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=-0.3 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 27E6FCA90AF for ; Tue, 12 May 2020 18:22:55 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E8979206A3 for ; Tue, 12 May 2020 18:22:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="SxSd3x+2" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E8979206A3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 4E10B6E15F; Tue, 12 May 2020 18:22:54 +0000 (UTC) Received: from mail-wr1-x42b.google.com (mail-wr1-x42b.google.com [IPv6:2a00:1450:4864:20::42b]) by gabe.freedesktop.org (Postfix) with ESMTPS id 998686E15F for ; Tue, 12 May 2020 18:22:52 +0000 (UTC) Received: by mail-wr1-x42b.google.com with SMTP id s8so16875057wrt.9 for ; Tue, 12 May 2020 11:22:52 -0700 (PDT) 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; bh=erHlwe62ipbsUpRuE6/WtSlHbqnjKseZxDfTEJqAVL0=; b=SxSd3x+2wd6CdTZ+MXCZYBL4338dyYUmlWhjtC1Ft+CV/05SQZbPCHQFb4gs6N0+yD hMQY927kLhbi0Y2E7CU3Zd7DEi6tib83GmF6EP7T6JyTt2gc3IhiP9jz8OhQs/0UbMim CDolL3KTxdyfzy74Nq4tMCjLb3TpHWIeZZ8t7KMFR/LVTdJvEmLXYfl5XROwZ13MUKkv TEjYhlXYqAGJnKZDBLP9+ypvbxxtrfzwmzniX7oTYtO7UAnCH58mkN/QSYZr5WX5pVGD 6p9xr+eJbZEL62/A9OGPkSLLaMcF+O20XAXWCY06HLJntlNcGW+w+sYwE5UUSvZd64z1 NwMw== 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; bh=erHlwe62ipbsUpRuE6/WtSlHbqnjKseZxDfTEJqAVL0=; b=Tyx1d5u/EVWxMPXiArzYx89AgMcMgytJ2oLYGQVooVzU09xYSIdsSO/UfHU4fIQoq/ wl8Wa3LCJpdhP5fES0Wk9XcweAuSRtH1m9asDPoa+8OZ9yWvgBlbxRopAXizm+1JNNdX Prt+/RA9bvHoel90X7WQcX1h07G4AxAxM27Qv4Ck5w4/Ye4r0W8ktRx4pPd6XapDhcRy IWmJKgBYv/4/RLl3GkbbkUI1/pmvoUCs4oo81Gh+hpLDAg/sPtXJagJ3fAAnTt4HeCfS s7b9pALVqCHdE/rI8sK+OMkDtdVbPIQRHZmCiCETeNTAOuh0g8bmUmMQV1MIQnfyBotp a9KA== X-Gm-Message-State: AGi0PuZ4jfEjCPV9vSewdZzVGE9T01GzdVCPgeEWfev8UkbVfqa1esNH wZFmeJTHPVdH8lQCETkq6bMpNWH73GWB/ghk0H8= X-Google-Smtp-Source: APiQypIIl+6fV8X30pszz+V2CqKrnXWwu+jTn0uDLATGckHOlIJwYKLnfWuGUue/sRFa1sAcrgj6h44SKKhXoLuSdzM= X-Received: by 2002:a5d:4389:: with SMTP id i9mr27145171wrq.374.1589307771266; Tue, 12 May 2020 11:22:51 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Alex Deucher Date: Tue, 12 May 2020 14:22:40 -0400 Message-ID: Subject: Re: [RFC] Remove AGP support from Radeon/Nouveau/TTM To: Daniel Vetter X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: =?UTF-8?Q?Christian_K=C3=B6nig?= , =?UTF-8?Q?Michel_D=C3=A4nzer?= , Maling list - DRI developers , Rui Salvaterra , "debian-powerpc@lists.debian.org" , John Paul Adrian Glaubitz , "Karoly Balogh \(Charlie/SGR\)" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tue, May 12, 2020 at 12:38 PM Daniel Vetter wrote: > > On Tue, May 12, 2020 at 3:22 PM Alex Deucher wrote: > > > > On Tue, May 12, 2020 at 5:40 AM Karoly Balogh (Charlie/SGR) > > wrote: > > > > > > Hi, > > > > > > On Tue, 12 May 2020, Rui Salvaterra wrote: > > > > > > > > FWIW, on my last-generation PowerBook with RV350 (IIRC), there was a > > > > > big performance difference between AGP and PCI GART. The latter was > > > > > sort of usable for normal desktop operation, but not so much for > > > > > OpenGL apps (which were usable with AGP). > > > > > > > > I never really understood what were the issues with AGP on PowerPC > > > > (well, Apple, the only ones I've tested) machines. I mean, did OS X also > > > > disable AGP entirely, or did it have workarounds somewhere else on the > > > > stack nobody was able to figure out? > > > > > > I don't know about OS X, but I doubt there is a major/blocker hardware > > > issue, at least not one which affects every AGP machine. > > > > > > MorphOS' own Radeon driver uses the AGP facilities to some degree on all > > > AGP PowerPC Macs supported by that OS, which is from PMac AGP Graphics > > > (3,1) all the way up to the AGP G5 (7,3), including the various portables > > > and the Mac mini G4. For example it can utilize it to stream video data > > > directly from mainboard RAM, so you don't have to copy it with the CPU, > > > allowing reasonably good 720p h264 video playback on most systems above > > > the 1Ghz mark with the native MPlayer port. I'm sure the 3D part of the > > > driver also use it to some degree, given the performance improvement we > > > experienced when the AGP support was enabled (initially the system was > > > running without it), but to which extent I can't say. > > > > The problem is AGP doesn't support CPU cache snooping. Technically > > PCI must support coherent device access to system memory. Unsnooped > > access is an optional feature and some platforms may not support it at > > all. Unfortunately, AGP required unsnooped access. x8t generally > > provides a way to do this, but other platforms, not so much. I don't > > recall to what extent PowerPC supported this. The Linux DMA API > > doesn't really have a way to get uncached memory for DMA so there is > > that too. Windows and Mac may provide a way to do this depending on > > the platforms. What probably should have been done on AGP boards was > > to use both the AGP GART and the device GART. The former for uncached > > memory (if the platform supported it) and the latter for cached > > memory. That never happened. > > Slight correction on the dma-api side of things: The dma-api very much > can give you uncached memory, but only on some platforms, and the > dma-api is very opinionated about which those are. And it refuses to > tell you whether your memory ends up being uncached or cached. That's > all done in the name of platform portability, which is good for most > drivers, but just too much pain for gpu drivers. Out of curiosity how do you do that without manually messing around with PAT or MTRRs? Alex > > Otherwise all agree, agp is a mighty mess and essentially just > crapshot outside of x86. It kinda worked for the much more static > allocations for dri1, but with in-kernel memory managers all the cache > flushing issues showed up big time and it all fell to pieces. Plus a > lot of these host chipset back then where designed for the rather > static windows gpu managers, so even on x86 the coherency issues for > agp mode when used together with ttm or something else really dynamic > is pretty bad because the hw just doesn't really cope and has all > kinds of flushing troubles and races. I think the later agp chipsets > were better. > -Daniel > -- > Daniel Vetter > Software Engineer, Intel Corporation > +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel