[PATCH v3 2/4] firmware: arm_scmi: Skip requests for standard protocol devices

[Sudeep Holla]

The SCMI core creates devices for the standard protocol IDs during
protocol enumeration, without waiting for an SCMI driver request.
Recording a request for one of these devices also rejects a second
driver registering the same protocol/name pair.

When the first driver unregisters, unrequesting that pair destroys the
core-created device. No other driver can be bound to it at that point,
but removing it also removes the device that a later driver could bind
to or use for module autoloading.

Skip request tracking for standard devices. Keep request tracking and
rollback for nonstandard devices unchanged.

Reviewed-by: Hans de Goede <johannes.goede at oss.qualcomm.com>
Tested-by: Peng Fan <peng.fan at nxp.com> #i.MX95 EVK
Signed-off-by: Sudeep Holla <sudeep.holla at kernel.org>
---
 drivers/firmware/arm_scmi/bus.c | 77 ++++++++++++++++++++++-------------------
 1 file changed, 41 insertions(+), 36 deletions(-)

diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c
index f2e2ed56bc32..ed5bed545030 100644
--- a/drivers/firmware/arm_scmi/bus.c
+++ b/drivers/firmware/arm_scmi/bus.c
@@ -186,12 +186,44 @@ static void scmi_protocol_device_unrequest(const struct scmi_device_id *id_table
 	}
 }
 
+/* Standard protocols table */
+static const struct scmi_device_id scmi_std_id_table[] = {
+	{ SCMI_PROTOCOL_POWER, "genpd" },
+	{ SCMI_PROTOCOL_SYSTEM, "syspower" },
+	{ SCMI_PROTOCOL_PERF, "perf" },
+	{ SCMI_PROTOCOL_PERF, "cpufreq" },
+	{ SCMI_PROTOCOL_CLOCK, "clocks" },
+	{ SCMI_PROTOCOL_SENSOR, "hwmon" },
+	{ SCMI_PROTOCOL_SENSOR, "iiodev" },
+	{ SCMI_PROTOCOL_RESET, "reset" },
+	{ SCMI_PROTOCOL_VOLTAGE, "regulator" },
+	{ SCMI_PROTOCOL_POWERCAP, "powercap" },
+	{ SCMI_PROTOCOL_PINCTRL, "pinctrl" },
+	{ SCMI_PROTOCOL_PINCTRL, "pinctrl-imx" },
+	{ },
+};
+
+static bool scmi_device_id_in_std_id_table(const struct scmi_device_id *id)
+{
+	for (int i = 0; scmi_std_id_table[i].name[0]; i++) {
+		if (scmi_std_id_table[i].protocol_id == id->protocol_id &&
+		    !strcmp(scmi_std_id_table[i].name, id->name))
+			return true;
+	}
+
+	return false;
+}
+
 static int scmi_protocol_table_register(const struct scmi_device_id *id_table)
 {
 	const struct scmi_device_id *entry;
 	int ret;
 
 	for (entry = id_table; entry->name[0]; entry++) {
+		/* Skip standard devices as they are created unconditionally */
+		if (scmi_device_id_in_std_id_table(entry))
+			continue;
+
 		ret = scmi_protocol_device_request(entry);
 		if (ret)
 			goto err_unrequest;
@@ -200,8 +232,11 @@ static int scmi_protocol_table_register(const struct scmi_device_id *id_table)
 	return 0;
 
 err_unrequest:
-	while (entry != id_table)
-		scmi_protocol_device_unrequest(--entry);
+	while (entry != id_table) {
+		--entry;
+		if (!scmi_device_id_in_std_id_table(entry))
+			scmi_protocol_device_unrequest(entry);
+	}
 
 	return ret;
 }
@@ -211,8 +246,10 @@ scmi_protocol_table_unregister(const struct scmi_device_id *id_table)
 {
 	const struct scmi_device_id *entry;
 
-	for (entry = id_table; entry->name[0]; entry++)
-		scmi_protocol_device_unrequest(entry);
+	for (entry = id_table; entry->name[0]; entry++) {
+		if (!scmi_device_id_in_std_id_table(entry))
+			scmi_protocol_device_unrequest(entry);
+	}
 }
 
 static bool scmi_device_name_is_transport(const char *name)
@@ -542,34 +579,6 @@ _scmi_device_create(struct fwnode_handle *fwnode, struct device *parent,
 	return sdev;
 }
 
-/* Standard protocols table */
-static const struct scmi_device_id scmi_std_id_table[] = {
-	{ SCMI_PROTOCOL_POWER, "genpd" },
-	{ SCMI_PROTOCOL_SYSTEM, "syspower" },
-	{ SCMI_PROTOCOL_PERF, "perf" },
-	{ SCMI_PROTOCOL_PERF, "cpufreq" },
-	{ SCMI_PROTOCOL_CLOCK, "clocks" },
-	{ SCMI_PROTOCOL_SENSOR, "hwmon" },
-	{ SCMI_PROTOCOL_SENSOR, "iiodev" },
-	{ SCMI_PROTOCOL_RESET, "reset" },
-	{ SCMI_PROTOCOL_VOLTAGE, "regulator" },
-	{ SCMI_PROTOCOL_POWERCAP, "powercap" },
-	{ SCMI_PROTOCOL_PINCTRL, "pinctrl" },
-	{ SCMI_PROTOCOL_PINCTRL, "pinctrl-imx" },
-	{ },
-};
-
-static bool scmi_device_id_in_std_id_table(const struct scmi_device_id *id)
-{
-	for (int i = 0; scmi_std_id_table[i].name[0]; i++) {
-		if (scmi_std_id_table[i].protocol_id == id->protocol_id &&
-		    !strcmp(scmi_std_id_table[i].name, id->name))
-			return true;
-	}
-
-	return false;
-}
-
 /**
  * scmi_device_create  - A method to create one or more SCMI devices
  *
@@ -634,10 +643,6 @@ struct scmi_device *scmi_device_create(struct fwnode_handle *fwnode,
 
 	/* Walk the list of requested devices for protocol and create them */
 	list_for_each_entry(rdev, phead, node) {
-		/* Standard proto matches already have their dev created above */
-		if (scmi_device_id_in_std_id_table(rdev->id_table))
-			continue;
-
 		sdev = _scmi_device_create(fwnode, parent,
 					   rdev->id_table->protocol_id,
 					   rdev->id_table->name);

-- 
2.43.0