firmware: arm_scmi: Extend protocol registration interfaces

Extend common protocol registration routines and provide some new generic
protocols get/put helpers that can track protocols usage and automatically
perform the proper initialization and de-initialization on demand when
required.

Convert all standard protocols to use this new registration scheme while
keeping them all still using the usual initialization logic bound to SCMI
devices probing.

Link: https://lore.kernel.org/r/20210316124903.35011-2-cristian.marussi@arm.com
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

1 files changed, 180 insertions, 2 deletions

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 3e748e57deab..c1ec80e00734 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -11,11 +11,12 @@
  * various power domain DVFS including the core/cluster, certain system
  * clocks configuration, thermal sensors and many others.
  *
- * Copyright (C) 2018 ARM Ltd.
+ * Copyright (C) 2018-2021 ARM Ltd.
  */
 
 #include <linux/bitmap.h>
 #include <linux/export.h>
+#include <linux/idr.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/ktime.h>
@@ -23,6 +24,7 @@
 #include <linux/of_address.h>
 #include <linux/of_device.h>
 #include <linux/processor.h>
+#include <linux/refcount.h>
 #include <linux/slab.h>
 
 #include "common.h"
@@ -69,6 +71,21 @@ struct scmi_xfers_info {
 };
 
 /**
+ * struct scmi_protocol_instance  - Describe an initialized protocol instance.
+ * @proto: A reference to the protocol descriptor.
+ * @gid: A reference for per-protocol devres management.
+ * @users: A refcount to track effective users of this protocol.
+ *
+ * Each protocol is initialized independently once for each SCMI platform in
+ * which is defined by DT and implemented by the SCMI server fw.
+ */
+struct scmi_protocol_instance {
+	const struct scmi_protocol	*proto;
+	void				*gid;
+	refcount_t			users;
+};
+
+/**
  * struct scmi_info - Structure representing a SCMI instance
  *
  * @dev: Device pointer
@@ -80,6 +97,10 @@ struct scmi_xfers_info {
  * @rx_minfo: Universal Receive Message management info
  * @tx_idr: IDR object to map protocol id to Tx channel info pointer
  * @rx_idr: IDR object to map protocol id to Rx channel info pointer
+ * @protocols: IDR for protocols' instance descriptors initialized for
+ *	       this SCMI instance: populated on protocol's first attempted
+ *	       usage.
+ * @protocols_mtx: A mutex to protect protocols instances initialization.
  * @protocols_imp: List of protocols implemented, currently maximum of
  *	MAX_PROTOCOLS_IMP elements allocated by the base protocol
  * @node: List head
@@ -94,6 +115,9 @@ struct scmi_info {
 	struct scmi_xfers_info rx_minfo;
 	struct idr tx_idr;
 	struct idr rx_idr;
+	struct idr protocols;
+	/* Ensure mutual exclusive access to protocols instance array */
+	struct mutex protocols_mtx;
 	u8 *protocols_imp;
 	struct list_head node;
 	int users;
@@ -519,6 +543,150 @@ int scmi_version_get(const struct scmi_handle *handle, u8 protocol,
 	return ret;
 }
 
+/**
+ * scmi_alloc_init_protocol_instance  - Allocate and initialize a protocol
+ * instance descriptor.
+ * @info: The reference to the related SCMI instance.
+ * @proto: The protocol descriptor.
+ *
+ * Allocate a new protocol instance descriptor, using the provided @proto
+ * description, against the specified SCMI instance @info, and initialize it;
+ * all resources management is handled via a dedicated per-protocol devres
+ * group.
+ *
+ * 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.
+ */
+static struct scmi_protocol_instance *
+scmi_alloc_init_protocol_instance(struct scmi_info *info,
+				  const struct scmi_protocol *proto)
+{
+	int ret = -ENOMEM;
+	void *gid;
+	struct scmi_protocol_instance *pi;
+	struct scmi_handle *handle = &info->handle;
+
+	/* Protocol specific devres group */
+	gid = devres_open_group(handle->dev, NULL, GFP_KERNEL);
+	if (!gid)
+		goto out;
+
+	pi = devm_kzalloc(handle->dev, sizeof(*pi), GFP_KERNEL);
+	if (!pi)
+		goto clean;
+
+	pi->gid = gid;
+	pi->proto = proto;
+	refcount_set(&pi->users, 1);
+	/* proto->init is assured NON NULL by scmi_protocol_register */
+	ret = pi->proto->instance_init(handle);
+	if (ret)
+		goto clean;
+
+	ret = idr_alloc(&info->protocols, pi, proto->id, proto->id + 1,
+			GFP_KERNEL);
+	if (ret != proto->id)
+		goto clean;
+
+	devres_close_group(handle->dev, pi->gid);
+	dev_dbg(handle->dev, "Initialized protocol: 0x%X\n", pi->proto->id);
+
+	return pi;
+
+clean:
+	devres_release_group(handle->dev, gid);
+out:
+	return ERR_PTR(ret);
+}
+
+/**
+ * scmi_get_protocol_instance  - Protocol initialization helper.
+ * @handle: A reference to the SCMI platform instance.
+ * @protocol_id: The protocol being requested.
+ *
+ * In case the required protocol has never been requested before for this
+ * 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.
+ */
+static struct scmi_protocol_instance * __must_check
+scmi_get_protocol_instance(struct scmi_handle *handle, u8 protocol_id)
+{
+	struct scmi_protocol_instance *pi;
+	struct scmi_info *info = handle_to_scmi_info(handle);
+
+	mutex_lock(&info->protocols_mtx);
+	pi = idr_find(&info->protocols, protocol_id);
+
+	if (pi) {
+		refcount_inc(&pi->users);
+	} else {
+		const struct scmi_protocol *proto;
+
+		/* Fails if protocol not registered on bus */
+		proto = scmi_protocol_get(protocol_id);
+		if (proto)
+			pi = scmi_alloc_init_protocol_instance(info, proto);
+		else
+			pi = ERR_PTR(-ENODEV);
+	}
+	mutex_unlock(&info->protocols_mtx);
+
+	return pi;
+}
+
+/**
+ * scmi_protocol_acquire  - Protocol acquire
+ * @handle: A reference to the SCMI platform instance.
+ * @protocol_id: The protocol being requested.
+ *
+ * Register a new user for the requested protocol on the specified SCMI
+ * platform instance, possibly triggering its initialization on first user.
+ *
+ * Return: 0 if protocol was acquired successfully.
+ */
+int scmi_protocol_acquire(struct scmi_handle *handle, u8 protocol_id)
+{
+	return PTR_ERR_OR_ZERO(scmi_get_protocol_instance(handle, protocol_id));
+}
+
+/**
+ * scmi_protocol_release  - Protocol de-initialization helper.
+ * @handle: A reference to the SCMI platform instance.
+ * @protocol_id: The protocol being requested.
+ *
+ * Remove one user for the specified protocol and triggers de-initialization
+ * and resources de-allocation once the last user has gone.
+ */
+void scmi_protocol_release(struct scmi_handle *handle, u8 protocol_id)
+{
+	struct scmi_info *info = handle_to_scmi_info(handle);
+	struct scmi_protocol_instance *pi;
+
+	mutex_lock(&info->protocols_mtx);
+	pi = idr_find(&info->protocols, protocol_id);
+	if (WARN_ON(!pi))
+		goto out;
+
+	if (refcount_dec_and_test(&pi->users)) {
+		void *gid = pi->gid;
+
+		if (pi->proto->instance_deinit)
+			pi->proto->instance_deinit(handle);
+
+		idr_remove(&info->protocols, protocol_id);
+
+		devres_release_group(handle->dev, gid);
+		dev_dbg(handle->dev, "De-Initialized protocol: 0x%X\n",
+			protocol_id);
+	}
+
+out:
+	mutex_unlock(&info->protocols_mtx);
+}
+
 void scmi_setup_protocol_implemented(const struct scmi_handle *handle,
 				     u8 *prot_imp)
 {
@@ -786,6 +954,8 @@ static int scmi_probe(struct platform_device *pdev)
 	info->dev = dev;
 	info->desc = desc;
 	INIT_LIST_HEAD(&info->node);
+	idr_init(&info->protocols);
+	mutex_init(&info->protocols_mtx);
 
 	platform_set_drvdata(pdev, info);
 	idr_init(&info->tx_idr);
@@ -860,6 +1030,10 @@ static int scmi_remove(struct platform_device *pdev)
 
 	scmi_notification_exit(&info->handle);
 
+	mutex_lock(&info->protocols_mtx);
+	idr_destroy(&info->protocols);
+	mutex_unlock(&info->protocols_mtx);
+
 	/* Safe to free channels since no more users */
 	ret = idr_for_each(idr, info->desc->ops->chan_free, idr);
 	idr_destroy(&info->tx_idr);
@@ -942,6 +1116,8 @@ static int __init scmi_driver_init(void)
 {
 	scmi_bus_init();
 
+	scmi_base_register();
+
 	scmi_clock_register();
 	scmi_perf_register();
 	scmi_power_register();
@@ -956,7 +1132,7 @@ subsys_initcall(scmi_driver_init);
 
 static void __exit scmi_driver_exit(void)
 {
-	scmi_bus_exit();
+	scmi_base_unregister();
 
 	scmi_clock_unregister();
 	scmi_perf_unregister();
@@ -966,6 +1142,8 @@ static void __exit scmi_driver_exit(void)
 	scmi_voltage_unregister();
 	scmi_system_unregister();
 
+	scmi_bus_exit();
+
 	platform_driver_unregister(&scmi_driver);
 }
 module_exit(scmi_driver_exit);