Date: 06 Nov 2002 23:53:46 -0800 From: Eric Anholt <eta@lclark.edu> To: Nate Lawson <nate@root.org> Cc: "hackers@FreeBSD.ORG" <hackers@FreeBSD.ORG> Subject: Re: busdma in the DRM Message-ID: <1036655638.3888.12.camel@anholt.dyndns.org> In-Reply-To: <Pine.BSF.4.21.0211062332450.17375-100000@root.org> References: <Pine.BSF.4.21.0211062332450.17375-100000@root.org>
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On Wed, 2002-11-06 at 23:36, Nate Lawson wrote: > On 6 Nov 2002, Eric Anholt wrote: > > I've been trying to figure out how to use the bus_dma* functions in the > > DRM. What I'm working on at the moment is the ATI PCIGART. How it > > works right now is an ioctl is done which mallocs a chunk of memory (up > > to 32MB). Later, the ioctl that sets up dma allocates a physically > > contiguous 32K of memory which contains pointers (by vtophys) into the > > pages of the 32MB. The physical address of that 32K is then written to > > the card. The 32MB is mapped by both the kernel and userspace (the X > > Server). > > > > So, I'm trying to convert it to busdma. I'm making a tag (is making it > > without having a parent tag a bad thing?) for the 32K contiguous, > > allocing 32K, and loading, with a callback to drop the dma address into > > a place of my choice. However, how do I do the 32MB? It only has to > > consist of pages, with nothing else special for alignment. For > > nsegments in bus_dma_tag_create it says it can't be more than 250-300, > > while I've got possibly 8192 segments. I'm thinking I would have to > > make a tag for the 32MB, allocate it, then loop and create PAGE_SIZE, > > nsegments=1 tags with the 32MB as parent, and bus_dmamap_load on those > > tags with offsets from the first map's vaddr and PAGE_SIZE long. Am I > > totally off base here? Is this even possible? > > Check out /sys/pci/agp* So are you saying I shouldn't be using busdma at all? How do I limit my allocations to pages accessible by pci in that case? Is the address returned by VM_PAGE_TO_PHYS accessible by the card on any architecture? -- Eric Anholt <eta@lclark.edu> http://people.freebsd.org/~anholt/dri/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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