Matt, Thanks very much for your advice. You have saved me a big headache!
> I really recommend using the linuxppc_2_4_devel tree as a starting > kernel source base...but it's your choice. I will try using the linuxppc_2_4_devel tree. Unforeseen problems I don't need. > Do you really have to map a contiguous 384MB of physical address > space? If these are typical RTC and PIC parts...why? The RTC is typical but the PIC is split between a custom ASIC and another device. The RTC is at 0xE400_0000phys, one part of the PIC is at 0xEC00_0000phys and the other part is at 0xF700_0000phys. Their size is small, but they are spread out. If I have to map them with BATs, I would have to map 384Mb (because the BAT base address must be a multiple of the mapped size.) Once the KVM is up, I think that I can use ioremap(), or io_block_mapping() to map in only what I need. Is that right? > You are misunderstanding the mapping of kernel RAM using BATs. The > 16MB mapping is a temporary translation used before MMU_init(). > If you look at arch/ppc/mm/ppc_mmu.c:bat_mapin_ram() you'll see > that the final mapping is done using BAT2 and BAT3 (the third > pair of bats is only used if total_lowmem > 256MB). Does this mean that before MMU_init() I can use BATs 2&3, then in ppc_md.setup_io_mappings() (called after mapin_ram()) I would use io_block_mapping() (as is done in chrp_setup.c?) This helps a lot! Thanks again for your advice. Greg Griffes ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
