linux-kernel - Re: [PATCH v4 08/10] powerpc/powernv: Add platform support for stop instruction

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Date:	Wed, 25 May 2016 10:35:36 +0530
From:	Gautham R Shenoy <ego@...ux.vnet.ibm.com>
To:	"Shreyas B. Prabhu" <shreyas@...ux.vnet.ibm.com>
Cc:	mpe@...erman.id.au, linuxppc-dev@...ts.ozlabs.org,
	paulus@...abs.org, linux-kernel@...r.kernel.org, mikey@...ling.org,
	ego@...ux.vnet.ibm.com, maddy@...ux.vnet.ibm.com
Subject: Re: [PATCH v4 08/10] powerpc/powernv: Add platform support for stop
 instruction

Hi Shreyas,

On Tue, May 24, 2016 at 06:45:12PM +0530, 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 Processor Stop Status and Control Register
> 	(PSSCR) is added which controls the behavior of stop instruction.
> 
> PSSCR layout:
> ----------------------------------------------------------
> | PLS | /// | SD | ESL | EC | PSLL | /// | TR | MTL | RL |
> ----------------------------------------------------------
> 0      4     41   42    43   44     48    54   56    60
> 
> PSSCR key fields:
> 	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.

This version looks good to me.

Reviewed-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>

--
Thanks and Regards
gautham.