On Wed, 2016-04-20 at 12:59 +1000, Michael Ellerman wrote: > On Sat, 2016-09-04 at 06:14:04 UTC, "Aneesh Kumar K.V" wrote:
> > We can depend on ibm,pa-features to enable/disable radix. This gives us > > a nice way to test p9 hash config, by changing device tree property. > > I think we might want to be more careful here. > > You set MMU_FTR_RADIX in the cputable entry. So it's on by default on P9 cpus. > > Then if there is an ibm,pa-features property *and* it is >= 41 bytes long, the > below feature entry will hit. In that case the firmware controls whether it's > on > or off. > > I think it would be clearer if we removed RADIX from the cputable, and the > below > became the only way to turn it on. Would that break anything? I don't think it'll break anything. FWIW I'm good with this approach. We'll need to teach firmware about this feature, but I think we should do that anyway. skiboot is a bit of a mess WRT to this property with HDAT vs device tree, but we can clean that up there. Mikey > > > diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c > > index 7030b035905d..a4d1f44364b8 100644 > > --- a/arch/powerpc/kernel/prom.c > > +++ b/arch/powerpc/kernel/prom.c > > @@ -165,6 +165,7 @@ static struct ibm_pa_feature { > > * which is 0 if the kernel doesn't support TM. > > */ > > {CPU_FTR_TM_COMP, 0, 0, 22, 0, 0}, > > + {0, MMU_FTR_RADIX, 0, 40, 0, 0}, > > So that says bit 0 of byte 40 enables MMU_FTR_RADIX. Where is that documented? > > cheers > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev