linux-kernel - Re: [PATCH v3 7/9] powerpc/powernv: Add platform support for stop instruction

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Message-Id: <201605250212.u4P28ued046877@mx0a-001b2d01.pphosted.com>
Date:	Wed, 25 May 2016 07:42:17 +0530
From:	Shreyas B Prabhu <shreyas@...ux.vnet.ibm.com>
To:	Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>, mpe@...erman.id.au
CC:	linuxppc-dev@...ts.ozlabs.org, paulus@...abs.org,
	linux-kernel@...r.kernel.org, mikey@...ling.org,
	ego@...ux.vnet.ibm.com
Subject: Re: [PATCH v3 7/9] powerpc/powernv: Add platform support for stop
 instruction



On 05/24/2016 02:17 PM, Madhavan Srinivasan wrote:
> 
> 
> On Monday 23 May 2016 08:48 PM, Shreyas B. Prabhu wrote:
>> POWER ISA v3 defines a new idle processor core mechanism. In summary,
>>  a) new instruction named stop is added. This instruction replaces
>> 	instructions like nap, sleep, rvwinkle.
>>  b) new per thread SPR named PSSCR is added which controls the behavior
>> 	of stop instruction.
> 
> Kindly expand the register name at first use like
> Processor Stop Status and Control Register (PSSCR)
> 
>>
>> PSSCR has following key fields
> 
> Having the PSSCR layout here will help? something like this
> 
> ----------------------------------------------------------
> | PLS | /// | SD | ESL | EC | PSLL | /// | TR | MTL | RL |
> ----------------------------------------------------------
> 0      4     41   42    43   44     48    54   56    60  
> 
>> 	Bits 0:3  - Power-Saving Level Status. This field indicates the lowest
>> 	power-saving state the thread entered since stop instruction was last
>> 	executed.
>>
>> 	Bit 42 - Enable State Loss
>> 	0 - No state is lost irrespective of other fields
>> 	1 - Allows state loss
>>
>> 	Bits 44:47 - Power-Saving Level Limit
>> 	This limits the power-saving level that can be entered into.
>>
>> 	Bits 60:63 - Requested Level
>> 	Used to specify which power-saving level must be entered on executing
>> 	stop instruction
>>
>> This patch adds support for stop instruction and PSSCR handling.
>>
>> Signed-off-by: Shreyas B. Prabhu <shreyas@...ux.vnet.ibm.com>
>> ---

Hi Madhavan,

Thanks for the review. I have incorporated your review comments in v4.


Thanks,
Shreyas