7450 bugs & fixes

Tom Rini trini at kernel.crashing.org
Sat Dec 15 07:02:37 EST 2001

On Fri, Dec 14, 2001 at 08:19:20PM +0100, Benjamin Herrenschmidt wrote:

> >>  - errata 29: do we ever switch MSR:IR off via an mtmsr ? If yes, we
> >>    need to add a sync, but I don't think we do.
> >
> >No, because kernel is not mapped 1:1 to physical memory, doing this would
> >cause an implicit jump, which is prohibited by the architecture. Note that
> >it also solves erratum 37 (different symptom and bug, same cure).
> Yup. I just wanted to ask anyway ;) Maybe some early bootloaders do that.

Actually, I _think_ there's a possibility.  In
arch/ppc/boot/common/util.S we do:
        .globl  disable_6xx_mmu
        /* Establish default MSR value, exception prefix 0xFFF.
         * If necessary, this function must fix up the LR if we
         * return to a different address space once the MMU is
         * disabled.
        li      r8,MSR_IP|MSR_FP
        mtmsr   r8

So we should probably throw a 'sync' at the end of that, yes?

Tom Rini (TR1265)

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