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Fri, 18 May 2018 13:28:28 -0400 Received: from smtprelay6.synopsys.com ([198.182.37.59]:58524 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751488AbeERR2Z (ORCPT ); Fri, 18 May 2018 13:28:25 -0400 Subject: Re: [PATCH 02/20] dma-mapping: provide a generic dma-noncoherent implementation To: "hch@lst.de" , Alexey Brodkin CC: "linux-arch@vger.kernel.org" , "linux-xtensa@linux-xtensa.org" , "monstr@monstr.eu" , "linux-snps-arc@lists.infradead.org" , "linux-c6x-dev@linux-c6x.org" , "linux-parisc@vger.kernel.org" , "linux-sh@vger.kernel.org" , "linux-hexagon@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "iommu@lists.linux-foundation.org" , "linux-m68k@lists.linux-m68k.org" , "openrisc@lists.librecores.org" , "green.hu@gmail.com" , "linux-alpha@vger.kernel.org" , "sparclinux@vger.kernel.org" , "nios2-dev@lists.rocketboards.org" , "deanbo422@gmail.com" , "linux-arm-kernel@lists.infradead.org" , "linux-mm@kvack.org" , Andrew Morton References: <20180511075945.16548-1-hch@lst.de> <20180511075945.16548-3-hch@lst.de> <20180518132731.GA31125@lst.de> From: Vineet Gupta Message-ID: <482e343c-bc87-9c0e-b6a8-bb69bcbeecda@synopsys.com> Date: Fri, 18 May 2018 10:28:09 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180518132731.GA31125@lst.de> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [10.10.161.52] Sender: linux-arch-owner@vger.kernel.org X-Mailing-List: linux-arch@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 05/18/2018 06:23 AM, hch@lst.de wrote: > Fri, May 18, 2018 at 01:03:46PM +0000, Alexey Brodkin wrote: >> Note mmc_get_dma_dir() is just "data->flags & MMC_DATA_WRITE ? DMA_TO_DEVICE : DMA_FROM_DEVICE". >> I.e. if we're preparing for sending data dma_noncoherent_map_sg() will have DMA_TO_DEVICE which >> is quite OK for passing to dma_noncoherent_sync_sg_for_device() but in case of reading we'll have >> DMA_FROM_DEVICE which we'll pass to dma_noncoherent_sync_sg_for_device() in dma_noncoherent_map_sg(). >> >> I'd say this is not entirely correct because IMHO arch_sync_dma_for_cpu() is supposed to only be used >> in case of DMA_FROM_DEVICE and arch_sync_dma_for_device() only in case of DMA_TO_DEVICE. > arc overrides the dir paramter of the dma_sync_single_for_device/ > dma_sync_single_for_cpu calls. My patches dropped that, and I have > restored that, and audit for the other architectures is pending. Right, for now lets retain that and do a sweeping audit of @direction - to me it seems extraneous (as it did 10 years ago), but I'm not an expert in this are so perhaps it is needed for some device / arches and it would be good to understand that finally. > That being said the existing arc code still looks rather odd as it > didn't do the same thing for the scatterlist versions of the calls. > I've thrown in a few patches into my new tree to make the sg versions > make the normal calls, and to clean up the area a bit. Not calling names or anything here, but it doesn't exist for sg variants, because I didn't write that code :-) It was introduced by your commi: 2016-01-20 052c96dbe33b arc: convert to dma_map_ops