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=-6.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 68560C432BE for ; Sun, 25 Jul 2021 22:29:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4B48B60F11 for ; Sun, 25 Jul 2021 22:29:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230338AbhGYVs5 (ORCPT ); Sun, 25 Jul 2021 17:48:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:34792 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229531AbhGYVsz (ORCPT ); Sun, 25 Jul 2021 17:48:55 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 94F8F60F43; Sun, 25 Jul 2021 22:29:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1627252165; bh=LXdv3SNozGddEOtTXiweAPm33gFyubUEqk9QT+fHMHc=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=NBPZZmLXXECARRRpEYQnILLiWAelyx07J8u147xeLgLnvwVuOuCbSyWtEgjGZdGXZ qczGtqvXBsxZc3Az2W3EwEoNOBBYlO16DwuPkJprDfNylmKUSeVQ3oCdothZgb2Bni 9rQiM6bwtcPjqV3EfCv8OvpNve5f6FFEM6tPO6mUf1oWARwt2aBLkvV4tYPGnS0ifn reMmxDr85ZhAAxogPTTL8v3QrLWdyVkGkF5/MmZ6l9GlDyP2q3+tFQJpEqTHYN4Wqj lSlGFU29w6nStaab2+shG0nR9K87pYEGuvSnGCORJ80K0d5pqHvRyeMrP6BLDerHKd qZfasI1lM/seA== Received: by mail-ej1-f51.google.com with SMTP id o5so13601005ejy.2; Sun, 25 Jul 2021 15:29:25 -0700 (PDT) X-Gm-Message-State: AOAM532JlAfb+maw244hpLVG1+kfIBa/6vW+pkTWe/54pZw7vG61U4NQ ELpflc0AkmGRSJy1Ac+GQTG8pRf9AlqzkAMGTA== X-Google-Smtp-Source: ABdhPJwfSEK/zGq4H+iwJok9IKltb7Tkin7X2hIbv0FMn04qW6BMg5NfENWFO8APXBMeuB8xHMIhsh3UlasWyhyEfQE= X-Received: by 2002:a17:906:95ce:: with SMTP id n14mr5509121ejy.130.1627252164182; Sun, 25 Jul 2021 15:29:24 -0700 (PDT) MIME-Version: 1.0 References: <20210723214031.3251801-1-atish.patra@wdc.com> <20210723214031.3251801-4-atish.patra@wdc.com> In-Reply-To: <20210723214031.3251801-4-atish.patra@wdc.com> From: Rob Herring Date: Sun, 25 Jul 2021 16:29:12 -0600 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC 3/5] dma-mapping: Enable global non-coherent pool support for RISC-V To: Atish Patra Cc: "linux-kernel@vger.kernel.org" , Albert Ou , Christoph Hellwig , devicetree@vger.kernel.org, Dmitry Vyukov , Frank Rowand , Guo Ren , Linux IOMMU , linux-riscv , Marek Szyprowski , Palmer Dabbelt , Paul Walmsley , Robin Murphy , Tobias Klauser Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 23, 2021 at 3:40 PM Atish Patra wrote: > > Currently, linux,dma-default is used to reserve a global non-coherent pool > to allocate memory for dma operations. This can be useful for RISC-V as > well as the ISA specification doesn't specify a method to modify PMA > attributes or page table entries to define non-cacheable area yet. > A non-cacheable memory window is an alternate options for vendors to > support non-coherent devices. "dma-ranges" must be used in conjunction with > "linux,dma-default" property to define one or more mappings between device > and cpu accesible memory regions. 'dma-ranges' applies to buses. And, well, maybe devices when the bus is not well defined. It is not a reserved-memory property. Rob