Messages in this thread | | | Subject | Re: [PATCH v2] powerpc32: memcpy/memset: only use dcbz once cache is enabled | From | Michael Ellerman <> | Date | Mon, 14 Sep 2015 19:59:10 +1000 |
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On Sat, 2015-09-12 at 11:57 +0200, christophe leroy wrote: > > Le 11/09/2015 03:24, Michael Ellerman a écrit : > > On Thu, 2015-09-10 at 17:05 -0500, Scott Wood wrote: > >> > >> I don't think this duplication is what Michael meant by "the normal cpu > >> feature sections". What else is going to use this very specific > >> infrastructure? > > Yeah, sorry, I was hoping you could do it with the existing cpu feature > > mechanism. > > > > It looks like the timing doesn't work, ie. you need to patch this stuff in > > machine_init(), which is later than the regular patching which gets done in > > early_init(). > > > > This is one of the festering differences we have between the 32 and 64-bit > > initialisation code, ie. on 64-bit we do the patching much later. > > I've just thought about maybe another alternative. > Is there any issue with calling do_feature_fixups() twice for the same > features ?
Not that I can think of, but you never know.
> If not, we could define a MMU_CACHE_NOW_ON dummy MMU feature, then > call again do_feature_fixups() in machine_init() to patch memcpy/memset > stuff, something like: > > In arch/powerpc/include/asm/mmu.h: > +#define MMU_CACHE_NOW_ON ASM_CONST(0x00008000) > > In arch/powerpc/kernel/setup_32.c: @machine_init() > > udbg_early_init(); > > + spec = identify_cpu(0, mfspr(SPRN_PVR)); > + do_feature_fixups(spec->mmu_features | MMU_CACHE_NOW_ON, > + &__start___mmu_ftr_fixup, > + &__stop___mmu_ftr_fixup);
Did you try that? It would be cleaner, especially now that you have to do memset as well.
cheers
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