> > What's wrong with GFP_DMA ? Doesn't it solve exactly this problem ? > Personally I don't like the hack but you have to ask what he needs. > kmalloc grabs memory from the CPU cache. GFP_DMA insures that cache memory > is continues. I think Geoffrey needs to use a specific memory address in > PCI space. Tho I like Geoffrey to try using GFP_DMA. The reason I don't > like the hack is that skbuff's is bus independent. Not all ethernet cards > are PCI based. Please try using GFP_DMA and let us know if it worked. Yes, I originally thought this was what addressed it. Is "setting dma_mask" what is meant by "using GFP_DMA"? The problem is drivers call dev_alloc_skb() which can allocate memory anywhere in (my 32M) memory. The PCI host controller part of the uPD98052 with its VR4120a core (doc at http://www.idiom.com/~espin/nec/hwdoc/uPD98502-UM.pdf) allows you to program a 4M window onto DRAM. I use top 4M of 32M, but it's arbitrary. Then only this area can be transferred to by/from the PCI devices. So its not the PCI devices that is the problem, but access to the host-side DRAM. Currently, my private pci_alloc/free_consistent() routines manage the 4M at top of memory (its not added to kernel with add_memory_region() in prom.c). With these hacks (including net/core/skbuff.c:alloc_skb->pci_alloc_consistent) I've been successfully using the Tulip Ethernet (LinkSys) card (with no changes to the driver). Geoff -- Geoffrey Espin espin@idiom.com
