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 <psam...@linux.ibm.com>
> ---
>  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)) {

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

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