[PATCH 2/2] powerpc/powernv: Enable POWER8 doorbell IPIs

[Michael Neuling]

On Wed, 2014-06-04 at 18:03 +1000, Michael Ellerman wrote:
> On Mon, 2014-06-02 at 16:57 +1000, Michael Neuling wrote:
> > This patch enables POWER8 doorbell IPIs on powernv.
> > 
> > Since doorbells can only IPI within a core, we test to see when we can use
> > doorbells and if not we fall back to XICS.  This also enables hypervisor
> > doorbells to wakeup us up from nap/sleep via the LPCR PECEDH bit.
> > 
> > Based on tests by Anton, the best case IPI latency between two threads dropped
> > from 894ns to 512ns.
> > 
> > Signed-off-by: Michael Neuling <mikey at neuling.org>
> > ---
> >  arch/powerpc/kernel/cpu_setup_power.S | 2 ++
> >  arch/powerpc/platforms/powernv/smp.c  | 6 ++++++
> >  arch/powerpc/sysdev/xics/icp-native.c | 9 ++++++++-
> >  3 files changed, 16 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/powerpc/kernel/cpu_setup_power.S b/arch/powerpc/kernel/cpu_setup_power.S
> > index 1557e7c..4673353 100644
> > --- a/arch/powerpc/kernel/cpu_setup_power.S
> > +++ b/arch/powerpc/kernel/cpu_setup_power.S
> > @@ -56,6 +56,7 @@ _GLOBAL(__setup_cpu_power8)
> >  	li	r0,0
> >  	mtspr	SPRN_LPID,r0
> >  	mfspr	r3,SPRN_LPCR
> > +	ori	r3, r3, LPCR_PECEDH
> >  	bl	__init_LPCR
> >  	bl	__init_HFSCR
> >  	bl	__init_tlb_power8
> > @@ -74,6 +75,7 @@ _GLOBAL(__restore_cpu_power8)
> >  	li	r0,0
> >  	mtspr	SPRN_LPID,r0
> >  	mfspr   r3,SPRN_LPCR
> > +	ori	r3, r3, LPCR_PECEDH
> >  	bl	__init_LPCR
> >  	bl	__init_HFSCR
> >  	bl	__init_tlb_power8
> > diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c
> > index 0062a43..5fcfcf4 100644
> > --- a/arch/powerpc/platforms/powernv/smp.c
> > +++ b/arch/powerpc/platforms/powernv/smp.c
> > @@ -32,6 +32,7 @@
> >  #include <asm/opal.h>
> >  #include <asm/runlatch.h>
> >  #include <asm/code-patching.h>
> > +#include <asm/dbell.h>
> >  
> >  #include "powernv.h"
> >  
> > @@ -46,6 +47,11 @@ static void pnv_smp_setup_cpu(int cpu)
> >  {
> >  	if (cpu != boot_cpuid)
> >  		xics_setup_cpu();
> > +
> > +#ifdef CONFIG_PPC_DOORBELL
> > +	if (cpu_has_feature(CPU_FTR_DBELL))
> > +		doorbell_setup_this_cpu();
> > +#endif
> >  }
> 
> Where does CONFIG_PPC_DOORBELL get set?

No where.

> It looks like the only place you can be getting it is from CONFIG_PPC_PSERIES.
> If you build a POWERNV only kernel it will get disabled, which I don't think is
> what we want.
> 
> I think we should select it for POWERNV as well as PSERIES. That would mean
> it's always enabled for any build of the files you touch, so you shouldn't need
> the #ifdefs.

Ok, I'll add and resend.

Mikey