From: Michael Ellerman <mpe@ellerman•id.au>
To: christophe leroy <christophe.leroy@c-s•fr>
Cc: Scott Wood <scottwood@freescale•com>,
Benjamin Herrenschmidt <benh@kernel•crashing.org>,
Paul Mackerras <paulus@samba•org>,
sojkam1@fel•cvut.cz, linux-kernel@vger•kernel.org,
linuxppc-dev@lists•ozlabs.org
Subject: Re: [PATCH v2] powerpc32: memcpy/memset: only use dcbz once cache is enabled
Date: Mon, 14 Sep 2015 19:59:10 +1000 [thread overview]
Message-ID: <1442224750.21802.2.camel@ellerman.id.au> (raw)
In-Reply-To: <55F3F701.5030303@c-s.fr>
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
next prev parent reply other threads:[~2015-09-14 9:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-10 6:41 [PATCH v2] powerpc32: memcpy/memset: only use dcbz once cache is enabled Christophe Leroy
2015-09-10 22:05 ` Scott Wood
2015-09-11 1:24 ` Michael Ellerman
2015-09-12 9:57 ` christophe leroy
2015-09-14 9:59 ` Michael Ellerman [this message]
2015-09-14 16:32 ` Scott Wood
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