Over the past few months, I've been using bitfield - a script to decode the fields within a register. It does neat stuff like this:
[jk@pokey ~]$ bitfield IOC_PTE 0xb80000000140031c
decoding as Cell IOMMU Page table entry
0xb80000000140031c [13258597302999712540]
Page protection: 0x2 [write]
Coherence required: 0x1
Storage ordering: 0x3 [reads & writes]
RPN: 0x1400
IOID: 0x31c
It's handy for those "did I really tell the hardware to do that?" problems.
Download and documentation over here.