[PATCH v9 12/13] powercap: arm_scmi: Add get_power_uw to synthetic node

[Philip Radford <philip.radford@arm.com>]

Exposes the current power usage from the immediate children of the
synthetic (root) powercap node. Iterates over pr->spzones and sums per-zone
power.

Signed-off-by: Philip Radford <philip.radford@arm.com>
---
V8->V9
- Removed redundant if (!pr) check from instance_root_get_power_uw()
- Stopped returning a partial sum if one child read fails
---
 drivers/powercap/arm_scmi_powercap.c | 34 ++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/powercap/arm_scmi_powercap.c b/drivers/powercap/arm_scmi_powercap.c
index b5397d7675e6..aac0b00490b2 100644
--- a/drivers/powercap/arm_scmi_powercap.c
+++ b/drivers/powercap/arm_scmi_powercap.c
@@ -17,6 +17,9 @@
 #define to_scmi_powercap_zone(z)		\
 	container_of(z, struct scmi_powercap_zone, zone)
 
+#define to_scmi_powercap_root(z)		\
+	container_of(z, struct scmi_powercap_root, instance_root.zone)
+
 static const struct scmi_powercap_proto_ops *powercap_ops;
 
 struct scmi_powercap_zone {
@@ -453,9 +456,36 @@ static int instance_root_release(struct powercap_zone *pz)
 	return 0;
 }
 
-static int instance_root_get_power_uw(struct powercap_zone *pz, u64 *v)
+static int instance_root_get_power_uw(struct powercap_zone *pz, u64 *power_uw)
 {
-	*v = 0;
+	struct scmi_powercap_root *pr = to_scmi_powercap_root(pz);
+	struct scmi_powercap_zone *child;
+
+	u64 p, acc = 0;
+	int i, ret;
+
+	if (!pz || !power_uw)
+		return -EINVAL;
+
+	for (i = 0; i < pr->num_zones; i++) {
+		child = &pr->spzones[i];
+
+		if (!child->registered || child->invalid)
+			continue;
+
+		if (child->info->parent_id != SCMI_POWERCAP_ROOT_ZONE_ID)
+			continue;
+
+		ret = scmi_powercap_get_power_uw(&child->zone, &p);
+		if (ret) {
+			dev_dbg(child->dev, "Failed to read child power: %d\n", ret);
+			return ret;
+		}
+
+		acc += p;
+	}
+
+	*power_uw = acc;
 	return 0;
 }
 
-- 
2.25.1