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,UNPARSEABLE_RELAY,URIBL_BLOCKED, 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 F0E15C4CEC9 for ; Wed, 18 Sep 2019 20:01:13 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (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 C0DB0222BD for ; Wed, 18 Sep 2019 20:01:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C0DB0222BD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-mips.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id 85B33DBE; Wed, 18 Sep 2019 20:01:13 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 33CFDD97 for ; Wed, 18 Sep 2019 20:01:12 +0000 (UTC) X-Greylist: delayed 00:12:30 by SQLgrey-1.7.6 Received: from cvs.linux-mips.org (eddie.linux-mips.org [148.251.95.138]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id 5D7E5711 for ; Wed, 18 Sep 2019 20:01:11 +0000 (UTC) Received: (from localhost user: 'macro', uid#1010) by eddie.linux-mips.org with ESMTP id S23994204AbfIRTuBXltuQ (ORCPT ); Wed, 18 Sep 2019 21:50:01 +0200 Date: Wed, 18 Sep 2019 20:50:01 +0100 (BST) From: "Maciej W. Rozycki" To: Christoph Hellwig Subject: Re: [PATCH 2/2] MIPS: remove support for DMA_ATTR_WRITE_COMBINE In-Reply-To: <20190807061602.31217-3-hch@lst.de> Message-ID: References: <20190807061602.31217-1-hch@lst.de> <20190807061602.31217-3-hch@lst.de> User-Agent: Alpine 2.21 (LFD 202 2017-01-01) MIME-Version: 1.0 Cc: Shawn Anastasio , Michael Ellerman , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Russell King , linux-mips@vger.kernel.org, iommu@lists.linux-foundation.org, Paul Burton , Catalin Marinas , James Hogan , Will Deacon , linux-arm-kernel@lists.infradead.org, Robin Murphy X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org On Wed, 7 Aug 2019, Christoph Hellwig wrote: > Mips uses the KSEG1 kernel memory segment to map dma coherent > allocations for non-coherent devices as uncacheable, and does not have > any kind of special support for DMA_ATTR_WRITE_COMBINE in the allocation > path. Thus supporting DMA_ATTR_WRITE_COMBINE in dma_mmap_attrs will > lead to multiple mappings with different caching attributes. FYI, AFAIK _CACHE_UNCACHED_ACCELERATED (where supported) is effectively write-combine. Though IIUC someone would have to wire it in first. Maciej _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu