Re: [PATCH v2 2/3] powerpc/powernv/idle: save-restore DAWR0,DAWRX0 for P10

[Pratik Sampat]

On 24/07/20 6:55 am, Michael Neuling wrote:
> On Fri, 2020-07-10 at 10:52 +0530, Pratik Rajesh Sampat wrote:
> > Additional registers DAWR0, DAWRX0 may be lost on Power 10 for
> > stop levels < 4.
> > Therefore save the values of these SPRs before entering a  "stop"
> > state and restore their values on wakeup.
> >
> > Signed-off-by: Pratik Rajesh Sampat <psampat@xxxxxxxxxxxxx>
> > ---
> >   arch/powerpc/platforms/powernv/idle.c | 10 ++++++++++
> >   1 file changed, 10 insertions(+)
> >
> > diff --git a/arch/powerpc/platforms/powernv/idle.c
> > b/arch/powerpc/platforms/powernv/idle.c
> > index 19d94d021357..f2e2a6a4c274 100644
> > --- a/arch/powerpc/platforms/powernv/idle.c
> > +++ b/arch/powerpc/platforms/powernv/idle.c
> > @@ -600,6 +600,8 @@ struct p9_sprs {
> >   	u64 iamr;
> >   	u64 amor;
> >   	u64 uamor;
> > +	u64 dawr0;
> > +	u64 dawrx0;
> >   };
> >   
> >   static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
> > @@ -687,6 +689,10 @@ static unsigned long power9_idle_stop(unsigned long
> > psscr, bool mmu_on)
> >   	sprs.iamr	= mfspr(SPRN_IAMR);
> >   	sprs.amor	= mfspr(SPRN_AMOR);
> >   	sprs.uamor	= mfspr(SPRN_UAMOR);
> > +	if (cpu_has_feature(CPU_FTR_ARCH_31)) {

You are actually viewing an old version of the patches
The main point of change were based on comments from Nick Piggin, I
have changed the top level function check from ARCH_300 to a P9 PVR
check instead.

A similar thing needs to be done for P10, however as the P10 PVR isn't
exposed yet, I've shelved this particular patch.

Nick's comment to check based on PVR:https://lkml.org/lkml/2020/7/13/1018
v4 of the series:https://lkml.org/lkml/2020/7/21/784

Thanks for your review,
Pratik

> Can you add a comment here saying even though DAWR0 is ARCH_30, it's only
> required to be saved on 31. Otherwise this looks pretty odd.
>
> > +		sprs.dawr0 = mfspr(SPRN_DAWR0);
> > +		sprs.dawrx0 = mfspr(SPRN_DAWRX0);
> > +	}
> >   
> >   	srr1 = isa300_idle_stop_mayloss(psscr);		/* go idle */
> >   
> > @@ -710,6 +716,10 @@ static unsigned long power9_idle_stop(unsigned long
> > psscr, bool mmu_on)
> >   		mtspr(SPRN_IAMR,	sprs.iamr);
> >   		mtspr(SPRN_AMOR,	sprs.amor);
> >   		mtspr(SPRN_UAMOR,	sprs.uamor);
> > +		if (cpu_has_feature(CPU_FTR_ARCH_31)) {
> > +			mtspr(SPRN_DAWR0, sprs.dawr0);
> > +			mtspr(SPRN_DAWRX0, sprs.dawrx0);
> > +		}
> >   
> >   		/*
> >   		 * Workaround for POWER9 DD2.0, if we lost resources, the ERAT