firmware: arm_ffa: Add initial FFA bus support for device enumeration

The Arm FF for Armv8-A specification has concept of endpoints or
partitions. In the Normal world, a partition could be a VM when
the Virtualization extension is enabled or the kernel itself.

In order to handle multiple partitions, we can create a FFA device for
each such partition on a dedicated FFA bus. Similarly, different drivers
requiring FFA transport can be registered on the same bus. We can match
the device and drivers using UUID. This is mostly for the in-kernel
users with FFA drivers.

Link: https://lore.kernel.org/r/20210521151033.181846-2-sudeep.holla@arm.com
Tested-by: Jens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

MAINTAINERS

@@ -7069,6 +7069,13 @@ F:	include/linux/firewire.h
 F:	include/uapi/linux/firewire*.h
 F:	tools/firewire/
 
+FIRMWARE FRAMEWORK FOR ARMV8-A
+M:	Sudeep Holla <sudeep.holla@arm.com>
+L:	linux-arm-kernel@lists.infradead.org
+S:	Maintained
+F:	drivers/firmware/arm_ffa/
+F:	include/linux/arm_ffa.h
+
 FIRMWARE LOADER (request_firmware)
 M:	Luis Chamberlain <mcgrof@kernel.org>
 L:	linux-kernel@vger.kernel.org

drivers/firmware/Kconfig

@@ -296,6 +296,7 @@ config TURRIS_MOX_RWTM
 	  other manufacturing data and also utilize the Entropy Bit Generator
 	  for hardware random number generation.
 
+source "drivers/firmware/arm_ffa/Kconfig"
 source "drivers/firmware/broadcom/Kconfig"
 source "drivers/firmware/google/Kconfig"
 source "drivers/firmware/efi/Kconfig"

drivers/firmware/Makefile

@@ -22,6 +22,7 @@ obj-$(CONFIG_TI_SCI_PROTOCOL)	+= ti_sci.o
 obj-$(CONFIG_TRUSTED_FOUNDATIONS) += trusted_foundations.o
 obj-$(CONFIG_TURRIS_MOX_RWTM)	+= turris-mox-rwtm.o
 
+obj-y				+= arm_ffa/
 obj-y				+= arm_scmi/
 obj-y				+= broadcom/
 obj-y				+= meson/

drivers/firmware/arm_ffa/Kconfig

@@ -0,0 +1,16 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config ARM_FFA_TRANSPORT
+	tristate "Arm Firmware Framework for Armv8-A"
+	depends on OF
+	depends on ARM64
+	default n
+	help
+	  This Firmware Framework(FF) for Arm A-profile processors describes
+	  interfaces that standardize communication between the various
+	  software images which includes communication between images in
+	  the Secure world and Normal world. It also leverages the
+	  virtualization extension to isolate software images provided
+	  by an ecosystem of vendors from each other.
+
+	  This driver provides interface for all the client drivers making
+	  use of the features offered by ARM FF-A.

drivers/firmware/arm_ffa/Makefile

@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
+ffa-bus-y = bus.o
+ffa-module-objs := $(ffa-bus-y)
+obj-$(CONFIG_ARM_FFA_TRANSPORT) = ffa-module.o

drivers/firmware/arm_ffa/bus.c

@@ -0,0 +1,207 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 ARM Ltd.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/arm_ffa.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+static int ffa_device_match(struct device *dev, struct device_driver *drv)
+{
+	const struct ffa_device_id *id_table;
+	struct ffa_device *ffa_dev;
+
+	id_table = to_ffa_driver(drv)->id_table;
+	ffa_dev = to_ffa_dev(dev);
+
+	while (!uuid_is_null(&id_table->uuid)) {
+		if (uuid_equal(&ffa_dev->uuid, &id_table->uuid))
+			return 1;
+		id_table++;
+	}
+
+	return 0;
+}
+
+static int ffa_device_probe(struct device *dev)
+{
+	struct ffa_driver *ffa_drv = to_ffa_driver(dev->driver);
+	struct ffa_device *ffa_dev = to_ffa_dev(dev);
+
+	if (!ffa_device_match(dev, dev->driver))
+		return -ENODEV;
+
+	return ffa_drv->probe(ffa_dev);
+}
+
+static int ffa_device_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+	struct ffa_device *ffa_dev = to_ffa_dev(dev);
+
+	return add_uevent_var(env, "MODALIAS=arm_ffa:%04x:%pUb",
+			      ffa_dev->vm_id, &ffa_dev->uuid);
+}
+
+static ssize_t partition_id_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	struct ffa_device *ffa_dev = to_ffa_dev(dev);
+
+	return sprintf(buf, "0x%04x\n", ffa_dev->vm_id);
+}
+static DEVICE_ATTR_RO(partition_id);
+
+static ssize_t uuid_show(struct device *dev, struct device_attribute *attr,
+			 char *buf)
+{
+	struct ffa_device *ffa_dev = to_ffa_dev(dev);
+
+	return sprintf(buf, "%pUb\n", &ffa_dev->uuid);
+}
+static DEVICE_ATTR_RO(uuid);
+
+static struct attribute *ffa_device_attributes_attrs[] = {
+	&dev_attr_partition_id.attr,
+	&dev_attr_uuid.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(ffa_device_attributes);
+
+struct bus_type ffa_bus_type = {
+	.name		= "arm_ffa",
+	.match		= ffa_device_match,
+	.probe		= ffa_device_probe,
+	.uevent		= ffa_device_uevent,
+	.dev_groups	= ffa_device_attributes_groups,
+};
+EXPORT_SYMBOL_GPL(ffa_bus_type);
+
+int ffa_driver_register(struct ffa_driver *driver, struct module *owner,
+			const char *mod_name)
+{
+	int ret;
+
+	driver->driver.bus = &ffa_bus_type;
+	driver->driver.name = driver->name;
+	driver->driver.owner = owner;
+	driver->driver.mod_name = mod_name;
+
+	ret = driver_register(&driver->driver);
+	if (!ret)
+		pr_debug("registered new ffa driver %s\n", driver->name);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ffa_driver_register);
+
+void ffa_driver_unregister(struct ffa_driver *driver)
+{
+	driver_unregister(&driver->driver);
+}
+EXPORT_SYMBOL_GPL(ffa_driver_unregister);
+
+static void ffa_release_device(struct device *dev)
+{
+	struct ffa_device *ffa_dev = to_ffa_dev(dev);
+
+	kfree(ffa_dev);
+}
+
+static int __ffa_devices_unregister(struct device *dev, void *data)
+{
+	ffa_release_device(dev);
+
+	return 0;
+}
+
+static void ffa_devices_unregister(void)
+{
+	bus_for_each_dev(&ffa_bus_type, NULL, NULL,
+			 __ffa_devices_unregister);
+}
+
+bool ffa_device_is_valid(struct ffa_device *ffa_dev)
+{
+	bool valid = false;
+	struct device *dev = NULL;
+	struct ffa_device *tmp_dev;
+
+	do {
+		dev = bus_find_next_device(&ffa_bus_type, dev);
+		tmp_dev = to_ffa_dev(dev);
+		if (tmp_dev == ffa_dev) {
+			valid = true;
+			break;
+		}
+		put_device(dev);
+	} while (dev);
+
+	put_device(dev);
+
+	return valid;
+}
+
+struct ffa_device *ffa_device_register(const uuid_t *uuid, int vm_id)
+{
+	int ret;
+	struct device *dev;
+	struct ffa_device *ffa_dev;
+
+	ffa_dev = kzalloc(sizeof(*ffa_dev), GFP_KERNEL);
+	if (!ffa_dev)
+		return NULL;
+
+	dev = &ffa_dev->dev;
+	dev->bus = &ffa_bus_type;
+	dev->release = ffa_release_device;
+	dev_set_name(&ffa_dev->dev, "arm-ffa-%04x", vm_id);
+
+	ffa_dev->vm_id = vm_id;
+	uuid_copy(&ffa_dev->uuid, uuid);
+
+	ret = device_register(&ffa_dev->dev);
+	if (ret) {
+		dev_err(dev, "unable to register device %s err=%d\n",
+			dev_name(dev), ret);
+		put_device(dev);
+		return NULL;
+	}
+
+	return ffa_dev;
+}
+EXPORT_SYMBOL_GPL(ffa_device_register);
+
+void ffa_device_unregister(struct ffa_device *ffa_dev)
+{
+	if (!ffa_dev)
+		return;
+
+	device_unregister(&ffa_dev->dev);
+}
+EXPORT_SYMBOL_GPL(ffa_device_unregister);
+
+static int __init arm_ffa_bus_init(void)
+{
+	return bus_register(&ffa_bus_type);
+}
+module_init(arm_ffa_bus_init);
+
+static void __exit arm_ffa_bus_exit(void)
+{
+	ffa_devices_unregister();
+	bus_unregister(&ffa_bus_type);
+}
+
+module_exit(arm_ffa_bus_exit);
+
+MODULE_ALIAS("arm-ffa-bus");
+MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
+MODULE_DESCRIPTION("Arm FF-A bus driver");
+MODULE_LICENSE("GPL v2");

include/linux/arm_ffa.h

@@ -0,0 +1,91 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 ARM Ltd.
+ */
+
+#ifndef _LINUX_ARM_FFA_H
+#define _LINUX_ARM_FFA_H
+
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/uuid.h>
+
+/* FFA Bus/Device/Driver related */
+struct ffa_device {
+	int vm_id;
+	uuid_t uuid;
+	struct device dev;
+};
+
+#define to_ffa_dev(d) container_of(d, struct ffa_device, dev)
+
+struct ffa_device_id {
+	uuid_t uuid;
+};
+
+struct ffa_driver {
+	const char *name;
+	int (*probe)(struct ffa_device *sdev);
+	void (*remove)(struct ffa_device *sdev);
+	const struct ffa_device_id *id_table;
+
+	struct device_driver driver;
+};
+
+#define to_ffa_driver(d) container_of(d, struct ffa_driver, driver)
+
+static inline void ffa_dev_set_drvdata(struct ffa_device *fdev, void *data)
+{
+	fdev->dev.driver_data = data;
+}
+
+#if IS_REACHABLE(CONFIG_ARM_FFA_TRANSPORT)
+struct ffa_device *ffa_device_register(const uuid_t *uuid, int vm_id);
+void ffa_device_unregister(struct ffa_device *ffa_dev);
+int ffa_driver_register(struct ffa_driver *driver, struct module *owner,
+			const char *mod_name);
+void ffa_driver_unregister(struct ffa_driver *driver);
+bool ffa_device_is_valid(struct ffa_device *ffa_dev);
+
+#else
+static inline
+struct ffa_device *ffa_device_register(const uuid_t *uuid, int vm_id)
+{
+	return NULL;
+}
+
+static inline void ffa_device_unregister(struct ffa_device *dev) {}
+
+static inline int
+ffa_driver_register(struct ffa_driver *driver, struct module *owner,
+		    const char *mod_name)
+{
+	return -EINVAL;
+}
+
+static inline void ffa_driver_unregister(struct ffa_driver *driver) {}
+
+static inline
+bool ffa_device_is_valid(struct ffa_device *ffa_dev) { return false; }
+
+#endif /* CONFIG_ARM_FFA_TRANSPORT */
+
+#define ffa_register(driver) \
+	ffa_driver_register(driver, THIS_MODULE, KBUILD_MODNAME)
+#define ffa_unregister(driver) \
+	ffa_driver_unregister(driver)
+
+/**
+ * module_ffa_driver() - Helper macro for registering a psa_ffa driver
+ * @__ffa_driver: ffa_driver structure
+ *
+ * Helper macro for psa_ffa 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_ffa_driver(__ffa_driver)	\
+	module_driver(__ffa_driver, ffa_register, ffa_unregister)
+
+#endif /* _LINUX_ARM_FFA_H */