From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: radeon, apertures & memory mapping Date: Mon, 14 Mar 2005 11:10:05 +1100 Message-ID: <1110759005.5787.198.camel@gaston> References: <1110705646.14684.126.camel@gaston> <20050313103936.GA11002@sci.fi> <1110715499.14684.132.camel@gaston> <9e473391050313081937cde207@mail.gmail.com> <1110750553.5787.155.camel@gaston> <9e47339105031314101c89e50e@mail.gmail.com> <1110752401.19810.177.camel@gaston> <9e47339105031315002a444f00@mail.gmail.com> <20050313232735.GA19781@sci.fi> <1110757699.5787.196.camel@gaston> <20050314000835.GA20393@sci.fi> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit In-Reply-To: <20050314000835.GA20393@sci.fi> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: xorg-bounces@lists.freedesktop.org Errors-To: xorg-bounces@lists.freedesktop.org Content-Type: text/plain; charset="us-ascii" To: Ville =?ISO-8859-1?Q?Syrj=E4l=E4?= Cc: Jon Smirl , Linux Fbdev development list , dri-devel@lists.sourceforge.net, xorg@lists.freedesktop.org > I don't think "normal" drivers do them at all. I did experiment with > DirectFB at one point and had it place all offscreen surfaces to AGP > memory. It worked really well on my hardware (G400 + VIA KT133 > northbridge). I also tried it with PCI transfers and that too worked but > was naturally slower. I'd like to make DirectFB use AGP again since 32MB > of video memory isn't always enough. > > > (Which is interesting, that means that if we want to copy something out > > of video memory, we can't write it to AGP memory and then read it, we > > need to actually do the blit from the CPU, good to know for our memory > > manager. That also means that we have a problem if the video memory > > isn't entirely accessible by the CPU ...) > > What about PCI master writes? Are there bridges that don't support even > those? Usually, those work. I have a list of errata of Apple bridges at least in Darwin, some do not support PCI master writes, but it's only apparently some never-released revisions :) > > That's something we should probably think about doing properly: Have a > > list of AGP "issues" (errata ?) bits that are communicated by the AGP > > host driver to the DRM. > > > > At least all the early Apple AGP bridges don't do writes, and I remember > > we have trouble with a few x86 ones as well. There are also issues when > > a single AGP burst crosses a page boundary, and other things like that. > > :( > -- Benjamin Herrenschmidt