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

2020-07-24 Thread Pratik Sampat 




On 24/07/20 6:55 am, Michael Neuling wrote:

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 
---
  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)) {


You are actually viewing an old version of the patches
The main point of change were based on comments from Nick Piggin, I
have changed the top level function check from ARCH_300 to a P9 PVR
check instead.

A similar thing needs to be done for P10, however as the P10 PVR isn't
exposed yet, I've shelved this particular patch.

Nick's comment to check based on PVR:https://lkml.org/lkml/2020/7/13/1018
v4 of the series:https://lkml.org/lkml/2020/7/21/784

Thanks for your review,
Pratik


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

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

2020-07-23 Thread Michael Neuling 
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 
> ---
>  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

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

2020-07-19 Thread Ravi Bangoria 

Hi Nick,

On 7/13/20 11:22 AM, Nicholas Piggin wrote:

Excerpts from Pratik Rajesh Sampat's message of July 10, 2020 3:22 pm:

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.


Hmm, where do you get this from? Documentation I see says DAWR is lost
on POWER9 but not P10.

Does idle thread even need to save DAWR, or does it get switched when
going to a thread that has a watchpoint set?


I don't know how idle states works internally but IIUC, we need to save/restore
DAWRs. This is needed when user creates per-cpu watchpoint event.

Ravi

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

2020-07-19 Thread Ravi Bangoria 

Hi Pratik,

On 7/10/20 10:52 AM, Pratik Rajesh Sampat wrote:

Additional registers DAWR0, DAWRX0 may be lost on Power 10 for
stop levels < 4.


p10 has one more pair DAWR1/DAWRX1. Please include that as well.

Ravi

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

2020-07-12 Thread Nicholas Piggin 
Excerpts from Pratik Rajesh Sampat's message of July 10, 2020 3:22 pm:
> 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.

Hmm, where do you get this from? Documentation I see says DAWR is lost
on POWER9 but not P10.

Does idle thread even need to save DAWR, or does it get switched when
going to a thread that has a watchpoint set?

Thanks,
Nick

> 
> Signed-off-by: Pratik Rajesh Sampat 
> ---
>  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)) {
> + 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
> -- 
> 2.25.4
> 
>

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

2020-07-09 Thread Pratik Rajesh Sampat 
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 
---
 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)) {
+   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
-- 
2.25.4