Received: by 2002:ad5:474a:0:0:0:0:0 with SMTP id i10csp28421imu; Mon, 10 Dec 2018 15:22:33 -0800 (PST) X-Google-Smtp-Source: AFSGD/VZNhyLjlk6F+K+yf5BhLez1MD6LpCwAAbMCviotJYTuWnQ40gVFd7qxZ/eU5JungI54w1y X-Received: by 2002:a63:9b11:: with SMTP id r17mr12728344pgd.416.1544484153824; Mon, 10 Dec 2018 15:22:33 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1544484153; cv=none; d=google.com; s=arc-20160816; b=esNDTRJT1seQgS4C33Lo6TgqM/64QmTXd2NTATfYAlE1tWONqqwJ/ODG+x+3kiYp7K 3X7cL89nfa/DY3peleI2iIxTzSzF7m/woaKxoH/clSymjb6ilM04EOA+WN2UV3Cj2jjm S1nm1r+tWhMbX1fx2g82cK07gdVb6ArOhyEiEySdQCcbf0eMI1N2DN4Qzkg3xe+ZPEU0 5kUtvOSGVadEPSdeJfFQrEr5SQjqeQOx0J6BfenQyLAby0gx2BaHYXFj8ToDKNSE8dWS y/RC0dXMUBqhhIKu0xFiQkFyIQZDUFZAffGh0X7G6IQgLc2DAgZjMIGxDa/CdJ2fqwc/ GakA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:user-agent:in-reply-to :content-transfer-encoding:content-disposition:mime-version :references:message-id:subject:cc:to:from:date; bh=O0M2KzDg6uhEi6JCG5sFxn6T9EavqBAHRoWvdZjFoe0=; b=PEg8YbmTAdSU/Qq97TXc/4SnoIJI4W8MWnCYKqq83BIe+kJVK2wfTxqOdAJK0sauy6 kdSunQm86BAKUMYEgDV1es3fMTItPjuWovARiDvQAjxtxDeS0BfN/uf+Iv/Bw0oBRiuU HGHTDxgaM+IoVBQO2nAdczM9AHXw4ypzmWLm+ITlcHCmYvvvHfsKaDBrR9MHZqRIRyNm +lENKXbLBJcan5n0aBgncvBCPqzoZ09K1Z465pw8fP4n0FOeTqk7KQeq74EFJ8bf4uqs jqvUYnrqXm3puT0lOPoV+Mtm/upUu80DxKqQdit1GnncFAjevX7XWs8UbMtmEhc3wARw fbsQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id 33si11100161plt.228.2018.12.10.15.22.18; Mon, 10 Dec 2018 15:22:33 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729347AbeLJTdT (ORCPT + 99 others); Mon, 10 Dec 2018 14:33:19 -0500 Received: from verein.lst.de ([213.95.11.211]:50758 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727501AbeLJTdT (ORCPT ); Mon, 10 Dec 2018 14:33:19 -0500 Received: by newverein.lst.de (Postfix, from userid 2407) id 99BD268DD2; Mon, 10 Dec 2018 20:33:17 +0100 (CET) Date: Mon, 10 Dec 2018 20:33:17 +0100 From: Christoph Hellwig To: Rui Salvaterra Cc: hch@lst.de, benh@kernel.crashing.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: use generic DMA mapping code in powerpc V4 Message-ID: <20181210193317.GA31514@lst.de> References: <20181130103222.GA23393@lst.de> <42b1408cafe77ebac1b1ad909db237fe34e4d177.camel@kernel.crashing.org> <20181208171746.GB15228@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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 Mon, Dec 10, 2018 at 05:04:46PM +0000, Rui Salvaterra wrote: > Hi, Christoph and Ben, > > It just came to my mind (and this is most likely a stupid question, > but still)… Is there any possibility of these changes having an > (positive) effect on the long-standing problem of Power Mac machines > with AGP graphics cards (which have to be limited to PCI transfers, > otherwise they'll hang, due to coherence issues)? If so, I have a G4 > machine where I'd gladly test them. These patches themselves are not going to affect that directly. But IFF the problem really is that the AGP needs to be treated as not cache coherent (I have no idea if that is true) the generic direct mapping code has full support for a per-device coherent flag, so support for a non-coherent AGP slot could be implemented relatively simply.