From patchwork Wed Sep 11 18:25:46 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Saenz Julienne X-Patchwork-Id: 11141711 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 2032514E5 for ; Wed, 11 Sep 2019 18:26:07 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E9A1A2089F for ; Wed, 11 Sep 2019 18:26:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E9A1A2089F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 743886B026B; Wed, 11 Sep 2019 14:25:56 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 71B466B026D; Wed, 11 Sep 2019 14:25:56 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 656576B026E; Wed, 11 Sep 2019 14:25:56 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0119.hostedemail.com [216.40.44.119]) by kanga.kvack.org (Postfix) with ESMTP id 3C14F6B026B for ; Wed, 11 Sep 2019 14:25:56 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id EE5BA180AD805 for ; Wed, 11 Sep 2019 18:25:55 +0000 (UTC) X-FDA: 75923468670.24.crush85_33bd9bbb3bf28 X-Spam-Summary: 1,0,0,,d41d8cd98f00b204,nsaenzjulienne@suse.de,:catalin.marinas@arm.com:hch@lst.de:wahrenst@gmx.net:marc.zyngier@arm.com:robh+dt@kernel.org:f.fainelli@gmail.com:will@kernel.org::robin.murphy@arm.com:nsaenzjulienne@suse.de:linux-kernel@vger.kernel.org:mbrugger@suse.com:linux-rpi-kernel@lists.infradead.org:phill@raspberrypi.org:linux-arm-kernel@lists.infradead.org:m.szyprowski@samsung.com,RULES_HIT:30003:30054:30070:30090,0,RBL:195.135.220.15:@suse.de:.lbl8.mailshell.net-62.2.6.2 64.100.201.201,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:31,LUA_SUMMARY:none X-HE-Tag: crush85_33bd9bbb3bf28 X-Filterd-Recvd-Size: 4298 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf03.hostedemail.com (Postfix) with ESMTP for ; Wed, 11 Sep 2019 18:25:55 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 09BFBAE53; Wed, 11 Sep 2019 18:25:54 +0000 (UTC) From: Nicolas Saenz Julienne To: catalin.marinas@arm.com, hch@lst.de, wahrenst@gmx.net, marc.zyngier@arm.com, robh+dt@kernel.org Cc: f.fainelli@gmail.com, will@kernel.org, linux-mm@kvack.org, robin.murphy@arm.com, nsaenzjulienne@suse.de, linux-kernel@vger.kernel.org, mbrugger@suse.com, linux-rpi-kernel@lists.infradead.org, phill@raspberrypi.org, linux-arm-kernel@lists.infradead.org, m.szyprowski@samsung.com Subject: [PATCH v6 4/4] mm: refresh ZONE_DMA and ZONE_DMA32 comments in 'enum zone_type' Date: Wed, 11 Sep 2019 20:25:46 +0200 Message-Id: <20190911182546.17094-5-nsaenzjulienne@suse.de> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190911182546.17094-1-nsaenzjulienne@suse.de> References: <20190911182546.17094-1-nsaenzjulienne@suse.de> MIME-Version: 1.0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: These zones usage has evolved with time and the comments were outdated. This joins both ZONE_DMA and ZONE_DMA32 explanation and gives up to date examples on how they are used on different architectures. Signed-off-by: Nicolas Saenz Julienne Reviewed-by: Christoph Hellwig Reviewed-by: Catalin Marinas --- Changes in v3: - Update comment to match changes in arm64 Changes in v2: - Try another approach merging both ZONE_DMA comments into one - Address Christoph's comments - If this approach doesn't get much traction I'll just drop the patch from the series as it's not really essential include/linux/mmzone.h | 45 ++++++++++++++++++++++++------------------ 1 file changed, 26 insertions(+), 19 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 3f38c30d2f13..bf1b916c9ecb 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -357,33 +357,40 @@ struct per_cpu_nodestat { #endif /* !__GENERATING_BOUNDS.H */ enum zone_type { -#ifdef CONFIG_ZONE_DMA /* - * ZONE_DMA is used when there are devices that are not able - * to do DMA to all of addressable memory (ZONE_NORMAL). Then we - * carve out the portion of memory that is needed for these devices. - * The range is arch specific. + * ZONE_DMA and ZONE_DMA32 are used when there are peripherals not able + * to DMA to all of the addressable memory (ZONE_NORMAL). + * On architectures where this area covers the whole 32 bit address + * space ZONE_DMA32 is used. ZONE_DMA is left for the ones with smaller + * DMA addressing constraints. This distinction is important as a 32bit + * DMA mask is assumed when ZONE_DMA32 is defined. Some 64-bit + * platforms may need both zones as they support peripherals with + * different DMA addressing limitations. + * + * Some examples: + * + * - i386 and x86_64 have a fixed 16M ZONE_DMA and ZONE_DMA32 for the + * rest of the lower 4G. + * + * - arm only uses ZONE_DMA, the size, up to 4G, may vary depending on + * the specific device. + * + * - arm64 has a fixed 1G ZONE_DMA and ZONE_DMA32 for the rest of the + * lower 4G. * - * Some examples + * - powerpc only uses ZONE_DMA, the size, up to 2G, may vary + * depending on the specific device. * - * Architecture Limit - * --------------------------- - * parisc, ia64, sparc <4G - * s390, powerpc <2G - * arm Various - * alpha Unlimited or 0-16MB. + * - s390 uses ZONE_DMA fixed to the lower 2G. * - * i386, x86_64 and multiple other arches - * <16M. + * - ia64 and riscv only use ZONE_DMA32. + * + * - parisc uses neither. */ +#ifdef CONFIG_ZONE_DMA 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. - */ ZONE_DMA32, #endif /*