Merge tag 'pwrseq-updates-for-v6.11-rc1' of...

Merge tag 'pwrseq-updates-for-v6.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux

Pull power sequencing updates from Bartosz Golaszewski:
 "This has been in development since last year's Linux Plumbers
  Conference and was inspired by the need to enable support upstream for
  Bluetooth/WLAN chips on Qualcomm platforms.

  The main problem we're fixing is powering up devices which are
  represented as separate objects in the kernel (binding to different
  drivers) but which share parts of the power-up sequence and thus need
  some kind of a mediator who knows the possible interactions and can
  assure they don't interfere with neither device's bring up. An example
  of such an inter-driver interaction is the WCN family of BT/WLAN chips
  from Qualcomm of which some models require the user to observe a
  certain delay between driving the bt-enable and wlan-enable GPIOs.

  This is not a new problem but up to this point all attempts at
  addressing it ended up hitting one wall or another and being dropped.
  The main obstacle was the fact that most these attempts tried to
  introduce the concept of a "power sequence" into the device-tree
  bindings which breaks the main DT rule: describe the hardware, not its
  behavior. The solution I proposed focuses on making the power
  sequencer drivers interpret the actual HW description flexibly. More
  details on that are in the linked cover letter.

  The second problem fixed here is powering up PCI devices before they
  are detected on the bus. This is achieved by creating special platform
  devices for device-tree nodes describing hard-wired PCI devices which
  bind to the so-called PCI power control drivers which enable required
  resources and trigger a bus rescan once the controlled device is up
  then setup the correct devlink hierarchy for power-management.

  By combining the two new frameworks we implemented the power
  sequencing PCI power control driver which is capable of powering up
  the WLAN modules of the QCom WCN family of chipsets.

  All this has spent a significant amount of time in linux-next and
  enabled WLAN/BT support on several Qualcomm platforms. To further
  prove that this is useful and needed: right after this was picked up
  into next, I was sent a series using the subsystem for a similar
  use-case on Amlogic platforms.

  This contains the core power sequencing framework, the first driver,
  PCI changes using the pwrseq library (blessed by Bjorn Helgaas) and
  some fixes that came later"

* tag 'pwrseq-updates-for-v6.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux:
  PCI/pwrctl: only call of_platform_populate() if CONFIG_OF is enabled
  power: sequencing: simplify returning pointer without cleanup
  PCI/pwrctl: Add a PCI power control driver for power sequenced devices
  PCI/pwrctl: Add PCI power control core code
  PCI/pwrctl: Create platform devices for child OF nodes of the port node
  PCI/pwrctl: Reuse the OF node for power controlled devices
  PCI: Hold the rescan mutex when scanning for the first time
  power: pwrseq: add a driver for the PMU module on the QCom WCN chipsets
  power: sequencing: implement the pwrseq core

MAINTAINERS

@@ -17361,6 +17361,14 @@ F:	Documentation/driver-api/pci/p2pdma.rst
 F:	drivers/pci/p2pdma.c
 F:	include/linux/pci-p2pdma.h
 
+PCI POWER CONTROL
+M:	Bartosz Golaszewski <brgl@bgdev.pl>
+L:	linux-pci@vger.kernel.org
+S:	Maintained
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git
+F:	drivers/pci/pwrctl/*
+F:	include/linux/pci-pwrctl.h
+
 PCI SUBSYSTEM
 M:	Bjorn Helgaas <bhelgaas@google.com>
 L:	linux-pci@vger.kernel.org
@@ -17901,6 +17909,14 @@ 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>

drivers/pci/Kconfig

@@ -296,5 +296,6 @@ source "drivers/pci/hotplug/Kconfig"
 source "drivers/pci/controller/Kconfig"
 source "drivers/pci/endpoint/Kconfig"
 source "drivers/pci/switch/Kconfig"
+source "drivers/pci/pwrctl/Kconfig"
 
 endif

drivers/pci/Makefile

@@ -9,6 +9,7 @@ obj-$(CONFIG_PCI)		+= access.o bus.o probe.o host-bridge.o \
 
 obj-$(CONFIG_PCI)		+= msi/
 obj-$(CONFIG_PCI)		+= pcie/
+obj-$(CONFIG_PCI)		+= pwrctl/
 
 ifdef CONFIG_PCI
 obj-$(CONFIG_PROC_FS)		+= proc.o

drivers/pci/bus.c

@@ -12,6 +12,7 @@
 #include <linux/errno.h>
 #include <linux/ioport.h>
 #include <linux/of.h>
+#include <linux/of_platform.h>
 #include <linux/proc_fs.h>
 #include <linux/slab.h>
 
@@ -354,6 +355,14 @@ void pci_bus_add_device(struct pci_dev *dev)
 		pci_warn(dev, "device attach failed (%d)\n", retval);
 
 	pci_dev_assign_added(dev, true);
+
+	if (IS_ENABLED(CONFIG_OF) && pci_is_bridge(dev)) {
+		retval = of_platform_populate(dev->dev.of_node, NULL, NULL,
+					      &dev->dev);
+		if (retval)
+			pci_err(dev, "failed to populate child OF nodes (%d)\n",
+				retval);
+	}
 }
 EXPORT_SYMBOL_GPL(pci_bus_add_device);
 

drivers/pci/of.c

@@ -6,6 +6,7 @@
  */
 #define pr_fmt(fmt)	"PCI: OF: " fmt
 
+#include <linux/cleanup.h>
 #include <linux/irqdomain.h>
 #include <linux/kernel.h>
 #include <linux/pci.h>
@@ -13,6 +14,7 @@
 #include <linux/of_irq.h>
 #include <linux/of_address.h>
 #include <linux/of_pci.h>
+#include <linux/platform_device.h>
 #include "pci.h"
 
 #ifdef CONFIG_PCI
@@ -25,16 +27,20 @@
  */
 int pci_set_of_node(struct pci_dev *dev)
 {
-	struct device_node *node;
-
 	if (!dev->bus->dev.of_node)
 		return 0;
 
-	node = of_pci_find_child_device(dev->bus->dev.of_node, dev->devfn);
+	struct device_node *node __free(device_node) =
+		of_pci_find_child_device(dev->bus->dev.of_node, dev->devfn);
 	if (!node)
 		return 0;
 
-	device_set_node(&dev->dev, of_fwnode_handle(node));
+	struct device *pdev __free(put_device) =
+		bus_find_device_by_of_node(&platform_bus_type, node);
+	if (pdev)
+		dev->bus->dev.of_node_reused = true;
+
+	device_set_node(&dev->dev, of_fwnode_handle(no_free_ptr(node)));
 	return 0;
 }
 

drivers/pci/probe.c

@@ -3069,7 +3069,9 @@ int pci_host_probe(struct pci_host_bridge *bridge)
 	struct pci_bus *bus, *child;
 	int ret;
 
+	pci_lock_rescan_remove();
 	ret = pci_scan_root_bus_bridge(bridge);
+	pci_unlock_rescan_remove();
 	if (ret < 0) {
 		dev_err(bridge->dev.parent, "Scanning root bridge failed");
 		return ret;

drivers/pci/pwrctl/Kconfig

+# SPDX-License-Identifier: GPL-2.0-only
+
+menu "PCI Power control drivers"
+
+config PCI_PWRCTL
+	tristate
+
+config PCI_PWRCTL_PWRSEQ
+	tristate "PCI Power Control driver using the Power Sequencing subsystem"
+	select POWER_SEQUENCING
+	select PCI_PWRCTL
+	default m if ((ATH11K_PCI || ATH12K) && ARCH_QCOM)
+	help
+	  Enable support for the PCI power control driver for device
+	  drivers using the Power Sequencing subsystem.
+
+endmenu

drivers/pci/pwrctl/Makefile

+# SPDX-License-Identifier: GPL-2.0-only
+
+obj-$(CONFIG_PCI_PWRCTL)		+= pci-pwrctl-core.o
+pci-pwrctl-core-y			:= core.o
+
+obj-$(CONFIG_PCI_PWRCTL_PWRSEQ)		+= pci-pwrctl-pwrseq.o

drivers/pci/pwrctl/core.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Linaro Ltd.
+ */
+
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/pci.h>
+#include <linux/pci-pwrctl.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+
+static int pci_pwrctl_notify(struct notifier_block *nb, unsigned long action,
+			     void *data)
+{
+	struct pci_pwrctl *pwrctl = container_of(nb, struct pci_pwrctl, nb);
+	struct device *dev = data;
+
+	if (dev_fwnode(dev) != dev_fwnode(pwrctl->dev))
+		return NOTIFY_DONE;
+
+	switch (action) {
+	case BUS_NOTIFY_ADD_DEVICE:
+		/*
+		 * We will have two struct device objects bound to two different
+		 * drivers on different buses but consuming the same DT node. We
+		 * must not bind the pins twice in this case but only once for
+		 * the first device to be added.
+		 *
+		 * If we got here then the PCI device is the second after the
+		 * power control platform device. Mark its OF node as reused.
+		 */
+		dev->of_node_reused = true;
+		break;
+	case BUS_NOTIFY_BOUND_DRIVER:
+		pwrctl->link = device_link_add(dev, pwrctl->dev,
+					       DL_FLAG_AUTOREMOVE_CONSUMER);
+		if (!pwrctl->link)
+			dev_err(pwrctl->dev, "Failed to add device link\n");
+		break;
+	case BUS_NOTIFY_UNBOUND_DRIVER:
+		if (pwrctl->link)
+			device_link_remove(dev, pwrctl->dev);
+		break;
+	}
+
+	return NOTIFY_DONE;
+}
+
+/**
+ * pci_pwrctl_device_set_ready() - Notify the pwrctl subsystem that the PCI
+ * device is powered-up and ready to be detected.
+ *
+ * @pwrctl: PCI power control data.
+ *
+ * Returns:
+ * 0 on success, negative error number on error.
+ *
+ * Note:
+ * This function returning 0 doesn't mean the device was detected. It means,
+ * that the bus rescan was successfully started. The device will get bound to
+ * its PCI driver asynchronously.
+ */
+int pci_pwrctl_device_set_ready(struct pci_pwrctl *pwrctl)
+{
+	int ret;
+
+	if (!pwrctl->dev)
+		return -ENODEV;
+
+	pwrctl->nb.notifier_call = pci_pwrctl_notify;
+	ret = bus_register_notifier(&pci_bus_type, &pwrctl->nb);
+	if (ret)
+		return ret;
+
+	pci_lock_rescan_remove();
+	pci_rescan_bus(to_pci_dev(pwrctl->dev->parent)->bus);
+	pci_unlock_rescan_remove();
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pci_pwrctl_device_set_ready);
+
+/**
+ * pci_pwrctl_device_unset_ready() - Notify the pwrctl subsystem that the PCI
+ * device is about to be powered-down.
+ *
+ * @pwrctl: PCI power control data.
+ */
+void pci_pwrctl_device_unset_ready(struct pci_pwrctl *pwrctl)
+{
+	/*
+	 * We don't have to delete the link here. Typically, this function
+	 * is only called when the power control device is being detached. If
+	 * it is being detached then the child PCI device must have already
+	 * been unbound too or the device core wouldn't let us unbind.
+	 */
+	bus_unregister_notifier(&pci_bus_type, &pwrctl->nb);
+}
+EXPORT_SYMBOL_GPL(pci_pwrctl_device_unset_ready);
+
+static void devm_pci_pwrctl_device_unset_ready(void *data)
+{
+	struct pci_pwrctl *pwrctl = data;
+
+	pci_pwrctl_device_unset_ready(pwrctl);
+}
+
+/**
+ * devm_pci_pwrctl_device_set_ready - Managed variant of
+ * pci_pwrctl_device_set_ready().
+ *
+ * @dev: Device managing this pwrctl provider.
+ * @pwrctl: PCI power control data.
+ *
+ * Returns:
+ * 0 on success, negative error number on error.
+ */
+int devm_pci_pwrctl_device_set_ready(struct device *dev,
+				     struct pci_pwrctl *pwrctl)
+{
+	int ret;
+
+	ret = pci_pwrctl_device_set_ready(pwrctl);
+	if (ret)
+		return ret;
+
+	return devm_add_action_or_reset(dev,
+					devm_pci_pwrctl_device_unset_ready,
+					pwrctl);
+}
+EXPORT_SYMBOL_GPL(devm_pci_pwrctl_device_set_ready);
+
+MODULE_AUTHOR("Bartosz Golaszewski <bartosz.golaszewski@linaro.org>");
+MODULE_DESCRIPTION("PCI Device Power Control core driver");
+MODULE_LICENSE("GPL");

drivers/pci/pwrctl/pci-pwrctl-pwrseq.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Linaro Ltd.
+ */
+
+#include <linux/device.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/pci-pwrctl.h>
+#include <linux/platform_device.h>
+#include <linux/pwrseq/consumer.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+struct pci_pwrctl_pwrseq_data {
+	struct pci_pwrctl ctx;
+	struct pwrseq_desc *pwrseq;
+};
+
+static void devm_pci_pwrctl_pwrseq_power_off(void *data)
+{
+	struct pwrseq_desc *pwrseq = data;
+
+	pwrseq_power_off(pwrseq);
+}
+
+static int pci_pwrctl_pwrseq_probe(struct platform_device *pdev)
+{
+	struct pci_pwrctl_pwrseq_data *data;
+	struct device *dev = &pdev->dev;
+	int ret;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->pwrseq = devm_pwrseq_get(dev, of_device_get_match_data(dev));
+	if (IS_ERR(data->pwrseq))
+		return dev_err_probe(dev, PTR_ERR(data->pwrseq),
+				     "Failed to get the power sequencer\n");
+
+	ret = pwrseq_power_on(data->pwrseq);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Failed to power-on the device\n");
+
+	ret = devm_add_action_or_reset(dev, devm_pci_pwrctl_pwrseq_power_off,
+				       data->pwrseq);
+	if (ret)
+		return ret;
+
+	data->ctx.dev = dev;
+
+	ret = devm_pci_pwrctl_device_set_ready(dev, &data->ctx);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Failed to register the pwrctl wrapper\n");
+
+	return 0;
+}
+
+static const struct of_device_id pci_pwrctl_pwrseq_of_match[] = {
+	{
+		/* ATH11K in QCA6390 package. */
+		.compatible = "pci17cb,1101",
+		.data = "wlan",
+	},
+	{
+		/* ATH12K in WCN7850 package. */
+		.compatible = "pci17cb,1107",
+		.data = "wlan",
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, pci_pwrctl_pwrseq_of_match);
+
+static struct platform_driver pci_pwrctl_pwrseq_driver = {
+	.driver = {
+		.name = "pci-pwrctl-pwrseq",
+		.of_match_table = pci_pwrctl_pwrseq_of_match,
+	},
+	.probe = pci_pwrctl_pwrseq_probe,
+};
+module_platform_driver(pci_pwrctl_pwrseq_driver);
+
+MODULE_AUTHOR("Bartosz Golaszewski <bartosz.golaszewski@linaro.org>");
+MODULE_DESCRIPTION("Generic PCI Power Control module for power sequenced devices");
+MODULE_LICENSE("GPL");

drivers/pci/remove.c

 // SPDX-License-Identifier: GPL-2.0
 #include <linux/pci.h>
 #include <linux/module.h>
+#include <linux/of_platform.h>
 #include "pci.h"
 
 static void pci_free_resources(struct pci_dev *dev)
@@ -18,7 +19,7 @@ static void pci_stop_dev(struct pci_dev *dev)
 	pci_pme_active(dev, false);
 
 	if (pci_dev_is_added(dev)) {
-
+		of_platform_depopulate(&dev->dev);
 		device_release_driver(&dev->dev);
 		pci_proc_detach_device(dev);
 		pci_remove_sysfs_dev_files(dev);

drivers/power/Kconfig

 # SPDX-License-Identifier: GPL-2.0-only
 source "drivers/power/reset/Kconfig"
+source "drivers/power/sequencing/Kconfig"
 source "drivers/power/supply/Kconfig"

drivers/power/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
 obj-$(CONFIG_POWER_RESET)	+= reset/
+obj-$(CONFIG_POWER_SEQUENCING)	+= sequencing/
 obj-$(CONFIG_POWER_SUPPLY)	+= supply/

drivers/power/sequencing/Kconfig

+# 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.
+
+if POWER_SEQUENCING
+
+config POWER_SEQUENCING_QCOM_WCN
+	tristate "Qualcomm WCN family PMU driver"
+	default m if ARCH_QCOM
+	help
+	  Say Y here to enable the power sequencing driver for Qualcomm
+	  WCN Bluetooth/WLAN chipsets.
+
+	  Typically, a package from the Qualcomm WCN family contains the BT
+	  and WLAN modules whose power is controlled by the PMU module. As the
+	  former two share the power-up sequence which is executed by the PMU,
+	  this driver is needed for correct power control or else we'd risk not
+	  respecting the required delays between enabling Bluetooth and WLAN.
+
+endif

drivers/power/sequencing/Makefile

+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_POWER_SEQUENCING)		+= pwrseq-core.o
+pwrseq-core-y				:= core.o
+
+obj-$(CONFIG_POWER_SEQUENCING_QCOM_WCN)	+= pwrseq-qcom-wcn.o

drivers/power/sequencing/core.c

+// 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(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_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(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");

drivers/power/sequencing/pwrseq-qcom-wcn.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Linaro Ltd.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/gpio/consumer.h>
+#include <linux/jiffies.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+#include <linux/pwrseq/provider.h>
+#include <linux/string.h>
+#include <linux/types.h>
+
+struct pwrseq_qcom_wcn_pdata {
+	const char *const *vregs;
+	size_t num_vregs;
+	unsigned int pwup_delay_ms;
+	unsigned int gpio_enable_delay_ms;
+};
+
+struct pwrseq_qcom_wcn_ctx {
+	struct pwrseq_device *pwrseq;
+	struct device_node *of_node;
+	const struct pwrseq_qcom_wcn_pdata *pdata;
+	struct regulator_bulk_data *regs;
+	struct gpio_desc *bt_gpio;
+	struct gpio_desc *wlan_gpio;
+	struct clk *clk;
+	unsigned long last_gpio_enable_jf;
+};
+
+static void pwrseq_qcom_wcn_ensure_gpio_delay(struct pwrseq_qcom_wcn_ctx *ctx)
+{
+	unsigned long diff_jiffies;
+	unsigned int diff_msecs;
+
+	if (!ctx->pdata->gpio_enable_delay_ms)
+		return;
+
+	diff_jiffies = jiffies - ctx->last_gpio_enable_jf;
+	diff_msecs = jiffies_to_msecs(diff_jiffies);
+
+	if (diff_msecs < ctx->pdata->gpio_enable_delay_ms)
+		msleep(ctx->pdata->gpio_enable_delay_ms - diff_msecs);
+}
+
+static int pwrseq_qcom_wcn_vregs_enable(struct pwrseq_device *pwrseq)
+{
+	struct pwrseq_qcom_wcn_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
+
+	return regulator_bulk_enable(ctx->pdata->num_vregs, ctx->regs);
+}
+
+static int pwrseq_qcom_wcn_vregs_disable(struct pwrseq_device *pwrseq)
+{
+	struct pwrseq_qcom_wcn_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
+
+	return regulator_bulk_disable(ctx->pdata->num_vregs, ctx->regs);
+}
+
+static const struct pwrseq_unit_data pwrseq_qcom_wcn_vregs_unit_data = {
+	.name = "regulators-enable",
+	.enable = pwrseq_qcom_wcn_vregs_enable,
+	.disable = pwrseq_qcom_wcn_vregs_disable,
+};
+
+static int pwrseq_qcom_wcn_clk_enable(struct pwrseq_device *pwrseq)
+{
+	struct pwrseq_qcom_wcn_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
+
+	return clk_prepare_enable(ctx->clk);
+}
+
+static int pwrseq_qcom_wcn_clk_disable(struct pwrseq_device *pwrseq)
+{
+	struct pwrseq_qcom_wcn_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
+
+	clk_disable_unprepare(ctx->clk);
+
+	return 0;
+}
+
+static const struct pwrseq_unit_data pwrseq_qcom_wcn_clk_unit_data = {
+	.name = "clock-enable",
+	.enable = pwrseq_qcom_wcn_clk_enable,
+	.disable = pwrseq_qcom_wcn_clk_disable,
+};
+
+static const struct pwrseq_unit_data *pwrseq_qcom_wcn_unit_deps[] = {
+	&pwrseq_qcom_wcn_vregs_unit_data,
+	&pwrseq_qcom_wcn_clk_unit_data,
+	NULL
+};
+
+static int pwrseq_qcom_wcn_bt_enable(struct pwrseq_device *pwrseq)
+{
+	struct pwrseq_qcom_wcn_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
+
+	pwrseq_qcom_wcn_ensure_gpio_delay(ctx);
+	gpiod_set_value_cansleep(ctx->bt_gpio, 1);
+	ctx->last_gpio_enable_jf = jiffies;
+
+	return 0;
+}
+
+static int pwrseq_qcom_wcn_bt_disable(struct pwrseq_device *pwrseq)
+{
+	struct pwrseq_qcom_wcn_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
+
+	gpiod_set_value_cansleep(ctx->bt_gpio, 0);
+
+	return 0;
+}
+
+static const struct pwrseq_unit_data pwrseq_qcom_wcn_bt_unit_data = {
+	.name = "bluetooth-enable",
+	.deps = pwrseq_qcom_wcn_unit_deps,
+	.enable = pwrseq_qcom_wcn_bt_enable,
+	.disable = pwrseq_qcom_wcn_bt_disable,
+};
+
+static int pwrseq_qcom_wcn_wlan_enable(struct pwrseq_device *pwrseq)
+{
+	struct pwrseq_qcom_wcn_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
+
+	pwrseq_qcom_wcn_ensure_gpio_delay(ctx);
+	gpiod_set_value_cansleep(ctx->wlan_gpio, 1);
+	ctx->last_gpio_enable_jf = jiffies;
+
+	return 0;
+}
+
+static int pwrseq_qcom_wcn_wlan_disable(struct pwrseq_device *pwrseq)
+{
+	struct pwrseq_qcom_wcn_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
+
+	gpiod_set_value_cansleep(ctx->wlan_gpio, 0);
+
+	return 0;
+}
+
+static const struct pwrseq_unit_data pwrseq_qcom_wcn_wlan_unit_data = {
+	.name = "wlan-enable",
+	.deps = pwrseq_qcom_wcn_unit_deps,
+	.enable = pwrseq_qcom_wcn_wlan_enable,
+	.disable = pwrseq_qcom_wcn_wlan_disable,
+};
+
+static int pwrseq_qcom_wcn_pwup_delay(struct pwrseq_device *pwrseq)
+{
+	struct pwrseq_qcom_wcn_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
+
+	if (ctx->pdata->pwup_delay_ms)
+		msleep(ctx->pdata->pwup_delay_ms);
+
+	return 0;
+}
+
+static const struct pwrseq_target_data pwrseq_qcom_wcn_bt_target_data = {
+	.name = "bluetooth",
+	.unit = &pwrseq_qcom_wcn_bt_unit_data,
+	.post_enable = pwrseq_qcom_wcn_pwup_delay,
+};
+
+static const struct pwrseq_target_data pwrseq_qcom_wcn_wlan_target_data = {
+	.name = "wlan",
+	.unit = &pwrseq_qcom_wcn_wlan_unit_data,
+	.post_enable = pwrseq_qcom_wcn_pwup_delay,
+};
+
+static const struct pwrseq_target_data *pwrseq_qcom_wcn_targets[] = {
+	&pwrseq_qcom_wcn_bt_target_data,
+	&pwrseq_qcom_wcn_wlan_target_data,
+	NULL
+};
+
+static const char *const pwrseq_qca6390_vregs[] = {
+	"vddio",
+	"vddaon",
+	"vddpmu",
+	"vddrfa0p95",
+	"vddrfa1p3",
+	"vddrfa1p9",
+	"vddpcie1p3",
+	"vddpcie1p9",
+};
+
+static const struct pwrseq_qcom_wcn_pdata pwrseq_qca6390_of_data = {
+	.vregs = pwrseq_qca6390_vregs,
+	.num_vregs = ARRAY_SIZE(pwrseq_qca6390_vregs),
+	.pwup_delay_ms = 60,
+	.gpio_enable_delay_ms = 100,
+};
+
+static const char *const pwrseq_wcn7850_vregs[] = {
+	"vdd",
+	"vddio",
+	"vddio1p2",
+	"vddaon",
+	"vdddig",
+	"vddrfa1p2",
+	"vddrfa1p8",
+};
+
+static const struct pwrseq_qcom_wcn_pdata pwrseq_wcn7850_of_data = {
+	.vregs = pwrseq_wcn7850_vregs,
+	.num_vregs = ARRAY_SIZE(pwrseq_wcn7850_vregs),
+	.pwup_delay_ms = 50,
+};
+
+static int pwrseq_qcom_wcn_match(struct pwrseq_device *pwrseq,
+				 struct device *dev)
+{
+	struct pwrseq_qcom_wcn_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
+	struct device_node *dev_node = dev->of_node;
+
+	/*
+	 * The PMU supplies power to the Bluetooth and WLAN modules. both
+	 * consume the PMU AON output so check the presence of the
+	 * 'vddaon-supply' property and whether it leads us to the right
+	 * device.
+	 */
+	if (!of_property_present(dev_node, "vddaon-supply"))
+		return 0;
+
+	struct device_node *reg_node __free(device_node) =
+			of_parse_phandle(dev_node, "vddaon-supply", 0);
+	if (!reg_node)
+		return 0;
+
+	/*
+	 * `reg_node` is the PMU AON regulator, its parent is the `regulators`
+	 * node and finally its grandparent is the PMU device node that we're
+	 * looking for.
+	 */
+	if (!reg_node->parent || !reg_node->parent->parent ||
+	    reg_node->parent->parent != ctx->of_node)
+		return 0;
+
+	return 1;
+}
+
+static int pwrseq_qcom_wcn_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct pwrseq_qcom_wcn_ctx *ctx;
+	struct pwrseq_config config;
+	int i, ret;
+
+	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	ctx->of_node = dev->of_node;
+
+	ctx->pdata = of_device_get_match_data(dev);
+	if (!ctx->pdata)
+		return dev_err_probe(dev, -ENODEV,
+				     "Failed to obtain platform data\n");
+
+	ctx->regs = devm_kcalloc(dev, ctx->pdata->num_vregs,
+				 sizeof(*ctx->regs), GFP_KERNEL);
+	if (!ctx->regs)
+		return -ENOMEM;
+
+	for (i = 0; i < ctx->pdata->num_vregs; i++)
+		ctx->regs[i].supply = ctx->pdata->vregs[i];
+
+	ret = devm_regulator_bulk_get(dev, ctx->pdata->num_vregs, ctx->regs);
+	if (ret < 0)
+		return dev_err_probe(dev, ret,
+				     "Failed to get all regulators\n");
+
+	ctx->bt_gpio = devm_gpiod_get_optional(dev, "bt-enable", GPIOD_OUT_LOW);
+	if (IS_ERR(ctx->bt_gpio))
+		return dev_err_probe(dev, PTR_ERR(ctx->bt_gpio),
+				     "Failed to get the Bluetooth enable GPIO\n");
+
+	ctx->wlan_gpio = devm_gpiod_get_optional(dev, "wlan-enable",
+						 GPIOD_OUT_LOW);
+	if (IS_ERR(ctx->wlan_gpio))
+		return dev_err_probe(dev, PTR_ERR(ctx->wlan_gpio),
+				     "Failed to get the WLAN enable GPIO\n");
+
+	ctx->clk = devm_clk_get_optional(dev, NULL);
+	if (IS_ERR(ctx->clk))
+		return dev_err_probe(dev, PTR_ERR(ctx->clk),
+				     "Failed to get the reference clock\n");
+
+	memset(&config, 0, sizeof(config));
+
+	config.parent = dev;
+	config.owner = THIS_MODULE;
+	config.drvdata = ctx;
+	config.match = pwrseq_qcom_wcn_match;
+	config.targets = pwrseq_qcom_wcn_targets;
+
+	ctx->pwrseq = devm_pwrseq_device_register(dev, &config);
+	if (IS_ERR(ctx->pwrseq))
+		return dev_err_probe(dev, PTR_ERR(ctx->pwrseq),
+				     "Failed to register the power sequencer\n");
+
+	return 0;
+}
+
+static const struct of_device_id pwrseq_qcom_wcn_of_match[] = {
+	{
+		.compatible = "qcom,qca6390-pmu",
+		.data = &pwrseq_qca6390_of_data,
+	},
+	{
+		.compatible = "qcom,wcn7850-pmu",
+		.data = &pwrseq_wcn7850_of_data,
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, pwrseq_qcom_wcn_of_match);
+
+static struct platform_driver pwrseq_qcom_wcn_driver = {
+	.driver = {
+		.name = "pwrseq-qcom_wcn",
+		.of_match_table = pwrseq_qcom_wcn_of_match,
+	},
+	.probe = pwrseq_qcom_wcn_probe,
+};
+module_platform_driver(pwrseq_qcom_wcn_driver);
+
+MODULE_AUTHOR("Bartosz Golaszewski <bartosz.golaszewski@linaro.org>");
+MODULE_DESCRIPTION("Qualcomm WCN PMU power sequencing driver");
+MODULE_LICENSE("GPL");

include/linux/pci-pwrctl.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2024 Linaro Ltd.
+ */
+
+#ifndef __PCI_PWRCTL_H__
+#define __PCI_PWRCTL_H__
+
+#include <linux/notifier.h>
+
+struct device;
+struct device_link;
+
+/*
+ * This is a simple framework for solving the issue of PCI devices that require
+ * certain resources (regulators, GPIOs, clocks) to be enabled before the
+ * device can actually be detected on the PCI bus.
+ *
+ * The idea is to reuse the platform bus to populate OF nodes describing the
+ * PCI device and its resources, let these platform devices probe and enable
+ * relevant resources and then trigger a rescan of the PCI bus allowing for the
+ * same device (with a second associated struct device) to be registered with
+ * the PCI subsystem.
+ *
+ * To preserve a correct hierarchy for PCI power management and device reset,
+ * we create a device link between the power control platform device (parent)
+ * and the supplied PCI device (child).
+ */
+
+/**
+ * struct pci_pwrctl - PCI device power control context.
+ * @dev: Address of the power controlling device.
+ *
+ * An object of this type must be allocated by the PCI power control device and
+ * passed to the pwrctl subsystem to trigger a bus rescan and setup a device
+ * link with the device once it's up.
+ */
+struct pci_pwrctl {
+	struct device *dev;
+
+	/* Private: don't use. */
+	struct notifier_block nb;
+	struct device_link *link;
+};
+
+int pci_pwrctl_device_set_ready(struct pci_pwrctl *pwrctl);
+void pci_pwrctl_device_unset_ready(struct pci_pwrctl *pwrctl);
+int devm_pci_pwrctl_device_set_ready(struct device *dev,
+				     struct pci_pwrctl *pwrctl);
+
+#endif /* __PCI_PWRCTL_H__ */

include/linux/pwrseq/consumer.h

+/* 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__ */

include/linux/pwrseq/provider.h

+/* 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__ */