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=-5.5 required=3.0 tests=BAYES_00, 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 93443C2BB84 for ; Thu, 3 Sep 2020 08:42:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 636EF2065E for ; Thu, 3 Sep 2020 08:42:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728185AbgICImf (ORCPT ); Thu, 3 Sep 2020 04:42:35 -0400 Received: from verein.lst.de ([213.95.11.211]:37001 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726025AbgICImd (ORCPT ); Thu, 3 Sep 2020 04:42:33 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 2B13F68BEB; Thu, 3 Sep 2020 10:42:27 +0200 (CEST) Date: Thu, 3 Sep 2020 10:42:26 +0200 From: Christoph Hellwig To: Thomas Bogendoerfer Cc: Christoph Hellwig , alsa-devel@alsa-project.org, linux-ia64@vger.kernel.org, linux-doc@vger.kernel.org, nouveau@lists.freedesktop.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, "James E.J. Bottomley" , linux-mm@kvack.org, Marek Szyprowski , linux-samsung-soc@vger.kernel.org, Joonyoung Shim , linux-scsi@vger.kernel.org, Kyungmin Park , Ben Skeggs , Matt Porter , linux-media@vger.kernel.org, Tom Lendacky , Pawel Osciak , Mauro Carvalho Chehab , linux-arm-kernel@lists.infradead.org, linux-parisc@vger.kernel.org, netdev@vger.kernel.org, Seung-Woo Kim , linux-mips@vger.kernel.org, iommu@lists.linux-foundation.org Subject: Re: [PATCH 22/28] sgiseeq: convert from dma_cache_sync to dma_sync_single_for_device Message-ID: <20200903084226.GA24410@lst.de> References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-23-hch@lst.de> <20200901152209.GA14288@alpha.franken.de> <20200901171241.GA20685@alpha.franken.de> <20200901171627.GA8255@lst.de> <20200901173810.GA25282@alpha.franken.de> <20200902213809.GA7998@alpha.franken.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200902213809.GA7998@alpha.franken.de> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Wed, Sep 02, 2020 at 11:38:09PM +0200, Thomas Bogendoerfer wrote: > the patch below fixes the problem. But is very wrong unfortunately. > static inline void dma_sync_desc_cpu(struct net_device *dev, void *addr) > { > - dma_cache_sync(dev->dev.parent, addr, sizeof(struct sgiseeq_rx_desc), > - DMA_FROM_DEVICE); > + struct sgiseeq_private *sp = netdev_priv(dev); > + > + dma_sync_single_for_device(dev->dev.parent, VIRT_TO_DMA(sp, addr), > + sizeof(struct sgiseeq_rx_desc), DMA_FROM_DEVICE); > } > > static inline void dma_sync_desc_dev(struct net_device *dev, void *addr) > { > - dma_cache_sync(dev->dev.parent, addr, sizeof(struct sgiseeq_rx_desc), > - DMA_TO_DEVICE); > + struct sgiseeq_private *sp = netdev_priv(dev); > + > + dma_sync_single_for_device(dev->dev.parent, VIRT_TO_DMA(sp, addr), > + sizeof(struct sgiseeq_rx_desc), DMA_TO_DEVICE); This is not how the DMA API works. You can only call dma_sync_single_for_{device,cpu} with the direction that the memory was mapped. It then transfer ownership to the device or the cpu, and the ownership of the memory is a fundamental concept that allows for reasoning about the caching interaction. > } > > -- > Crap can work. Given enough thrust pigs will fly, but it's not necessarily a > good idea. [ RFC1925, 2.3 ] ---end quoted text---