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=-8.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 3D62FC433E7 for ; Wed, 14 Oct 2020 13:36:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ED0B422202 for ; Wed, 14 Oct 2020 13:36:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728872AbgJNNgv (ORCPT ); Wed, 14 Oct 2020 09:36:51 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:15287 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728666AbgJNNgv (ORCPT ); Wed, 14 Oct 2020 09:36:51 -0400 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 8D4C92EF973859B1596E; Wed, 14 Oct 2020 21:36:09 +0800 (CST) Received: from [127.0.0.1] (10.174.177.134) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.487.0; Wed, 14 Oct 2020 21:36:05 +0800 Subject: Re: [PATCH 1/2] arm64: dts: broadcom: remove an unused property dma-ranges To: Arnd Bergmann , Florian Fainelli CC: Rob Herring , Ray Jui , "Scott Branden" , bcm-kernel-feedback-list , Andy Gross , Bjorn Andersson , linux-arm-msm , devicetree , linux-arm-kernel , linux-kernel References: <20201013060623.1711-1-thunder.leizhen@huawei.com> <20201013060623.1711-2-thunder.leizhen@huawei.com> From: "Leizhen (ThunderTown)" Message-ID: Date: Wed, 14 Oct 2020 21:36:03 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.134] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On 2020/10/14 15:38, Arnd Bergmann wrote: > On Wed, Oct 14, 2020 at 5:15 AM Florian Fainelli wrote: >> On 10/12/2020 11:06 PM, Zhen Lei wrote: >>> stingray-usb.dtsi is finally included by three dts files: >>> bcm958802a802x.dts, bcm958742k.dts and bcm958742t.dts. I searched all >>> these three entire expanded dts files, and each of them contains only one >>> dma-ranges. No conversion range is specified, so it cannot work properly. >>> I think this property "dma-ranges" is added by mistake, just remove it. >>> Otherwise, the following error will be reported when any YAML detection >>> is performed on arm64. >>> >>> arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \ >>> (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \ >>> its #address-cells (1) differs from / (2) >>> arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \ >>> (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \ >>> its #size-cells (1) differs from / (2) >>> >>> Signed-off-by: Zhen Lei >> >> This looks fine to me, Scott, Ray do you want to Ack this patch before I >> take it? > > Does it mean that there are no devices on this bus that can do DMA? > > Usually there should be a dma-ranges property to identify that DMA > is possible and what the limits are, though we have failed to enforce > that. Documentation/devicetree/bindings/iommu/iommu.txt +79 When an "iommus" property is specified in a device tree node, the IOMMU will be used for address translation. If a "dma-ranges" property exists in the device's parent node it will be ignored. An exception to this rule is if the referenced IOMMU is disabled, in which case the "dma-ranges" property of the parent shall take effect. The dma-ranges is only required by IOMMU disabled case. And should exist in the parent node of IOMMU device. But this deleted dma-ranges is under the usb bus node. > > Also note that the #address-cells=<1> means that any device under > this bus is assumed to only support 32-bit addressing, and DMA will > have to go through a slow swiotlb in the absence of an IOMMU. The dma_alloc_coherent() will allocate memory with GFP_DMA32 flag and try the 0-4G first. The reserved swiotlb buffer memory is used only when the allocation failed. memory@80000000: device_type: ["memory"] reg: [[0x0, 0x80000000, 0x0, 0x80000000], [0x8, 0x80000000, 0x1, 0x80000000]] If this is the actual physical memory size, the #address-cells should be set to <1>. > > Arnd > > . >