Subject: Re: [PATCH/RFC 00/14] R-Car X5H Ironhide SCMI CPG/MDLC remapping

From: Kevin Hilman <[email-masked]>
Date: Wed, 22 Apr 2026 15:48:37 -0700

Geert Uytterhoeven <[email-masked]> writes:

> 	Hi all,
>
> TL;DR:
>
>     Describe hardware in DT, and perform the mapping to SCMI in Linux.
>
> The Renesas R-Car X5H-based Ironhide board is the first Renesas
> SoC/board combination that implements the ARM System Control and
> Management Interface (SCMI).
>
> This means Linux can no longer perform various system operations (e.g.
> clock, power domain, and reset control) by accessing the hardware
> directly.  Instead, these operations are abstracted according to various
> SCMI sub-protocols, and Linux has to send messages to an SCMI-compliant
> firmware running on a System Control Processor (SCP).
> More specifically, the R-Car X5H SCP FW SCMI controls access to:
>   1. Core clocks and module clocks,
>   2. Module resets,
>   3. Power domains,

I'm very curious how power domain hierarchy is described on this SoC,
because one more issue to add to your list is that hierarchy cannot be
described for power domains in SCMI.

I know you're aware of it already, but just FYI for anyone else
exploring this space, I have a series[1] in-flight right now to address
this limitation of SCMI so that we can at least describe this hierarchy
in DT and the pmdomain framework.

Kevin

[1] https://lore.kernel.org/linux-pm/[email-masked]/