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=-2.2 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 DB751C38A2E for ; Sat, 18 Apr 2020 12:53:01 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 7892321D79 for ; Sat, 18 Apr 2020 12:53:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7892321D79 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=8bytes.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 494CYR0XNSzDqxL for ; Sat, 18 Apr 2020 22:52:59 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=8bytes.org (client-ip=81.169.241.247; helo=theia.8bytes.org; envelope-from=joro@8bytes.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=8bytes.org Received: from theia.8bytes.org (8bytes.org [81.169.241.247]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 494CVz1yfSzDqFG for ; Sat, 18 Apr 2020 22:50:49 +1000 (AEST) Received: by theia.8bytes.org (Postfix, from userid 1000) id B57C0342; Sat, 18 Apr 2020 14:42:06 +0200 (CEST) Date: Sat, 18 Apr 2020 14:42:05 +0200 From: Joerg Roedel To: Christoph Hellwig Subject: Re: [PATCH 3/4] dma-mapping: add a dma_ops_bypass flag to struct device Message-ID: <20200418124205.GD6113@8bytes.org> References: <20200414122506.438134-1-hch@lst.de> <20200414122506.438134-4-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200414122506.438134-4-hch@lst.de> User-Agent: Mutt/1.10.1 (2018-07-13) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexey Kardashevskiy , Greg Kroah-Hartman , Robin Murphy , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org, Lu Baolu Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi Christoph, On Tue, Apr 14, 2020 at 02:25:05PM +0200, Christoph Hellwig wrote: > +static inline bool dma_map_direct(struct device *dev, > + const struct dma_map_ops *ops) > +{ > + if (likely(!ops)) > + return true; > + if (!dev->dma_ops_bypass) > + return false; > + > + return min_not_zero(*dev->dma_mask, dev->bus_dma_limit) >= > + dma_direct_get_required_mask(dev); Why is the dma-mask check done here? The dma-direct code handles memory outside of the devices dma-mask with swiotlb, no? I also don't quite get what the difference between setting the dma_ops_bypass flag non-zero and setting ops to NULL is. Joerg