From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 8/8] mm: comment arm64's usage of 'enum zone_type' Date: Thu, 1 Aug 2019 16:08:20 +0200 Message-ID: <20190801140820.GC23435@lst.de> References: <20190731154752.16557-1-nsaenzjulienne@suse.de> <20190731154752.16557-9-nsaenzjulienne@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190731154752.16557-9-nsaenzjulienne@suse.de> Sender: linux-kernel-owner@vger.kernel.org To: Nicolas Saenz Julienne Cc: catalin.marinas@arm.com, hch@lst.de, wahrenst@gmx.net, marc.zyngier@arm.com, Robin Murphy , linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, iommu@lists.linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, phill@raspberryi.org, f.fainelli@gmail.com, will@kernel.org, robh+dt@kernel.org, eric@anholt.net, mbrugger@suse.com, akpm@linux-foundation.org, frowand.list@gmail.com, m.szyprowski@samsung.com, linux-rpi-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org On Wed, Jul 31, 2019 at 05:47:51PM +0200, Nicolas Saenz Julienne wrote: > + * Architecture Limit > + * ---------------------------------- > + * parisc, ia64, sparc, arm64 <4G > + * s390, powerpc <2G > + * arm Various > + * alpha Unlimited or 0-16MB. > * > * i386, x86_64 and multiple other arches > - * <16M. > + * <16M. powerpc is also Various now, arm64 isn't really < 4G, ia64 only uses ZONE_DMA32 these days, and parisc doesn't seem to use neither ZONE_DMA nor ZONE_DMA32. Based on that I'm not sure the list really makes much sense. > */ > ZONE_DMA, > #endif > #ifdef CONFIG_ZONE_DMA32 > /* > - * x86_64 needs two ZONE_DMAs because it supports devices that are > - * only able to do DMA to the lower 16M but also 32 bit devices that > - * can only do DMA areas below 4G. > + * x86_64 and arm64 need two ZONE_DMAs because they support devices > + * that are only able to DMA a fraction of the 32 bit addressable > + * memory area, but also devices that are limited to that whole 32 bit > + * area. > */ > ZONE_DMA32, Maybe just say various architectures instead of mentioning specific ones? Something like "Some 64-bit platforms need.."