firmware: arm_scmi: Add support for standalone transport drivers

Extend the core SCMI stack with structures and methods to allow for
transports to be split out as standalone drivers, while still supporting
old style transports, defined as built into the SCMI core stack.

No functional change.
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Tested-by: Peng Fan <peng.fan@nxp.com>  #i.MX95 19x19 EVK
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Message-Id: <20240812173340.3912830-5-cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/common.h

@@ -373,6 +373,8 @@ struct scmi_shared_mem_operations {
 				     bool tx, struct resource *res);
 };
 
+const struct scmi_shared_mem_operations *scmi_shared_mem_operations_get(void);
+
 /* declarations for message passing transports */
 struct scmi_msg_payld;
 
@@ -400,6 +402,88 @@ struct scmi_message_operations {
 				   size_t max_len, struct scmi_xfer *xfer);
 };
 
+const struct scmi_message_operations *scmi_message_operations_get(void);
+
+/**
+ * struct scmi_transport_core_operations  - Transpoert core operations
+ *
+ * @bad_message_trace: An helper to report a malformed/unexpected message
+ * @rx_callback: Callback to report received messages
+ * @shmem: Datagram operations for shared memory based transports
+ * @msg: Datagram operations for message based transports
+ */
+struct scmi_transport_core_operations {
+	void (*bad_message_trace)(struct scmi_chan_info *cinfo,
+				  u32 msg_hdr, enum scmi_bad_msg err);
+	void (*rx_callback)(struct scmi_chan_info *cinfo, u32 msg_hdr,
+			    void *priv);
+	const struct scmi_shared_mem_operations *shmem;
+	const struct scmi_message_operations *msg;
+};
+
+/**
+ * struct scmi_transport  - A structure representing a configured transport
+ *
+ * @supplier: Device representing the transport and acting as a supplier for
+ *	      the core SCMI stack
+ * @desc: Transport descriptor
+ * @core_ops: A pointer to a pointer used by the core SCMI stack to make the
+ *	      core transport operations accessible to the transports.
+ */
+struct scmi_transport {
+	struct device *supplier;
+	const struct scmi_desc *desc;
+	struct scmi_transport_core_operations **core_ops;
+};
+
+#define DEFINE_SCMI_TRANSPORT_DRIVER(__tag, __drv, __desc, __match, __core_ops)\
+static void __tag##_dev_free(void *data)				       \
+{									       \
+	struct platform_device *spdev = data;				       \
+									       \
+	platform_device_unregister(spdev);				       \
+}									       \
+									       \
+static int __tag##_probe(struct platform_device *pdev)			       \
+{									       \
+	struct device *dev = &pdev->dev;				       \
+	struct platform_device *spdev;					       \
+	struct scmi_transport strans;					       \
+	int ret;							       \
+									       \
+	spdev = platform_device_alloc("arm-scmi", PLATFORM_DEVID_AUTO);	       \
+	if (!spdev)							       \
+		return -ENOMEM;						       \
+									       \
+	device_set_of_node_from_dev(&spdev->dev, dev);			       \
+									       \
+	strans.supplier = dev;						       \
+	strans.desc = &(__desc);					       \
+	strans.core_ops = &(__core_ops);				       \
+									       \
+	ret = platform_device_add_data(spdev, &strans, sizeof(strans));	       \
+	if (ret)							       \
+		goto err;						       \
+									       \
+	ret = platform_device_add(spdev);				       \
+	if (ret)							       \
+		goto err;						       \
+									       \
+	return devm_add_action_or_reset(dev, __tag##_dev_free, spdev);	       \
+									       \
+err:									       \
+	platform_device_put(spdev);					       \
+	return ret;							       \
+}									       \
+									       \
+static struct platform_driver __drv = {					       \
+	.driver = {							       \
+		   .name = #__tag "_transport",				       \
+		   .of_match_table = __match,				       \
+		   },							       \
+	.probe = __tag##_probe,						       \
+}
+
 extern const struct scmi_shared_mem_operations scmi_shmem_ops;
 extern const struct scmi_message_operations scmi_msg_ops;
 

drivers/firmware/arm_scmi/driver.c

@@ -196,6 +196,11 @@ struct scmi_info {
 #define bus_nb_to_scmi_info(nb)	container_of(nb, struct scmi_info, bus_nb)
 #define req_nb_to_scmi_info(nb)	container_of(nb, struct scmi_info, dev_req_nb)
 
+static struct scmi_transport_core_operations scmi_trans_core_ops = {
+	.bad_message_trace = scmi_bad_message_trace,
+	.rx_callback = scmi_rx_callback,
+};
+
 static unsigned long
 scmi_vendor_protocol_signature(unsigned int protocol_id, char *vendor_id,
 			       char *sub_vendor_id, u32 impl_ver)
@@ -3017,6 +3022,28 @@ static int scmi_debugfs_raw_mode_setup(struct scmi_info *info)
 	return ret;
 }
 
+static const struct scmi_desc *scmi_transport_setup(struct device *dev)
+{
+	struct scmi_transport *trans;
+
+	trans = dev_get_platdata(dev);
+	if (!trans || !trans->desc || !trans->supplier || !trans->core_ops)
+		return NULL;
+
+	if (!device_link_add(dev, trans->supplier, DL_FLAG_AUTOREMOVE_CONSUMER)) {
+		dev_err(dev,
+			"Adding link to supplier transport device failed\n");
+		return NULL;
+	}
+
+	/* Provide core transport ops */
+	*trans->core_ops = &scmi_trans_core_ops;
+
+	dev_info(dev, "Using %s\n", dev_driver_string(trans->supplier));
+
+	return trans->desc;
+}
+
 static int scmi_probe(struct platform_device *pdev)
 {
 	int ret;
@@ -3029,8 +3056,14 @@ static int scmi_probe(struct platform_device *pdev)
 	struct device_node *child, *np = dev->of_node;
 
 	desc = of_device_get_match_data(dev);
-	if (!desc)
-		return -EINVAL;
+	if (!desc) {
+		desc = scmi_transport_setup(dev);
+		if (!desc) {
+			err_str = "transport invalid\n";
+			ret = -EINVAL;
+			goto out_err;
+		}
+	}
 
 	info = devm_kzalloc(dev, sizeof(*info), GFP_KERNEL);
 	if (!info)
@@ -3197,6 +3230,7 @@ static int scmi_probe(struct platform_device *pdev)
 clear_ida:
 	ida_free(&scmi_id, info->id);
 
+out_err:
 	return dev_err_probe(dev, ret, "%s", err_str);
 }
 
@@ -3388,6 +3422,12 @@ static int __init scmi_driver_init(void)
 	if (ret)
 		return ret;
 
+	if (IS_ENABLED(CONFIG_ARM_SCMI_HAVE_SHMEM))
+		scmi_trans_core_ops.shmem = scmi_shared_mem_operations_get();
+
+	if (IS_ENABLED(CONFIG_ARM_SCMI_HAVE_MSG))
+		scmi_trans_core_ops.msg = scmi_message_operations_get();
+
 	if (IS_ENABLED(CONFIG_ARM_SCMI_NEED_DEBUGFS))
 		scmi_top_dentry = scmi_debugfs_init();
 

drivers/firmware/arm_scmi/msg.c

@@ -118,3 +118,8 @@ const struct scmi_message_operations scmi_msg_ops = {
 	.fetch_response = msg_fetch_response,
 	.fetch_notification = msg_fetch_notification,
 };
+
+const struct scmi_message_operations *scmi_message_operations_get(void)
+{
+	return &scmi_msg_ops;
+}

drivers/firmware/arm_scmi/shmem.c

@@ -187,3 +187,8 @@ const struct scmi_shared_mem_operations scmi_shmem_ops = {
 	.channel_intr_enabled = shmem_channel_intr_enabled,
 	.setup_iomap = shmem_setup_iomap,
 };
+
+const struct scmi_shared_mem_operations *scmi_shared_mem_operations_get(void)
+{
+	return &scmi_shmem_ops;
+}