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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 92F6AC43613 for ; Mon, 24 Jun 2019 14:23:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 71CFF208E4 for ; Mon, 24 Jun 2019 14:23:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727968AbfFXOXN (ORCPT ); Mon, 24 Jun 2019 10:23:13 -0400 Received: from foss.arm.com ([217.140.110.172]:51752 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727170AbfFXOXN (ORCPT ); Mon, 24 Jun 2019 10:23:13 -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 4151B344; Mon, 24 Jun 2019 07:23:12 -0700 (PDT) Received: from [10.1.32.158] (unknown [10.1.32.158]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7C9083F71E; Mon, 24 Jun 2019 07:23:10 -0700 (PDT) Subject: Re: [PATCH 1/7] arm-nommu: remove the partial DMA_ATTR_NON_CONSISTENT support To: Christoph Hellwig , Vineet Gupta Cc: Jonas Bonn , Stefan Kristiansson , Stafford Horne , Helge Deller , linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linux-xtensa@linux-xtensa.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <20190614144431.21760-1-hch@lst.de> <20190614144431.21760-2-hch@lst.de> From: Vladimir Murzin Message-ID: Date: Mon, 24 Jun 2019 15:23:08 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190614144431.21760-2-hch@lst.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On 6/14/19 3:44 PM, Christoph Hellwig wrote: > The arm-nommu DMA code supports DMA_ATTR_NON_CONSISTENT allocations, but > does not provide a cache_sync operation. This means any user of it > will never be able to actually transfer cache ownership and thus cause > coherency bugs. By the way, Documentation/DMA-attributes.txt doesn't specify cache_sync() as requirement for DMA_ATTR_NON_CONSISTENT it only states that it is responsibility of the driver to have all the correct and necessary sync points. > > Signed-off-by: Christoph Hellwig > --- > arch/arm/mm/dma-mapping-nommu.c | 24 +++--------------------- > 1 file changed, 3 insertions(+), 21 deletions(-) > > diff --git a/arch/arm/mm/dma-mapping-nommu.c b/arch/arm/mm/dma-mapping-nommu.c > index f304b10e23a4..bc003df45546 100644 > --- a/arch/arm/mm/dma-mapping-nommu.c > +++ b/arch/arm/mm/dma-mapping-nommu.c > @@ -39,18 +39,7 @@ static void *arm_nommu_dma_alloc(struct device *dev, size_t size, > unsigned long attrs) > > { > - void *ret; > - > - /* > - * Try generic allocator first if we are advertised that > - * consistency is not required. > - */ > - > - if (attrs & DMA_ATTR_NON_CONSISTENT) > - return dma_direct_alloc_pages(dev, size, dma_handle, gfp, > - attrs); > - > - ret = dma_alloc_from_global_coherent(size, dma_handle); > + void *ret = dma_alloc_from_global_coherent(size, dma_handle); > > /* > * dma_alloc_from_global_coherent() may fail because: > @@ -70,16 +59,9 @@ static void arm_nommu_dma_free(struct device *dev, size_t size, > void *cpu_addr, dma_addr_t dma_addr, > unsigned long attrs) > { > - if (attrs & DMA_ATTR_NON_CONSISTENT) { > - dma_direct_free_pages(dev, size, cpu_addr, dma_addr, attrs); > - } else { > - int ret = dma_release_from_global_coherent(get_order(size), > - cpu_addr); > - > - WARN_ON_ONCE(ret == 0); > - } > + int ret = dma_release_from_global_coherent(get_order(size), cpu_addr); > > - return; > + WARN_ON_ONCE(ret == 0); > } > > static int arm_nommu_dma_mmap(struct device *dev, struct vm_area_struct *vma, > FWIW: Reviewed-by: Vladimir Murzin Cheers Vladimir