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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 B2676C433E0 for ; Fri, 29 May 2020 04:08:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8FD8820723 for ; Fri, 29 May 2020 04:08:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="aDyIrVEV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391512AbgE2EIH (ORCPT ); Fri, 29 May 2020 00:08:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56910 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391176AbgE2EIE (ORCPT ); Fri, 29 May 2020 00:08:04 -0400 Received: from mail-pl1-x62f.google.com (mail-pl1-x62f.google.com [IPv6:2607:f8b0:4864:20::62f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6936DC08C5C8 for ; Thu, 28 May 2020 21:08:02 -0700 (PDT) Received: by mail-pl1-x62f.google.com with SMTP id x11so518903plv.9 for ; Thu, 28 May 2020 21:08:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=blfLTQ8AXvWApf1/HEAMujKiLPEaU1hVA3OXltkKPFM=; b=aDyIrVEVyonnjpvrsy1C4E5ng5f/zsS95lj82O9yN+h5UfMRmrNJHJ4Z59I+AMyxGF mlMaM/XQXBkYUPlkVmCjel1GFo2yZnCrSJO/sDZVelbaIKk1c+YPajeS+zaRnUT6zesQ YlPRWbLDOxX2wX6cpAqcKIuoRSnec/KqwZzcEM4lwf4JWlTspk/cIz+CIhGgW433imGk UQZo1Ai4TTsS3yCK+STK5bOOmDHUiFl+bZgHvd8IABTcsEY6P/7yZ66qDIxZeW8r+Udm hw7UM7Tu2r2HCQh0yHTTWmvx0YloqORi+w3i9ehwcJh+H/BO705+lZQaK7Trry0HyATa qEug== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=blfLTQ8AXvWApf1/HEAMujKiLPEaU1hVA3OXltkKPFM=; b=p28G5tCbhYwRB2M1XufzzVHndSS0kM4DxuuqCM8NybgliZ+RKojz12quqR6OC6loST nzrzOLSd0xAlQId/+YyQ5l/eIeARhE+gOnRp1VVeYUuvbyW2C7ti0lSpE5GkSMgR3Ea+ eV4hOJWXtvm7KVO1MMgS+Jz1PURDlQZiFxLruXaXm8veP8peOQMQebDLVx418Vwa2brt XdrdeNd1tC6wtr9B3WK6yytHKpvUfdx6BCxNw1kK2caZv7ZPnNB+lrOtQyLQ2yWH0ZQs 19UEVuCnqpwl0g3WkMFGM6HnPZk6T6d2L/zjdG8qnvyYP3b2EkRGuD59pPSdtw5hEm7m PxMQ== X-Gm-Message-State: AOAM5322VJEcHzHas+yrAzi+ziULsYADSs+FGwrhbb5pOtOrNSmMadOQ 5+kOc21Tb5AXdvsdRjj0mbe8yA== X-Google-Smtp-Source: ABdhPJz06MPKrnYiQjl2aYS2OiLYzIlNkn9of65Fn9om3cFtzDZwYzRQA7dzd9nGBdXcUmk7igXl5Q== X-Received: by 2002:a17:90a:9f02:: with SMTP id n2mr7758540pjp.173.1590725281193; Thu, 28 May 2020 21:08:01 -0700 (PDT) Received: from localhost ([122.172.60.59]) by smtp.gmail.com with ESMTPSA id o11sm5945789pfd.195.2020.05.28.21.07.59 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 May 2020 21:08:00 -0700 (PDT) Date: Fri, 29 May 2020 09:37:58 +0530 From: Viresh Kumar To: Rob Herring Cc: Jassi Brar , Arnd Bergmann , Frank Rowand , Bjorn Andersson , Vincent Guittot , linux-arm-kernel@lists.infradead.org, Sudeep Holla , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC] dt-bindings: mailbox: add doorbell support to ARM MHU Message-ID: <20200529040758.kneg2j4n3gxh2rfv@vireshk-i7> References: <0a50f0cf5593baeb628dc8606c523665e5e2ae6c.1589519600.git.viresh.kumar@linaro.org> <20200528192005.GA494874@bogus> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200528192005.GA494874@bogus> User-Agent: NeoMutt/20180716-391-311a52 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28-05-20, 13:20, Rob Herring wrote: > Whether Linux > requires serializing mailbox accesses is a separate issue. On that side, > it seems silly to not allow driving the h/w in the most efficient way > possible. That's exactly what we are trying to say. The hardware allows us to write all 32 bits in parallel, without any hardware issues, why shouldn't we do that ? The delay (which Sudeep will find out, he is facing issues with hardware access because of lockdown right now) which may be small in transmitting across a mailbox becomes significant because of the fact that it happens synchronously and the receiver will send some sort of acknowledgement (and that depends on the firmware there) and the kernel needs to wait for it, while the kernel doesn't really need to. There is no reason IMHO for being inefficient here while we can do better. -- viresh