when sb_load64() returns.
Some 32-bit arithmetic operations (e.g. subu) have unpredicatable results
when operating on 64-bit registers that are not properly sign-extended.
Getting the little-endian PCI bus working on the big-endian CPU proved to be
quite challenging. We let the PCI devices be mapped in the "match byte lanes"
address window. This is where they are mapped by the CFE and DMA transfers
generated to or from addresses within this window are not subject to automatic
byte-swapping.
However any access by the driver to memory-mapped pci space is redirected
via the "match bit lanes" address window. We get the benefit of automatic
byte swapping through this address window and drivers don't need to change
to deal with CPU big-endianness.
The platform that supports SMP currently is a SWARM with a dual-core Sibyte
processor. The kernel config file to use is SWARM_SMP.
Reviewed by: imp, rrs
The only reason we need to have the sb_load64() and sb_store64()
functions in assembly is to cheat the compiler and generate the
'ld' and 'sd' instructions which it otherwise will not do when
compiling for a 32-bit architecture. There are some 64-bit
registers in the SCD unit that must be accessed using 64-bit
load and store instructions.
