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=-5.3 required=3.0 tests=BAYES_00, 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 A2D4FC388F9 for ; Tue, 27 Oct 2020 16:50:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 56EEE2224A for ; Tue, 27 Oct 2020 16:50:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1813510AbgJ0Quf (ORCPT ); Tue, 27 Oct 2020 12:50:35 -0400 Received: from verein.lst.de ([213.95.11.211]:41106 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1813158AbgJ0QtB (ORCPT ); Tue, 27 Oct 2020 12:49:01 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 5CA9967373; Tue, 27 Oct 2020 17:48:58 +0100 (CET) Date: Tue, 27 Oct 2020 17:48:58 +0100 From: Christoph Hellwig To: Alexey Kardashevskiy Cc: linuxppc-dev@lists.ozlabs.org, Christoph Hellwig , Michael Ellerman , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH kernel v2 1/2] dma: Allow mixing bypass and normal IOMMU operation Message-ID: <20201027164858.GA30651@lst.de> References: <20201027101841.96056-1-aik@ozlabs.ru> <20201027101841.96056-2-aik@ozlabs.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201027101841.96056-2-aik@ozlabs.ru> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > +static inline bool dma_handle_direct(struct device *dev, dma_addr_t dma_handle) > +{ > + return dma_handle >= dev->archdata.dma_offset; > +} This won't compile except for powerpc, and directly accesing arch members in common code is a bad idea. Maybe both your helpers need to be supplied by arch code to better abstract this out. > if (dma_map_direct(dev, ops)) > addr = dma_direct_map_page(dev, page, offset, size, dir, attrs); > +#ifdef CONFIG_DMA_OPS_BYPASS_BUS_LIMIT > + else if (dev->bus_dma_limit && > + can_map_direct(dev, (phys_addr_t) page_to_phys(page) + offset + size)) > + addr = dma_direct_map_page(dev, page, offset, size, dir, attrs); > +#endif I don't think page_to_phys needs a phys_addr_t on the return value. I'd also much prefer if we make this a little more beautiful, here are a few suggestions: - hide the bus_dma_limit check inside can_map_direct, and provide a stub so that we can avoid the ifdef - use a better name for can_map_direct, and maybe also a better calling convention by passing the page (the sg code also has the page), and maybe even hide the dma_map_direct inside it. if (dma_map_direct(dev, ops) || arch_dma_map_page_direct(dev, page, offset, size)) addr = dma_direct_map_page(dev, page, offset, size, dir, attrs); > BUG_ON(!valid_dma_direction(dir)); > if (dma_map_direct(dev, ops)) > dma_direct_unmap_page(dev, addr, size, dir, attrs); > +#ifdef CONFIG_DMA_OPS_BYPASS_BUS_LIMIT > + else if (dev->bus_dma_limit && dma_handle_direct(dev, addr + size)) > + dma_direct_unmap_page(dev, addr, size, dir, attrs); > +#endif Same here. > if (dma_map_direct(dev, ops)) > ents = dma_direct_map_sg(dev, sg, nents, dir, attrs); > +#ifdef CONFIG_DMA_OPS_BYPASS_BUS_LIMIT > + else if (dev->bus_dma_limit) { > + struct scatterlist *s; > + bool direct = true; > + int i; > + > + for_each_sg(sg, s, nents, i) { > + direct = can_map_direct(dev, sg_phys(s) + s->offset + s->length); > + if (!direct) > + break; > + } > + if (direct) > + ents = dma_direct_map_sg(dev, sg, nents, dir, attrs); > + else > + ents = ops->map_sg(dev, sg, nents, dir, attrs); > + } > +#endif This needs to go into a helper as well. I think the same style as above would work pretty nicely as well: if (dma_map_direct(dev, ops) || arch_dma_map_sg_direct(dev, sg, nents)) ents = dma_direct_map_sg(dev, sg, nents, dir, attrs); else ents = ops->map_sg(dev, sg, nents, dir, attrs); > +#ifdef CONFIG_DMA_OPS_BYPASS_BUS_LIMIT > + if (dev->bus_dma_limit) { > + struct scatterlist *s; > + bool direct = true; > + int i; > + > + for_each_sg(sg, s, nents, i) { > + direct = dma_handle_direct(dev, s->dma_address + s->length); > + if (!direct) > + break; > + } > + if (direct) { > + dma_direct_unmap_sg(dev, sg, nents, dir, attrs); > + return; > + } > + } > +#endif One more time here..