On Tue, 2008-07-22 at 09:31 +0100, Matt Sealey wrote: > Jon Smirl wrote: > > On 7/20/08, Matt Sealey <[EMAIL PROTECTED]> wrote: > >> Hi guys, > >> > >> I know this isn't a PPC question, but since some of the RadeonFB > >> developers > >> live here I thought best (and it's about a PPC platform). > >> > >> Is there any way to hack up the RadeonFB driver - or anything related - to > >> reserve portions of the memory for a "fake" MTD or so, and still use the > >> Radeon as a graphics device? What I am talking about basically is turning > >> a 64MB Radeon card into a 32MB Radeon card, or a 128MB one into a 64MB > >> card.. > > > > Somebody write this long ago. Maybe around 2000. That's all I > > remember. I think they made the video memory into a ram disk. > > Yeah making it into a ramdisk precludes the use of the card as a video card > though.. this is what I am trying to get around. If fbdev and X can cooperate > on believing that a 64MB card is a 32MB card, then the upper 32MB can be used > to attach the MTD "ram" driver at a certain address (maybe we can even make a > hacky stub driver that recognizes this configuration based on OF tree..) > > There are obvious limitations in that the Pegasos/Efika firmware only will > map 128MB of video memory, and the PCI BAR is limited to 256MB chunks anyway, > but that shouldn't matter. I just wonder, how it can be done that radeonfb > or other graphics drivers can be told "please only use the first 32MB" and > then either manually or automatically, map the rest as ramdisk.
You can limit the amount of video RAM used by X using the VideoRam directive in xorg.conf(5). > > I believe there is more to it, the GART window may be smaller than the > > total RAM on the card. You need to use the GART to map in the > > appropriate pieces. > > The problem here is the PCI bus on the Efika is a PCI bus, with an AGP > riser. It doesn't add any AGP functionality like real GART on the host > controller side, so there is nothing to map system memory into AGP's > view of the system.. it always confused me how "pcigart" is meant to > work and how an AGP GART does anything different to how PCI works in > the first place (the documentation/spec doesn't make it that clear in > my opinion :) GART doesn't have anything to do with this. I suspect he was thinking of the PCI BARs not covering all video RAM. -- Earthling Michel Dänzer | http://tungstengraphics.com Libre software enthusiast | Debian, X and DRI developer _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
