From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kleber Sacilotto de Souza Subject: Re: [PATCH] drm/radeon: Disable writeback by default on ppc Date: Mon, 25 Nov 2013 22:11:42 -0200 Message-ID: <5293E73E.8050704@linux.vnet.ibm.com> References: <1371477978-25440-1-git-send-email-ajax@redhat.com> <1371485240.13840.78.camel@localhost> <1383863356.4776.202.camel@pasglop> <527CEA7D.4060704@linux.vnet.ibm.com> <1385334947.4882.153.camel@pasglop> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from e24smtp04.br.ibm.com (e24smtp04.br.ibm.com [32.104.18.25]) by gabe.freedesktop.org (Postfix) with ESMTP id B5728FAA01 for ; Mon, 25 Nov 2013 16:11:49 -0800 (PST) Received: from /spool/local by e24smtp04.br.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 25 Nov 2013 22:11:47 -0200 Received: from d24relay02.br.ibm.com (d24relay02.br.ibm.com [9.13.184.26]) by d24dlp02.br.ibm.com (Postfix) with ESMTP id 61D651DC0070 for ; Mon, 25 Nov 2013 19:11:45 -0500 (EST) Received: from d24av02.br.ibm.com (d24av02.br.ibm.com [9.8.31.93]) by d24relay02.br.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id rAQ0BU7d48693290 for ; Mon, 25 Nov 2013 22:11:31 -0200 Received: from d24av02.br.ibm.com (localhost [127.0.0.1]) by d24av02.br.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id rAQ0BhQJ003186 for ; Mon, 25 Nov 2013 22:11:43 -0200 In-Reply-To: <1385334947.4882.153.camel@pasglop> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dri-devel-bounces@lists.freedesktop.org Errors-To: dri-devel-bounces@lists.freedesktop.org To: Benjamin Herrenschmidt Cc: dri-devel@lists.freedesktop.org, Brian King , Jerome Glisse , Thadeu Lima de Souza Cascardo List-Id: dri-devel@lists.freedesktop.org On 11/24/2013 09:15 PM, Benjamin Herrenschmidt wrote: > On Fri, 2013-11-08 at 11:43 -0200, Kleber Sacilotto de Souza wrote: >> On 11/07/2013 08:29 PM, Benjamin Herrenschmidt wrote: >>> On Mon, 2013-06-17 at 18:57 -0400, Alex Deucher wrote: >>> >>>> Weird. I wonder if there is an issue with cache snoops on PPC. We >>>> currently use the gart in cached mode (GPU snoops CPU cache) with >>>> cached pages. I wonder if we need to use uncached pages on PPC. >>> There is no such issue and no known bugs with DMA writes on those >>> PCIe host bridges (and they do get hammered pretty bad here). >>> >>> This needs further investigation by the lab/hw guys to find out what's >>> actually happening on the bus and the host bridge. >>> >>> Thadeu, Kleber: Jerome suggested writing a test case in userspace that >>> continuously writes to a spare scratch register (thus triggering the >>> corresponding writeback DMA) and checks the memory location to compare >>> the writeback value (using a debugfs file for example, or mmap). >>> >> I can look into that. > Any news ? Only now I've got the bandwidth to actually take a look at this. I will start to write some code and let you guys know of the results. Thanks, Kleber > > Ben. > >> Thanks, >> >> Kleber >> >>> Can you guys do something like that ? Then we need the analyzer on >>> and/or the lab guys to look at the fabric trace & PHB trace. >>> >>> Ben. >>> >>> >> > -- Kleber Sacilotto de Souza IBM Linux Technology Center