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Groups > linux.kernel > #1527799 > unrolled thread

[PATCH] powernv: Clear SPRN_PSSCR when a POWER9 CPU comes online

Started by"Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
First post2016-11-22 19:10 +0100
Last post2016-11-23 01:40 +0100
Articles 4 — 3 participants

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  [PATCH] powernv: Clear SPRN_PSSCR when a POWER9 CPU comes online "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> - 2016-11-22 19:10 +0100
    Re: [PATCH] powernv: Clear SPRN_PSSCR when a POWER9 CPU comes online Michael Ellerman <mpe@ellerman.id.au> - 2016-11-23 00:40 +0100
      Re: [PATCH] powernv: Clear SPRN_PSSCR when a POWER9 CPU comes online Michael Neuling <mikey@neuling.org> - 2016-11-23 00:40 +0100
    Re: [PATCH] powernv: Clear SPRN_PSSCR when a POWER9 CPU comes online Michael Neuling <mikey@neuling.org> - 2016-11-23 01:40 +0100

#1527799 — [PATCH] powernv: Clear SPRN_PSSCR when a POWER9 CPU comes online

From"Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
Date2016-11-22 19:10 +0100
Subject[PATCH] powernv: Clear SPRN_PSSCR when a POWER9 CPU comes online
Message-ID<sGnG2-2it-9@gated-at.bofh.it>
From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>

Ensure that PSSCR is set to a safe value corresponding to no
state-loss each time a POWER9 CPU comes online.

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
---
 arch/powerpc/kernel/cpu_setup_power.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/powerpc/kernel/cpu_setup_power.S b/arch/powerpc/kernel/cpu_setup_power.S
index 52ff3f0..37ad045 100644
--- a/arch/powerpc/kernel/cpu_setup_power.S
+++ b/arch/powerpc/kernel/cpu_setup_power.S
@@ -96,6 +96,7 @@ _GLOBAL(__setup_cpu_power9)
 	mtlr	r11
 	beqlr
 	li	r0,0
+	mtspr	SPRN_PSSCR,r0
 	mtspr	SPRN_LPID,r0
 	mfspr	r3,SPRN_LPCR
 	ori	r3, r3, LPCR_PECEDH
@@ -116,6 +117,7 @@ _GLOBAL(__restore_cpu_power9)
 	mtlr	r11
 	beqlr
 	li	r0,0
+	mtspr	SPRN_PSSCR,r0
 	mtspr	SPRN_LPID,r0
 	mfspr   r3,SPRN_LPCR
 	ori	r3, r3, LPCR_PECEDH
-- 
1.9.4

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#1528025

FromMichael Ellerman <mpe@ellerman.id.au>
Date2016-11-23 00:40 +0100
Message-ID<sGsPn-5rk-3@gated-at.bofh.it>
In reply to#1527799
"Gautham R. Shenoy" <ego@linux.vnet.ibm.com> writes:

> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
>
> Ensure that PSSCR is set to a safe value corresponding to no
> state-loss each time a POWER9 CPU comes online.

Is this a bug fix? I can't tell from the change log.

cheers

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#1528027

FromMichael Neuling <mikey@neuling.org>
Date2016-11-23 00:40 +0100
Message-ID<sGsPo-5rk-11@gated-at.bofh.it>
In reply to#1528025
On Wed, 2016-11-23 at 10:30 +1100, Michael Ellerman wrote:
> "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> writes:
> 
> > From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
> > 
> > Ensure that PSSCR is set to a safe value corresponding to no
> > state-loss each time a POWER9 CPU comes online.
> 
> Is this a bug fix? I can't tell from the change log.

There are no known bugs it's fixing.  

It's just safer to run with a known default value, rather than what we randomly
inherit from previous firmware.

Mikey

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#1528045

FromMichael Neuling <mikey@neuling.org>
Date2016-11-23 01:40 +0100
Message-ID<sGtLs-63s-21@gated-at.bofh.it>
In reply to#1527799
On Tue, 2016-11-22 at 23:36 +0530, Gautham R. Shenoy wrote:
> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
> 
> Ensure that PSSCR is set to a safe value corresponding to no
> state-loss each time a POWER9 CPU comes online.
> 
> Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>

Tested here on my configuration... FWIW

Acked-By: Michael Neuling <mikey@neuling.org>

> ---
>  arch/powerpc/kernel/cpu_setup_power.S | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/cpu_setup_power.S
> b/arch/powerpc/kernel/cpu_setup_power.S
> index 52ff3f0..37ad045 100644
> --- a/arch/powerpc/kernel/cpu_setup_power.S
> +++ b/arch/powerpc/kernel/cpu_setup_power.S
> @@ -96,6 +96,7 @@ _GLOBAL(__setup_cpu_power9)
>  	mtlr	r11
>  	beqlr
>  	li	r0,0
> +	mtspr	SPRN_PSSCR,r0
>  	mtspr	SPRN_LPID,r0
>  	mfspr	r3,SPRN_LPCR
>  	ori	r3, r3, LPCR_PECEDH
> @@ -116,6 +117,7 @@ _GLOBAL(__restore_cpu_power9)
>  	mtlr	r11
>  	beqlr
>  	li	r0,0
> +	mtspr	SPRN_PSSCR,r0
>  	mtspr	SPRN_LPID,r0
>  	mfspr   r3,SPRN_LPCR
>  	ori	r3, r3, LPCR_PECEDH

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