From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>,
Michael Neuling <mikey@neuling.org>,
Nicholas Piggin <npiggin@gmail.com>,
Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>,
Akshay Adiga <akshay.adiga@linux.vnet.ibm.com>
Cc: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [v3, 1/2] powernv/powerpc:Save/Restore additional SPRs for stop4 cpuidle
Date: Mon, 7 Aug 2017 20:41:53 +1000 (AEST) [thread overview]
Message-ID: <3xQvGp1NXbz9tWT@ozlabs.org> (raw)
In-Reply-To: <57ed82bcd92cd4d0af7ae5113710d597a331c433.1500631040.git.ego@linux.vnet.ibm.com>
On Fri, 2017-07-21 at 10:41:37 UTC, "Gautham R. Shenoy" wrote:
> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
>
> The stop4 idle state on POWER9 is a deep idle state which loses
> hypervisor resources, but whose latency is low enough that it can be
> exposed via cpuidle.
>
> Until now, the deep idle states which lose hypervisor resources (eg:
> winkle) were only exposed via CPU-Hotplug. Hence currently on wakeup
> from such states, barring a few SPRs which need to be restored to
> their older value, rest of the SPRS are reinitialized to their values
> corresponding to that at boot time.
>
> When stop4 is used in the context of cpuidle, we want these additional
> SPRs to be restored to their older value, to ensure that the context
> on the CPU coming back from idle is same as it was before going idle.
>
> In this patch, we define a SPR save area in PACA (since we have used
> up the volatile register space in the stack) and on POWER9, we restore
> SPRN_PID, SPRN_LDBAR, SPRN_FSCR, SPRN_HFSCR, SPRN_MMCRA, SPRN_MMCR1,
> SPRN_MMCR2 to the values they had before entering stop.
>
> Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Series applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/e1c1cfed54326fd2b17c78f0c85092
cheers
next prev parent reply other threads:[~2017-08-07 10:41 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-21 10:41 [v3 PATCH 0/2] powerpc: powernv: Enable stop4 via cpuidle Gautham R. Shenoy
2017-07-21 10:41 ` [v3 PATCH 1/2] powernv/powerpc:Save/Restore additional SPRs for stop4 cpuidle Gautham R. Shenoy
2017-07-26 10:38 ` Nicholas Piggin
2017-08-01 10:56 ` Michael Ellerman
2017-08-07 5:23 ` Gautham R Shenoy
2017-08-07 8:26 ` Michael Ellerman
2017-08-07 14:56 ` Gautham R Shenoy
2017-08-07 10:41 ` Michael Ellerman [this message]
2017-07-21 11:01 ` [RESEND] [v3 PATCH 2/2] powernv/powerpc: Clear PECE1 in LPCR via stop-api only on Hotplug Gautham R. Shenoy
2017-07-26 10:40 ` Nicholas Piggin
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