From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Garry Subject: Re: [PATCH] dma-debug: Kconfig for PREALLOC_DMA_DEBUG_ENTRIES Date: Mon, 3 Dec 2018 11:56:11 +0000 Message-ID: <53ab96d7-5dc9-e1a9-4cf2-bb8bf80a3acf@huawei.com> References: <20181130175449.2625-1-cai@gmx.us> <20181201163657.GA19557@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20181201163657.GA19557-jcswGhMUV9g@public.gmane.org> 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: Christoph Hellwig , Robin Murphy Cc: Qian Cai , netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linuxarm-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, yisen.zhuang-hv44wF8Li93QT0dZR+AlfA@public.gmane.org List-Id: iommu@lists.linux-foundation.org On 01/12/2018 16:36, Christoph Hellwig wrote: > On Fri, Nov 30, 2018 at 07:39:50PM +0000, Robin Murphy wrote: >> I was assuming the point was to also add something like >> >> default 131072 if HNS_ENET >> >> so that DMA debug doesn't require too much thought from the user. If they >> still have to notice the overflow message and empirically figure out a >> value that does work, rebuilding the kernel each time is far less >> convenient than simply adding "dma_debug_entries=..." to their kernel >> command line and rebooting, which they can do today. If they do already >> know up-front that the default will need overriding and what the >> appropriate value is, then the command line still seems seems just as >> convenient. > > I'm not so fond of random drivers changing the defaults. My idea > was rather to have the config option so that the defconfig files for > the Hisilicon SOCs with this hardware could select a larger number > without making a total mess of the kernel configuration. > > If we really have to we could do different defaults, but I'd still > much rather do this on a arch/platform basis than specific drivers. As I understand, some drivers could even use much more than this (131072), to such a point where I can't imagine that we would want to set an arch default to support them. For this HNS_ENET case, it is arm64 specific so it would be an arch defconfig. Thanks, John > _______________________________________________ > iommu mailing list > iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu > > . >