ppc: Remove broken partial PVR matching
The ppc target contains a ppc_find_by_pvr() function, which looks up a CPU spec based on a PVR (that is, based on the value in the target cpu's Processor Version Register). PVR values contain information on both the cpu model (upper 16 bits, usually) and on the precise revision (low 16 bits, usually). ppc_find_by_pvr, as well as making exact PVR matches, attempts to find "close" PVR matches, when we don't have a CPU spec for the exact revision specified. This sounds like a good idea, execpt that the current logic is completely nonsensical. It seems to assume CPU families are subdivided bit by bit in the PVR in a way they just aren't. Specifically, it requires a match on all bits of the specified pvr up to the last non-zero bit. This has the bizarre effect that when the low bits are simply a sequential revision number (a common though not universal pattern), then odd specified revisions must be matched exactly, whereas even specified revisions will also match the next odd revision, likewise for powers of 4, 8 and so forth. To correctly do inexact matching we'd need to re-organize the table of CPU specs to include a mask showing what PVR range the spec is compatible with (similar to the cputable code in the Linux kernel). For now, just remove the bogosity by only permitting exact PVR matches. That at least makes the matching simple and consistent. If we need inexact matching we can add the necessary per-subfamily masks later. Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au> Signed-off-by: NAlexander Graf <agraf@suse.de>
Showing
想要评论请 注册 或 登录