Regions, power domains and voltage domains

[titan73]

What is the links between regions, power domains and voltage domains.

In upf module, the power domain area can be set with the upf command:

set_domain_area
    domain_name
    -area {llx lly urx ury}

I suppose the domain_name is the one created with create_power_domain

In odb module, a voltage domain can be created and its area set with the odb command:

create_voltage_domain
    domain_name
    -area {llx lly urx ury}

What is this the difference with a power domain?

Also in pdn module, voltages and regions are used with the pdn command:

set_voltage_domain
    -ground ground_net_name
    -name domain_name
    -power power_net_name
    [-region region_name]
    [-secondary_power secondary_power_net]
    [-switched_power switched_power_net]

The doc for name and region are:

-name | Defines the name of the voltage domain. The default is "Core" or region name if provided.
[-region] | Specifies a region of the design occupied by this voltage domain.

I don't know what are -name and -region.
Is -name the voltage domain created by create_voltage_domain?
I don't understand the "The default is "Core" or region name if provided". -name is not optional so there couldn't have a default values.
Also "region name if provided". The region provided by the option -region option?

A region must exists before the command called. How is region created?

I've seen recent commits where some C++ variables names are renamed from power_doamin to region.

Could someone clarify all this?

[maliberty]

@LucasYuki please clarify. I think some of this is historical as create_voltage_domain preceeded our ability to read UPF.

[titan73]

@LucasYuki Any idea?