From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3qqfhS5lTSzDqZD for ; Wed, 20 Apr 2016 21:26:00 +1000 (AEST) Message-ID: <1461151559.2643.65.camel@neuling.org> Subject: Re: [V2, 68/68] powerpc/mm/radix: Use firmware feature to disable radix From: Michael Neuling To: Michael Ellerman , "Aneesh Kumar K.V" , benh@kernel.crashing.org, paulus@samba.org Cc: linuxppc-dev@lists.ozlabs.org, Stewart Smith , oliveroh Date: Wed, 20 Apr 2016 21:25:59 +1000 In-Reply-To: <3qqRSV5jq0z9sRB@ozlabs.org> References: <3qqRSV5jq0z9sRB@ozlabs.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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. >=20 > I think we might want to be more careful here. >=20 > You set MMU_FTR_RADIX in the cputable entry. So it's on by default on P9 = cpus. >=20 > Then if there is an ibm,pa-features property *and* it is >=3D 41 bytes lo= ng, the > below feature entry will hit. In that case the firmware controls whether = it's on > or off. >=20 > I think it would be clearer if we removed RADIX from the cputable, and th= e 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 >=20 > > 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}, >=20 > So that says bit 0 of byte 40 enables MMU_FTR_RADIX. Where is that docume= nted? >=20 > cheers > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev