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[23.128.96.18]) by mx.google.com with ESMTP id z20si958048edq.433.2020.10.13.17.24.43; Tue, 13 Oct 2020 17:25:06 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=nZ3kr1Zv; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731550AbgJMQLj (ORCPT + 99 others); Tue, 13 Oct 2020 12:11:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51942 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731536AbgJMQLj (ORCPT ); Tue, 13 Oct 2020 12:11:39 -0400 Received: from mail-wr1-x442.google.com (mail-wr1-x442.google.com [IPv6:2a00:1450:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0752EC0613D0; Tue, 13 Oct 2020 09:11:39 -0700 (PDT) Received: by mail-wr1-x442.google.com with SMTP id s9so12642055wro.8; Tue, 13 Oct 2020 09:11:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=UHsDQCy295Hvw56mXeSaZ5ilmXgdKd81n9fHINsRJmg=; b=nZ3kr1ZvmphGw+hCXwxd1FBiNBdH15+XmV7uCx/N1aEPWdhltNbxfRJsOrYzCW5DYi p28N16Qv3CesL618NYcwzKJl8ExdPBSsAxEVpNuBjc2t7Y3vSDiCUCXqUsTPP3ri+xa3 pYSiUdCkoFloRscJR5nF2nOA0n77jg0+DyulydlIg2O5dvN37b/KSTRSu0SrWqgYipLY Bv2SinElVWGIxKdfjR2keb0VyF7cTpeW4ZZMmz56ud2NUc4LXZYnfMSWKg7cjru34Jnt +3aGTZF5ErCoVoAaJUURuRybNuDUZmE1TuG1eiCC2mcWhrl0X3gWCU5HjivWDiRih7lu Lf+A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=UHsDQCy295Hvw56mXeSaZ5ilmXgdKd81n9fHINsRJmg=; b=PTpbtiXljQi3qRZNjRLRZJWSeFaPG6VvtotqXKrNKdZiBA83yw83C4o+MWf0N3u/SI qpYbIFJUbLA4LViBIm2WarlA8Coke1DHWZLijFWdvn3Fk22p5UvqJfYZQX+HtrvGPzcw 1pOUWQmzpiAD62t5VTPD6AaY2VAT5dpFLEjzaSyGuCcnC6vH0o4Yn6cgXvZqUM0u2wnX FfIImvlsjQqNd2+Jt7vG5P/ZtUGKv3jrAib930fJfr/u2Xssf5ErRBfQA2IJ9S5+QEw9 7AZVbWWnVrWT1lddguPsumJv597Efevxva1ym9PCqTDT+cuJteu1JsJBFKGoLMssHxSc Qvcg== X-Gm-Message-State: AOAM530CkMARURhcZHJVotRPmr0Vo1O7SBv8BrERMGiL7VIlSNH7Sd/i 2Z3MfXCpctmsXQI6o5JE+2//605iOn9s4AHKh/Q= X-Received: by 2002:a5d:4987:: with SMTP id r7mr377398wrq.327.1602605497546; Tue, 13 Oct 2020 09:11:37 -0700 (PDT) MIME-Version: 1.0 References: <20201001002709.21361-1-jonathan@marek.ca> <20201001002709.21361-3-jonathan@marek.ca> <20201002075321.GA7547@infradead.org> <20201005082914.GA31702@infradead.org> <3e0b91be-e4a4-4ea5-7d58-6e71b8d51932@marek.ca> <20201006072306.GA12834@infradead.org> <148a1660-f0fc-7163-2240-6b94725342b5@marek.ca> <20201007062519.GA23519@infradead.org> In-Reply-To: From: Rob Clark Date: Tue, 13 Oct 2020 09:11:26 -0700 Message-ID: Subject: Re: [PATCH 2/3] drm/msm: add DRM_MSM_GEM_SYNC_CACHE for non-coherent cache maintenance To: Robin Murphy Cc: Christoph Hellwig , Jonathan Marek , freedreno , Sean Paul , David Airlie , Daniel Vetter , "open list:DRM DRIVER FOR MSM ADRENO GPU" , "open list:DRM DRIVER FOR MSM ADRENO GPU" , open list , "list@263.net:IOMMU DRIVERS , Joerg Roedel ," , Joerg Roedel Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 13, 2020 at 6:42 AM Robin Murphy wrote: > > On 2020-10-07 07:25, Christoph Hellwig wrote: > > On Tue, Oct 06, 2020 at 09:19:32AM -0400, Jonathan Marek wrote: > >> One example why drm/msm can't use DMA API is multiple page table support > >> (that is landing in 5.10), which is something that definitely couldn't work > >> with DMA API. > >> > >> Another one is being able to choose the address for mappings, which AFAIK > >> DMA API can't do (somewhat related to this: qcom hardware often has ranges > >> of allowed addresses, which the dma_mask mechanism fails to represent, what > >> I see is drivers using dma_mask as a "maximum address", and since addresses > >> are allocated from the top it generally works) > > > > That sounds like a good enough rason to use the IOMMU API. I just > > wanted to make sure this really makes sense. > > I still think this situation would be best handled with a variant of > dma_ops_bypass that also guarantees to bypass SWIOTLB, and can be set > automatically when attaching to an unmanaged IOMMU domain. That way the > device driver can make DMA API calls in the appropriate places that do > the right thing either way, and only needs logic to decide whether to > use the returned DMA addresses directly or ignore them if it knows > they're overridden by its own IOMMU mapping. > That would be pretty ideal from my PoV BR, -R