[PATCH v2 11/14] firmware: arm_scmi: Clear SystemPower flag on create failure

[Sudeep Holla]

__scmi_device_create() reserves the singleton SystemPower protocol
device by setting scmi_syspower_registered before allocating and
registering the SCMI device.

If any later step fails, the function returns NULL but leaves the flag
set. A subsequent retry, for example after probe deferral, then observes
the stale reservation and rejects creation of the SystemPower protocol
device permanently.

Route all failures after the successful reservation through a common
unwind path which clears scmi_syspower_registered again. Keep the
duplicate-device rejection path unchanged because that path did not acquire
the reservation.

Fixes: 2c3e674465e7 ("firmware: arm_scmi: Refactor device create/destroy helpers")
Reported-by: Sashiko <sashiko-bot at kernel.org>
Signed-off-by: Sudeep Holla <sudeep.holla at kernel.org>
---
 drivers/firmware/arm_scmi/bus.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c
index e1deb1b3011d..cdfcd8e96e93 100644
--- a/drivers/firmware/arm_scmi/bus.c
+++ b/drivers/firmware/arm_scmi/bus.c
@@ -431,6 +431,7 @@ __scmi_device_create(struct device_node *np, struct device *parent,
 {
 	int id, retval;
 	struct scmi_device *scmi_dev;
+	bool syspower = (protocol == SCMI_PROTOCOL_SYSTEM);
 
 	/*
 	 * If the same protocol/name device already exist under the same parent
@@ -446,14 +447,12 @@ __scmi_device_create(struct device_node *np, struct device *parent,
 	}
 
 	/*
-	 * Ignore any possible subsequent failures while creating the device
-	 * since we are doomed anyway at that point; not using a mutex which
-	 * spans across this whole function to keep things simple and to avoid
-	 * to serialize all the __scmi_device_create calls across possibly
-	 * different SCMI server instances (parent)
+	 * Reserve the singleton SystemPower protocol device before
+	 * allocation and registration. This keeps creation simple without
+	 * a mutex spanning the whole function; error paths after the
+	 * reservation must drop it again.
 	 */
-	if (protocol == SCMI_PROTOCOL_SYSTEM &&
-	    atomic_cmpxchg(&scmi_syspower_registered, 0, 1)) {
+	if (syspower && atomic_cmpxchg(&scmi_syspower_registered, 0, 1)) {
 		dev_warn(parent,
 			 "SCMI SystemPower protocol device must be unique !\n");
 		return NULL;
@@ -461,19 +460,19 @@ __scmi_device_create(struct device_node *np, struct device *parent,
 
 	scmi_dev = kzalloc_obj(*scmi_dev);
 	if (!scmi_dev)
-		return NULL;
+		goto clear_syspower;
 
 	scmi_dev->name = kstrdup_const(name ?: "unknown", GFP_KERNEL);
 	if (!scmi_dev->name) {
 		kfree(scmi_dev);
-		return NULL;
+		goto clear_syspower;
 	}
 
 	id = ida_alloc_min(&scmi_bus_id, 1, GFP_KERNEL);
 	if (id < 0) {
 		kfree_const(scmi_dev->name);
 		kfree(scmi_dev);
-		return NULL;
+		goto clear_syspower;
 	}
 
 	scmi_dev->id = id;
@@ -495,6 +494,9 @@ __scmi_device_create(struct device_node *np, struct device *parent,
 put_dev:
 	ida_free(&scmi_bus_id, scmi_dev->id);
 	put_device(&scmi_dev->dev);
+clear_syspower:
+	if (syspower)
+		atomic_set(&scmi_syspower_registered, 0);
 	return NULL;
 }
 

-- 
2.43.0