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 16A10C54E4A for ; Tue, 12 May 2020 13:22:19 +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 D9505206DD for ; Tue, 12 May 2020 13:22:18 +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="IJDgKyD+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D9505206DD 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 489216E91C; Tue, 12 May 2020 13:22:18 +0000 (UTC) Received: from mail-wm1-x32c.google.com (mail-wm1-x32c.google.com [IPv6:2a00:1450:4864:20::32c]) by gabe.freedesktop.org (Postfix) with ESMTPS id 846FB6E91C for ; Tue, 12 May 2020 13:22:17 +0000 (UTC) Received: by mail-wm1-x32c.google.com with SMTP id z72so13651110wmc.2 for ; Tue, 12 May 2020 06:22:17 -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=+EnH0KWqC8dwxn54jn+UlKp1qHLV0xeQE4GDKe1+aoY=; b=IJDgKyD+Re5mAyXKVTtPZ1TN5qOKdpTV7RbZnR/px2smOPqS0ugf6heO0YEMhT+HiG 3MAKjlgol/bOVoZ+w6yilXS1oZZ2KxnTn8Iac6rHKCmLo7CURmM+uTWcfqWW4koArGgq jR8ll0K8frGzlqj1D983L/SvQS3+Pqg+5B8x2TfkiBdzMqAK6hnxojELvyymv25iYTLc 5hvETpasvRFGvya8oOzIZIhOTOK443TGz5C8/KGuA8Vo+HmGiVbHYBYbUUJ1T6YrGdE4 yuTlz7Fn444rAvfT9MLvjDPP5Z9HTGdlrsJ7dPWNuh50dzw+FC2t89xKd3vJ5sNNVKHX 6ZCw== 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=+EnH0KWqC8dwxn54jn+UlKp1qHLV0xeQE4GDKe1+aoY=; b=Wad/9DAmIH0jj61Jev4xFDmxoUjFZ7im/QbJt0/n9PNk4wIYPbtZicQ4CqXT9HNIqH DaEktEKW0kBIkeqwOD5FJ44ZY38AQSfEv5UEbXsrvTEJMrLlNANnZVepCsqwdWvsGHSb SijbooWNms0ha6me+Ap+46bjVylz1OBHDLxTBYLuv2u3pXd5XWIOekDil6+GM4TlSuzs YavkXLJ8OAP776SGusg8+TPAjAEdfGSC4exBvIP//htbqO0rFF/VkkLcnQyLG/vsZF1b 424d+ELSM8XKHcdlLGCz5HnmoA3sdJo6ncW9nEIL3hXOvZSMCcHlk619nlfAS5OJ3KGe Q6zg== X-Gm-Message-State: AGi0PuZuXlS+IICv7g0WVeZHXurrjahZ1RRiAiaKG18uiAJXqOnnc4gY DYWbL2eP61yoAC2+5aQ9v4LGCs02ymmu8pCXldYlcQ== X-Google-Smtp-Source: APiQypL3iC2BiMlySCWAPlOWSye+X6XQgW9Ch6hWxB3MXivgb0piU/pZBmM2hSQyuJuf+ck+m899TnaDa2SXCqR4+gY= X-Received: by 2002:a1c:1d41:: with SMTP id d62mr16930524wmd.79.1589289736063; Tue, 12 May 2020 06:22:16 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Alex Deucher Date: Tue, 12 May 2020 09:22:05 -0400 Message-ID: Subject: Re: [RFC] Remove AGP support from Radeon/Nouveau/TTM To: "Karoly Balogh (Charlie/SGR)" 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 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 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. Alex _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel