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=-2.3 required=3.0 tests=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 9CFD5C3A59B for ; Fri, 30 Aug 2019 14:45:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6C4EA23426 for ; Fri, 30 Aug 2019 14:45:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728088AbfH3Opm (ORCPT ); Fri, 30 Aug 2019 10:45:42 -0400 Received: from foss.arm.com ([217.140.110.172]:33318 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727135AbfH3Opm (ORCPT ); Fri, 30 Aug 2019 10:45:42 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 307CB344; Fri, 30 Aug 2019 07:45:41 -0700 (PDT) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 657F23F703; Fri, 30 Aug 2019 07:45:38 -0700 (PDT) Date: Fri, 30 Aug 2019 15:45:36 +0100 From: Catalin Marinas To: Nicolas Saenz Julienne Cc: Christoph Hellwig , eric@anholt.net, linux-riscv@lists.infradead.org, frowand.list@gmail.com, m.szyprowski@samsung.com, linux-arch@vger.kernel.org, f.fainelli@gmail.com, will@kernel.org, devicetree@vger.kernel.org, Arnd Bergmann , marc.zyngier@arm.com, robh+dt@kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, phill@raspberryi.org, mbrugger@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, wahrenst@gmx.net, akpm@linux-foundation.org, Robin Murphy Subject: Re: [PATCH v2 01/11] asm-generic: add dma_zone_size Message-ID: <20190830144536.GJ36992@arrakis.emea.arm.com> References: <20190820145821.27214-1-nsaenzjulienne@suse.de> <20190820145821.27214-2-nsaenzjulienne@suse.de> <20190826070939.GD11331@lst.de> <027272c27398b950f207101a2c5dbc07a30a36bc.camel@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <027272c27398b950f207101a2c5dbc07a30a36bc.camel@suse.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 26, 2019 at 03:46:52PM +0200, Nicolas Saenz Julienne wrote: > On Mon, 2019-08-26 at 09:09 +0200, Christoph Hellwig wrote: > > On Tue, Aug 20, 2019 at 04:58:09PM +0200, Nicolas Saenz Julienne wrote: > > > Some architectures have platform specific DMA addressing limitations. > > > This will allow for hardware description code to provide the constraints > > > in a generic manner, so as for arch code to properly setup it's memory > > > zones and DMA mask. > > > > I know this just spreads the arm code, but I still kinda hate it. > > Rob's main concern was finding a way to pass the constraint from HW definition > to arch without widening fdt's architecture specific function surface. I'd say > it's fair to argue that having a generic mechanism makes sense as it'll now > traverse multiple archs and subsystems. > > I get adding globals like this is not very appealing, yet I went with it as it > was the easier to integrate with arm's code. Any alternative suggestions? In some discussion with Robin, since it's just RPi4 that we are aware of having such requirement on arm64, he suggested that we have a permanent ZONE_DMA on arm64 with a default size of 1GB. It should cover all arm64 SoCs we know of without breaking the single Image binary. The arch/arm can use its current mach-* support. I may like this more than the proposed early_init_dt_get_dma_zone_size() here which checks for specific SoCs (my preferred way was to build the mask from all buses described in DT but I hadn't realised the complications). -- Catalin