On Thu, May 31, 2018 at 08:23:04AM +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,enabled-stop-levels = <0xec000000>;
> ibm,cpu-idle-state-psscr-mask = <0x0 0x3003ff 0x0 0x3003ff>;
> ibm,cpu-idle-state-latencies-ns = <0x3e8 0x7d0>;
> ibm,cpu-idle-state-psscr = <0x0 0x330 0x0 0x300330>;
> ibm,cpu-idle-state-flags = <0x100000 0x101000>;
> ibm,cpu-idle-state-residency-ns = <0x2710 0x4e20>;
> ibm,idle-states {
> phandle = <0xff>;
> stop4 {
> flags = <0x207000>;
> compatible = "ibm,cpuidle-state-v1";
> psscr-mask = <0x0 0x3003ff>;
> handle = <0x102>;
> latency-ns = <0x186a0>;
> residency-ns = <0x989680>;
> psscr = <0x0 0x300374>;
> };
>
> ...
> stop11 {
> ...
> compatible = "ibm,cpuoffline-state-v1";
> ...
>
> };
> };
>
> Signed-off-by: Akshay Adiga <akshay.ad...@linux.vnet.ibm.com>
This is intended to be a RFC patch.
The skiboot patch for the device tree is posted here :
https://patchwork.ozlabs.org/patch/923120/
