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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 39DBBC7618B for ; Wed, 24 Jul 2019 13:57:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0F7E921926 for ; Wed, 24 Jul 2019 13:57:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728216AbfGXN5B (ORCPT ); Wed, 24 Jul 2019 09:57:01 -0400 Received: from verein.lst.de ([213.95.11.211]:51214 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727532AbfGXN5A (ORCPT ); Wed, 24 Jul 2019 09:57:00 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 4D0A368B20; Wed, 24 Jul 2019 15:56:57 +0200 (CEST) Date: Wed, 24 Jul 2019 15:56:57 +0200 From: Christoph Hellwig To: Catalin Marinas Cc: Nicolas Saenz Julienne , Christoph Hellwig , linux-arm-kernel@lists.infradead.org, Marek Szyprowski , Robin Murphy , will@kernel.org, phil@raspberrypi.org, stefan.wahren@i2se.com, f.fainelli@gmail.com, mbrugger@suse.com, Jisheng.Zhang@synaptics.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [RFC 3/4] dma-direct: add dma_direct_min_mask Message-ID: <20190724135657.GA9075@lst.de> References: <20190717153135.15507-1-nsaenzjulienne@suse.de> <20190717153135.15507-4-nsaenzjulienne@suse.de> <20190718091526.GA25321@lst.de> <13dd1a4f33fcf814545f0d93f18429e853de9eaf.camel@suse.de> <58753252bd7964e3b9e9558b633bd325c4a898a1.camel@suse.de> <20190724135124.GA44864@arrakis.emea.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190724135124.GA44864@arrakis.emea.arm.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 24, 2019 at 02:51:24PM +0100, Catalin Marinas wrote: > I think it may be better if we have both ZONE_DMA and ZONE_DMA32 on > arm64. ZONE_DMA would be based on the smallest dma-ranges as described > in the DT while DMA32 covers the first naturally aligned 4GB of RAM > (unchanged). When a smaller ZONE_DMA is not needed, it could be expanded > to cover what would normally be ZONE_DMA32 (or could we have ZONE_DMA as > 0-bytes? I don't think GFP_DMA can still allocate memory in this case). > > We'd probably have to define ARCH_ZONE_DMA_BITS for arm64 to something > smaller than 32-bit but sufficient to cover the known platforms like > RPi4 (the current 24 is too small, so maybe 30). AFAICT, > __dma_direct_optimal_gfp_mask() figures out whether GFP_DMA or GFP_DMA32 > should be passed. ARCH_ZONE_DMA_BITS should probably become a variable. That way we can just initialize it to the default 24 bits in kernel/dma/direct.c and allow architectures to override it in their early boot code.