Re: [PATCH v3 11/11] cxl: Enable AMD Zen5 address translation using ACPI PRMT

[Gregory Price]

On Fri, Sep 12, 2025 at 04:45:13PM +0200, Robert Richter wrote:
> +static void cxl_prm_init(struct cxl_port *port)
> +{
> +	u64 spa;
> +	struct prm_cxl_dpa_spa_data data = { .out = &spa, };
> +	int rc;
> +
> +	if (!check_prm_address_translation(port))
> +		return;
> +
> +	/* Check kernel (-EOPNOTSUPP) and firmware support (-ENODEV) */
> +	rc = acpi_call_prm_handler(prm_cxl_dpa_spa_guid, &data);
> +	if (rc == -EOPNOTSUPP || rc == -ENODEV)
> +		return;
> +
> +	port->to_hpa = cxl_prm_to_hpa;
> +
> +	dev_dbg(port->host_bridge, "PRM address translation enabled for %s.\n",
> +		dev_name(&port->dev));
> +}

Is it possible that the PRMT function is present but uninitialize?
For example if expanders are not in a normalized address mode.

This code would likely still add the to_hpa() function reference even
if the underlying PRMT function hasn't been set up for translation.

~Gregory