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[PATCH 07/10] ARC: [plat-eznps] disabled stall counter due to a HW bug

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  [PATCH 07/10] ARC: [plat-eznps] disabled stall counter due to a HW bug Noam Camus <noamca@mellanox.com> - 2017-05-25 04:40 +0200
    Re: [PATCH 07/10] ARC: [plat-eznps] disabled stall counter due to a  HW bug Alexey Brodkin <Alexey.Brodkin@synopsys.com> - 2017-05-25 13:20 +0200
      RE: [PATCH 07/10] ARC: [plat-eznps] disabled stall counter due to a  HW bug Noam Camus <noamca@mellanox.com> - 2017-05-25 13:20 +0200

#1650124 — [PATCH 07/10] ARC: [plat-eznps] disabled stall counter due to a HW bug

From: Noam Camus <noamca@mellanox.com>

This counter represents threshold for consecutive stall that which
trigger HW threads scheduling.
Low values of this counter cause downgrade in performance
and in the worst case even a livelock.

Signed-off-by: Noam Camus <noamca@mellanox.com>
---
 arch/arc/plat-eznps/mtm.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/arch/arc/plat-eznps/mtm.c b/arch/arc/plat-eznps/mtm.c
index aaaaffd..e0cb36b 100644
--- a/arch/arc/plat-eznps/mtm.c
+++ b/arch/arc/plat-eznps/mtm.c
@@ -119,8 +119,6 @@ void mtm_enable_core(unsigned int cpu)
 	mt_ctrl.value = 0;
 	mt_ctrl.hsen = 1;
 	mt_ctrl.hs_cnt = MT_CTRL_HS_CNT;
-	mt_ctrl.sten = 1;
-	mt_ctrl.st_cnt = MT_CTRL_ST_CNT;
 	mt_ctrl.mten = 1;
 	write_aux_reg(CTOP_AUX_MT_CTRL, mt_ctrl.value);
 
-- 
1.7.1

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#1650374 — Re: [PATCH 07/10] ARC: [plat-eznps] disabled stall counter due to a HW bug

Hi Noam,

On Thu, 2017-05-25 at 05:34 +0300, Noam Camus wrote:
> From: Noam Camus <noamca@mellanox.com>
> 
> This counter represents threshold for consecutive stall that which
> trigger HW threads scheduling.
> Low values of this counter cause downgrade in performance
> and in the worst case even a livelock.
> 
> Signed-off-by: Noam Camus <noamca@mellanox.com>
> ---
>  arch/arc/plat-eznps/mtm.c |    2 --
>  1 files changed, 0 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arc/plat-eznps/mtm.c b/arch/arc/plat-eznps/mtm.c
> index aaaaffd..e0cb36b 100644
> --- a/arch/arc/plat-eznps/mtm.c
> +++ b/arch/arc/plat-eznps/mtm.c
> @@ -119,8 +119,6 @@ void mtm_enable_core(unsigned int cpu)
>  	mt_ctrl.value = 0;
>  	mt_ctrl.hsen = 1;
>  	mt_ctrl.hs_cnt = MT_CTRL_HS_CNT;
> -	mt_ctrl.sten = 1;
> -	mt_ctrl.st_cnt = MT_CTRL_ST_CNT;

Even though I don't know your architecture this change doesn't
make enough sense to me in absence of better explanation of what is
really done here.

I.e. how removal of those 2 lines above improve your situation.

-Alexey

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#1650377 — RE: [PATCH 07/10] ARC: [plat-eznps] disabled stall counter due to a HW bug

>From: Alexey Brodkin [mailto:Alexey.Brodkin@synopsys.com] 
>Sent: Thursday, May 25, 2017 14:10 PM
...
>> diff --git a/arch/arc/plat-eznps/mtm.c b/arch/arc/plat-eznps/mtm.c 
>> index aaaaffd..e0cb36b 100644
>> --- a/arch/arc/plat-eznps/mtm.c
>> +++ b/arch/arc/plat-eznps/mtm.c
>> @@ -119,8 +119,6 @@ void mtm_enable_core(unsigned int cpu)
>>  	mt_ctrl.value = 0;
>>  	mt_ctrl.hsen = 1;
>>  	mt_ctrl.hs_cnt = MT_CTRL_HS_CNT;
>> -	mt_ctrl.sten = 1;
>> -	mt_ctrl.st_cnt = MT_CTRL_ST_CNT;

>Even though I don't know your architecture this change doesn't make enough sense to me in absence of better explanation of what is really done here.

>I.e. how removal of those 2 lines above improve your situation.
By removing 2 lines I am resorting to HW reset value where sten=0 i.e. feature is disabled.
I will rewrite the explanation

-Noam

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