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

From: Gautham R Shenoy
Date: Wed May 25 2016 - 01:05:51 EST


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@xxxxxxxxxxxxxxxxxx>

--
Thanks and Regards
gautham.