pmdomain: core: add support for power-domains-child-ids

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 a new property
`power-domains-child-ids` to describe the parent/child relationship.

For example, an SCMI PM domain provider has multiple domains, each of
which might be a child of diffeent 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-domains = <&MAIN_PD>, <&WKUP_PD>;
        power-domains-child-ids = <15>, <19>;
    };

With this example using the new property, SCMI PM domain 15 becomes a
child domain of MAIN_PD, and SCMI domain 19 becomes a child domain of
WKUP_PD.

To support this feature, add two new core functions

- of_genpd_add_child_ids()
- of_genpd_remove_child_ids()

which can be called by pmdomain providers to add/remove child domains
if they support the new property power-domains-child-ids.

The add function is "all or nothing".  If it cannot add all of the
child domains in the list, it will unwind any additions already made
and report a failure.

Signed-off-by: Kevin Hilman (TI) <khilman@baylibre.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

1 files changed, 167 insertions, 0 deletions

diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c
index 71e930e80178..f7731270015d 100644
--- a/drivers/pmdomain/core.c
+++ b/drivers/pmdomain/core.c
@@ -2925,6 +2925,173 @@ static struct generic_pm_domain *genpd_get_from_provider(
 }
 
 /**
+ * of_genpd_add_child_ids() - Parse power-domains-child-ids property
+ * @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 and power-domains-child-ids properties to establish
+ * parent-child relationships for PM domains. The power-domains property lists
+ * parent domains, and power-domains-child-ids lists which child domain IDs
+ * should be associated with each parent.
+ *
+ * Uses "all or nothing" semantics: either all relationships are established
+ * successfully, or none are (any partially-added relationships are unwound
+ * on error).
+ *
+ * Returns the number of parent-child relationships established on success,
+ * 0 if the properties don't exist, or a negative error code on failure.
+ */
+int of_genpd_add_child_ids(struct device_node *np,
+			   struct genpd_onecell_data *data)
+{
+	struct of_phandle_args parent_args;
+	struct generic_pm_domain *parent_genpd, *child_genpd;
+	struct generic_pm_domain **pairs; /* pairs[2*i]=parent, pairs[2*i+1]=child */
+	u32 child_id;
+	int i, ret, count, child_count, added = 0;
+
+	/* Check if both properties exist */
+	count = of_count_phandle_with_args(np, "power-domains", "#power-domain-cells");
+	if (count <= 0)
+		return 0;
+
+	child_count = of_property_count_u32_elems(np, "power-domains-child-ids");
+	if (child_count < 0)
+		return 0;
+	if (child_count != count)
+		return -EINVAL;
+
+	/* Allocate tracking array for error unwind (parent/child pairs) */
+	pairs = kmalloc_array(count * 2, sizeof(*pairs), GFP_KERNEL);
+	if (!pairs)
+		return -ENOMEM;
+
+	for (i = 0; i < count; i++) {
+		ret = of_property_read_u32_index(np, "power-domains-child-ids",
+						 i, &child_id);
+		if (ret)
+			goto err_unwind;
+
+		/* Validate child ID is within bounds */
+		if (child_id >= data->num_domains) {
+			pr_err("Child ID %u out of bounds (max %u) for %pOF\n",
+			       child_id, data->num_domains - 1, np);
+			ret = -EINVAL;
+			goto err_unwind;
+		}
+
+		/* Get the child domain */
+		child_genpd = data->domains[child_id];
+		if (!child_genpd) {
+			pr_err("Child domain %u is NULL for %pOF\n", child_id, np);
+			ret = -EINVAL;
+			goto err_unwind;
+		}
+
+		ret = of_parse_phandle_with_args(np, "power-domains",
+						 "#power-domain-cells", i,
+						 &parent_args);
+		if (ret)
+			goto err_unwind;
+
+		/* Get the parent domain */
+		parent_genpd = genpd_get_from_provider(&parent_args);
+		of_node_put(parent_args.np);
+		if (IS_ERR(parent_genpd)) {
+			pr_err("Failed to get parent domain for %pOF: %ld\n",
+			       np, PTR_ERR(parent_genpd));
+			ret = PTR_ERR(parent_genpd);
+			goto err_unwind;
+		}
+
+		/* Establish parent-child relationship */
+		ret = pm_genpd_add_subdomain(parent_genpd, child_genpd);
+		if (ret) {
+			pr_err("Failed to add child domain %u to parent in %pOF: %d\n",
+			       child_id, np, ret);
+			goto err_unwind;
+		}
+
+		/* Track for potential unwind */
+		pairs[2 * added] = parent_genpd;
+		pairs[2 * added + 1] = child_genpd;
+		added++;
+
+		pr_debug("Added child domain %u (%s) to parent %s for %pOF\n",
+			 child_id, child_genpd->name, parent_genpd->name, np);
+	}
+
+	kfree(pairs);
+	return count;
+
+err_unwind:
+	/* Reverse all previously established relationships */
+	while (added-- > 0)
+		pm_genpd_remove_subdomain(pairs[2 * added], pairs[2 * added + 1]);
+	kfree(pairs);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(of_genpd_add_child_ids);
+
+/**
+ * of_genpd_remove_child_ids() - Remove parent-child PM domain relationships
+ * @np: Device node pointer associated with the PM domain provider.
+ * @data: Pointer to the onecell data associated with the PM domain provider.
+ *
+ * Reverses the effect of of_genpd_add_child_ids() by parsing the same
+ * power-domains and power-domains-child-ids properties and calling
+ * pm_genpd_remove_subdomain() for each established relationship.
+ *
+ * Returns 0 on success, -ENOENT if properties don't exist, or negative error
+ * code on failure.
+ */
+int of_genpd_remove_child_ids(struct device_node *np,
+			   struct genpd_onecell_data *data)
+{
+	struct of_phandle_args parent_args;
+	struct generic_pm_domain *parent_genpd, *child_genpd;
+	u32 child_id;
+	int i, ret, count, child_count;
+
+	/* Check if both properties exist */
+	count = of_count_phandle_with_args(np, "power-domains", "#power-domain-cells");
+	if (count <= 0)
+		return -ENOENT;
+
+	child_count = of_property_count_u32_elems(np, "power-domains-child-ids");
+	if (child_count < 0)
+		return -ENOENT;
+	if (child_count != count)
+		return -EINVAL;
+
+	for (i = 0; i < count; i++) {
+		if (of_property_read_u32_index(np, "power-domains-child-ids",
+					       i, &child_id))
+			continue;
+
+		if (child_id >= data->num_domains || !data->domains[child_id])
+			continue;
+
+		ret = of_parse_phandle_with_args(np, "power-domains",
+						 "#power-domain-cells", i,
+						 &parent_args);
+		if (ret)
+			continue;
+
+		parent_genpd = genpd_get_from_provider(&parent_args);
+		of_node_put(parent_args.np);
+		if (IS_ERR(parent_genpd))
+			continue;
+
+		child_genpd = data->domains[child_id];
+		pm_genpd_remove_subdomain(parent_genpd, child_genpd);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(of_genpd_remove_child_ids);
+
+/**
  * of_genpd_add_device() - Add a device to an I/O PM domain
  * @genpdspec: OF phandle args to use for look-up PM domain
  * @dev: Device to be added.