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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 E372CC4332B for ; Tue, 9 Mar 2021 15:41:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B370B65279 for ; Tue, 9 Mar 2021 15:41:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231837AbhCIPk2 (ORCPT ); Tue, 9 Mar 2021 10:40:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45854 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231911AbhCIPkW (ORCPT ); Tue, 9 Mar 2021 10:40:22 -0500 Received: from mail-lj1-x22c.google.com (mail-lj1-x22c.google.com [IPv6:2a00:1450:4864:20::22c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 93FD8C061761 for ; Tue, 9 Mar 2021 07:40:21 -0800 (PST) Received: by mail-lj1-x22c.google.com with SMTP id a17so21244691ljq.2 for ; Tue, 09 Mar 2021 07:40:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=lu+kK3nSAEUTNwnDM4pW2WC6uWJJmrapOL1I+PVvtnU=; b=RGZPUNMxbSls/6ut21Ur6KbghdWogF4sL+NXMIA9cKyeKwNKL0Hz0mhyFsSXv/OBtb jnTPF5TJwRfP2h3ns1CWqPwbvZ4FlR8eSaemHeyxekynGvXftNVUqM65k0VzJehBmDiy owGLAG6He59RMMoToMWvTXpswEBmJpDEWhPBCvrtWjGEFW10PpYT6vEhruku3/ccszps RiZ0KG+sggU/vWnMvLxnqun6CIJ+9PI9QkRuasLDeWjdRis4tG9zoBRBzMgZyJc7uNlS tDF2cw3jmG11uhRjhoVDbmrssDArdZ/i28IYjqFlv8rJaqbzR0I9MClkeGzwb4zyqUyh kn4g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=lu+kK3nSAEUTNwnDM4pW2WC6uWJJmrapOL1I+PVvtnU=; b=FN5h2Yx0kp6il7lPP7N5YnNaBvueV6LEEAvwBtc9HbKldz17xjsbfH5/+1qJT1J0Xn XLEeIiaTyrmmEDSzI5ORgkINw1VUkwSnLTugLOsiCnUQWYiYE9UYWu8dEuMOcQDiVApM UTgc5+i4qgMvl93AKN74L2cWuFUs3d5ZhKqKi4Bw5AYJpbw/JZkOqYVDly5QZ/Q/UCp/ 69YCYPRlAXbmpIfM6y9rogYwyZ9qdHBfKZcSwD/LUtBMMUgJYV+D5UU39MPT7n83BXeu 2inn1GTM849e6GxhAaDcw+dqssCJbmgE8hbLl6lYVUmcXxnYLF9Tu4zwi+8Su5d2Csy7 Tcag== X-Gm-Message-State: AOAM53241CbcdSayc3qWNLeDmso6vjd4FB3wO02jGa+/BUbtjXdKUp9c 2Fs/NPiKeKAL2SQ3Q2vmgL8BZSv0aFwPPwwZol7wjg== X-Google-Smtp-Source: ABdhPJwEI7sL2ZOe/ozOi+pJFvTfLuJFts7EVCGgPZapWZODVntgxp5IN5ZQc/HGdbEc0f45tW7JoT/HzKQUQHQUuLQ= X-Received: by 2002:a2e:864a:: with SMTP id i10mr16814623ljj.467.1615304420049; Tue, 09 Mar 2021 07:40:20 -0800 (PST) MIME-Version: 1.0 References: <20210304213902.83903-1-marcan@marcan.st> <20210304213902.83903-13-marcan@marcan.st> <6e4880b3-1fb6-0cbf-c1a5-7a46fd9ccf62@marcan.st> <20210308211306.GA2920998@robh.at.kernel.org> In-Reply-To: From: Linus Walleij Date: Tue, 9 Mar 2021 16:40:09 +0100 Message-ID: Subject: Re: [RFT PATCH v3 12/27] of/address: Add infrastructure to declare MMIO as non-posted To: Arnd Bergmann Cc: Rob Herring , Hector Martin , linux-arm-kernel , Marc Zyngier , Olof Johansson , Krzysztof Kozlowski , Mark Kettenis , Tony Lindgren , Mohamed Mediouni , Stan Skowronek , Alexander Graf , Will Deacon , Mark Rutland , Andy Shevchenko , Greg Kroah-Hartman , Jonathan Corbet , Catalin Marinas , Christoph Hellwig , "David S. Miller" , DTML , "open list:SERIAL DRIVERS" , Linux Doc Mailing List , linux-samsung-soc , "open list:GENERIC INCLUDE/ASM HEADER FILES" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Tue, Mar 9, 2021 at 1:41 PM Arnd Bergmann wrote: > - A driver writer may want to choose between posted and > nonposted mmio based on performance considerations: > if writes are never serialized, posted writes should always > be faster. However, if the driver uses a spinlock to serialize > writes, then a nonposted write is likely faster than a posted > write followed by a read that serializes the spin_unlock. > In this case we want the driver to explicitly pick one over > the other, and not have rely on bus specific magic. OK then I am all for having drivers explicitly choose access method. Openness to speed optimization is a well established Linux kernel design principle. Yours, Linus Walleij