firmware: arm_scmi: Add SCMI v3.1 VOLTAGE_LEVEL_SET_COMPLETE

Add SCMI v3.1 voltage protocol support for asynchronous VOLTAGE_LEVEL_SET
command.

Note that, if a voltage domain is advertised to support the asynchronous
version of VOLTAGE_LEVEL_SET, the command will be issued asynchronously
unless explicitly requested to use the synchronous version by setting the
mode to SCMI_VOLTAGE_LEVEL_SET_SYNC when calling voltage_ops->level_set.

The SCMI regulator driver level_set invocation has been left unchanged
so that it will transparently use the asynchronous version if available.

Link: https://lore.kernel.org/r/20220330150551.2573938-21-cristian.marussi@arm.com
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/voltage.c

@@ -28,6 +28,7 @@ enum scmi_voltage_protocol_cmd {
 
 struct scmi_msg_resp_domain_attributes {
 	__le32 attr;
+#define SUPPORTS_ASYNC_LEVEL_SET(x)	((x) & BIT(31))
 #define SUPPORTS_EXTENDED_NAMES(x)	((x) & BIT(30))
 	u8 name[SCMI_SHORT_NAME_MAX_SIZE];
 };
@@ -56,6 +57,11 @@ struct scmi_msg_cmd_level_set {
 	__le32 voltage_level;
 };
 
+struct scmi_resp_voltage_level_set_complete {
+	__le32 domain_id;
+	__le32 voltage_level;
+};
+
 struct voltage_info {
 	unsigned int version;
 	unsigned int num_domains;
@@ -214,6 +220,7 @@ static int scmi_voltage_descriptors_get(const struct scmi_protocol_handle *ph,
 	resp_dom = td->rx.buf;
 
 	for (dom = 0; dom < vinfo->num_domains; dom++) {
+		u32 attributes;
 		struct scmi_voltage_info *v;
 
 		/* Retrieve domain attributes at first ... */
@@ -225,18 +232,22 @@ static int scmi_voltage_descriptors_get(const struct scmi_protocol_handle *ph,
 
 		v = vinfo->domains + dom;
 		v->id = dom;
-		v->attributes = le32_to_cpu(resp_dom->attr);
+		attributes = le32_to_cpu(resp_dom->attr);
 		strlcpy(v->name, resp_dom->name, SCMI_MAX_STR_SIZE);
 
 		/*
 		 * If supported overwrite short name with the extended one;
 		 * on error just carry on and use already provided short name.
 		 */
-		if (PROTOCOL_REV_MAJOR(vinfo->version) >= 0x2 &&
+		if (PROTOCOL_REV_MAJOR(vinfo->version) >= 0x2) {
-		    SUPPORTS_EXTENDED_NAMES(v->attributes))
+			if (SUPPORTS_EXTENDED_NAMES(attributes))
-			ph->hops->extended_name_get(ph, VOLTAGE_DOMAIN_NAME_GET,
+				ph->hops->extended_name_get(ph,
-						    v->id, v->name,
+							VOLTAGE_DOMAIN_NAME_GET,
-						    SCMI_MAX_STR_SIZE);
+							v->id, v->name,
+							SCMI_MAX_STR_SIZE);
+			if (SUPPORTS_ASYNC_LEVEL_SET(attributes))
+				v->async_level_set = true;
+		}
 
 		ret = scmi_voltage_levels_get(ph, v);
 		/* Skip invalid voltage descriptors */
@@ -308,12 +319,15 @@ static int scmi_voltage_config_get(const struct scmi_protocol_handle *ph,
 }
 
 static int scmi_voltage_level_set(const struct scmi_protocol_handle *ph,
-				  u32 domain_id, u32 flags, s32 volt_uV)
+				  u32 domain_id,
+				  enum scmi_voltage_level_mode mode,
+				  s32 volt_uV)
 {
 	int ret;
 	struct scmi_xfer *t;
 	struct voltage_info *vinfo = ph->get_priv(ph);
 	struct scmi_msg_cmd_level_set *cmd;
+	struct scmi_voltage_info *v;
 
 	if (domain_id >= vinfo->num_domains)
 		return -EINVAL;
@@ -323,12 +337,31 @@ static int scmi_voltage_level_set(const struct scmi_protocol_handle *ph,
 	if (ret)
 		return ret;
 
+	v = vinfo->domains + domain_id;
+
 	cmd = t->tx.buf;
 	cmd->domain_id = cpu_to_le32(domain_id);
-	cmd->flags = cpu_to_le32(flags);
 	cmd->voltage_level = cpu_to_le32(volt_uV);
 
-	ret = ph->xops->do_xfer(ph, t);
+	if (!v->async_level_set || mode != SCMI_VOLTAGE_LEVEL_SET_AUTO) {
+		cmd->flags = cpu_to_le32(0x0);
+		ret = ph->xops->do_xfer(ph, t);
+	} else {
+		cmd->flags = cpu_to_le32(0x1);
+		ret = ph->xops->do_xfer_with_response(ph, t);
+		if (!ret) {
+			struct scmi_resp_voltage_level_set_complete *resp;
+
+			resp = t->rx.buf;
+			if (le32_to_cpu(resp->domain_id) == domain_id)
+				dev_dbg(ph->dev,
+					"Voltage domain %d set async to %d\n",
+					v->id,
+					le32_to_cpu(resp->voltage_level));
+			else
+				ret = -EPROTO;
+		}
+	}
 
 	ph->xops->xfer_put(ph, t);
 	return ret;

include/linux/scmi_protocol.h

@@ -495,6 +495,11 @@ struct scmi_reset_proto_ops {
 	int (*deassert)(const struct scmi_protocol_handle *ph, u32 domain);
 };
 
+enum scmi_voltage_level_mode {
+	SCMI_VOLTAGE_LEVEL_SET_AUTO,
+	SCMI_VOLTAGE_LEVEL_SET_SYNC,
+};
+
 /**
  * struct scmi_voltage_info - describe one available SCMI Voltage Domain
  *
@@ -507,7 +512,8 @@ struct scmi_reset_proto_ops {
  *	         supported voltage level
  * @negative_volts_allowed: True if any of the entries of @levels_uv represent
  *			    a negative voltage.
- * @attributes: represents Voltage Domain advertised attributes
+ * @async_level_set: True when the voltage domain supports asynchronous level
+ *		     set commands.
  * @name: name assigned to the Voltage Domain by platform
  * @num_levels: number of total entries in @levels_uv.
  * @levels_uv: array of entries describing the available voltage levels for
@@ -517,7 +523,7 @@ struct scmi_voltage_info {
 	unsigned int id;
 	bool segmented;
 	bool negative_volts_allowed;
-	unsigned int attributes;
+	bool async_level_set;
 	char name[SCMI_MAX_STR_SIZE];
 	unsigned int num_levels;
 #define SCMI_VOLTAGE_SEGMENT_LOW	0
@@ -548,7 +554,7 @@ struct scmi_voltage_proto_ops {
 	int (*config_get)(const struct scmi_protocol_handle *ph, u32 domain_id,
 			  u32 *config);
 	int (*level_set)(const struct scmi_protocol_handle *ph, u32 domain_id,
-			 u32 flags, s32 volt_uV);
+			 enum scmi_voltage_level_mode mode, s32 volt_uV);
 	int (*level_get)(const struct scmi_protocol_handle *ph, u32 domain_id,
 			 s32 *volt_uV);
 };