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Subject: Re: [PATCH v3 1/6] powerpc/mm: any thread in one core can be the
 first to setup TLB1
From: Scott Wood <scottwood@freescale.com>
To: Chenhui Zhao <chenhui.zhao@freescale.com>, Denis Kirjanov
 <kda@linux-powerpc.org>
CC: <linuxppc-dev@lists.ozlabs.org>
Date: Wed, 23 Dec 2015 15:27:53 -0600
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On Thu, 2015-12-03 at 19:27 +0800, Chenhui Zhao wrote:
> 
> On Wed, Dec 2, 2015 at 8:12 PM, Denis Kirjanov <kda@linux-powerpc.org> 
> wrote:
> > On 11/20/15, Chenhui Zhao <chenhui.zhao@freescale.com> wrote:
> > >  On e6500, in the case of cpu hotplug, either thread in one core
> > >  may be the first thread initilzing the TLB1. The subsequent threads
> > >  must not setup it again.
> > > 
> > >  The code is derived from the comment of Scott Wood.
> > > 
> > >  Signed-off-by: Chenhui Zhao <chenhui.zhao@freescale.com>
> > >  ---
> > >   arch/powerpc/include/asm/cputhreads.h | 7 +++++++
> > >   arch/powerpc/mm/tlb_nohash.c          | 4 +---
> > >   2 files changed, 8 insertions(+), 3 deletions(-)
> > > 
> > >  diff --git a/arch/powerpc/include/asm/cputhreads.h
> > >  b/arch/powerpc/include/asm/cputhreads.h
> > >  index ba42e46..b56cece 100644
> > >  --- a/arch/powerpc/include/asm/cputhreads.h
> > >  +++ b/arch/powerpc/include/asm/cputhreads.h
> > >  @@ -94,6 +94,13 @@ static inline int cpu_last_thread_sibling(int 
> > > cpu)
> > >   	return cpu | (threads_per_core - 1);
> > >   }
> > > 
> > >  +static inline u32 get_tensr(void)
> > >  +{
> > >  +	if (cpu_has_feature(CPU_FTR_SMT))
> > >  +		return mfspr(SPRN_TENSR);
> > >  +	else
> > >  +		return 1;
> > >  +}
> > If i get it right, SPRN_TENSR used in the code only if CONFIG_PPC64
> > is defined. Then we can make it noop on ppc32.
> > 
> > Thanks!
> 
> Yeah, SPRN_TENSR is defined when CONFIG_BOOKE or CONFIG_40x is enabled. 
> I'd like to change the code like:
> 
> static inline u32 get_tensr(void)
> {
> #ifdef CONFIG_BOOKE
>         if (cpu_has_feature(CPU_FTR_SMT))
>                 return mfspr(SPRN_TENSR);
> #endif
>         return 1;
> }

Are you going to respin?

-Scott