Received: by 2002:ad5:474a:0:0:0:0:0 with SMTP id i10csp3990434imu; Mon, 10 Dec 2018 11:08:19 -0800 (PST) X-Google-Smtp-Source: AFSGD/V5slX5Q1nlqmz6cO61zwvUrXxGp9arNGGJnCldoAZova0SMDh4Dpwr3gqEvtvlywCiYw1L X-Received: by 2002:a62:7504:: with SMTP id q4mr13226011pfc.180.1544468899793; Mon, 10 Dec 2018 11:08:19 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1544468899; cv=none; d=google.com; s=arc-20160816; b=HlDIrsJS9LpYlr6lmdezvTM0PJ22bYNjw7hMCkolyqyDv/wr9X9CeABllZu4DOvkgL emn+8yDqv5ZA1n3I8qWMHtjsA0Bo0QtDYYJequJjnZeiyJc4trLlFGK3nRoIthgZuCy+ mvF3J4TiIK8gWgw+N3eT7Py7ylD1Tx7EHnxV7RYy0yCgcTaB6YAofugAR8UWUhwQ8NwT TbpSsm14YJ4dqHqcomhj5xHZeLWzPpXXpSmuKz6vXeTOjuvCY7c5cdx8px5I5zJt9aNS ObahB/2UoX8O+BvR8h4DcbSZTx5jChvBSYntXaPgOdT8KMaE6wQVY1Z8lGC14/CuwUZq HW1w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:content-transfer-encoding:cc:to:subject :message-id:date:from:in-reply-to:references:mime-version :dkim-signature; bh=8d6hJDj9WYGcZt3sOxU9jJpzctdAC7KsWBf92Fbncno=; b=UG8H0GNthyAw/ZyVqZ9tSjc9zWq7yEiisOuRhDt1lzsDTtlAmJzbiNC3GfGhGuzO+Y g/OFsQCldAxPwP4pnhMeSi9XC/msDi7DMuQKUjfZBPjNwCRobr831hFkbyf8SKLnEy0P 5+PGaWCkaThq52+Puye6GC8Q8VgbjVVSWGV5wJBzybLKVrRhpiAlljelLLn7r3elmIIx OAH3r+lcwIrjkwhl79Bg1BUu1n5xSnOJXdGgYR+O+266R6Cj/xwa/w7WBEr9WKTgo71Z x7CwJcTZSQ+ziUdDHZSytuzqT823nHRM58HU78mjiwdAy2A7PQicUK4XSa8afxED8QGC rQHg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=IG6frN4I; 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; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id m8si10492319plt.171.2018.12.10.11.08.04; Mon, 10 Dec 2018 11:08:19 -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; dkim=pass header.i=@gmail.com header.s=20161025 header.b=IG6frN4I; 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; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728068AbeLJRFB (ORCPT + 99 others); Mon, 10 Dec 2018 12:05:01 -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-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