From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vineet Gupta Date: Fri, 18 May 2018 17:28:09 +0000 Subject: Re: [PATCH 02/20] dma-mapping: provide a generic dma-noncoherent implementation Message-Id: <482e343c-bc87-9c0e-b6a8-bb69bcbeecda@synopsys.com> List-Id: References: <20180511075945.16548-1-hch@lst.de> <20180511075945.16548-3-hch@lst.de> <20180518132731.GA31125@lst.de> In-Reply-To: <20180518132731.GA31125-jcswGhMUV9g@public.gmane.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: "hch-jcswGhMUV9g@public.gmane.org" , Alexey Brodkin Cc: "linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-xtensa-PjhNF2WwrV/0Sa2dR60CXw@public.gmane.org" , "monstr-pSz03upnqPeHXe+LvDLADg@public.gmane.org" , "deanbo422-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org" , "linux-c6x-dev-jPsnJVOj+W6hPH1hqNUYSQ@public.gmane.org" , "linux-parisc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-sh-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-m68k-cunTk1MwBs8S/qaLPR03pWD2FQJk+8+b@public.gmane.org" , "linux-hexagon-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , "openrisc-cunTk1MwBs9a3B2Vnqf2dGD2FQJk+8+b@public.gmane.org" , "green.hu-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org" , "linux-alpha-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , sparclinux@vg 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