Messages in this thread | | | Date | Wed, 18 Aug 2004 07:16:51 -0400 | From | Mark Hounschell <> | Subject | Re: Help with mapping memory into kernel space? |
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William Lee Irwin III wrote: > > On Tue, Aug 17, 2004 at 10:39:38PM -0700, Brian McGrew wrote: > > The overall problem is that the more system memory we install, > > the fewer IBB's we can use. For instance, 256MB lets us use > > four IBB's; 512MB lets us use three IBB's and so on. Basicly, > > the kernel blows up trying to map memory. Each IBB has two > > banks of 64MB of RAM on them which we try and memmap to system > > memory for speed of addressing. So essentaily, we're sending > > out four camera systems with only 256MB of memory which is only > > about one quarter of what we need. > > I can't think of any better way to explain it other than it's > > almost like adding system memory subtracts from kernel memory. > > Does that make any sense? We've tried building the kernel with > > the 4GB memory model and the 64GB memory model and had no success. > > You appear to be trying to ioremap() vast areas. ia32 has limited > address space, so you need to do one of two things: > (a) subdivide into portions mapped into different address spaces > (b) map portions on demand > > There is no support for (a) in Linux. >
You might try the bigphysarea patch. We have basically the same problem with hardware not capabile of hardware scatter/gather in DMA mode. Bigphysarea was our solution. It does not appear to be available for the 2.6 kernel however
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