[Skiboot] [PATCH v12 10/10] skiboot: Add documentation for IMC opal call

[Michael Neuling]

> OPAL_IMC_COUNTERS_INIT
> +==============================
> +OPAL call interface to initialize In-memory collection
> +infrastructure. Call does multiple scom writes on each
> +incavation for Core IMC initialization. And for the
> +Nest IMC, at this point, call is a no-op and returns
> +OPAL_SUCCESS.

So why doesn't skiboot do this itself?  

What happens on kexec where init() has already been called by the first kernel? 
Wouldn't that be similar to skiboot doing it itself?

> +
> +Parameters
> +----------
> +``uint32_t type``
> +  This parameter specifies the imc counter domain.
> +  The value should be 'OPAL_IMC_COUNTERS_CORE'
> +
> +``uint64_t addr``
> +  This parameter must have a non-zero value.
> +  This value must be a physical address of the core.
> +
> +``uint64_t cpu_pir``
> +  This parameter specifices target cpu pir
> +
> +Returns
> +-------
> +OPAL_PARAMETER - In case of  unsupported ``type``
> +OPAL_HARDWARE  - If any error in setting up the hardware.
> +OPAL_SUCCESS   - On succesfully initialized or even if init operation is a
> no-op.
> +
> +
> +OPAL_IMC_COUNTERS_START
> +============================
> +OPAL call interface for starting the In-Memory Collection
> +counters for a specified domain (NEST/CORE).
> +
> +Parameters
> +----------
> +``uint32_t type``
> + This parameter specifies the imc counter domain.
> + The value can be either 'OPAL_IMC_COUNTERS_NEST'
> + or 'OPAL_IMC_COUNTERS_CORE'

How do I know if this is going to work?  

What happens on the next generation where we have OPAL_IMC_COUNTERS_PONY?  How
do we know skiboot supports that call?

> +
> +Returns
> +-------
> +OPAL_PARAMETER - In case of  Unsupported ``type``
> +OPAL_HARDWARE  - If any error in setting up the hardware.
> +OPAL_SUCCESS   - On successful execution of the operation for the given
> ``type``.
> +
> +
> +OPAL_IMC_COUNTERS_STOP
> +===========================
> +OPAL call interface for stoping In-Memory
> +Collection counters for a specified domain (NEST/CORE).
> +STOP should always be called after a related START.
> +While STOP *may* run successfully without an associated
> +START call, this is not gaurenteed.
> +
> +Parameters
> +----------
> +``uint32_t type``
> + This parameter specifies the imc counter domain.
> + The value can be either 'OPAL_IMC_COUNTERS_NEST'
> + or 'OPAL_IMC_COUNTERS_CORE'
> +
> +Returns
> +-------
> +OPAL_PARAMETER - In case of  Unsupported ``type``
> +OPAL_HARDWARE  - If any error in setting up the hardware.
> +OPAL_SUCCESS   - On successful execution of the operation for the given
> ``type``.