[PATCH v2 4/4] firmware: arm_scmi: optee: Rework transport probe sequence

[Cristian Marussi <cristian.marussi@arm.com>]

Use the new per-instance transport handles helpers to synchronize and
optionally defer the core SCMI driver probe up until the transport driver
has completely been initialized and it is fully operational as a supplier.

Introduce proper module init/exit routines while removing the ugly trick of
registering a driver from within the probe sequence of another one, just to
avoid to have to deal with probe deferrals.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
v1 -> v2
 - fixed __MUTEX_INITILIAZER() usage
 - use common generic supplier definitions
 - get rid of init/cleanup wrappers
 - use proper barrier on scmi_optee_agent
---
 drivers/firmware/arm_scmi/transports/optee.c | 46 +++++++++++++++-----
 1 file changed, 36 insertions(+), 10 deletions(-)

diff --git a/drivers/firmware/arm_scmi/transports/optee.c b/drivers/firmware/arm_scmi/transports/optee.c
index 07ae18d5279d..dbe32e141748 100644
--- a/drivers/firmware/arm_scmi/transports/optee.c
+++ b/drivers/firmware/arm_scmi/transports/optee.c
@@ -154,6 +154,8 @@ static struct scmi_transport_core_operations *core;
 /* There can be only 1 SCMI service in OP-TEE we connect to */
 static struct scmi_optee_agent *scmi_optee_private;
 
+static DEFINE_SCMI_TRANSPORT_SUPPLIER(scmi_optee_supplier);
+
 /* Open a session toward SCMI OP-TEE service with REE_KERNEL identity */
 static int open_session(struct scmi_optee_agent *agent, u32 *tee_session)
 {
@@ -522,7 +524,7 @@ static struct scmi_desc scmi_optee_desc = {
 };
 
 static const struct of_device_id scmi_of_match[] = {
-	{ .compatible = "linaro,scmi-optee" },
+	{ .compatible = "linaro,scmi-optee", .data = &scmi_optee_supplier.th},
 	{ /* Sentinel */ },
 };
 
@@ -561,18 +563,20 @@ static int scmi_optee_service_probe(struct tee_client_device *scmi_pta)
 	if (ret)
 		goto err;
 
-	/* Ensure agent resources are all visible before scmi_optee_private is */
+	/* Ensure initialized scmi_optee_private is visible */
 	smp_mb();
 	scmi_optee_private = agent;
 
-	ret = platform_driver_register(&scmi_optee_driver);
-	if (ret) {
-		scmi_optee_private = NULL;
-		goto err;
-	}
+	ret = scmi_transport_supplier_put(&scmi_optee_supplier.th, agent->dev);
+	if (ret)
+		goto err_put;
 
 	return 0;
 
+err_put:
+	/* Ensure cleared reference is visible before resources are released */
+	smp_store_mb(scmi_optee_private, NULL);
+
 err:
 	tee_client_close_context(tee_ctx);
 
@@ -586,13 +590,12 @@ static void scmi_optee_service_remove(struct tee_client_device *scmi_pta)
 	if (!scmi_optee_private)
 		return;
 
-	platform_driver_unregister(&scmi_optee_driver);
-
 	if (!list_empty(&scmi_optee_private->channel_list))
 		return;
 
 	/* Ensure cleared reference is visible before resources are released */
 	smp_store_mb(scmi_optee_private, NULL);
+	scmi_transport_supplier_put(&scmi_optee_supplier.th, agent->dev);
 
 	tee_client_close_context(agent->tee_ctx);
 }
@@ -616,7 +619,30 @@ static struct tee_client_driver scmi_optee_service_driver = {
 	},
 };
 
-module_tee_client_driver(scmi_optee_service_driver);
+static int __init scmi_transport_optee_init(void)
+{
+	int ret;
+
+	ret = tee_client_driver_register(&scmi_optee_service_driver);
+	if (ret)
+		return ret;
+
+	ret = platform_driver_register(&scmi_optee_driver);
+	if (ret) {
+		tee_client_driver_unregister(&scmi_optee_service_driver);
+		return ret;
+	}
+
+	return ret;
+}
+module_init(scmi_transport_optee_init);
+
+static void __exit scmi_transport_optee_exit(void)
+{
+	platform_driver_unregister(&scmi_optee_driver);
+	tee_client_driver_unregister(&scmi_optee_service_driver);
+}
+module_exit(scmi_transport_optee_exit);
 
 MODULE_AUTHOR("Etienne Carriere <etienne.carriere@foss.st.com>");
 MODULE_DESCRIPTION("SCMI OPTEE Transport driver");
-- 
2.53.0