From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754776AbaKSDTe (ORCPT ); Tue, 18 Nov 2014 22:19:34 -0500 Received: from szxga03-in.huawei.com ([119.145.14.66]:9952 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754178AbaKSDTd (ORCPT ); Tue, 18 Nov 2014 22:19:33 -0500 Message-ID: <546C0BBB.9070000@huawei.com> Date: Wed, 19 Nov 2014 11:17:15 +0800 From: Ding Tianhong User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Thunderbird/24.0.1 MIME-Version: 1.0 To: Catalin Marinas , Arnd Bergmann CC: "linux-arm-kernel@lists.infradead.org" , Will Deacon , "linux-kernel@vger.kernel.org" Subject: Re: For the problem when using swiotlb References: <5469E26B.2010905@huawei.com> <1650523.IrjSXzxF5O@wuerfel> <20141117180947.GI29595@e104818-lin.cambridge.arm.com> In-Reply-To: <20141117180947.GI29595@e104818-lin.cambridge.arm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.22.246] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020203.546C0BC3.0168,ss=1,re=0.001,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-05-26 15:14:31, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 66a215c03747970b51084b178798d672 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014/11/18 2:09, Catalin Marinas wrote: > On Mon, Nov 17, 2014 at 12:18:42PM +0000, Arnd Bergmann wrote: >> On Monday 17 November 2014 19:56:27 Ding Tianhong wrote: >>> The commit 3690951fc6d42f3a0903987677d0e592c49dd8db(arm64: Use swiotlb late initialisation) >>> switches the DMA mapping code to swiotlb_tlb_late_init_with_default_size(), this will occur a problem >>> when I run the scsi stress tests, the message as below: >>> >>> sas_controller b1000000.sas: swiotlb buffer is full (sz: 65536 bytes).. >>> DMA: Out of SW-IOMMU space for 65536 bytes at device b1000000.sas >>> >>> The reason is that the swiotlb_tlb_late_init_with_default_size() could only alloc 16M memory for DMA-mapping, >>> and the param in cmdline "swiotlb=xxx" is useless because the get_free_pages() only use the buddy to assigned a >>> maximum memory of 16M(The MAX_ORDER is 13 for 4k pages), obviously 16M is too small in many scenes, but >>> the swiotlb_init() which could reserved a bigger memory as wished could work well for most drivers. >>> >>> I could not get a better way to fix this problem except to revert this patch, so could you please give me some >>> advise and help me, thanks very much. >> >> In general, you should not need to use swiotlb for most devices, in >> particular for high-performance devices like network or block. >> >> Please make sure that you have set up the dma-ranges properties in >> your DT properly to allow 64-bit DMA if the device supports it. > > That's the problem indeed, the DMA API ends up using swiotlb bounce > buffers because the physical address of the pages passed to (or > allocated by) the driver are beyond 32-bit limit (which is the default > dma mask). > Thanks everyone, I think I found the way to fix it, need to enable DMA_CMA, to reserve a big memory for CMA and set coherent mask for dev, then dma_alloc and dma_mapping will not use the swiotlb until the memory out of mask or swiotlb_force is enabled. If I still understand uncorrectly, please inform me. Regards Ding