[PATCH v3 1/6] powerpc/mm: any thread in one core can be the first to setup TLB1

[Denis Kirjanov]

On 12/3/15, Scott Wood <scottwood at freescale.com> wrote:
> On Wed, 2015-12-02 at 15:12 +0300, Denis Kirjanov wrote:
>> On 11/20/15, Chenhui Zhao <chenhui.zhao at 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 at 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.
>
> Please don't.  It accomplishes nothing other than adding an obstacle to
> supporting this on ppc32.

The idea is make it noop since the function defined in header file and
some core parts include it like:

arch/powerpc/kernel/smp.c
arch/powerpc/kernel/setup-common.c


>
> -Scott
>
>