Re: [PATCH] POWER9 PMU stops after idle workaround

[Anton Blanchard]

Hi Nick,

> POWER9 DD2 PMU can stop after a state-loss idle in some conditions.
> 
> A solution is to set then clear MMCRA[60] after wake from state-loss
> idle.

Looks good.

Acked-by: Anton Blanchard 

Anton

> Signed-off-by: Nicholas Piggin 
> ---
>  arch/powerpc/kernel/idle_book3s.S | 8 +++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/idle_book3s.S
> b/arch/powerpc/kernel/idle_book3s.S index 516ebef905c0..e6252c5a57a4
> 100644 --- a/arch/powerpc/kernel/idle_book3s.S
> +++ b/arch/powerpc/kernel/idle_book3s.S
> @@ -460,11 +460,17 @@ pnv_restore_hyp_resource_arch300:
>   /*
>* Workaround for POWER9, if we lost resources, the ERAT
>* might have been mixed up and needs flushing. We also need
> -  * to reload MMCR0 (see comment above).
> +  * to reload MMCR0 (see comment above). We also need to set
> +  * then clear bit 60 in MMCRA to ensure the PMU starts
> running. */
>   blt cr3,1f
>   PPC_INVALIDATE_ERAT
>   ld  r1,PACAR1(r13)
> + mfspr   r4,SPRN_MMCRA
> + ori r4,r4,(1 << (63-60))
> + mtspr   SPRN_MMCRA,r4
> + xorir4,r4,(1 << (63-60))
> + mtspr   SPRN_MMCRA,r4
>   ld  r4,_MMCR0(r1)
>   mtspr   SPRN_MMCR0,r4
>  1:

Re: [PATCH] POWER9 PMU stops after idle workaround

[Vaidyanathan Srinivasan]

* Nicholas Piggin  [2017-07-20 11:53:22]:

> POWER9 DD2 PMU can stop after a state-loss idle in some conditions.
> 
> A solution is to set then clear MMCRA[60] after wake from state-loss
> idle.
> 
> Signed-off-by: Nicholas Piggin 

Reviewed-by: Vaidyanathan Srinivasan 


> ---
>  arch/powerpc/kernel/idle_book3s.S | 8 +++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/idle_book3s.S 
> b/arch/powerpc/kernel/idle_book3s.S
> index 516ebef905c0..e6252c5a57a4 100644
> --- a/arch/powerpc/kernel/idle_book3s.S
> +++ b/arch/powerpc/kernel/idle_book3s.S
> @@ -460,11 +460,17 @@ pnv_restore_hyp_resource_arch300:
>   /*
>* Workaround for POWER9, if we lost resources, the ERAT
>* might have been mixed up and needs flushing. We also need
> -  * to reload MMCR0 (see comment above).
> +  * to reload MMCR0 (see comment above). We also need to set
> +  * then clear bit 60 in MMCRA to ensure the PMU starts running.
>*/
>   blt cr3,1f
>   PPC_INVALIDATE_ERAT
>   ld  r1,PACAR1(r13)
> + mfspr   r4,SPRN_MMCRA
> + ori r4,r4,(1 << (63-60))
> + mtspr   SPRN_MMCRA,r4
> + xorir4,r4,(1 << (63-60))
> + mtspr   SPRN_MMCRA,r4


Timing is ok to resolve the issue?  Does back-to-back bit flip of
MMCRA[60] gets the job done for all cases?  Just asking since this
issue in itself is a corner case ;)

--Vaidy

Re: [PATCH] POWER9 PMU stops after idle workaround

[Madhavan Srinivasan]

On Thursday 20 July 2017 07:23 AM, Nicholas Piggin wrote:

POWER9 DD2 PMU can stop after a state-loss idle in some conditions.

A solution is to set then clear MMCRA[60] after wake from state-loss
idle.

Acked-by: Madhavan Srinivasan 



Signed-off-by: Nicholas Piggin 
---
  arch/powerpc/kernel/idle_book3s.S | 8 +++-
  1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/idle_book3s.S 
b/arch/powerpc/kernel/idle_book3s.S
index 516ebef905c0..e6252c5a57a4 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -460,11 +460,17 @@ pnv_restore_hyp_resource_arch300:
/*
 * Workaround for POWER9, if we lost resources, the ERAT
 * might have been mixed up and needs flushing. We also need
-* to reload MMCR0 (see comment above).
+* to reload MMCR0 (see comment above). We also need to set
+* then clear bit 60 in MMCRA to ensure the PMU starts running.
 */
blt cr3,1f
PPC_INVALIDATE_ERAT
ld  r1,PACAR1(r13)
+   mfspr   r4,SPRN_MMCRA
+   ori r4,r4,(1 << (63-60))
+   mtspr   SPRN_MMCRA,r4
+   xorir4,r4,(1 << (63-60))
+   mtspr   SPRN_MMCRA,r4
ld  r4,_MMCR0(r1)
mtspr   SPRN_MMCR0,r4
  1:

[PATCH] POWER9 PMU stops after idle workaround

[Nicholas Piggin]

POWER9 DD2 PMU can stop after a state-loss idle in some conditions.

A solution is to set then clear MMCRA[60] after wake from state-loss
idle.

Signed-off-by: Nicholas Piggin 
---
 arch/powerpc/kernel/idle_book3s.S | 8 +++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/idle_book3s.S 
b/arch/powerpc/kernel/idle_book3s.S
index 516ebef905c0..e6252c5a57a4 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -460,11 +460,17 @@ pnv_restore_hyp_resource_arch300:
/*
 * Workaround for POWER9, if we lost resources, the ERAT
 * might have been mixed up and needs flushing. We also need
-* to reload MMCR0 (see comment above).
+* to reload MMCR0 (see comment above). We also need to set
+* then clear bit 60 in MMCRA to ensure the PMU starts running.
 */
blt cr3,1f
PPC_INVALIDATE_ERAT
ld  r1,PACAR1(r13)
+   mfspr   r4,SPRN_MMCRA
+   ori r4,r4,(1 << (63-60))
+   mtspr   SPRN_MMCRA,r4
+   xorir4,r4,(1 << (63-60))
+   mtspr   SPRN_MMCRA,r4
ld  r4,_MMCR0(r1)
mtspr   SPRN_MMCR0,r4
 1:
-- 
2.11.0