On Friday, September 12, 2003, at 10:12 AM, Benjamin Herrenschmidt wrote: On Monday, September 8, 2003, at 10:19 PM, Ryan Rempel wrote: I'm updating a driver for the new memory mapping limitations, and I've got a couple of DMA-related questions. The driver uses a couple of functions in <osfmk/ppc/pmap.h>, namely: extern void invalidate_dcache(vm_offset_t va, unsigned length, boolean_t phys); extern void flush_dcache(vm_offset_t va, unsigned length, boolean_t phys); The calls to invalidate_dcache are accompanied by this comment "Purge cache references for the DBDMA entry we are about to look at". The calls to flush_dcache are accompanied by this comnment "Push DMA commands to physical memory". Do you actually need to do that at all ? What driver is this ? Those machines are supposed to be cache coherent... I know there seem to be cache coherency bugs with earlier hardware, though I couldn't get any useful detail from Apple, I had some weird problems when a DBDMA wrote in a middle of a cache line with the MESH driver on a 8500 and possibly others. So if you are trying to deal with such issues, you need to flush/invalidate your data as well and make sure everything is cache line aligned. I don't know if I actually need to do this. The drivers are the AppleCurio and AppleMaceEthernet drivers (i.e. the external SCSI and built-in ethernet on the older machines). The calls are in the original drivers from Darwin 0.9 (that is, I didn't put them there), so I'm not sure if they're absolutely required. I haven't tried removing them to see what happens yet. _______________________________________________ darwin-kernel mailing list | darwin-kernel@lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.