From: Gautham R Shenoy <ego@linux.vnet.ibm.com>
To: Pratik Rajesh Sampat <psampat@linux.ibm.com>
Cc: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org, benh@kernel.crashing.org,
paulus@samba.org, ego@linux.vnet.ibm.com, svaidy@linux.ibm.com,
pratik.r.sampat@gmail.com,
Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Subject: Re: [PATCH 2/2] powerpc/powernv/idle: save-restore DAWR0,DAWRX0 for P10
Date: Thu, 9 Jul 2020 14:39:48 +0530 [thread overview]
Message-ID: <20200709090948.GB24354@in.ibm.com> (raw)
In-Reply-To: <20200703124640.42820-2-psampat@linux.ibm.com>
On Fri, Jul 03, 2020 at 06:16:40PM +0530, Pratik Rajesh Sampat wrote:
> Additional registers DAWR0, DAWRX0 may be lost on Power 10 for
> stop levels < 4.
Adding Ravi Bangoria <ravi.bangoria@linux.ibm.com> to the cc.
> 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>
The saving and restoration looks good to me.
> ---
> 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..471d4a65b1fa 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)
> @@ -677,6 +679,10 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
> sprs.tscr = mfspr(SPRN_TSCR);
> if (!firmware_has_feature(FW_FEATURE_ULTRAVISOR))
> sprs.ldbar = mfspr(SPRN_LDBAR);
> + if (cpu_has_feature(CPU_FTR_ARCH_31)) {
> + sprs.dawr0 = mfspr(SPRN_DAWR0);
> + sprs.dawrx0 = mfspr(SPRN_DAWRX0);
> + }
>
But this is within the if condition which says
if ((psscr & PSSCR_RL_MASK) >= pnv_first_spr_loss_level)
This if condition is meant for stop4 and stop5 since these are stop
levels that have OPAL_PM_LOSE_HYP_CONTEXT set.
Since we can lose DAWR*, on states that lose limited hypervisor
context, such as stop0-2, we need to unconditionally save them
like AMR, IAMR etc.
> sprs_saved = true;
>
> @@ -792,6 +798,10 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
> mtspr(SPRN_MMCR2, sprs.mmcr2);
> if (!firmware_has_feature(FW_FEATURE_ULTRAVISOR))
> mtspr(SPRN_LDBAR, sprs.ldbar);
> + if (cpu_has_feature(CPU_FTR_ARCH_31)) {
> + mtspr(SPRN_DAWR0, sprs.dawr0);
> + mtspr(SPRN_DAWRX0, sprs.dawrx0);
> + }
Likewise, we need to unconditionally restore these SPRs.
>
> mtspr(SPRN_SPRG3, local_paca->sprg_vdso);
>
> --
> 2.25.4
>
next prev parent reply other threads:[~2020-07-09 10:58 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-03 12:46 [PATCH 1/2] powerpc/powernv/idle: Exclude mfspr on HID1,4,5 on P9 and above Pratik Rajesh Sampat
2020-07-03 12:46 ` [PATCH 2/2] powerpc/powernv/idle: save-restore DAWR0,DAWRX0 for P10 Pratik Rajesh Sampat
2020-07-09 9:09 ` Gautham R Shenoy [this message]
2020-07-09 11:21 ` Pratik Sampat
2020-07-09 9:01 ` [PATCH 1/2] powerpc/powernv/idle: Exclude mfspr on HID1,4,5 on P9 and above Gautham R Shenoy
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