (as you may have seen), >> 'carpet-polling' non-for-testing for all the commands on A2P seems a lot >> inefficient and heavy...is it really a viable solution ? or these >> systems use such a low rate of SCMI messages that polling after each and >> every message is negligible ? >> >> ..just to understand the context... > > These systems are early in development and it is likely that the SCP > will be updated to generate interrupts properly. Currently, this is not > the case, hence the carpet-polling, until this is resolved. While I was going through the SCMI spec, DEN0056F , page 209 , section "4.1 Shared memory based transport" , bullet • Completion interrupts, I found it explicitly states: " This transport supports polling or interrupt driven modes of communication. In interrupt mode, when the callee completes processing a message, it raises an interrupt to the caller. Hardware support for completion interrupts is optional. " -- Best regards, Marek Vasut