From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexey Brodkin Subject: Re: [PATCH 02/20] dma-mapping: provide a generic dma-noncoherent implementation Date: Fri, 18 May 2018 14:13:47 +0000 Message-ID: <913e288c5aabf0224cedcf2eb0c9be309745eace.camel@synopsys.com> References: <20180511075945.16548-1-hch@lst.de> <20180511075945.16548-3-hch@lst.de> <20180518132731.GA31125@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180518132731.GA31125-jcswGhMUV9g@public.gmane.org> Content-Language: en-US Content-ID: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: "hch-jcswGhMUV9g@public.gmane.org" Cc: "linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-xtensa-PjhNF2WwrV/0Sa2dR60CXw@public.gmane.org" , "monstr-pSz03upnqPeHXe+LvDLADg@public.gmane.org" , "linux-snps-arc-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "linux-c6x-dev-jPsnJVOj+W6hPH1hqNUYSQ@public.gmane.org" , "linux-parisc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-sh-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-hexagon-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , "linux-m68k-cunTk1MwBs8S/qaLPR03pWD2FQJk+8+b@public.gmane.org" , "openrisc-cunTk1MwBs9a3B2Vnqf2dGD2FQJk+8+b@public.gmane.org" , "green.hu-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org" , "linux-alpha-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , sparclinux-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Hi Christoph, On Fri, 2018-05-18 at 15:27 +0200, hch-jcswGhMUV9g@public.gmane.org wrote: > On 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. Well at least for me that's a confusion what is a reason to pass direction to function which purpose is already known. I'd say that XXX_sync_for_device() doesn't need _variable_ direction as an argument, otherwise what does that mean if we pass DMA_FROM_DEVICE to that function? > 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. That might easily be the case so good we caught that now and it will be fixed :) > 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. I'll try your newer series now, thanks! -Alexey