[PATCH v2 2/2] regulator: scmi: add support for registering SCMI regulators by name

[David Collins]

Add support to register SCMI regulator subnodes based on an SCMI
Voltage Domain name specified via the "arm,scmi-domain-name" device
tree property.  In doing so, make the "reg" property optional with
the constraint that at least one of "reg" or "arm,scmi-domain-name"
must be specified.  If both are specified, then both must match the
Voltage Domain data exposed by the SCMI platform.

Name based SCMI regulator registration helps ensure that an SCMI
agent doesn't need to be aware of the numbering scheme used for
Voltage Domains by the SCMI platform.  It also ensures that the
correct Voltage Domain is selected for a given physical regulator.
This cannot be guaranteed with numeric Voltage Domain IDs alone.

Signed-off-by: David Collins <quic_collinsd@xxxxxxxxxxx>
---
 drivers/regulator/scmi-regulator.c | 58 ++++++++++++++++++++++++++++--
 1 file changed, 55 insertions(+), 3 deletions(-)

diff --git a/drivers/regulator/scmi-regulator.c b/drivers/regulator/scmi-regulator.c
index 1f02f60ad136..15f9167b96ab 100644
--- a/drivers/regulator/scmi-regulator.c
+++ b/drivers/regulator/scmi-regulator.c
@@ -31,6 +31,7 @@
 #include <linux/regulator/of_regulator.h>
 #include <linux/scmi_protocol.h>
 #include <linux/slab.h>
+#include <linux/string.h>
 #include <linux/types.h>
 
 static const struct scmi_voltage_proto_ops *voltage_ops;
@@ -252,16 +253,67 @@ static int scmi_regulator_common_init(struct scmi_regulator *sreg)
 	return 0;
 }
 
+static int scmi_regulator_map_name(struct scmi_protocol_handle *ph,
+				   struct scmi_regulator_info *rinfo,
+				   const char *name)
+{
+	const struct scmi_voltage_info *vinfo;
+	int i;
+
+	for (i = 0; i < rinfo->num_doms; i++) {
+		vinfo = voltage_ops->info_get(ph, i);
+		if (!vinfo)
+			continue;
+		if (!strncmp(vinfo->name, name, sizeof(vinfo->name)))
+			return i;
+	}
+
+	return -ENODEV;
+}
+
 static int process_scmi_regulator_of_node(struct scmi_device *sdev,
 					  struct scmi_protocol_handle *ph,
 					  struct device_node *np,
 					  struct scmi_regulator_info *rinfo)
 {
 	u32 dom, ret;
+	int name_dom;
+	const char *name;
 
-	ret = of_property_read_u32(np, "reg", &dom);
-	if (ret)
-		return ret;
+	dom = rinfo->num_doms;
+	if (of_find_property(np, "reg", NULL)) {
+		ret = of_property_read_u32(np, "reg", &dom);
+		if (ret)
+			return ret;
+
+		if (dom >= rinfo->num_doms)
+			return -ENODEV;
+	}
+
+	if (of_find_property(np, "arm,scmi-domain-name", NULL)) {
+		ret = of_property_read_string(np, "arm,scmi-domain-name",
+					      &name);
+		if (ret)
+			return ret;
+
+		name_dom = scmi_regulator_map_name(ph, rinfo, name);
+		if (name_dom < 0) {
+			dev_err(&sdev->dev,
+				"No SCMI Voltage Domain found named %s. Skipping: %s\n",
+				name, np->full_name);
+			return name_dom;
+		}
+
+		if (dom >= rinfo->num_doms)
+			dom = name_dom;
+
+		if (name_dom != dom) {
+			dev_err(&sdev->dev,
+				"SCMI Voltage Domain %s ID mismatch, %u (DT) != %d (firmware). Skipping: %s\n",
+				name, dom, name_dom, np->full_name);
+			return -EINVAL;
+		}
+	}
 
 	if (dom >= rinfo->num_doms)
 		return -ENODEV;
-- 
2.17.1