You can now use flashrom on PowerPC and MIPS with most programmers. I added the last bit of infrastructure in version 0.9.2-r1111, and we got a few success reports since then. All USB/serial/network drivers work, and quite a few PCI drivers work fine as well.
Added bonus: If your flashrom driver selection does not need direct hardware access (e.g. USB programmers, serial programmers, dummy, …) you can now compile flashrom on all architectures, even those which are not explicitly supported. That feature was added in version 0.9.2-r1116.
This is a big step forward for flashrom which had been x86 centric since the beginning.
A patch to handle the onboard flash of MIPS boards exists and has been tested successfully with the Lemote Yeeloong laptop.
Support for I/O (port) space accesses has not been implemented yet, and this means atahpt, nic3com, nicnatsemi, nicrealtek and rayer_spi won’t work on non-x86 (yet). On quite a few architectures I/O space accesses are mapped to memory space accesses with obscure rules, and those rules have to be replicated in flashrom, or the individual drivers have to be changed to use memory space accesses directly if the hardware supports that.
I have a patch for Alpha and SPARC pending, and it should be possible to handle ARM as well, but it is really difficult to find ARM boards with PCI slots or other interesting hardware attached.