register_rom weirdness #96
Description
Hi,
I am trying to get the papilo pro build working and the first error I got was :
Traceback (most recent call last):
File "/usr/lib/python3.6/runpy.py", line 193, in _run_module_as_main
"__main__", mod_spec)
File "/usr/lib/python3.6/runpy.py", line 85, in _run_code
exec(code, run_globals)
File "/home/dus/projects/sdfsadfsd/migen/misoc/misoc/targets/papilio_pro.py", line 103, in <module>
main()
File "/home/dus/projects/sdfsadfsd/migen/misoc/misoc/targets/papilio_pro.py", line 97, in main
soc = BaseSoC(**soc_sdram_argdict(args))
File "/home/dus/projects/sdfsadfsd/migen/misoc/misoc/targets/papilio_pro.py", line 87, in __init__
self.register_rom(self.spiflash.bus)
File "/home/dus/projects/sdfsadfsd/migen/misoc/misoc/integration/soc_core.py", line 138, in register_rom
assert self.cpu_reset_address < rom_size
AssertionError
The code in question looks like the following and really looks strange to me
def register_rom(self, interface, rom_size=0xa000):
self.add_wb_slave(self.mem_map["rom"], rom_size, interface)
assert self.cpu_reset_address < rom_size
self.add_memory_region("rom", self.cpu_reset_address,
rom_size-self.cpu_reset_address)
I can understand that the reset address needs to point to a valid part (and preferably the reset vectors of the CPU) but why does the address need to be smaller than the rom_size. should this code not read
assert cpu_reset_address >= mem_map["rom"]
and
assert cpu_reset_address < mem_map["rom"] + rom_size
the next strange thing is the next line. why is the memory region set to the start address of the cpu reset and not simply the mem_map["rom"] address. I am even more intrigued by the size of the region that is set to rom_size-self.cpu_reset_address.
To me it looks like the code only really will work if the reset_address is 0 (and this is often the case)
I have tried to create a patch that would do something more meaningful but I think I might be lacking some context.
The register_rom function (in my case) is called from https://github.com/m-labs/misoc/blob/master/misoc/targets/papilio_pro.py#L87 (to map the boot code to be flash I guess for being executed xip?).