[Sound-open-firmware] Generic power management layer

[Marcin Maka]

On 6/4/2020 6:27 PM, Daniel Baluta wrote:
> 
> On 04.06.2020 19:20, Sridharan, Ranjani wrote:
>> On Thu, 2020-06-04 at 17:42 +0300, Daniel Baluta wrote:
>>> Hi Liam, Ranjani,
>>>
>>> I am now looking at implementing the PM features
>>> on i.MX platforms and I have some questions.
>>>
>>> 1) Where can I find some documentation about the SHIM
>>> layer PM related registers.
>> Hi Daniel,
>>
>> I am afraid the documentation related to these registers in Intel
>> confidential and cannot be shared externally.
>>> e.g apollolake/include/platform/lib/shim.h:
>>>
>>> #define SHIM_PWRCTL              0
>>>
>>> 2) I am looking if it makes sense to have some generic Xtensa
>>> code to put the core in reset at PM suspend. I have seen this
>>> registers:
>>>
>>> arch/xtensa/include/xtensa/xdm-regs.h:
>>> #define PWRCTL_CORE_RESET
>> But these are platform-specific registers and should be done in the
>> platform-specific code isnt it?
>>
> It is my impression that PWRCTL_* registers from
> 
> src/xtensa/include/xtensa/xdm-regs are not platform specific
> 
> but Xtensa arch specific. So, in theory because NXP/Intel
> 
> use the same architecture we could design some basic generic
> 
> PM functions.
> 

Both common PM flows implemented in the generic layer as well as Intel 
specific mechanisms are documented here

https://thesofproject.github.io/latest/developer_guides/firmware/pm-runtime/index.html

We do not use any Xtensa registers directly. All PM on Intel platforms, 
including things I was talking about during the last TSC meeting, is 
done via shim registers which are platform specific.

Regards,
Marcin

> 
> Anyhow, for now I will concentrate on NXP specific stuff.
> 
> 
> Thanks a lot for your answer.
> 
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