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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 EC048C33CA1 for ; Thu, 9 Jan 2020 14:14:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CD97E2067D for ; Thu, 9 Jan 2020 14:14:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731568AbgAIOOk (ORCPT ); Thu, 9 Jan 2020 09:14:40 -0500 Received: from verein.lst.de ([213.95.11.211]:54875 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731559AbgAIOOk (ORCPT ); Thu, 9 Jan 2020 09:14:40 -0500 Received: by verein.lst.de (Postfix, from userid 2407) id 30C4468C4E; Thu, 9 Jan 2020 15:14:37 +0100 (CET) Date: Thu, 9 Jan 2020 15:14:36 +0100 From: Christoph Hellwig To: Woody Suwalski Cc: hch@lst.de, DRI mailing list , LKML , Christian =?iso-8859-1?Q?K=F6nig?= , "Deucher, Alexander" , Pavel Machek Subject: Re: Regression in 5.4 kernel on 32-bit Radeon IBM T40 Message-ID: <20200109141436.GA22111@lst.de> References: <400f6ce9-e360-0860-ca2a-fb8bccdcdc9b@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <400f6ce9-e360-0860-ca2a-fb8bccdcdc9b@gmail.com> 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 Hi Woody, sorry for the late reply, I've been off to a vacation over the holidays. On Sat, Dec 14, 2019 at 10:17:15PM -0500, Woody Suwalski wrote: > Regression in 5.4 kernel on 32-bit Radeon IBM T40 > triggered by > commit 33b3ad3788aba846fc8b9a065fe2685a0b64f713 > Author: Christoph Hellwig > Date:   Thu Aug 15 09:27:00 2019 +0200 > > Howdy, > The above patch has triggered a display problem on IBM Thinkpad T40, where > the screen is covered with a lots of random short black horizontal lines, > or distorted letters in X terms. > > The culprit seems to be that the dma_get_required_mask() is returning a > value 0x3fffffff > which is smaller than dma_get_mask()0xffffffff.That results in > dma_addressing_limited()==0 in ttm_bo_device(), and using 40-bits dma > instead of 32-bits. Which is the intended behavior assuming your system has 1GB of memory. Does it? > If I hardcode "1" as the last parameter to ttm_bo_device_init() in place of > a call to dma_addressing_limited(),the problem goes away. I'll need some help from the drm / radeon / TTM maintainers if there are any other side effects from not passing the need_dma32 paramters. Obviously if the device doesn't have more than 32-bits worth of dram and no DMA offset we can't feed unaddressable memory to the device. Unfortunately I have a very hard time following the implementation of the TTM pool if it does anything else in this case.