FROMLIST: 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 Standard protocols built into the SCMI core.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>

Bug: 171409184
Link: https://lore.kernel.org/linux-arm-kernel/20210202221555.41167-1-cristian.marussi@arm.com/
Change-Id: I75f2e400c0fe6a0692a1acc2e20f54a3c7336ab7
Signed-off-by: Rishabh Bhatnagar <quic_rishabhb@quicinc.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,
 	.init_instance = &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_get_protocol(int protocol_id)
 	const struct scmi_protocol *proto;
 
 	proto = idr_find(&scmi_available_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_get_protocol(int protocol_id)
 	return proto;
 }
 
+void scmi_put_protocol(int protocol_id)
+{
+	const struct scmi_protocol *proto;
+
+	proto = idr_find(&scmi_available_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) 2018-2020 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,
 	.init_instance = &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.
  * @init_instance: Mandatory protocol initialization function.
  * @deinit_instance: 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		init_instance;
 	const scmi_prot_init_ph_fn_t		deinit_instance;
 	const void				*ops;
@@ -255,6 +258,7 @@ void __exit scmi_##name##_unregister(void) \
 }
 
 const struct scmi_protocol *scmi_get_protocol(int protocol_id);
+void scmi_put_protocol(int protocol_id);
 
 int scmi_acquire_protocol(const struct scmi_handle *handle, u8 protocol_id);
 void scmi_release_protocol(const struct scmi_handle *handle, u8 protocol_id);

drivers/firmware/arm_scmi/driver.c

@@ -677,7 +677,7 @@ scmi_get_protocol_instance(const struct scmi_handle *handle, u8 protocol_id)
 		/* Fail if protocol not registered on bus */
 		proto = scmi_get_protocol(protocol_id);
 		if (!proto) {
-			ret = -ENODEV;
+			ret = -EPROBE_DEFER;
 			goto out;
 		}
 
@@ -722,6 +722,7 @@ scmi_get_protocol_instance(const struct scmi_handle *handle, u8 protocol_id)
 	return pi;
 
 clean:
+	scmi_put_protocol(protocol_id);
 	devres_release_group(handle->dev, gid);
 out:
 	mutex_unlock(&info->protocols_mtx);
@@ -772,6 +773,8 @@ void scmi_release_protocol(const struct scmi_handle *handle, u8 protocol_id)
 
 		idr_remove(&info->protocols, protocol_id);
 
+		scmi_put_protocol(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,
 	.init_instance = &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,
 	.init_instance = &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,
 	.init_instance = &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,
 	.init_instance = &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,
 	.init_instance = &scmi_system_protocol_init,
 	.ops = NULL,
 	.events = &system_protocol_events,

include/linux/scmi_protocol.h

@@ -709,6 +709,18 @@ 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);