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