From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 20C20C49ED6 for ; Mon, 9 Sep 2019 09:59:50 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E8FDA2086D for ; Mon, 9 Sep 2019 09:59:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="MqGo1Mlx" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E8FDA2086D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Vd3MKkVbMakWHtPp774SMRe4Zard2owBnh6/I4Zcn7s=; b=MqGo1Mlxmfv67P z8d9LkAqju8OLlAFUpjuBuZvZAVwtPVg3LtoP5B6cPU20E4BkZHaSJg+VsznFPtRluE9TuEuYzqEV hNwd4Ao9TXPWnfCYutNFooYhxwwKultk1+2Ok3z7A99Q6cnyfSWYEnDGT/aYFslC5KO116Hf9MpZz 0Vj4G+uEskZQL3AU1MjENKu7xca3P5yc3vaW+ZGDAfrZbDhBGvUWH+b8HVafmeP09rWIaH7SyyiC5 onJI18IT+hhRBxF2bcT93/gKAi0cEkCphIp2B2g5JGl+ltmxT9mCqQcT1x+pPGmCOkvoWOLjoOg+K rhe+ZzaazmHHfimdigyA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i7GSW-0004pU-HK; Mon, 09 Sep 2019 09:59:44 +0000 Received: from mx2.suse.de ([195.135.220.15] helo=mx1.suse.de) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1i7GR9-0003ij-J4; Mon, 09 Sep 2019 09:58:21 +0000 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 17B6FABE3; Mon, 9 Sep 2019 09:58:18 +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, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, Paul Walmsley , Palmer Dabbelt , Albert Ou Subject: [PATCH v5 4/4] mm: refresh ZONE_DMA and ZONE_DMA32 comments in 'enum zone_type' Date: Mon, 9 Sep 2019 11:58:07 +0200 Message-Id: <20190909095807.18709-5-nsaenzjulienne@suse.de> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190909095807.18709-1-nsaenzjulienne@suse.de> References: <20190909095807.18709-1-nsaenzjulienne@suse.de> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190909_025819_996313_E3C21695 X-CRM114-Status: GOOD ( 14.18 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: f.fainelli@gmail.com, will@kernel.org, linux-kernel@vger.kernel.org, mbrugger@suse.com, linux-rpi-kernel@lists.infradead.org, phill@raspberrypi.org, robin.murphy@arm.com, nsaenzjulienne@suse.de, m.szyprowski@samsung.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 /* -- 2.23.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel