Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758668Ab1D2K5E (ORCPT ); Fri, 29 Apr 2011 06:57:04 -0400 Received: from smtp-outbound-1.vmware.com ([65.115.85.69]:40048 "EHLO smtp-outbound-1.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758598Ab1D2K5C (ORCPT ); Fri, 29 Apr 2011 06:57:02 -0400 Message-ID: <4DBA990F.6040203@vmware.com> Date: Fri, 29 Apr 2011 12:55:11 +0200 From: Thomas Hellstrom User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100624 Mandriva/3.0.5-0.1mdv2009.1 (2009.1) Thunderbird/3.0.5 MIME-Version: 1.0 To: Benjamin Herrenschmidt CC: Jerome Glisse , linaro-mm-sig@lists.linaro.org, Russell King - ARM Linux , Arnd Bergmann , linux-kernel@vger.kernel.org, FUJITA Tomonori , linux-arm-kernel@lists.infradead.org Subject: Re: [Linaro-mm-sig] [RFC] ARM DMA mapping TODO, v1 References: <201104212129.17013.arnd@arndb.de> <201104281428.56780.arnd@arndb.de> <20110428131531.GK17290@n2100.arm.linux.org.uk> <201104281629.52863.arnd@arndb.de> <20110428143440.GP17290@n2100.arm.linux.org.uk> <1304036962.2513.202.camel@pasglop> <4DBA5194.7080609@vmware.com> <1304062523.2513.235.camel@pasglop> In-Reply-To: <1304062523.2513.235.camel@pasglop> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2131 Lines: 60 On 04/29/2011 09:35 AM, Benjamin Herrenschmidt wrote: > > We have problems with AGP and macs, we chose to mostly ignore them and > things have been working so-so ... with the old DRM. With DRI2 being > much more aggressive at mapping/unmapping things, things became a lot > less stable and it could be in part related to that. IE. Aliases are > similarily forbidden but we create them anyways. > > Do you have any idea how other OS's solve this AGP issue on Macs? Using a fixed pool of write-combined pages? >> c) If neither of the above applies, we might be able to either use >> explicit cache flushes (which will require a TTM cache sync API), or >> require the device to use snooping mode. The architecture may also >> perhaps have a pool of write-combined pages that we can use. This should >> be indicated by defines in the api header. >> > Right. We should still shoot HW designers who give up coherency for the > sake of 3D benchmarks. It's insanely stupid. > I agree. From a driver writer's perspective having the GPU always snooping the system pages would be a dream. On the GPUs that do support snooping that I have looked at, its internal MMU usually support both modes, but the snooping mode is way slower (we're talking 50-70% or so slower texturing operations), and often buggy causing crashes or scanout timing issues since system designers apparently don't really count on it being used. I've found it usable for device-to-system memory blits. In addition memcpy to device is usually way faster if the destination is write-combined. Probably due to cache thrashing effects. /Thomas > Cheers, > Ben. > > >> /Thomas >> >> >> >> >> >>> _______________________________________________ >>> Linaro-mm-sig mailing list >>> Linaro-mm-sig@lists.linaro.org >>> http://lists.linaro.org/mailman/listinfo/linaro-mm-sig >>> >>> > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/