[Skiboot] [RFC 1/1] SLW : Add new idle device-tree format

[Stewart Smith]

> On 25 Nov 2019, at 05:04, Klaus Heinrich Kiwi <klaus at linux.vnet.ibm.com> wrote:
> 
> On 11/17/2019 10:05 PM, Oliver O'Halloran wrote:
>>> On Fri, Aug 9, 2019 at 8:55 PM Abhishek Goel <huntbag at linux.vnet.ibm.com> wrote:
>>> Add stop states under ibm,idle-states in addition to the current array
>>> based device tree properties.
> I noted that Abhishek answered that a complete redesign will take place, but I couldn't help to ask...
>> How does the kernel know if one state node deeper than another? What
>> I'm really wondering is whether we need a reg for the individual
>> states e.g.:
>> 
>> stop at 11 {
>>  reg= <11>
>>  compatible="stop11-v1"
>>  ...
>> }
>> stop at 4 {
>>  reg = <4>;
>>  compatible="stop4-v1";
>>  ...
>> }
> 
> Your original patch apparently implies that stop states are naturally hierarchical (i.e., can only support stop4 if we support stop1, 2, 3). If that's the case, perhaps we should also have an hierarchical device-tree representation?

Kind of. The higher the stop number the higher the saving and latency (ie the deeper the stop), but there’s no reason that supported numbers are linear. Supporting only 0lite, 1, and 5 is possible.