Re: [PATCH] [SCHEME 2]powernv/cpuidle: Add support for new idle state device-tree format

[Akshay Adiga]

On Thu, May 31, 2018 at 08:23:20AM +0530, Akshay Adiga wrote:
> This patch adds support for new device-tree format for idle state
> description.
> 
> Previously if a older kernel runs on a newer firmware, it may enable
> all available states irrespective of its capability of handling it.
> New device tree format adds a compatible flag, so that only kernel
> which has the capability to handle the version of stop state will enable
> it.
> 
> Older kernel will still see stop0 and stop0_lite in older format and we
> will depricate it after some time.
> 
> Idea is to bump up the version in firmware if we find a bug or
> regression in stop states. A fix will be provided in linux which would
> now know about the bumped up version of stop states, where as kernel
> without fixes would ignore the states.
> 
> New idle state device tree format :
> 
>     power-mgt {
>         ibm,cpu-idle-state-names = "stop0_lite", "stop0";
>         ibm,cpu-idle-state-residency-ns = <0x2710 0x4e20>;
>         ibm,cpu-idle-state-latencies-ns = <0x3e8 0x7d0>;
>         ibm,cpu-idle-state-psscr-mask = <0x0 0x3003ff 0x0 0x3003ff>;
>         ibm,cpu-idle-state-psscr = <0x0 0x330 0x0 0x300330>;
>         ibm,cpu-idle-state-flags = <0x100000 0x101000>;
>         ibm,enabled-stop-levels = <0xec000000>;
>         ibm,idle-states {
>           ibm,cpu-idle-state-names = "stop1", "stop2", "stop4", "stop5";
>           ibm,cpu-idle-state-residency-ns = <0xc350 0x186a0 0x989680
>     0x1312d00>;
>           ibm,cpu-idle-state-latencies-ns = <0x1388 0x2710 0x186a0
>     0x30d40>;
>           ibm,cpu-idle-state-psscr-mask = <0x0 0x3003ff 0x0 0x3003ff 0x0
>     0x3003ff 0x0 0x3003ff>;
>           ibm,cpu-idle-state-psscr = <0x0 0x300331 0x0 0x300332 0x0
>     0x300374 0x0 0x300375>;
>           ibm,cpu-idle-state-versions = "ibm,idle-state-v1
>     ", "ibm,idle-state-v1", "ibm,idle-state-v1", "ibm,idle-state-v1";
>           ibm,cpu-idle-state-flags = <0x101000 0x101000 0x207000
> 0x207000>;
>        }
>      }
> 
> Signed-off-by: Akshay Adiga <akshay.adiga@xxxxxxxxxxxxxxxxxx>
> ---

This patch is intended to be a RFC.
The skiboot patch has been posted here :
https://patchwork.ozlabs.org/patch/923121/