firmware: arm_scmi: Add protocol modularization support

Extend SCMI protocols accounting mechanism to address possible module
usage and add the support to possibly define new protocols as loadable
modules.

Keep the standard protocols built into the SCMI core.

Link: https://lore.kernel.org/r/20210316124903.35011-38-cristian.marussi@arm.comTested-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NCristian Marussi <cristian.marussi@arm.com>
Signed-off-by: NSudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/base.c

@@ -7,6 +7,7 @@
 
 #define pr_fmt(fmt) "SCMI Notifications BASE - " fmt
 
+#include <linux/module.h>
 #include <linux/scmi_protocol.h>
 
 #include "common.h"
@@ -373,6 +374,7 @@ static int scmi_base_protocol_init(const struct scmi_protocol_handle *ph)
 
 static const struct scmi_protocol scmi_base = {
 	.id = SCMI_PROTOCOL_BASE,
+	.owner = NULL,
 	.instance_init = &scmi_base_protocol_init,
 	.ops = NULL,
 	.events = &base_protocol_events,

drivers/firmware/arm_scmi/bus.c

@@ -56,7 +56,7 @@ const struct scmi_protocol *scmi_protocol_get(int protocol_id)
 	const struct scmi_protocol *proto;
 
 	proto = idr_find(&scmi_protocols, protocol_id);
-	if (!proto) {
+	if (!proto || !try_module_get(proto->owner)) {
 		pr_warn("SCMI Protocol 0x%x not found!\n", protocol_id);
 		return NULL;
 	}
@@ -66,6 +66,15 @@ const struct scmi_protocol *scmi_protocol_get(int protocol_id)
 	return proto;
 }
 
+void scmi_protocol_put(int protocol_id)
+{
+	const struct scmi_protocol *proto;
+
+	proto = idr_find(&scmi_protocols, protocol_id);
+	if (proto)
+		module_put(proto->owner);
+}
+
 static int scmi_dev_probe(struct device *dev)
 {
 	struct scmi_driver *scmi_drv = to_scmi_driver(dev->driver);

drivers/firmware/arm_scmi/clock.c

@@ -5,6 +5,7 @@
  * Copyright (C) 2018-2021 ARM Ltd.
  */
 
+#include <linux/module.h>
 #include <linux/sort.h>
 
 #include "common.h"
@@ -367,6 +368,7 @@ static int scmi_clock_protocol_init(const struct scmi_protocol_handle *ph)
 
 static const struct scmi_protocol scmi_clock = {
 	.id = SCMI_PROTOCOL_CLOCK,
+	.owner = THIS_MODULE,
 	.instance_init = &scmi_clock_protocol_init,
 	.ops = &clk_proto_ops,
 };

drivers/firmware/arm_scmi/common.h

@@ -14,6 +14,7 @@
 #include <linux/device.h>
 #include <linux/errno.h>
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/scmi_protocol.h>
 #include <linux/types.h>
 
@@ -214,6 +215,7 @@ typedef int (*scmi_prot_init_ph_fn_t)(const struct scmi_protocol_handle *);
 /**
  * struct scmi_protocol  - Protocol descriptor
  * @id: Protocol ID.
+ * @owner: Module reference if any.
  * @instance_init: Mandatory protocol initialization function.
  * @instance_deinit: Optional protocol de-initialization function.
  * @ops: Optional reference to the operations provided by the protocol and
@@ -222,6 +224,7 @@ typedef int (*scmi_prot_init_ph_fn_t)(const struct scmi_protocol_handle *);
  */
 struct scmi_protocol {
 	const u8				id;
+	struct module				*owner;
 	const scmi_prot_init_ph_fn_t		instance_init;
 	const scmi_prot_init_ph_fn_t		instance_deinit;
 	const void				*ops;
@@ -257,6 +260,7 @@ void __exit scmi_##name##_unregister(void)			\
 }
 
 const struct scmi_protocol *scmi_protocol_get(int protocol_id);
+void scmi_protocol_put(int protocol_id);
 
 int scmi_protocol_acquire(const struct scmi_handle *handle, u8 protocol_id);
 void scmi_protocol_release(const struct scmi_handle *handle, u8 protocol_id);

drivers/firmware/arm_scmi/driver.c

@@ -660,7 +660,8 @@ scmi_revision_area_get(const struct scmi_protocol_handle *ph)
  *
  * Context: Assumes to be called with @protocols_mtx already acquired.
  * Return: A reference to a freshly allocated and initialized protocol instance
- *	   or ERR_PTR on failure.
+ *	   or ERR_PTR on failure. On failure the @proto reference is at first
+ *	   put using @scmi_protocol_put() before releasing all the devres group.
  */
 static struct scmi_protocol_instance *
 scmi_alloc_init_protocol_instance(struct scmi_info *info,
@@ -673,8 +674,10 @@ scmi_alloc_init_protocol_instance(struct scmi_info *info,
 
 	/* Protocol specific devres group */
 	gid = devres_open_group(handle->dev, NULL, GFP_KERNEL);
-	if (!gid)
+	if (!gid) {
+		scmi_protocol_put(proto->id);
 		goto out;
+	}
 
 	pi = devm_kzalloc(handle->dev, sizeof(*pi), GFP_KERNEL);
 	if (!pi)
@@ -718,6 +721,8 @@ scmi_alloc_init_protocol_instance(struct scmi_info *info,
 	return pi;
 
 clean:
+	/* Take care to put the protocol module's owner before releasing all */
+	scmi_protocol_put(proto->id);
 	devres_release_group(handle->dev, gid);
 out:
 	return ERR_PTR(ret);
@@ -732,7 +737,9 @@ scmi_alloc_init_protocol_instance(struct scmi_info *info,
  * instance, allocate and initialize all the needed structures while handling
  * resource allocation with a dedicated per-protocol devres subgroup.
  *
- * Return: A reference to an initialized protocol instance or error on failure.
+ * Return: A reference to an initialized protocol instance or error on failure:
+ *	   in particular returns -EPROBE_DEFER when the desired protocol could
+ *	   NOT be found.
  */
 static struct scmi_protocol_instance * __must_check
 scmi_get_protocol_instance(const struct scmi_handle *handle, u8 protocol_id)
@@ -753,7 +760,7 @@ scmi_get_protocol_instance(const struct scmi_handle *handle, u8 protocol_id)
 		if (proto)
 			pi = scmi_alloc_init_protocol_instance(info, proto);
 		else
-			pi = ERR_PTR(-ENODEV);
+			pi = ERR_PTR(-EPROBE_DEFER);
 	}
 	mutex_unlock(&info->protocols_mtx);
 
@@ -804,6 +811,8 @@ void scmi_protocol_release(const struct scmi_handle *handle, u8 protocol_id)
 
 		idr_remove(&info->protocols, protocol_id);
 
+		scmi_protocol_put(protocol_id);
+
 		devres_release_group(handle->dev, gid);
 		dev_dbg(handle->dev, "De-Initialized protocol: 0x%X\n",
 			protocol_id);

drivers/firmware/arm_scmi/perf.c

@@ -11,6 +11,7 @@
 #include <linux/of.h>
 #include <linux/io.h>
 #include <linux/io-64-nonatomic-hi-lo.h>
+#include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/pm_opp.h>
 #include <linux/scmi_protocol.h>
@@ -909,6 +910,7 @@ static int scmi_perf_protocol_init(const struct scmi_protocol_handle *ph)
 
 static const struct scmi_protocol scmi_perf = {
 	.id = SCMI_PROTOCOL_PERF,
+	.owner = THIS_MODULE,
 	.instance_init = &scmi_perf_protocol_init,
 	.ops = &perf_proto_ops,
 	.events = &perf_protocol_events,

drivers/firmware/arm_scmi/power.c

@@ -7,6 +7,7 @@
 
 #define pr_fmt(fmt) "SCMI Notifications POWER - " fmt
 
+#include <linux/module.h>
 #include <linux/scmi_protocol.h>
 
 #include "common.h"
@@ -312,6 +313,7 @@ static int scmi_power_protocol_init(const struct scmi_protocol_handle *ph)
 
 static const struct scmi_protocol scmi_power = {
 	.id = SCMI_PROTOCOL_POWER,
+	.owner = THIS_MODULE,
 	.instance_init = &scmi_power_protocol_init,
 	.ops = &power_proto_ops,
 	.events = &power_protocol_events,

drivers/firmware/arm_scmi/reset.c

@@ -7,6 +7,7 @@
 
 #define pr_fmt(fmt) "SCMI Notifications RESET - " fmt
 
+#include <linux/module.h>
 #include <linux/scmi_protocol.h>
 
 #include "common.h"
@@ -324,6 +325,7 @@ static int scmi_reset_protocol_init(const struct scmi_protocol_handle *ph)
 
 static const struct scmi_protocol scmi_reset = {
 	.id = SCMI_PROTOCOL_RESET,
+	.owner = THIS_MODULE,
 	.instance_init = &scmi_reset_protocol_init,
 	.ops = &reset_proto_ops,
 	.events = &reset_protocol_events,

drivers/firmware/arm_scmi/sensors.c

@@ -8,6 +8,7 @@
 #define pr_fmt(fmt) "SCMI Notifications SENSOR - " fmt
 
 #include <linux/bitfield.h>
+#include <linux/module.h>
 #include <linux/scmi_protocol.h>
 
 #include "common.h"
@@ -990,6 +991,7 @@ static int scmi_sensors_protocol_init(const struct scmi_protocol_handle *ph)
 
 static const struct scmi_protocol scmi_sensors = {
 	.id = SCMI_PROTOCOL_SENSOR,
+	.owner = THIS_MODULE,
 	.instance_init = &scmi_sensors_protocol_init,
 	.ops = &sensor_proto_ops,
 	.events = &sensor_protocol_events,

drivers/firmware/arm_scmi/system.c

@@ -7,6 +7,7 @@
 
 #define pr_fmt(fmt) "SCMI Notifications SYSTEM - " fmt
 
+#include <linux/module.h>
 #include <linux/scmi_protocol.h>
 
 #include "common.h"
@@ -130,6 +131,7 @@ static int scmi_system_protocol_init(const struct scmi_protocol_handle *ph)
 
 static const struct scmi_protocol scmi_system = {
 	.id = SCMI_PROTOCOL_SYSTEM,
+	.owner = THIS_MODULE,
 	.instance_init = &scmi_system_protocol_init,
 	.ops = NULL,
 	.events = &system_protocol_events,

drivers/firmware/arm_scmi/voltage.c

@@ -5,6 +5,7 @@
  * Copyright (C) 2020-2021 ARM Ltd.
  */
 
+#include <linux/module.h>
 #include <linux/scmi_protocol.h>
 
 #include "common.h"
@@ -371,6 +372,7 @@ static int scmi_voltage_protocol_init(const struct scmi_protocol_handle *ph)
 
 static const struct scmi_protocol scmi_voltage = {
 	.id = SCMI_PROTOCOL_VOLTAGE,
+	.owner = THIS_MODULE,
 	.instance_init = &scmi_voltage_protocol_init,
 	.ops = &voltage_proto_ops,
 };

include/linux/scmi_protocol.h

@@ -704,6 +704,18 @@ static inline void scmi_driver_unregister(struct scmi_driver *driver) {}
 #define module_scmi_driver(__scmi_driver)	\
 	module_driver(__scmi_driver, scmi_register, scmi_unregister)
 
+/**
+ * module_scmi_protocol() - Helper macro for registering a scmi protocol
+ * @__scmi_protocol: scmi_protocol structure
+ *
+ * Helper macro for scmi drivers to set up proper module init / exit
+ * functions.  Replaces module_init() and module_exit() and keeps people from
+ * printing pointless things to the kernel log when their driver is loaded.
+ */
+#define module_scmi_protocol(__scmi_protocol)	\
+	module_driver(__scmi_protocol,		\
+		      scmi_protocol_register, scmi_protocol_unregister)
+
 struct scmi_protocol;
 int scmi_protocol_register(const struct scmi_protocol *proto);
 void scmi_protocol_unregister(const struct scmi_protocol *proto);