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=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 08A7EC04EB8 for ; Sun, 2 Dec 2018 06:11:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BD909206B7 for ; Sun, 2 Dec 2018 06:11:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BD909206B7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org 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 S1725730AbeLBGL0 (ORCPT ); Sun, 2 Dec 2018 01:11:26 -0500 Received: from gate.crashing.org ([63.228.1.57]:47746 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725355AbeLBGL0 (ORCPT ); Sun, 2 Dec 2018 01:11:26 -0500 Received: from localhost (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id wB26B3sd012208; Sun, 2 Dec 2018 00:11:04 -0600 Message-ID: <42b1408cafe77ebac1b1ad909db237fe34e4d177.camel@kernel.crashing.org> Subject: Re: use generic DMA mapping code in powerpc V4 From: Benjamin Herrenschmidt To: Rui Salvaterra , hch@lst.de Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Date: Sun, 02 Dec 2018 17:11:02 +1100 In-Reply-To: References: <20181130103222.GA23393@lst.de> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.2 (3.30.2-2.fc29) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2018-11-30 at 11:44 +0000, Rui Salvaterra wrote: > Thanks for the quick response! I applied it on top of your > powerpc-dma.4 branch and retested. > I'm not seeing nouveau complaining anymore (I'm not using X11 or any > DE, though). > In any case and FWIW, this series is > > Tested-by: Rui Salvaterra 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. Cheers, Ben. > Thanks, > Rui