Re: [PATCH RFC v2 2/2] pmdomain: core: use DT map to support hierarchy

[Rob Herring <robh@kernel.org>]

On Wed, May 28, 2025 at 02:58:52PM -0700, Kevin Hilman wrote:
> Currently, PM domains can only support hierarchy for simple
> providers (e.g. ones with #power-domain-cells = 0).
> 
> Add support for oncell providers as well by adding support for a nexus
> node map, as described in section 2.5.1 of the DT spec.
> 
> For example, an SCMI PM domain provider might be a subdomain of
> multiple parent domains. In this example, the parent domains are
> MAIN_PD and WKUP_PD:
> 
>     scmi_pds: protocol@11 {
>         reg = <0x11>;
>         #power-domain-cells = <1>;
>         power-domain-map = <15 &MAIN_PD>,
>                            <19 &WKUP_PD>;
>     };
> 
> With the new map, child domain 15 (scmi_pds 15) becomes a
> subdomain of MAIN_PD, and child domain 19 (scmi_pds 19) becomes a
> subdomain of WKUP_PD.
> 
> Signed-off-by: Kevin Hilman <khilman@baylibre.com>
> ---
>  drivers/pmdomain/core.c | 166 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 166 insertions(+)
> 
> diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c
> index d6c1ddb807b2..b8e505516f3d 100644
> --- a/drivers/pmdomain/core.c
> +++ b/drivers/pmdomain/core.c
> @@ -2441,6 +2441,9 @@ static LIST_HEAD(of_genpd_providers);
>  /* Mutex to protect the list above. */
>  static DEFINE_MUTEX(of_genpd_mutex);
>  
> +static int of_genpd_parse_domains_map(struct device_node *np,
> +				      struct genpd_onecell_data *data);
> +
>  /**
>   * genpd_xlate_simple() - Xlate function for direct node-domain mapping
>   * @genpdspec: OF phandle args to map into a PM domain
> @@ -2635,6 +2638,14 @@ int of_genpd_add_provider_onecell(struct device_node *np,
>  	if (ret < 0)
>  		goto error;
>  
> +	/* Parse power-domains-map property for Nexus node mapping */
> +	ret = of_genpd_parse_domains_map(np, data);
> +	if (ret < 0 && ret != -ENOENT) {
> +		pr_err("Failed to parse power-domains-map for %pOF: %d\n", np, ret);
> +		of_genpd_del_provider(np);
> +		goto error;
> +	}
> +
>  	return 0;
>  
>  error:
> @@ -2734,6 +2745,161 @@ static struct generic_pm_domain *genpd_get_from_provider(
>  	return genpd;
>  }
>  
> +/**
> + * of_genpd_parse_domains_map() - Parse power-domains-map property for Nexus mapping
> + * @np: Device node pointer associated with the PM domain provider.
> + * @data: Pointer to the onecell data associated with the PM domain provider.
> + *
> + * Parse the power-domains-map property to establish parent-child relationships
> + * for PM domains using Nexus node mapping as defined in the device tree
> + * specification section v2.5.1.
> + *
> + * The power-domains-map property format is:
> + * power-domains-map = <child_specifier target_phandle [target_specifier]>, ...;
> + *
> + * Where:
> + * - child_specifier: The child domain ID that should be mapped
> + * - target_phandle: Phandle to the parent PM domain provider
> + * - target_specifier: Optional arguments for the parent provider (if it has #power-domain-cells > 0)
> + *
> + * Returns 0 on success, -ENOENT if property doesn't exist, or negative error code.
> + */
> +static int of_genpd_parse_domains_map(struct device_node *np,
> +				      struct genpd_onecell_data *data)
> +{
> +	struct of_phandle_args parent_args;
> +	struct generic_pm_domain *parent_genpd, *child_genpd;
> +	u32 *map_entries;
> +	int map_len, child_cells, i, ret;
> +	u32 child_id;
> +
> +	/* Check if power-domains-map property exists */
> +	map_len = of_property_count_u32_elems(np, "power-domains-map");
> +	if (map_len <= 0)
> +		return -ENOENT;

Don't implement your own map parsing. Use or extend 
of_parse_phandle_with_args_map().

Rob