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=-1.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 7A928C04EB8 for ; Mon, 10 Dec 2018 17:05:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3B4A62082F for ; Mon, 10 Dec 2018 17:05:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="IG6frN4I" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3B4A62082F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728125AbeLJRFC (ORCPT ); Mon, 10 Dec 2018 12:05:02 -0500 Received: from mail-vk1-f173.google.com ([209.85.221.173]:41065 "EHLO mail-vk1-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726261AbeLJRFB (ORCPT ); Mon, 10 Dec 2018 12:05:01 -0500 Received: by mail-vk1-f173.google.com with SMTP id t127so2681375vke.8 for ; Mon, 10 Dec 2018 09:04:59 -0800 (PST) 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:content-transfer-encoding; bh=8d6hJDj9WYGcZt3sOxU9jJpzctdAC7KsWBf92Fbncno=; b=IG6frN4IFhlnXf7eyBGJBso/GIv3zt8BhHbMAXIo/2+8/FzmSnipAK4TOGUNbD/fbx ALGPxa1j0Sr5UuWMR4PtuPUsWivjAEG6H5JGFVLGCgi6pL9iVex/+a2xLXidzM+cazoU 4jsCiJiD5MMi0ZSy6V2S4JdXIWH48qYyJB9pyO6n/UZSiz6cl9lflxv+LqEPPpUwYGnD OP834UdnBTkqgn4LqcYt3etoj9n4wtxlFs79+CIOU2LTvGH/U+i9A5hGYQm6NhpoTuq8 4tjPkz80mwZL+pjiL8Gn7ocP47/Jj2eaVgixeRMLxU51FKIsvHuCNQR9moX3AQJsNEpW G8yA== 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:content-transfer-encoding; bh=8d6hJDj9WYGcZt3sOxU9jJpzctdAC7KsWBf92Fbncno=; b=tVrE8NKCJTghmEqsI+zUuNO56LvvyC4YDerbWH3CuHNgNdEs7WGkGS9LIPK1rRjMVy syjD6hScvz1F7i7IOKaGQjya4322O5zS+aVcfN/akY5ppfhCJMYIwWkFarqPc/HDBtZJ mSKtgBMpOyGUnKY2oAYeVrUMQETXAEq313IlDtNdG2VCQ4dDRiuDD5UfAS80TyfOFRH1 rhYsjIk/8SSqOauMeFQ7zfE4KQBBVnIiHOginn1HJERDFD6yFJviT2q6bh621h1Jz1oA HgHeRYMHxHBwJRqwTejkjVRMOhIwt4iX+sDma+Kh3GnbtL6Y+CmoJ2jZxngjTkExXqyo JxAA== X-Gm-Message-State: AA+aEWYx4bIa/KlbnS9oapkwLYgSPoRy6PrwvDzdre50GbCtyVNZYZU8 E9PxUV+AXoCmwaHm2iCvjwPMjgVZdV/pyXYsihQWrPE= X-Google-Smtp-Source: AFSGD/XwD+ohLgnHVWDVpPif+ofSWFVZqhWkMcZLZLTLZ1xX5bP8T8LpKUW5pVPkDlxiOhTSZKX7OIonH6+NZYPeRkM= X-Received: by 2002:a1f:4982:: with SMTP id w124mr5436394vka.4.1544461498701; Mon, 10 Dec 2018 09:04:58 -0800 (PST) MIME-Version: 1.0 References: <20181130103222.GA23393@lst.de> <42b1408cafe77ebac1b1ad909db237fe34e4d177.camel@kernel.crashing.org> <20181208171746.GB15228@lst.de> In-Reply-To: <20181208171746.GB15228@lst.de> From: Rui Salvaterra Date: Mon, 10 Dec 2018 17:04:46 +0000 Message-ID: Subject: Re: use generic DMA mapping code in powerpc V4 To: hch@lst.de Cc: benh@kernel.crashing.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 8 Dec 2018 at 17:17, Christoph Hellwig wrote: > > On Sun, Dec 02, 2018 at 05:11:02PM +1100, Benjamin Herrenschmidt wrote: > > Talking of which ... Christoph, not sure if we can do something about > > this at the DMA API level or keep hacks but some adapters such as the > > nVidia GPUs have a HW hack we can use to work around their limitations > > in that case. > > > > They have a register that can program a fixed value for the top bits > > that they don't support. > > > > This works fine for any linear mapping with an offset, provided they > > can program the offset in that register and they have enough DMA range > > to cover all memory from that offset. > > > > I can probably get the info about this from them so we can exploit it > > in nouveau. > > I think we can expose the direct mapping offset if people care enough, > we just have to be very careful designing the API. I'll happily leave > that to those that actually want to use it, but I'll gladly help > reviewing it. Hi, Christoph and Ben, It just came to my mind (and this is most likely a stupid question, but still)=E2=80=A6 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. Thanks, Rui