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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 313ADC43219 for ; Tue, 30 Apr 2019 15:18:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F0AE120835 for ; Tue, 30 Apr 2019 15:18:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726299AbfD3PSx (ORCPT ); Tue, 30 Apr 2019 11:18:53 -0400 Received: from verein.lst.de ([213.95.11.211]:47154 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725942AbfD3PSw (ORCPT ); Tue, 30 Apr 2019 11:18:52 -0400 Received: by newverein.lst.de (Postfix, from userid 2407) id D457F67358; Tue, 30 Apr 2019 17:18:33 +0200 (CEST) Date: Tue, 30 Apr 2019 17:18:33 +0200 From: Christoph Hellwig To: Robin Murphy Cc: Christoph Hellwig , Nicolin Chen , m.szyprowski@samsung.com, vdumpa@nvidia.com, linux@armlinux.org.uk, catalin.marinas@arm.com, will.deacon@arm.com, chris@zankel.net, jcmvbkbc@gmail.com, joro@8bytes.org, dwmw2@infradead.org, tony@atomide.com, akpm@linux-foundation.org, sfr@canb.auug.org.au, treding@nvidia.com, keescook@chromium.org, iamjoonsoo.kim@lge.com, wsa+renesas@sang-engineering.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-xtensa@linux-xtensa.org, iommu@lists.linux-foundation.org Subject: Re: [RFC/RFT PATCH 1/2] dma-contiguous: Simplify dma_*_from_contiguous() function calls Message-ID: <20190430151833.GB25447@lst.de> References: <20190430015521.27734-1-nicoleotsuka@gmail.com> <20190430015521.27734-2-nicoleotsuka@gmail.com> <20190430105640.GA20021@lst.de> <0e3e6d8b-de44-d23e-a039-8d11b578ec5c@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0e3e6d8b-de44-d23e-a039-8d11b578ec5c@arm.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 30, 2019 at 01:37:54PM +0100, Robin Murphy wrote: > On 30/04/2019 11:56, Christoph Hellwig wrote: >> So while I really, really like this cleanup it turns out it isn't >> actually safe for arm :( arm remaps the CMA allocation in place >> instead of using a new mapping, which can be done because they don't >> share PMDs with the kernel. >> >> So we'll probably need a __dma_alloc_from_contiguous version with >> an additional bool fallback argument - everyone but arms uses >> dma_alloc_from_contiguous as in your patch, just arm will get the >> non-fallback one. > > Or we even just implement dma_{alloc,free}_contiguous() as a wrapper around > the existing APIs so that users can be thoroughly checked and converted > one-by-one. Yeah. Actually given all the contention I wonder if the easiest solution for now is to just open code the cma_alloc/cma_free calls in dma-direct and dma-iommu, with the hopes that everyone is going to migrate to those implementations in the mid-term anyway and dma_alloc_from_contiguous / dma_release_from_contiguous just go away..