Hello all, There have been some recent posts about Linux & Virtex-II Pro (FPGA with PPC405 hard core). & apparently people have it working.
One question before I start, though: Of course the kernel starts at *virtual* address 0xc0000000, regardless of the processor. But my understanding is that certain processors have zero-based *physical* addresses for RAM, and some don't -- x86 of course being an example of the former, and ARM being an example of the latter. I believe that PPC is an example of the former. Certainly our MPC857T board, and all the other boards of which I'm aware, have RAM starting at physical address 0x00000000. Now, on our custom Virtex-II Pro board, with Xilinx EDK setup, there's a bit (the MSB) in the physical address that specifies whether a memory region is on the LMB bus or OPB bus. We get to pick *which* bit, but there must be *a* bit set for the SDRAM. The upshot is that our SDRAM starts at physical address 0xb0000000. It can't be placed at address 0. And block RAM could be made low, but I can't see having megabytes of block RAM. So, I think I have to have the kernel at non-zero physical address with PPC405. Can anyone advise on success or failure of doing so? ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
