[v6,01/14] scmi: refactor the code to hide a channel from devices

diff --git a/drivers/clk/clk_scmi.c b/drivers/clk/clk_scmi.c
index d172fed24c9d..34a49363a51a 100644
--- a/drivers/clk/clk_scmi.c
+++ b/drivers/clk/clk_scmi.c
@@ -13,17 +13,8 @@ 
 #include <asm/types.h>
 #include <linux/clk-provider.h>
 
-/**
- * struct scmi_clk_priv - Private data for SCMI clocks
- * @channel: Reference to the SCMI channel to use
- */
-struct scmi_clk_priv {
-	struct scmi_channel *channel;
-};
-
 static int scmi_clk_get_num_clock(struct udevice *dev, size_t *num_clocks)
 {
-	struct scmi_clk_priv *priv = dev_get_priv(dev);
 	struct scmi_clk_protocol_attr_out out;
 	struct scmi_msg msg = {
 		.protocol_id = SCMI_PROTOCOL_ID_CLOCK,
@@ -33,7 +24,7 @@  static int scmi_clk_get_num_clock(struct udevice *dev, size_t *num_clocks)
 	};
 	int ret;
 
-	ret = devm_scmi_process_msg(dev, priv->channel, &msg);
+	ret = devm_scmi_process_msg(dev, &msg);
 	if (ret)
 		return ret;
 
@@ -44,7 +35,6 @@  static int scmi_clk_get_num_clock(struct udevice *dev, size_t *num_clocks)
 
 static int scmi_clk_get_attibute(struct udevice *dev, int clkid, char **name)
 {
-	struct scmi_clk_priv *priv = dev_get_priv(dev);
 	struct scmi_clk_attribute_in in = {
 		.clock_id = clkid,
 	};
@@ -59,7 +49,7 @@  static int scmi_clk_get_attibute(struct udevice *dev, int clkid, char **name)
 	};
 	int ret;
 
-	ret = devm_scmi_process_msg(dev, priv->channel, &msg);
+	ret = devm_scmi_process_msg(dev, &msg);
 	if (ret)
 		return ret;
 
@@ -70,7 +60,6 @@  static int scmi_clk_get_attibute(struct udevice *dev, int clkid, char **name)
 
 static int scmi_clk_gate(struct clk *clk, int enable)
 {
-	struct scmi_clk_priv *priv = dev_get_priv(clk->dev);
 	struct scmi_clk_state_in in = {
 		.clock_id = clk->id,
 		.attributes = enable,
@@ -81,7 +70,7 @@  static int scmi_clk_gate(struct clk *clk, int enable)
 					  in, out);
 	int ret;
 
-	ret = devm_scmi_process_msg(clk->dev, priv->channel, &msg);
+	ret = devm_scmi_process_msg(clk->dev, &msg);
 	if (ret)
 		return ret;
 
@@ -100,7 +89,6 @@  static int scmi_clk_disable(struct clk *clk)
 
 static ulong scmi_clk_get_rate(struct clk *clk)
 {
-	struct scmi_clk_priv *priv = dev_get_priv(clk->dev);
 	struct scmi_clk_rate_get_in in = {
 		.clock_id = clk->id,
 	};
@@ -110,7 +98,7 @@  static ulong scmi_clk_get_rate(struct clk *clk)
 					  in, out);
 	int ret;
 
-	ret = devm_scmi_process_msg(clk->dev, priv->channel, &msg);
+	ret = devm_scmi_process_msg(clk->dev, &msg);
 	if (ret < 0)
 		return ret;
 
@@ -123,7 +111,6 @@  static ulong scmi_clk_get_rate(struct clk *clk)
 
 static ulong scmi_clk_set_rate(struct clk *clk, ulong rate)
 {
-	struct scmi_clk_priv *priv = dev_get_priv(clk->dev);
 	struct scmi_clk_rate_set_in in = {
 		.clock_id = clk->id,
 		.flags = SCMI_CLK_RATE_ROUND_CLOSEST,
@@ -136,7 +123,7 @@  static ulong scmi_clk_set_rate(struct clk *clk, ulong rate)
 					  in, out);
 	int ret;
 
-	ret = devm_scmi_process_msg(clk->dev, priv->channel, &msg);
+	ret = devm_scmi_process_msg(clk->dev, &msg);
 	if (ret < 0)
 		return ret;
 
@@ -149,12 +136,11 @@  static ulong scmi_clk_set_rate(struct clk *clk, ulong rate)
 
 static int scmi_clk_probe(struct udevice *dev)
 {
-	struct scmi_clk_priv *priv = dev_get_priv(dev);
 	struct clk *clk;
 	size_t num_clocks, i;
 	int ret;
 
-	ret = devm_scmi_of_get_channel(dev, &priv->channel);
+	ret = devm_scmi_of_get_channel(dev);
 	if (ret)
 		return ret;
 
@@ -205,5 +191,4 @@  U_BOOT_DRIVER(scmi_clock) = {
 	.id = UCLASS_CLK,
 	.ops = &scmi_clk_ops,
 	.probe = scmi_clk_probe,
-	.priv_auto = sizeof(struct scmi_clk_priv *),
 };
diff --git a/drivers/firmware/scmi/scmi_agent-uclass.c b/drivers/firmware/scmi/scmi_agent-uclass.c
index 02de692d66f3..ec58ccd2bc5d 100644
--- a/drivers/firmware/scmi/scmi_agent-uclass.c
+++ b/drivers/firmware/scmi/scmi_agent-uclass.c
@@ -8,6 +8,7 @@ 
 #include <common.h>
 #include <dm.h>
 #include <errno.h>
+#include <scmi_agent.h>
 #include <scmi_agent-uclass.h>
 #include <scmi_protocols.h>
 #include <dm/device_compat.h>
@@ -110,18 +111,23 @@  static int scmi_bind_protocols(struct udevice *dev)
 	return ret;
 }
 
-static struct udevice *find_scmi_transport_device(struct udevice *dev)
+static struct udevice *find_scmi_protocol_device(struct udevice *dev)
 {
-	struct udevice *parent = dev;
+	struct udevice *parent = NULL, *protocol;
 
-	do {
-		parent = dev_get_parent(parent);
-	} while (parent && device_get_uclass_id(parent) != UCLASS_SCMI_AGENT);
+	for (protocol = dev; protocol; protocol = parent) {
+		parent = dev_get_parent(protocol);
+		if (!parent ||
+		    device_get_uclass_id(parent) == UCLASS_SCMI_AGENT)
+			break;
+	}
 
-	if (!parent)
+	if (!parent) {
 		dev_err(dev, "Invalid SCMI device, agent not found\n");
+		return NULL;
+	}
 
-	return parent;
+	return protocol;
 }
 
 static const struct scmi_agent_ops *transport_dev_ops(struct udevice *dev)
@@ -129,43 +135,90 @@  static const struct scmi_agent_ops *transport_dev_ops(struct udevice *dev)
 	return (const struct scmi_agent_ops *)dev->driver->ops;
 }
 
-int devm_scmi_of_get_channel(struct udevice *dev, struct scmi_channel **channel)
+/**
+ * scmi_of_get_channel() - Get SCMI channel handle
+ *
+ * @dev:	SCMI agent device
+ * @channel:	Output reference to the SCMI channel upon success
+ *
+ * On return, @channel will be set.
+ * Return	0 on success and a negative errno on failure
+ */
+static int scmi_of_get_channel(struct udevice *dev, struct scmi_channel **channel)
 {
-	struct udevice *parent;
+	const struct scmi_agent_ops *ops;
 
-	parent = find_scmi_transport_device(dev);
-	if (!parent)
+	ops = transport_dev_ops(dev);
+	if (ops->of_get_channel)
+		return ops->of_get_channel(dev, channel);
+	else
+		return -EPROTONOSUPPORT;
+}
+
+int devm_scmi_of_get_channel(struct udevice *dev)
+{
+	struct udevice *protocol;
+	struct scmi_agent_proto_priv *priv;
+	int ret;
+
+	protocol = find_scmi_protocol_device(dev);
+	if (!protocol)
 		return -ENODEV;
 
-	if (transport_dev_ops(parent)->of_get_channel)
-		return transport_dev_ops(parent)->of_get_channel(parent, channel);
+	priv = dev_get_parent_priv(protocol);
+	ret = scmi_of_get_channel(protocol->parent, &priv->channel);
+	if (ret == -EPROTONOSUPPORT) {
+		/* Drivers without a get_channel operator don't need a channel ref */
+		priv->channel = NULL;
 
-	/* Drivers without a get_channel operator don't need a channel ref */
-	*channel = NULL;
+		return 0;
+	}
 
-	return 0;
+	return ret;
 }
 
-int devm_scmi_process_msg(struct udevice *dev, struct scmi_channel *channel,
-			  struct scmi_msg *msg)
+/**
+ * scmi_process_msg() - Send and process an SCMI message
+ *
+ * Send a message to an SCMI server.
+ * Caller sets scmi_msg::out_msg_sz to the output message buffer size.
+ *
+ * @dev:	SCMI agent device
+ * @channel:	Communication channel for the device
+ * @msg:	Message structure reference
+ *
+ * On return, scmi_msg::out_msg_sz stores the response payload size.
+ * Return:	0 on success and a negative errno on failure
+ */
+static int scmi_process_msg(struct udevice *dev, struct scmi_channel *channel,
+			    struct scmi_msg *msg)
 {
 	const struct scmi_agent_ops *ops;
-	struct udevice *parent;
 
-	parent = find_scmi_transport_device(dev);
-	if (!parent)
-		return -ENODEV;
+	ops = transport_dev_ops(dev);
+	if (ops->process_msg)
+		return ops->process_msg(dev, channel, msg);
+	else
+		return -EPROTONOSUPPORT;
+}
 
-	ops = transport_dev_ops(parent);
+int devm_scmi_process_msg(struct udevice *dev, struct scmi_msg *msg)
+{
+	struct udevice *protocol;
+	struct scmi_agent_proto_priv *priv;
 
-	if (ops->process_msg)
-		return ops->process_msg(parent, channel, msg);
+	protocol = find_scmi_protocol_device(dev);
+	if (!protocol)
+		return -ENODEV;
+
+	priv = dev_get_parent_priv(protocol);
 
-	return -EPROTONOSUPPORT;
+	return scmi_process_msg(protocol->parent, priv->channel, msg);
 }
 
 UCLASS_DRIVER(scmi_agent) = {
 	.id		= UCLASS_SCMI_AGENT,
 	.name		= "scmi_agent",
 	.post_bind	= scmi_bind_protocols,
+	.per_child_auto	= sizeof(struct scmi_agent_proto_priv),
 };
diff --git a/drivers/power/regulator/scmi_regulator.c b/drivers/power/regulator/scmi_regulator.c
index 801148036ff6..9c72c35d039e 100644
--- a/drivers/power/regulator/scmi_regulator.c
+++ b/drivers/power/regulator/scmi_regulator.c
@@ -25,18 +25,9 @@  struct scmi_regulator_platdata {
 	u32 domain_id;
 };
 
-/**
- * struct scmi_regulator_priv - Private data for SCMI voltage regulator
- * @channel: Reference to the SCMI channel to use
- */
-struct scmi_regulator_priv {
-	struct scmi_channel *channel;
-};
-
 static int scmi_voltd_set_enable(struct udevice *dev, bool enable)
 {
 	struct scmi_regulator_platdata *pdata = dev_get_plat(dev);
-	struct scmi_regulator_priv *priv = dev_get_priv(dev);
 	struct scmi_voltd_config_set_in in = {
 		.domain_id = pdata->domain_id,
 		.config = enable ? SCMI_VOLTD_CONFIG_ON : SCMI_VOLTD_CONFIG_OFF,
@@ -47,7 +38,7 @@  static int scmi_voltd_set_enable(struct udevice *dev, bool enable)
 					  in, out);
 	int ret;
 
-	ret = devm_scmi_process_msg(dev, priv->channel, &msg);
+	ret = devm_scmi_process_msg(dev, &msg);
 	if (ret)
 		return ret;
 
@@ -57,7 +48,6 @@  static int scmi_voltd_set_enable(struct udevice *dev, bool enable)
 static int scmi_voltd_get_enable(struct udevice *dev)
 {
 	struct scmi_regulator_platdata *pdata = dev_get_plat(dev);
-	struct scmi_regulator_priv *priv = dev_get_priv(dev);
 	struct scmi_voltd_config_get_in in = {
 		.domain_id = pdata->domain_id,
 	};
@@ -67,7 +57,7 @@  static int scmi_voltd_get_enable(struct udevice *dev)
 					  in, out);
 	int ret;
 
-	ret = devm_scmi_process_msg(dev, priv->channel, &msg);
+	ret = devm_scmi_process_msg(dev, &msg);
 	if (ret < 0)
 		return ret;
 
@@ -80,7 +70,6 @@  static int scmi_voltd_get_enable(struct udevice *dev)
 
 static int scmi_voltd_set_voltage_level(struct udevice *dev, int uV)
 {
-	struct scmi_regulator_priv *priv = dev_get_priv(dev);
 	struct scmi_regulator_platdata *pdata = dev_get_plat(dev);
 	struct scmi_voltd_level_set_in in = {
 		.domain_id = pdata->domain_id,
@@ -92,7 +81,7 @@  static int scmi_voltd_set_voltage_level(struct udevice *dev, int uV)
 					  in, out);
 	int ret;
 
-	ret = devm_scmi_process_msg(dev, priv->channel, &msg);
+	ret = devm_scmi_process_msg(dev, &msg);
 	if (ret < 0)
 		return ret;
 
@@ -101,7 +90,6 @@  static int scmi_voltd_set_voltage_level(struct udevice *dev, int uV)
 
 static int scmi_voltd_get_voltage_level(struct udevice *dev)
 {
-	struct scmi_regulator_priv *priv = dev_get_priv(dev);
 	struct scmi_regulator_platdata *pdata = dev_get_plat(dev);
 	struct scmi_voltd_level_get_in in = {
 		.domain_id = pdata->domain_id,
@@ -112,7 +100,7 @@  static int scmi_voltd_get_voltage_level(struct udevice *dev)
 					  in, out);
 	int ret;
 
-	ret = devm_scmi_process_msg(dev, priv->channel, &msg);
+	ret = devm_scmi_process_msg(dev, &msg);
 	if (ret < 0)
 		return ret;
 
@@ -140,7 +128,6 @@  static int scmi_regulator_of_to_plat(struct udevice *dev)
 static int scmi_regulator_probe(struct udevice *dev)
 {
 	struct scmi_regulator_platdata *pdata = dev_get_plat(dev);
-	struct scmi_regulator_priv *priv = dev_get_priv(dev);
 	struct scmi_voltd_attr_in in = { 0 };
 	struct scmi_voltd_attr_out out = { 0 };
 	struct scmi_msg scmi_msg = {
@@ -153,14 +140,14 @@  static int scmi_regulator_probe(struct udevice *dev)
 	};
 	int ret;
 
-	ret = devm_scmi_of_get_channel(dev->parent, &priv->channel);
+	ret = devm_scmi_of_get_channel(dev);
 	if (ret)
 		return ret;
 
 	/* Check voltage domain is known from SCMI server */
 	in.domain_id = pdata->domain_id;
 
-	ret = devm_scmi_process_msg(dev, priv->channel, &scmi_msg);
+	ret = devm_scmi_process_msg(dev, &scmi_msg);
 	if (ret) {
 		dev_err(dev, "Failed to query voltage domain %u: %d\n",
 			pdata->domain_id, ret);
@@ -184,7 +171,6 @@  U_BOOT_DRIVER(scmi_regulator) = {
 	.probe = scmi_regulator_probe,
 	.of_to_plat = scmi_regulator_of_to_plat,
 	.plat_auto = sizeof(struct scmi_regulator_platdata),
-	.priv_auto = sizeof(struct scmi_regulator_priv *),
 };
 
 static int scmi_regulator_bind(struct udevice *dev)
diff --git a/drivers/reset/reset-scmi.c b/drivers/reset/reset-scmi.c
index 122556162ec3..b76711f0a8fb 100644
--- a/drivers/reset/reset-scmi.c
+++ b/drivers/reset/reset-scmi.c
@@ -13,17 +13,8 @@ 
 #include <scmi_protocols.h>
 #include <asm/types.h>
 
-/**
- * struct scmi_reset_priv - Private data for SCMI reset controller
- * @channel: Reference to the SCMI channel to use
- */
-struct scmi_reset_priv {
-	struct scmi_channel *channel;
-};
-
 static int scmi_reset_set_level(struct reset_ctl *rst, bool assert_not_deassert)
 {
-	struct scmi_reset_priv *priv = dev_get_priv(rst->dev);
 	struct scmi_rd_reset_in in = {
 		.domain_id = rst->id,
 		.flags = assert_not_deassert ? SCMI_RD_RESET_FLAG_ASSERT : 0,
@@ -35,7 +26,7 @@  static int scmi_reset_set_level(struct reset_ctl *rst, bool assert_not_deassert)
 					  in, out);
 	int ret;
 
-	ret = devm_scmi_process_msg(rst->dev, priv->channel, &msg);
+	ret = devm_scmi_process_msg(rst->dev, &msg);
 	if (ret)
 		return ret;
 
@@ -54,7 +45,6 @@  static int scmi_reset_deassert(struct reset_ctl *rst)
 
 static int scmi_reset_request(struct reset_ctl *rst)
 {
-	struct scmi_reset_priv *priv = dev_get_priv(rst->dev);
 	struct scmi_rd_attr_in in = {
 		.domain_id = rst->id,
 	};
@@ -68,7 +58,7 @@  static int scmi_reset_request(struct reset_ctl *rst)
 	 * We don't really care about the attribute, just check
 	 * the reset domain exists.
 	 */
-	ret = devm_scmi_process_msg(rst->dev, priv->channel, &msg);
+	ret = devm_scmi_process_msg(rst->dev, &msg);
 	if (ret)
 		return ret;
 
@@ -83,9 +73,7 @@  static const struct reset_ops scmi_reset_domain_ops = {
 
 static int scmi_reset_probe(struct udevice *dev)
 {
-	struct scmi_reset_priv *priv = dev_get_priv(dev);
-
-	return devm_scmi_of_get_channel(dev, &priv->channel);
+	return devm_scmi_of_get_channel(dev);
 }
 
 U_BOOT_DRIVER(scmi_reset_domain) = {
@@ -93,5 +81,4 @@  U_BOOT_DRIVER(scmi_reset_domain) = {
 	.id = UCLASS_RESET,
 	.ops = &scmi_reset_domain_ops,
 	.probe = scmi_reset_probe,
-	.priv_auto = sizeof(struct scmi_reset_priv *),
 };
diff --git a/include/scmi_agent.h b/include/scmi_agent.h
index ee6286366df7..577892029ff8 100644
--- a/include/scmi_agent.h
+++ b/include/scmi_agent.h
@@ -15,6 +15,14 @@ 
 struct udevice;
 struct scmi_channel;
 
+/**
+ * struct scmi_agent_proto_priv - Private data in device for SCMI agent
+ * @channel: Reference to the SCMI channel to use
+ */
+struct scmi_agent_proto_priv {
+	struct scmi_channel *channel;
+};
+
 /*
  * struct scmi_msg - Context of a SCMI message sent and the response received
  *
@@ -49,10 +57,9 @@  struct scmi_msg {
  * devm_scmi_of_get_channel() - Get SCMI channel handle from SCMI agent DT node
  *
  * @dev:	Device requesting a channel
- * @channel:	Output reference to the SCMI channel upon success
  * @return 0 on success and a negative errno on failure
  */
-int devm_scmi_of_get_channel(struct udevice *dev, struct scmi_channel **channel);
+int devm_scmi_of_get_channel(struct udevice *dev);
 
 /**
  * devm_scmi_process_msg() - Send and process an SCMI message
@@ -62,12 +69,10 @@  int devm_scmi_of_get_channel(struct udevice *dev, struct scmi_channel **channel)
  * On return, scmi_msg::out_msg_sz stores the response payload size.
  *
  * @dev:	SCMI device
- * @channel:	Communication channel for the device
  * @msg:	Message structure reference
  * Return: 0 on success and a negative errno on failure
  */
-int devm_scmi_process_msg(struct udevice *dev, struct scmi_channel *channel,
-			  struct scmi_msg *msg);
+int devm_scmi_process_msg(struct udevice *dev, struct scmi_msg *msg);
 
 /**
  * scmi_to_linux_errno() - Convert an SCMI error code into a Linux errno code