@@ -17931,6 +17931,14 @@ F: include/linux/pm_*
F: include/linux/powercap.h
F: kernel/configs/nopm.config
+POWER SEQUENCING
+M: Bartosz Golaszewski <brgl@bgdev.pl>
+L: linux-pm@vger.kernel.org
+S: Maintained
+T: git git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux.git
+F: drivers/power/sequencing/
+F: include/linux/pwrseq/
+
POWER STATE COORDINATION INTERFACE (PSCI)
M: Mark Rutland <mark.rutland@arm.com>
M: Lorenzo Pieralisi <lpieralisi@kernel.org>
@@ -1,3 +1,4 @@
# SPDX-License-Identifier: GPL-2.0-only
source "drivers/power/reset/Kconfig"
+source "drivers/power/sequencing/Kconfig"
source "drivers/power/supply/Kconfig"
@@ -1,3 +1,4 @@
# SPDX-License-Identifier: GPL-2.0-only
obj-$(CONFIG_POWER_RESET) += reset/
+obj-$(CONFIG_POWER_SEQUENCING) += sequencing/
obj-$(CONFIG_POWER_SUPPLY) += supply/
new file mode 100644
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+menuconfig POWER_SEQUENCING
+ tristate "Power Sequencing support"
+ help
+ Say Y here to enable the Power Sequencing subsystem.
+
+ This subsystem is designed to control power to devices that share
+ complex resources and/or require specific power sequences to be run
+ during power-up.
+
+ If unsure, say no.
new file mode 100644
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_POWER_SEQUENCING) += pwrseq-core.o
+pwrseq-core-y := core.o
new file mode 100644
@@ -0,0 +1,1105 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Linaro Ltd.
+ */
+
+#include <linux/bug.h>
+#include <linux/cleanup.h>
+#include <linux/debugfs.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/idr.h>
+#include <linux/kernel.h>
+#include <linux/kref.h>
+#include <linux/list.h>
+#include <linux/lockdep.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/property.h>
+#include <linux/pwrseq/consumer.h>
+#include <linux/pwrseq/provider.h>
+#include <linux/radix-tree.h>
+#include <linux/rwsem.h>
+#include <linux/slab.h>
+
+/*
+ * Power-sequencing framework for linux.
+ *
+ * This subsystem allows power sequence providers to register a set of targets
+ * that consumers may request and power-up/down.
+ *
+ * Glossary:
+ *
+ * Unit - a unit is a discreet chunk of a power sequence. For instance one unit
+ * may enable a set of regulators, another may enable a specific GPIO. Units
+ * can define dependencies in the form of other units that must be enabled
+ * before it itself can be.
+ *
+ * Target - a target is a set of units (composed of the "final" unit and its
+ * dependencies) that a consumer selects by its name when requesting a handle
+ * to the power sequencer. Via the dependency system, multiple targets may
+ * share the same parts of a power sequence but ignore parts that are
+ * irrelevant.
+ *
+ * Descriptor - a handle passed by the pwrseq core to every consumer that
+ * serves as the entry point to the provider layer. It ensures coherence
+ * between different users and keeps reference counting consistent.
+ *
+ * Each provider must define a .match() callback whose role is to determine
+ * whether a potential consumer is in fact associated with this sequencer.
+ * This allows creating abstraction layers on top of regular device-tree
+ * resources like regulators, clocks and other nodes connected to the consumer
+ * via phandle.
+ */
+
+static DEFINE_IDA(pwrseq_ida);
+
+/*
+ * Protects the device list on the pwrseq bus from concurrent modifications
+ * but allows simultaneous read-only access.
+ */
+static DECLARE_RWSEM(pwrseq_sem);
+
+/**
+ * struct pwrseq_unit - Private power-sequence unit data.
+ * @ref: Reference count for this object. When it goes to 0, the object is
+ * destroyed.
+ * @name: Name of this target.
+ * @list: Link to siblings on the list of all units of a single sequencer.
+ * @deps: List of units on which this unit depends.
+ * @enable: Callback running the part of the power-on sequence provided by
+ * this unit.
+ * @disable: Callback running the part of the power-off sequence provided
+ * by this unit.
+ * @enable_count: Current number of users that enabled this unit. May be the
+ * consumer of the power sequencer or other units that depend
+ * on this one.
+ */
+struct pwrseq_unit {
+ struct kref ref;
+ const char *name;
+ struct list_head list;
+ struct list_head deps;
+ pwrseq_power_state_func enable;
+ pwrseq_power_state_func disable;
+ unsigned int enable_count;
+};
+
+static struct pwrseq_unit *pwrseq_unit_new(const struct pwrseq_unit_data *data)
+{
+ struct pwrseq_unit *unit;
+
+ unit = kzalloc(sizeof(*unit), GFP_KERNEL);
+ if (!unit)
+ return NULL;
+
+ unit->name = kstrdup_const(data->name, GFP_KERNEL);
+ if (!unit->name) {
+ kfree(unit);
+ return NULL;
+ }
+
+ kref_init(&unit->ref);
+ INIT_LIST_HEAD(&unit->deps);
+ unit->enable = data->enable;
+ unit->disable = data->disable;
+
+ return unit;
+}
+
+static struct pwrseq_unit *pwrseq_unit_get(struct pwrseq_unit *unit)
+{
+ kref_get(&unit->ref);
+
+ return unit;
+}
+
+static void pwrseq_unit_release(struct kref *ref);
+
+static void pwrseq_unit_put(struct pwrseq_unit *unit)
+{
+ kref_put(&unit->ref, pwrseq_unit_release);
+}
+
+/**
+ * struct pwrseq_unit_dep - Wrapper around a reference to the unit structure
+ * allowing to keep it on multiple dependency lists
+ * in different units.
+ * @list: Siblings on the list.
+ * @unit: Address of the referenced unit.
+ */
+struct pwrseq_unit_dep {
+ struct list_head list;
+ struct pwrseq_unit *unit;
+};
+
+static struct pwrseq_unit_dep *pwrseq_unit_dep_new(struct pwrseq_unit *unit)
+{
+ struct pwrseq_unit_dep *dep;
+
+ dep = kzalloc(sizeof(*dep), GFP_KERNEL);
+ if (!dep)
+ return NULL;
+
+ dep->unit = unit;
+
+ return dep;
+}
+
+static void pwrseq_unit_dep_free(struct pwrseq_unit_dep *ref)
+{
+ pwrseq_unit_put(ref->unit);
+ kfree(ref);
+}
+
+static void pwrseq_unit_free_deps(struct list_head *list)
+{
+ struct pwrseq_unit_dep *dep, *next;
+
+ list_for_each_entry_safe(dep, next, list, list) {
+ list_del(&dep->list);
+ pwrseq_unit_dep_free(dep);
+ }
+}
+
+static void pwrseq_unit_release(struct kref *ref)
+{
+ struct pwrseq_unit *unit = container_of(ref, struct pwrseq_unit, ref);
+
+ pwrseq_unit_free_deps(&unit->deps);
+ list_del(&unit->list);
+ kfree_const(unit->name);
+ kfree(unit);
+}
+
+/**
+ * struct pwrseq_target - Private power-sequence target data.
+ * @list: Siblings on the list of all targets exposed by a power sequencer.
+ * @name: Name of the target.
+ * @unit: Final unit for this target.
+ * @post_enable: Callback run after the target unit has been enabled, *after*
+ * the state lock has been released. It's useful for implementing
+ * boot-up delays without blocking other users from powering up
+ * using the same power sequencer.
+ */
+struct pwrseq_target {
+ struct list_head list;
+ const char *name;
+ struct pwrseq_unit *unit;
+ pwrseq_power_state_func post_enable;
+};
+
+static struct pwrseq_target *
+pwrseq_target_new(const struct pwrseq_target_data *data)
+{
+ struct pwrseq_target *target;
+
+ target = kzalloc(sizeof(*target), GFP_KERNEL);
+ if (!target)
+ return NULL;
+
+ target->name = kstrdup_const(data->name, GFP_KERNEL);
+ if (!target->name) {
+ kfree(target);
+ return NULL;
+ }
+
+ target->post_enable = data->post_enable;
+
+ return target;
+}
+
+static void pwrseq_target_free(struct pwrseq_target *target)
+{
+ pwrseq_unit_put(target->unit);
+ kfree_const(target->name);
+ kfree(target);
+}
+
+/**
+ * struct pwrseq_device - Private power sequencing data.
+ * @dev: Device struct associated with this sequencer.
+ * @id: Device ID.
+ * @owner: Prevents removal of active power sequencing providers.
+ * @rw_lock: Protects the device from being unregistered while in use.
+ * @state_lock: Prevents multiple users running the power sequence at the same
+ * time.
+ * @match: Power sequencer matching callback.
+ * @targets: List of targets exposed by this sequencer.
+ * @units: List of all units supported by this sequencer.
+ */
+struct pwrseq_device {
+ struct device dev;
+ int id;
+ struct module *owner;
+ struct rw_semaphore rw_lock;
+ struct mutex state_lock;
+ pwrseq_match_func match;
+ struct list_head targets;
+ struct list_head units;
+};
+
+static struct pwrseq_device *to_pwrseq_device(struct device *dev)
+{
+ return container_of(dev, struct pwrseq_device, dev);
+}
+
+static struct pwrseq_device *pwrseq_device_get(struct pwrseq_device *pwrseq)
+{
+ get_device(&pwrseq->dev);
+
+ return pwrseq;
+}
+
+static void pwrseq_device_put(struct pwrseq_device *pwrseq)
+{
+ put_device(&pwrseq->dev);
+}
+
+/**
+ * struct pwrseq_desc - Wraps access to the pwrseq_device and ensures that one
+ * user cannot break the reference counting for others.
+ * @pwrseq: Reference to the power sequencing device.
+ * @target: Reference to the target this descriptor allows to control.
+ * @powered_on: Power state set by the holder of the descriptor (not necessarily
+ * corresponding to the actual power state of the device).
+ */
+struct pwrseq_desc {
+ struct pwrseq_device *pwrseq;
+ struct pwrseq_target *target;
+ bool powered_on;
+};
+
+static const struct bus_type pwrseq_bus = {
+ .name = "pwrseq",
+};
+
+static void pwrseq_release(struct device *dev)
+{
+ struct pwrseq_device *pwrseq = to_pwrseq_device(dev);
+ struct pwrseq_target *target, *pos;
+
+ list_for_each_entry_safe(target, pos, &pwrseq->targets, list) {
+ list_del(&target->list);
+ pwrseq_target_free(target);
+ }
+
+ mutex_destroy(&pwrseq->state_lock);
+ ida_free(&pwrseq_ida, pwrseq->id);
+ kfree(pwrseq);
+}
+
+static const struct device_type pwrseq_device_type = {
+ .name = "power_sequencer",
+ .release = pwrseq_release,
+};
+
+static int pwrseq_check_unit_deps(const struct pwrseq_unit_data *data,
+ struct radix_tree_root *visited_units)
+{
+ const struct pwrseq_unit_data *tmp, **cur;
+ int ret;
+
+ ret = radix_tree_insert(visited_units, (unsigned long)data,
+ (void *)data);
+ if (ret)
+ return ret;
+
+ for (cur = data->deps; cur && *cur; cur++) {
+ tmp = radix_tree_lookup(visited_units, (unsigned long)*cur);
+ if (tmp) {
+ WARN(1, "Circular dependency in power sequencing flow detected!\n");
+ return -EINVAL;
+ }
+
+ ret = pwrseq_check_unit_deps(*cur, visited_units);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+
+static int pwrseq_check_target_deps(const struct pwrseq_target_data *data)
+{
+ struct radix_tree_root visited_units;
+ struct radix_tree_iter iter;
+ void __rcu **slot;
+ int ret;
+
+ if (!data->unit)
+ return -EINVAL;
+
+ INIT_RADIX_TREE(&visited_units, GFP_KERNEL);
+ ret = pwrseq_check_unit_deps(data->unit, &visited_units);
+ radix_tree_for_each_slot(slot, &visited_units, &iter, 0)
+ radix_tree_delete(&visited_units, iter.index);
+
+ return ret;
+}
+
+static int pwrseq_unit_setup_deps(const struct pwrseq_unit_data **data,
+ struct list_head *dep_list,
+ struct list_head *unit_list,
+ struct radix_tree_root *processed_units);
+
+static struct pwrseq_unit *
+pwrseq_unit_setup(const struct pwrseq_unit_data *data,
+ struct list_head *unit_list,
+ struct radix_tree_root *processed_units)
+{
+ struct pwrseq_unit *unit;
+ int ret;
+
+ unit = radix_tree_lookup(processed_units, (unsigned long)data);
+ if (unit)
+ return pwrseq_unit_get(unit);
+
+ unit = pwrseq_unit_new(data);
+ if (!unit)
+ return ERR_PTR(-ENOMEM);
+
+ if (data->deps) {
+ ret = pwrseq_unit_setup_deps(data->deps, &unit->deps,
+ unit_list, processed_units);
+ if (ret) {
+ pwrseq_unit_put(unit);
+ return ERR_PTR(ret);
+ }
+ }
+
+ ret = radix_tree_insert(processed_units, (unsigned long)data, unit);
+ if (ret) {
+ pwrseq_unit_put(unit);
+ return ERR_PTR(ret);
+ }
+
+ list_add_tail(&unit->list, unit_list);
+
+ return unit;
+}
+
+static int pwrseq_unit_setup_deps(const struct pwrseq_unit_data **data,
+ struct list_head *dep_list,
+ struct list_head *unit_list,
+ struct radix_tree_root *processed_units)
+{
+ const struct pwrseq_unit_data *pos;
+ struct pwrseq_unit_dep *dep;
+ struct pwrseq_unit *unit;
+ int i;
+
+ for (i = 0; data[i]; i++) {
+ pos = data[i];
+
+ unit = pwrseq_unit_setup(pos, unit_list, processed_units);
+ if (IS_ERR(unit))
+ return PTR_ERR(unit);
+
+ dep = pwrseq_unit_dep_new(unit);
+ if (!dep) {
+ pwrseq_unit_put(unit);
+ return -ENOMEM;
+ }
+
+ list_add_tail(&dep->list, dep_list);
+ }
+
+ return 0;
+}
+
+static int pwrseq_do_setup_targets(const struct pwrseq_target_data **data,
+ struct pwrseq_device *pwrseq,
+ struct radix_tree_root *processed_units)
+{
+ const struct pwrseq_target_data *pos;
+ struct pwrseq_target *target;
+ int ret, i;
+
+ for (i = 0; data[i]; i++) {
+ pos = data[i];
+
+ ret = pwrseq_check_target_deps(pos);
+ if (ret)
+ return ret;
+
+ target = pwrseq_target_new(pos);
+ if (!target)
+ return -ENOMEM;
+
+ target->unit = pwrseq_unit_setup(pos->unit, &pwrseq->units,
+ processed_units);
+ if (IS_ERR(target->unit)) {
+ ret = PTR_ERR(target->unit);
+ pwrseq_target_free(target);
+ return ret;
+ }
+
+ list_add_tail(&target->list, &pwrseq->targets);
+ }
+
+ return 0;
+}
+
+static int pwrseq_setup_targets(const struct pwrseq_target_data **targets,
+ struct pwrseq_device *pwrseq)
+{
+ struct radix_tree_root processed_units;
+ struct radix_tree_iter iter;
+ void __rcu **slot;
+ int ret;
+
+ INIT_RADIX_TREE(&processed_units, GFP_KERNEL);
+ ret = pwrseq_do_setup_targets(targets, pwrseq, &processed_units);
+ radix_tree_for_each_slot(slot, &processed_units, &iter, 0)
+ radix_tree_delete(&processed_units, iter.index);
+
+ return ret;
+}
+
+/**
+ * pwrseq_device_register() - Register a new power sequencer.
+ * @config: Configuration of the new power sequencing device.
+ *
+ * The config structure is only used during the call and can be freed after
+ * the function returns. The config structure *must* have the parent device
+ * as well as the match() callback and at least one target set.
+ *
+ * Returns:
+ * Returns the address of the new pwrseq device or ERR_PTR() on failure.
+ */
+struct pwrseq_device *
+pwrseq_device_register(const struct pwrseq_config *config)
+{
+ struct pwrseq_device *pwrseq;
+ int ret, id;
+
+ if (!config->parent || !config->match || !config->targets ||
+ !config->targets[0])
+ return ERR_PTR(-EINVAL);
+
+ pwrseq = kzalloc(sizeof(*pwrseq), GFP_KERNEL);
+ if (!pwrseq)
+ return ERR_PTR(-ENOMEM);
+
+ pwrseq->dev.type = &pwrseq_device_type;
+ pwrseq->dev.bus = &pwrseq_bus;
+ pwrseq->dev.parent = config->parent;
+ device_set_node(&pwrseq->dev, dev_fwnode(config->parent));
+ dev_set_drvdata(&pwrseq->dev, config->drvdata);
+
+ id = ida_alloc(&pwrseq_ida, GFP_KERNEL);
+ if (id < 0) {
+ kfree(pwrseq);
+ return ERR_PTR(id);
+ }
+
+ pwrseq->id = id;
+
+ /*
+ * From this point onwards the device's release() callback is
+ * responsible for freeing resources.
+ */
+ device_initialize(&pwrseq->dev);
+
+ ret = dev_set_name(&pwrseq->dev, "pwrseq.%d", pwrseq->id);
+ if (ret)
+ goto err_put_pwrseq;
+
+ pwrseq->owner = config->owner ?: THIS_MODULE;
+ pwrseq->match = config->match;
+
+ init_rwsem(&pwrseq->rw_lock);
+ mutex_init(&pwrseq->state_lock);
+ INIT_LIST_HEAD(&pwrseq->targets);
+ INIT_LIST_HEAD(&pwrseq->units);
+
+ ret = pwrseq_setup_targets(config->targets, pwrseq);
+ if (ret)
+ goto err_put_pwrseq;
+
+ scoped_guard(rwsem_write, &pwrseq_sem) {
+ ret = device_add(&pwrseq->dev);
+ if (ret)
+ goto err_put_pwrseq;
+ }
+
+ return pwrseq;
+
+err_put_pwrseq:
+ pwrseq_device_put(pwrseq);
+ return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(pwrseq_device_register);
+
+/**
+ * pwrseq_device_unregister() - Unregister the power sequencer.
+ * @pwrseq: Power sequencer to unregister.
+ */
+void pwrseq_device_unregister(struct pwrseq_device *pwrseq)
+{
+ struct device *dev = &pwrseq->dev;
+ struct pwrseq_target *target;
+
+ scoped_guard(mutex, &pwrseq->state_lock) {
+ guard(rwsem_write)(&pwrseq->rw_lock);
+
+ list_for_each_entry(target, &pwrseq->targets, list)
+ WARN_ONCE(target->unit->enable_count,
+ "REMOVING POWER SEQUENCER WITH ACTIVE USERS\n");
+
+ guard(rwsem_write)(&pwrseq_sem);
+
+ device_del(dev);
+ }
+
+ pwrseq_device_put(pwrseq);
+}
+EXPORT_SYMBOL_GPL(pwrseq_device_unregister);
+
+static void devm_pwrseq_device_unregister(void *data)
+{
+ struct pwrseq_device *pwrseq = data;
+
+ pwrseq_device_unregister(pwrseq);
+}
+
+/**
+ * devm_pwrseq_device_register() - Managed variant of pwrseq_device_register().
+ * @dev: Managing device.
+ * @config: Configuration of the new power sequencing device.
+ *
+ * Returns:
+ * Returns the address of the new pwrseq device or ERR_PTR() on failure.
+ */
+struct pwrseq_device *
+devm_pwrseq_device_register(struct device *dev,
+ const struct pwrseq_config *config)
+{
+ struct pwrseq_device *pwrseq;
+ int ret;
+
+ pwrseq = pwrseq_device_register(config);
+ if (IS_ERR(pwrseq))
+ return pwrseq;
+
+ ret = devm_add_action_or_reset(dev, devm_pwrseq_device_unregister,
+ pwrseq);
+ if (ret)
+ return ERR_PTR(ret);
+
+ return pwrseq;
+}
+EXPORT_SYMBOL_GPL(devm_pwrseq_device_register);
+
+/**
+ * pwrseq_device_get_drvdata() - Get the driver private data associated with
+ * this sequencer.
+ * @pwrseq: Power sequencer object.
+ *
+ * Returns:
+ * Address of the private driver data.
+ */
+void *pwrseq_device_get_drvdata(struct pwrseq_device *pwrseq)
+{
+ return dev_get_drvdata(&pwrseq->dev);
+}
+EXPORT_SYMBOL_GPL(pwrseq_device_get_drvdata);
+
+struct pwrseq_match_data {
+ struct pwrseq_desc *desc;
+ struct device *dev;
+ const char *target;
+};
+
+static int pwrseq_match_device(struct device *pwrseq_dev, void *data)
+{
+ struct pwrseq_device *pwrseq = to_pwrseq_device(pwrseq_dev);
+ struct pwrseq_match_data *match_data = data;
+ struct pwrseq_target *target;
+ int ret;
+
+ lockdep_assert_held_read(&pwrseq_sem);
+
+ guard(rwsem_read)(&pwrseq->rw_lock);
+ if (!device_is_registered(&pwrseq->dev))
+ return 0;
+
+ ret = pwrseq->match(pwrseq, match_data->dev);
+ if (ret <= 0)
+ return ret;
+
+ /* We got the matching device, let's find the right target. */
+ list_for_each_entry(target, &pwrseq->targets, list) {
+ if (strcmp(target->name, match_data->target))
+ continue;
+
+ match_data->desc->target = target;
+ }
+
+ /*
+ * This device does not have this target. No point in deferring as it
+ * will not get a new target dynamically later.
+ */
+ if (!match_data->desc->target)
+ return -ENOENT;
+
+ if (!try_module_get(pwrseq->owner))
+ return -EPROBE_DEFER;
+
+ match_data->desc->pwrseq = pwrseq_device_get(pwrseq);
+
+ return 1;
+}
+
+/**
+ * pwrseq_get() - Get the power sequencer associated with this device.
+ * @dev: Device for which to get the sequencer.
+ * @target: Name of the target exposed by the sequencer this device wants to
+ * reach.
+ *
+ * Returns:
+ * New power sequencer descriptor for use by the consumer driver or ERR_PTR()
+ * on failure.
+ */
+struct pwrseq_desc *pwrseq_get(struct device *dev, const char *target)
+{
+ struct pwrseq_match_data match_data;
+ int ret;
+
+ struct pwrseq_desc *desc __free(kfree) = kzalloc(sizeof(*desc),
+ GFP_KERNEL);
+ if (!desc)
+ return ERR_PTR(-ENOMEM);
+
+ match_data.desc = desc;
+ match_data.dev = dev;
+ match_data.target = target;
+
+ guard(rwsem_read)(&pwrseq_sem);
+
+ ret = bus_for_each_dev(&pwrseq_bus, NULL, &match_data,
+ pwrseq_match_device);
+ if (ret < 0)
+ return ERR_PTR(ret);
+ if (ret == 0)
+ /* No device matched. */
+ return ERR_PTR(-EPROBE_DEFER);
+
+ return no_free_ptr(desc);
+}
+EXPORT_SYMBOL_GPL(pwrseq_get);
+
+/**
+ * pwrseq_put() - Release the power sequencer descriptor.
+ * @desc: Descriptor to release.
+ */
+void pwrseq_put(struct pwrseq_desc *desc)
+{
+ struct pwrseq_device *pwrseq;
+
+ if (!desc)
+ return;
+
+ pwrseq = desc->pwrseq;
+
+ if (desc->powered_on)
+ pwrseq_power_off(desc);
+
+ kfree(desc);
+ module_put(pwrseq->owner);
+ pwrseq_device_put(pwrseq);
+}
+EXPORT_SYMBOL_GPL(pwrseq_put);
+
+static void devm_pwrseq_put(void *data)
+{
+ struct pwrseq_desc *desc = data;
+
+ pwrseq_put(desc);
+}
+
+/**
+ * devm_pwrseq_get() - Managed variant of pwrseq_get().
+ * @dev: Device for which to get the sequencer and which also manages its
+ * lifetime.
+ * @target: Name of the target exposed by the sequencer this device wants to
+ * reach.
+ *
+ * Returns:
+ * New power sequencer descriptor for use by the consumer driver or ERR_PTR()
+ * on failure.
+ */
+struct pwrseq_desc *devm_pwrseq_get(struct device *dev, const char *target)
+{
+ struct pwrseq_desc *desc;
+ int ret;
+
+ desc = pwrseq_get(dev, target);
+ if (IS_ERR(desc))
+ return desc;
+
+ ret = devm_add_action_or_reset(dev, devm_pwrseq_put, desc);
+ if (ret)
+ return ERR_PTR(ret);
+
+ return desc;
+}
+EXPORT_SYMBOL_GPL(devm_pwrseq_get);
+
+static int pwrseq_unit_enable(struct pwrseq_device *pwrseq,
+ struct pwrseq_unit *target);
+static int pwrseq_unit_disable(struct pwrseq_device *pwrseq,
+ struct pwrseq_unit *target);
+
+static int pwrseq_unit_enable_deps(struct pwrseq_device *pwrseq,
+ struct list_head *list)
+{
+ struct pwrseq_unit_dep *pos;
+ int ret = 0;
+
+ list_for_each_entry(pos, list, list) {
+ ret = pwrseq_unit_enable(pwrseq, pos->unit);
+ if (ret) {
+ list_for_each_entry_continue_reverse(pos, list, list)
+ pwrseq_unit_disable(pwrseq, pos->unit);
+ break;
+ }
+ }
+
+ return ret;
+}
+
+static int pwrseq_unit_disable_deps(struct pwrseq_device *pwrseq,
+ struct list_head *list)
+{
+ struct pwrseq_unit_dep *pos;
+ int ret = 0;
+
+ list_for_each_entry_reverse(pos, list, list) {
+ ret = pwrseq_unit_disable(pwrseq, pos->unit);
+ if (ret) {
+ list_for_each_entry_continue(pos, list, list)
+ pwrseq_unit_enable(pwrseq, pos->unit);
+ break;
+ }
+ }
+
+ return ret;
+}
+
+static int pwrseq_unit_enable(struct pwrseq_device *pwrseq,
+ struct pwrseq_unit *unit)
+{
+ int ret;
+
+ lockdep_assert_held_read(&pwrseq->rw_lock);
+ lockdep_assert_held(&pwrseq->state_lock);
+
+ if (unit->enable_count != 0) {
+ unit->enable_count++;
+ return 0;
+ }
+
+ ret = pwrseq_unit_enable_deps(pwrseq, &unit->deps);
+ if (ret) {
+ dev_err(&pwrseq->dev,
+ "Failed to enable dependencies before power-on for target '%s': %d\n",
+ unit->name, ret);
+ return ret;
+ }
+
+ if (unit->enable) {
+ ret = unit->enable(pwrseq);
+ if (ret) {
+ dev_err(&pwrseq->dev,
+ "Failed to enable target '%s': %d\n",
+ unit->name, ret);
+ pwrseq_unit_disable_deps(pwrseq, &unit->deps);
+ return ret;
+ }
+ }
+
+ unit->enable_count++;
+
+ return 0;
+}
+
+static int pwrseq_unit_disable(struct pwrseq_device *pwrseq,
+ struct pwrseq_unit *unit)
+{
+ int ret;
+
+ lockdep_assert_held_read(&pwrseq->rw_lock);
+ lockdep_assert_held(&pwrseq->state_lock);
+
+ if (unit->enable_count == 0) {
+ WARN_ONCE(1, "Unmatched power-off for target '%s'\n",
+ unit->name);
+ return -EBUSY;
+ }
+
+ if (unit->enable_count != 1) {
+ unit->enable_count--;
+ return 0;
+ }
+
+ if (unit->disable) {
+ ret = unit->disable(pwrseq);
+ if (ret) {
+ dev_err(&pwrseq->dev,
+ "Failed to disable target '%s': %d\n",
+ unit->name, ret);
+ return ret;
+ }
+ }
+
+ ret = pwrseq_unit_disable_deps(pwrseq, &unit->deps);
+ if (ret) {
+ dev_err(&pwrseq->dev,
+ "Failed to disable dependencies after power-off for target '%s': %d\n",
+ unit->name, ret);
+ if (unit->enable)
+ unit->enable(pwrseq);
+ return ret;
+ }
+
+ unit->enable_count--;
+
+ return 0;
+}
+
+/**
+ * pwrseq_power_on() - Issue a power-on request on behalf of the consumer
+ * device.
+ * @desc: Descriptor referencing the power sequencer.
+ *
+ * This function tells the power sequencer that the consumer wants to be
+ * powered-up. The sequencer may already have powered-up the device in which
+ * case the function returns 0. If the power-up sequence is already in
+ * progress, the function will block until it's done and return 0. If this is
+ * the first request, the device will be powered up.
+ *
+ * Returns:
+ * 0 on success, negative error number on failure.
+ */
+int pwrseq_power_on(struct pwrseq_desc *desc)
+{
+ struct pwrseq_device *pwrseq;
+ struct pwrseq_target *target;
+ struct pwrseq_unit *unit;
+ int ret;
+
+ might_sleep();
+
+ if (!desc || desc->powered_on)
+ return 0;
+
+ pwrseq = desc->pwrseq;
+ target = desc->target;
+ unit = target->unit;
+
+ guard(rwsem_read)(&pwrseq->rw_lock);
+ if (!device_is_registered(&pwrseq->dev))
+ return -ENODEV;
+
+ scoped_guard(mutex, &pwrseq->state_lock) {
+ ret = pwrseq_unit_enable(pwrseq, unit);
+ if (!ret)
+ desc->powered_on = true;
+ }
+
+ if (target->post_enable) {
+ ret = target->post_enable(pwrseq);
+ if (ret) {
+ pwrseq_unit_disable(pwrseq, unit);
+ desc->powered_on = false;
+ }
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(pwrseq_power_on);
+
+/**
+ * pwrseq_power_off() - Issue a power-off request on behalf of the consumer
+ * device.
+ * @desc: Descriptor referencing the power sequencer.
+ *
+ * This undoes the effects of pwrseq_power_on(). It issues a power-off request
+ * on behalf of the consumer and when the last remaining user does so, the
+ * power-down sequence will be started. If one is in progress, the function
+ * will block until it's complete and then return.
+ *
+ * Returns:
+ * 0 on success, negative error number on failure.
+ */
+int pwrseq_power_off(struct pwrseq_desc *desc)
+{
+ struct pwrseq_device *pwrseq;
+ struct pwrseq_unit *unit;
+ int ret;
+
+ might_sleep();
+
+ if (!desc || !desc->powered_on)
+ return 0;
+
+ pwrseq = desc->pwrseq;
+ unit = desc->target->unit;
+
+ guard(rwsem_read)(&pwrseq->rw_lock);
+ if (!device_is_registered(&pwrseq->dev))
+ return -ENODEV;
+
+ guard(mutex)(&pwrseq->state_lock);
+
+ ret = pwrseq_unit_disable(pwrseq, unit);
+ if (!ret)
+ desc->powered_on = false;
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(pwrseq_power_off);
+
+#if IS_ENABLED(CONFIG_DEBUG_FS)
+
+struct pwrseq_debugfs_count_ctx {
+ struct device *dev;
+ loff_t index;
+};
+
+static int pwrseq_debugfs_seq_count(struct device *dev, void *data)
+{
+ struct pwrseq_debugfs_count_ctx *ctx = data;
+
+ ctx->dev = dev;
+
+ return ctx->index-- ? 0 : 1;
+}
+
+static void *pwrseq_debugfs_seq_start(struct seq_file *seq, loff_t *pos)
+{
+ struct pwrseq_debugfs_count_ctx ctx;
+
+ ctx.dev = NULL;
+ ctx.index = *pos;
+
+ /*
+ * We're holding the lock for the entire printout so no need to fiddle
+ * with device reference count.
+ */
+ down_read(&pwrseq_sem);
+
+ bus_for_each_dev(&pwrseq_bus, NULL, &ctx, pwrseq_debugfs_seq_count);
+ if (!ctx.index)
+ return NULL;
+
+ return ctx.dev;
+}
+
+static void *pwrseq_debugfs_seq_next(struct seq_file *seq, void *data,
+ loff_t *pos)
+{
+ struct device *curr = data;
+
+ ++*pos;
+
+ struct device *next __free(put_device) =
+ bus_find_next_device(&pwrseq_bus, curr);
+ return next;
+}
+
+static void pwrseq_debugfs_seq_show_target(struct seq_file *seq,
+ struct pwrseq_target *target)
+{
+ seq_printf(seq, " target: [%s] (target unit: [%s])\n",
+ target->name, target->unit->name);
+}
+
+static void pwrseq_debugfs_seq_show_unit(struct seq_file *seq,
+ struct pwrseq_unit *unit)
+{
+ struct pwrseq_unit_dep *ref;
+
+ seq_printf(seq, " unit: [%s] - enable count: %u\n",
+ unit->name, unit->enable_count);
+
+ if (list_empty(&unit->deps))
+ return;
+
+ seq_puts(seq, " dependencies:\n");
+ list_for_each_entry(ref, &unit->deps, list)
+ seq_printf(seq, " [%s]\n", ref->unit->name);
+}
+
+static int pwrseq_debugfs_seq_show(struct seq_file *seq, void *data)
+{
+ struct device *dev = data;
+ struct pwrseq_device *pwrseq = to_pwrseq_device(dev);
+ struct pwrseq_target *target;
+ struct pwrseq_unit *unit;
+
+ seq_printf(seq, "%s:\n", dev_name(dev));
+
+ seq_puts(seq, " targets:\n");
+ list_for_each_entry(target, &pwrseq->targets, list)
+ pwrseq_debugfs_seq_show_target(seq, target);
+
+ seq_puts(seq, " units:\n");
+ list_for_each_entry(unit, &pwrseq->units, list)
+ pwrseq_debugfs_seq_show_unit(seq, unit);
+
+ return 0;
+}
+
+static void pwrseq_debugfs_seq_stop(struct seq_file *seq, void *data)
+{
+ up_read(&pwrseq_sem);
+}
+
+static const struct seq_operations pwrseq_debugfs_sops = {
+ .start = pwrseq_debugfs_seq_start,
+ .next = pwrseq_debugfs_seq_next,
+ .show = pwrseq_debugfs_seq_show,
+ .stop = pwrseq_debugfs_seq_stop,
+};
+DEFINE_SEQ_ATTRIBUTE(pwrseq_debugfs);
+
+static struct dentry *pwrseq_debugfs_dentry;
+
+#endif /* CONFIG_DEBUG_FS */
+
+static int __init pwrseq_init(void)
+{
+ int ret;
+
+ ret = bus_register(&pwrseq_bus);
+ if (ret) {
+ pr_err("Failed to register the power sequencer bus\n");
+ return ret;
+ }
+
+#if IS_ENABLED(CONFIG_DEBUG_FS)
+ pwrseq_debugfs_dentry = debugfs_create_file("pwrseq", 0444, NULL, NULL,
+ &pwrseq_debugfs_fops);
+#endif /* CONFIG_DEBUG_FS */
+
+ return 0;
+}
+subsys_initcall(pwrseq_init);
+
+static void __exit pwrseq_exit(void)
+{
+#if IS_ENABLED(CONFIG_DEBUG_FS)
+ debugfs_remove_recursive(pwrseq_debugfs_dentry);
+#endif /* CONFIG_DEBUG_FS */
+
+ bus_unregister(&pwrseq_bus);
+}
+module_exit(pwrseq_exit);
+
+MODULE_AUTHOR("Bartosz Golaszewski <bartosz.golaszewski@linaro.org>");
+MODULE_DESCRIPTION("Power Sequencing subsystem core");
+MODULE_LICENSE("GPL");
new file mode 100644
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2024 Linaro Ltd.
+ */
+
+#ifndef __POWER_SEQUENCING_CONSUMER_H__
+#define __POWER_SEQUENCING_CONSUMER_H__
+
+#include <linux/err.h>
+
+struct device;
+struct pwrseq_desc;
+
+#if IS_ENABLED(CONFIG_POWER_SEQUENCING)
+
+struct pwrseq_desc * __must_check
+pwrseq_get(struct device *dev, const char *target);
+void pwrseq_put(struct pwrseq_desc *desc);
+
+struct pwrseq_desc * __must_check
+devm_pwrseq_get(struct device *dev, const char *target);
+
+int pwrseq_power_on(struct pwrseq_desc *desc);
+int pwrseq_power_off(struct pwrseq_desc *desc);
+
+#else /* CONFIG_POWER_SEQUENCING */
+
+static inline struct pwrseq_desc * __must_check
+pwrseq_get(struct device *dev, const char *target)
+{
+ return ERR_PTR(-ENOSYS);
+}
+
+static inline void pwrseq_put(struct pwrseq_desc *desc)
+{
+}
+
+static inline struct pwrseq_desc * __must_check
+devm_pwrseq_get(struct device *dev, const char *target)
+{
+ return ERR_PTR(-ENOSYS);
+}
+
+static inline int pwrseq_power_on(struct pwrseq_desc *desc)
+{
+ return -ENOSYS;
+}
+
+static inline int pwrseq_power_off(struct pwrseq_desc *desc)
+{
+ return -ENOSYS;
+}
+
+#endif /* CONFIG_POWER_SEQUENCING */
+
+#endif /* __POWER_SEQUENCING_CONSUMER_H__ */
new file mode 100644
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2024 Linaro Ltd.
+ */
+
+#ifndef __POWER_SEQUENCING_PROVIDER_H__
+#define __POWER_SEQUENCING_PROVIDER_H__
+
+struct device;
+struct module;
+struct pwrseq_device;
+
+typedef int (*pwrseq_power_state_func)(struct pwrseq_device *);
+typedef int (*pwrseq_match_func)(struct pwrseq_device *, struct device *);
+
+/**
+ * struct pwrseq_unit_data - Configuration of a single power sequencing
+ * unit.
+ * @name: Name of the unit.
+ * @deps: Units that must be enabled before this one and disabled after it
+ * in the order they come in this array. Must be NULL-terminated.
+ * @enable: Callback running the part of the power-on sequence provided by
+ * this unit.
+ * @disable: Callback running the part of the power-off sequence provided
+ * by this unit.
+ */
+struct pwrseq_unit_data {
+ const char *name;
+ const struct pwrseq_unit_data **deps;
+ pwrseq_power_state_func enable;
+ pwrseq_power_state_func disable;
+};
+
+/**
+ * struct pwrseq_target_data - Configuration of a power sequencing target.
+ * @name: Name of the target.
+ * @unit: Final unit that this target must reach in order to be considered
+ * enabled.
+ * @post_enable: Callback run after the target unit has been enabled, *after*
+ * the state lock has been released. It's useful for implementing
+ * boot-up delays without blocking other users from powering up
+ * using the same power sequencer.
+ */
+struct pwrseq_target_data {
+ const char *name;
+ const struct pwrseq_unit_data *unit;
+ pwrseq_power_state_func post_enable;
+};
+
+/**
+ * struct pwrseq_config - Configuration used for registering a new provider.
+ * @parent: Parent device for the sequencer. Must be set.
+ * @owner: Module providing this device.
+ * @drvdata: Private driver data.
+ * @match: Provider callback used to match the consumer device to the sequencer.
+ * @targets: Array of targets for this power sequencer. Must be NULL-terminated.
+ */
+struct pwrseq_config {
+ struct device *parent;
+ struct module *owner;
+ void *drvdata;
+ pwrseq_match_func match;
+ const struct pwrseq_target_data **targets;
+};
+
+struct pwrseq_device *
+pwrseq_device_register(const struct pwrseq_config *config);
+void pwrseq_device_unregister(struct pwrseq_device *pwrseq);
+struct pwrseq_device *
+devm_pwrseq_device_register(struct device *dev,
+ const struct pwrseq_config *config);
+
+void *pwrseq_device_get_drvdata(struct pwrseq_device *pwrseq);
+
+#endif /* __POWER_SEQUENCING_PROVIDER_H__ */