[PATCH v14 2/7] power: add power sequence library

[Peter Chen]

We have an well-known problem that the device needs to do some power
sequence before it can be recognized by related host, the typical
example like hard-wired mmc devices and usb devices.

This power sequence is hard to be described at device tree and handled by
related host driver, so we have created a common power sequence
library to cover this requirement. The core code has supplied
some common helpers for host driver, and individual power sequence
libraries handle kinds of power sequence for devices. The pwrseq
librares always need to allocate extra instance for compatible
string match.

pwrseq_generic is intended for general purpose of power sequence, which
handles gpios and clocks currently, and can cover other controls in
future. The host driver just needs to call of_pwrseq_on/of_pwrseq_off
if only one power sequence is needed, else call of_pwrseq_on_list
/of_pwrseq_off_list instead (eg, USB hub driver).

For new power sequence library, it can add its compatible string
to pwrseq_of_match_table, then the pwrseq core will match it with
DT's, and choose this library at runtime.

Signed-off-by: Peter Chen <peter.chen@xxxxxxx>
Tested-by: Maciej S. Szmigiero <mail@xxxxxxxxxxxxxxxxxxxxx>
Tested-by Joshua Clayton <stillcompiling@xxxxxxxxx>
Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
Tested-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
---
 Documentation/power/power-sequence/design.rst |  54 +++++
 MAINTAINERS                                   |   9 +
 drivers/power/Kconfig                         |   1 +
 drivers/power/Makefile                        |   1 +
 drivers/power/pwrseq/Kconfig                  |  20 ++
 drivers/power/pwrseq/Makefile                 |   2 +
 drivers/power/pwrseq/core.c                   | 335 ++++++++++++++++++++++++++
 drivers/power/pwrseq/pwrseq_generic.c         | 234 ++++++++++++++++++
 include/linux/power/pwrseq.h                  |  81 +++++++
 9 files changed, 737 insertions(+)
 create mode 100644 Documentation/power/power-sequence/design.rst
 create mode 100644 drivers/power/pwrseq/Kconfig
 create mode 100644 drivers/power/pwrseq/Makefile
 create mode 100644 drivers/power/pwrseq/core.c
 create mode 100644 drivers/power/pwrseq/pwrseq_generic.c
 create mode 100644 include/linux/power/pwrseq.h

diff --git a/Documentation/power/power-sequence/design.rst b/Documentation/power/power-sequence/design.rst
new file mode 100644
index 0000000..554608e
--- /dev/null
+++ b/Documentation/power/power-sequence/design.rst
@@ -0,0 +1,54 @@
+====================================
+Power Sequence Library
+====================================
+
+:Date: Feb, 2017
+:Author: Peter Chen <peter.chen@xxxxxxx>
+
+
+Introduction
+============
+
+We have an well-known problem that the device needs to do a power
+sequence before it can be recognized by related host, the typical
+examples are hard-wired mmc devices and usb devices. The host controller
+can't know what kinds of this device is in its bus if the power
+sequence has not done, since the related devices driver's probe calling
+is determined by runtime according to eunumeration results. Besides,
+the devices may have custom power sequence, so the power sequence library
+which is independent with the devices is needed.
+
+Design
+============
+
+The power sequence library includes the core file and customer power
+sequence library. The core file exports interfaces are called by
+host controller driver for power sequence and customer power sequence
+library files to register its power sequence instance to global
+power sequence list. The custom power sequence library creates power
+sequence instance and implement custom power sequence.
+
+Since the power sequence describes hardware design, the description is
+located at board description file, eg, device tree dts file. And
+a specific power sequence belongs to device, so its description
+is under the device node, please refer to:
+Documentation/devicetree/bindings/power/pwrseq/pwrseq-generic.txt
+
+Custom power sequence library allocates one power sequence instance at
+bootup periods using postcore_initcall, this static allocated instance is
+used to compare with device-tree (DT) node to see if this library can be
+used for the node or not. When the result is matched, the core API will
+try to get resourses (->get, implemented at each library) for power
+sequence, if all resources are got, it will try to allocate another
+instance for next possible request from host driver.
+
+Then, the host controller driver can carry out power sequence on for this
+DT node, the library will do corresponding operations, like open clocks,
+toggle gpio, etc. The power sequence off routine will close and free the
+resources, and is called when the parent is removed. And the power
+sequence suspend and resume routine can be called at host driver's
+suspend and resume routine if needed.
+
+The exported interfaces
+.. kernel-doc:: drivers/power/pwrseq/core.c
+   :export:
diff --git a/MAINTAINERS b/MAINTAINERS
index f7d568b..93b07aa 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10188,6 +10188,15 @@ F:	include/linux/pm_*
 F:	include/linux/powercap.h
 F:	drivers/powercap/
 
+POWER SEQUENCE LIBRARY
+M:	Peter Chen <Peter.Chen@xxxxxxx>
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/peter.chen/usb.git
+L:	linux-pm@xxxxxxxxxxxxxxx
+S:	Maintained
+F:	Documentation/devicetree/bindings/power/pwrseq/
+F:	drivers/power/pwrseq/
+F:	include/linux/power/pwrseq.h
+
 POWER SUPPLY CLASS/SUBSYSTEM and DRIVERS
 M:	Sebastian Reichel <sre@xxxxxxxxxx>
 L:	linux-pm@xxxxxxxxxxxxxxx
diff --git a/drivers/power/Kconfig b/drivers/power/Kconfig
index 63454b5..c1bb046 100644
--- a/drivers/power/Kconfig
+++ b/drivers/power/Kconfig
@@ -1,3 +1,4 @@
 source "drivers/power/avs/Kconfig"
 source "drivers/power/reset/Kconfig"
 source "drivers/power/supply/Kconfig"
+source "drivers/power/pwrseq/Kconfig"
diff --git a/drivers/power/Makefile b/drivers/power/Makefile
index ff35c71..7db8035 100644
--- a/drivers/power/Makefile
+++ b/drivers/power/Makefile
@@ -1,3 +1,4 @@
 obj-$(CONFIG_POWER_AVS)		+= avs/
 obj-$(CONFIG_POWER_RESET)	+= reset/
 obj-$(CONFIG_POWER_SUPPLY)	+= supply/
+obj-$(CONFIG_POWER_SEQUENCE)	+= pwrseq/
diff --git a/drivers/power/pwrseq/Kconfig b/drivers/power/pwrseq/Kconfig
new file mode 100644
index 0000000..c6b3569
--- /dev/null
+++ b/drivers/power/pwrseq/Kconfig
@@ -0,0 +1,20 @@
+#
+# Power Sequence library
+#
+
+menuconfig POWER_SEQUENCE
+	bool "Power sequence control"
+	help
+	   It is used for drivers which needs to do power sequence
+	   (eg, turn on clock, toggle reset gpio) before the related
+	   devices can be found by hardware, eg, USB bus.
+
+if POWER_SEQUENCE
+
+config PWRSEQ_GENERIC
+	bool "Generic power sequence control"
+	depends on OF
+	help
+	   This is the generic power sequence control library, and is
+	   supposed to support common power sequence usage.
+endif
diff --git a/drivers/power/pwrseq/Makefile b/drivers/power/pwrseq/Makefile
new file mode 100644
index 0000000..ad82389
--- /dev/null
+++ b/drivers/power/pwrseq/Makefile
@@ -0,0 +1,2 @@
+obj-$(CONFIG_POWER_SEQUENCE) += core.o
+obj-$(CONFIG_PWRSEQ_GENERIC) += pwrseq_generic.o
diff --git a/drivers/power/pwrseq/core.c b/drivers/power/pwrseq/core.c
new file mode 100644
index 0000000..3d19e62
--- /dev/null
+++ b/drivers/power/pwrseq/core.c
@@ -0,0 +1,335 @@
+/*
+ * core.c	power sequence core file
+ *
+ * Copyright (C) 2016 Freescale Semiconductor, Inc.
+ * Author: Peter Chen <peter.chen@xxxxxxx>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2  of
+ * the License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.
+ */
+
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/power/pwrseq.h>
+
+static DEFINE_MUTEX(pwrseq_list_mutex);
+static LIST_HEAD(pwrseq_list);
+
+static int pwrseq_get(struct device_node *np, struct pwrseq *p)
+{
+	if (p && p->get)
+		return p->get(np, p);
+
+	return -ENOTSUPP;
+}
+
+static int pwrseq_on(struct pwrseq *p)
+{
+	if (p && p->on)
+		return p->on(p);
+
+	return -ENOTSUPP;
+}
+
+static void pwrseq_off(struct pwrseq *p)
+{
+	if (p && p->off)
+		p->off(p);
+}
+
+static void pwrseq_put(struct pwrseq *p)
+{
+	if (p && p->put)
+		p->put(p);
+}
+
+/**
+ * pwrseq_register - Add pwrseq instance to global pwrseq list
+ *
+ * @pwrseq: the pwrseq instance
+ */
+void pwrseq_register(struct pwrseq *pwrseq)
+{
+	mutex_lock(&pwrseq_list_mutex);
+	list_add(&pwrseq->node, &pwrseq_list);
+	mutex_unlock(&pwrseq_list_mutex);
+}
+EXPORT_SYMBOL_GPL(pwrseq_register);
+
+/**
+ * pwrseq_unregister - Remove pwrseq instance from global pwrseq list
+ *
+ * @pwrseq: the pwrseq instance
+ */
+void pwrseq_unregister(struct pwrseq *pwrseq)
+{
+	mutex_lock(&pwrseq_list_mutex);
+	list_del(&pwrseq->node);
+	mutex_unlock(&pwrseq_list_mutex);
+}
+EXPORT_SYMBOL_GPL(pwrseq_unregister);
+
+static struct pwrseq *pwrseq_find_available_instance(struct device_node *np)
+{
+	struct pwrseq *pwrseq;
+
+	mutex_lock(&pwrseq_list_mutex);
+	list_for_each_entry(pwrseq, &pwrseq_list, node) {
+		if (pwrseq->used)
+			continue;
+
+		/* compare compatible string for pwrseq node */
+		if (of_match_node(pwrseq->pwrseq_of_match_table, np)) {
+			pwrseq->used = true;
+			mutex_unlock(&pwrseq_list_mutex);
+			return pwrseq;
+		}
+
+		/* return generic pwrseq instance */
+		if (!strcmp(pwrseq->pwrseq_of_match_table->compatible,
+				"generic")) {
+			pr_debug("using generic pwrseq instance for %s\n",
+				np->full_name);
+			pwrseq->used = true;
+			mutex_unlock(&pwrseq_list_mutex);
+			return pwrseq;
+		}
+	}
+	mutex_unlock(&pwrseq_list_mutex);
+	pr_debug("Can't find any pwrseq instances for %s\n", np->full_name);
+
+	return NULL;
+}
+
+/**
+ * of_pwrseq_on - Carry out power sequence on for device node
+ *
+ * @np: the device node would like to power on
+ *
+ * Carry out a single device power on.  If multiple devices
+ * need to be handled, use of_pwrseq_on_list() instead.
+ *
+ * Return a pointer to the power sequence instance on success,
+ * or an error code otherwise.
+ */
+struct pwrseq *of_pwrseq_on(struct device_node *np)
+{
+	struct pwrseq *pwrseq;
+	int ret;
+
+	pwrseq = pwrseq_find_available_instance(np);
+	if (!pwrseq)
+		return ERR_PTR(-ENOENT);
+
+	ret = pwrseq_get(np, pwrseq);
+	if (ret) {
+		/* Mark current pwrseq as unused */
+		pwrseq->used = false;
+		return ERR_PTR(ret);
+	}
+
+	ret = pwrseq_on(pwrseq);
+	if (ret)
+		goto pwr_put;
+
+	return pwrseq;
+
+pwr_put:
+	pwrseq_put(pwrseq);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(of_pwrseq_on);
+
+/**
+ * of_pwrseq_off - Carry out power sequence off for this pwrseq instance
+ *
+ * @pwrseq: the pwrseq instance which related device would like to be off
+ *
+ * This API is used to power off single device, it is the opposite
+ * operation for of_pwrseq_on.
+ */
+void of_pwrseq_off(struct pwrseq *pwrseq)
+{
+	pwrseq_off(pwrseq);
+	pwrseq_put(pwrseq);
+}
+EXPORT_SYMBOL_GPL(of_pwrseq_off);
+
+/**
+ * of_pwrseq_on_list - Carry out power sequence on for list
+ *
+ * @np: the device node would like to power on
+ * @head: the list head for pwrseq list on this bus
+ *
+ * This API is used to power on multiple devices at single bus.
+ * If there are several devices on bus (eg, USB bus), uses this
+ * this API. Otherwise, use of_pwrseq_on instead. After the device
+ * is powered on successfully, it will be added to pwrseq list for
+ * this bus. The caller needs to use mutex_lock for concurrent.
+ *
+ * Return 0 on success, or an error value otherwise.
+ */
+int of_pwrseq_on_list(struct device_node *np, struct list_head *head)
+{
+	struct pwrseq *pwrseq;
+	struct pwrseq_list_per_dev *pwrseq_list_node;
+
+	pwrseq_list_node = kzalloc(sizeof(*pwrseq_list_node), GFP_KERNEL);
+	if (!pwrseq_list_node)
+		return -ENOMEM;
+
+	pwrseq = of_pwrseq_on(np);
+	if (IS_ERR(pwrseq)) {
+		kfree(pwrseq_list_node);
+		return PTR_ERR(pwrseq);
+	}
+
+	pwrseq_list_node->pwrseq = pwrseq;
+	list_add(&pwrseq_list_node->list, head);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(of_pwrseq_on_list);
+
+/**
+ * of_pwrseq_off_list - Carry out power sequence off for the list
+ *
+ * @head: the list head for pwrseq instance list on this bus
+ *
+ * This API is used to power off all devices on this bus, it is
+ * the opposite operation for of_pwrseq_on_list.
+ * The caller needs to use mutex_lock for concurrent.
+ */
+void of_pwrseq_off_list(struct list_head *head)
+{
+	struct pwrseq *pwrseq;
+	struct pwrseq_list_per_dev *pwrseq_list_node, *tmp_node;
+
+	list_for_each_entry_safe(pwrseq_list_node, tmp_node, head, list) {
+		pwrseq = pwrseq_list_node->pwrseq;
+		of_pwrseq_off(pwrseq);
+		list_del(&pwrseq_list_node->list);
+		kfree(pwrseq_list_node);
+	}
+}
+EXPORT_SYMBOL_GPL(of_pwrseq_off_list);
+
+/**
+ * pwrseq_suspend - Carry out power sequence suspend for this pwrseq instance
+ *
+ * @pwrseq: the pwrseq instance
+ *
+ * This API is used to do suspend operation on pwrseq instance.
+ *
+ * Return 0 on success, or an error value otherwise.
+ */
+int pwrseq_suspend(struct pwrseq *p)
+{
+	int ret = 0;
+
+	if (p && p->suspend)
+		ret = p->suspend(p);
+	else
+		return ret;
+
+	if (!ret)
+		p->suspended = true;
+	else
+		pr_err("%s failed\n", __func__);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pwrseq_suspend);
+
+/**
+ * pwrseq_resume - Carry out power sequence resume for this pwrseq instance
+ *
+ * @pwrseq: the pwrseq instance
+ *
+ * This API is used to do resume operation on pwrseq instance.
+ *
+ * Return 0 on success, or an error value otherwise.
+ */
+int pwrseq_resume(struct pwrseq *p)
+{
+	int ret = 0;
+
+	if (p && p->resume)
+		ret = p->resume(p);
+	else
+		return ret;
+
+	if (!ret)
+		p->suspended = false;
+	else
+		pr_err("%s failed\n", __func__);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pwrseq_resume);
+
+/**
+ * pwrseq_suspend_list - Carry out power sequence suspend for list
+ *
+ * @head: the list head for pwrseq instance list on this bus
+ *
+ * This API is used to do suspend on all power sequence instances on this bus.
+ * The caller needs to use mutex_lock for concurrent.
+ */
+int pwrseq_suspend_list(struct list_head *head)
+{
+	struct pwrseq *pwrseq;
+	struct pwrseq_list_per_dev *pwrseq_list_node;
+	int ret = 0;
+
+	list_for_each_entry(pwrseq_list_node, head, list) {
+		ret = pwrseq_suspend(pwrseq_list_node->pwrseq);
+		if (ret)
+			break;
+	}
+
+	if (ret) {
+		list_for_each_entry(pwrseq_list_node, head, list) {
+			pwrseq = pwrseq_list_node->pwrseq;
+			if (pwrseq->suspended)
+				pwrseq_resume(pwrseq);
+		}
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pwrseq_suspend_list);
+
+/**
+ * pwrseq_resume_list - Carry out power sequence resume for the list
+ *
+ * @head: the list head for pwrseq instance list on this bus
+ *
+ * This API is used to do resume on all power sequence instances on this bus.
+ * The caller needs to use mutex_lock for concurrent.
+ */
+int pwrseq_resume_list(struct list_head *head)
+{
+	struct pwrseq_list_per_dev *pwrseq_list_node;
+	int ret = 0;
+
+	list_for_each_entry(pwrseq_list_node, head, list) {
+		ret = pwrseq_resume(pwrseq_list_node->pwrseq);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pwrseq_resume_list);
diff --git a/drivers/power/pwrseq/pwrseq_generic.c b/drivers/power/pwrseq/pwrseq_generic.c
new file mode 100644
index 0000000..4e7c090
--- /dev/null
+++ b/drivers/power/pwrseq/pwrseq_generic.c
@@ -0,0 +1,234 @@
+/*
+ * pwrseq_generic.c	Generic power sequence handling
+ *
+ * Copyright (C) 2016 Freescale Semiconductor, Inc.
+ * Author: Peter Chen <peter.chen@xxxxxxx>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2  of
+ * the License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
+#include <linux/of.h>
+#include <linux/of_gpio.h>
+#include <linux/slab.h>
+
+#include <linux/power/pwrseq.h>
+
+struct pwrseq_generic {
+	struct pwrseq pwrseq;
+	struct gpio_desc *gpiod_reset;
+	struct clk *clks[PWRSEQ_MAX_CLKS];
+	u32 duration_us;
+	bool suspended;
+};
+
+#define to_generic_pwrseq(p) container_of(p, struct pwrseq_generic, pwrseq)
+
+static int pwrseq_generic_alloc_instance(void);
+static const struct of_device_id generic_id_table[] = {
+	{ .compatible = "generic",},
+	{ /* sentinel */ }
+};
+
+static int pwrseq_generic_suspend(struct pwrseq *pwrseq)
+{
+	struct pwrseq_generic *pwrseq_gen = to_generic_pwrseq(pwrseq);
+	int clk;
+
+	for (clk = PWRSEQ_MAX_CLKS - 1; clk >= 0; clk--)
+		clk_disable_unprepare(pwrseq_gen->clks[clk]);
+
+	pwrseq_gen->suspended = true;
+	return 0;
+}
+
+static int pwrseq_generic_resume(struct pwrseq *pwrseq)
+{
+	struct pwrseq_generic *pwrseq_gen = to_generic_pwrseq(pwrseq);
+	int clk, ret = 0;
+
+	for (clk = 0; clk < PWRSEQ_MAX_CLKS && pwrseq_gen->clks[clk]; clk++) {
+		ret = clk_prepare_enable(pwrseq_gen->clks[clk]);
+		if (ret) {
+			pr_err("Can't enable clock, ret=%d\n", ret);
+			goto err_disable_clks;
+		}
+	}
+
+	pwrseq_gen->suspended = false;
+	return ret;
+
+err_disable_clks:
+	while (--clk >= 0)
+		clk_disable_unprepare(pwrseq_gen->clks[clk]);
+
+	return ret;
+}
+
+static void pwrseq_generic_put(struct pwrseq *pwrseq)
+{
+	struct pwrseq_generic *pwrseq_gen = to_generic_pwrseq(pwrseq);
+	int clk;
+
+	if (pwrseq_gen->gpiod_reset)
+		gpiod_put(pwrseq_gen->gpiod_reset);
+
+	for (clk = 0; clk < PWRSEQ_MAX_CLKS; clk++)
+		clk_put(pwrseq_gen->clks[clk]);
+
+	pwrseq_unregister(&pwrseq_gen->pwrseq);
+	kfree(pwrseq_gen);
+}
+
+static void pwrseq_generic_off(struct pwrseq *pwrseq)
+{
+	struct pwrseq_generic *pwrseq_gen = to_generic_pwrseq(pwrseq);
+	int clk;
+
+	if (pwrseq_gen->suspended)
+		return;
+
+	for (clk = PWRSEQ_MAX_CLKS - 1; clk >= 0; clk--)
+		clk_disable_unprepare(pwrseq_gen->clks[clk]);
+}
+
+static int pwrseq_generic_on(struct pwrseq *pwrseq)
+{
+	struct pwrseq_generic *pwrseq_gen = to_generic_pwrseq(pwrseq);
+	int clk, ret = 0;
+	struct gpio_desc *gpiod_reset = pwrseq_gen->gpiod_reset;
+
+	for (clk = 0; clk < PWRSEQ_MAX_CLKS && pwrseq_gen->clks[clk]; clk++) {
+		ret = clk_prepare_enable(pwrseq_gen->clks[clk]);
+		if (ret) {
+			pr_err("Can't enable clock, ret=%d\n", ret);
+			goto err_disable_clks;
+		}
+	}
+
+	if (gpiod_reset) {
+		u32 duration_us = pwrseq_gen->duration_us;
+
+		if (duration_us <= 10)
+			udelay(10);
+		else
+			usleep_range(duration_us, duration_us + 100);
+		gpiod_set_value(gpiod_reset, 0);
+	}
+
+	return ret;
+
+err_disable_clks:
+	while (--clk >= 0)
+		clk_disable_unprepare(pwrseq_gen->clks[clk]);
+
+	return ret;
+}
+
+static int pwrseq_generic_get(struct device_node *np, struct pwrseq *pwrseq)
+{
+	struct pwrseq_generic *pwrseq_gen = to_generic_pwrseq(pwrseq);
+	enum of_gpio_flags flags;
+	int reset_gpio, clk, ret = 0;
+
+	for (clk = 0; clk < PWRSEQ_MAX_CLKS; clk++) {
+		pwrseq_gen->clks[clk] = of_clk_get(np, clk);
+		if (IS_ERR(pwrseq_gen->clks[clk])) {
+			ret = PTR_ERR(pwrseq_gen->clks[clk]);
+			if (ret != -ENOENT)
+				goto err_put_clks;
+			pwrseq_gen->clks[clk] = NULL;
+			break;
+		}
+	}
+
+	reset_gpio = of_get_named_gpio_flags(np, "reset-gpios", 0, &flags);
+	if (gpio_is_valid(reset_gpio)) {
+		unsigned long gpio_flags;
+
+		if (flags & OF_GPIO_ACTIVE_LOW)
+			gpio_flags = GPIOF_ACTIVE_LOW | GPIOF_OUT_INIT_LOW;
+		else
+			gpio_flags = GPIOF_OUT_INIT_HIGH;
+
+		ret = gpio_request_one(reset_gpio, gpio_flags,
+				"pwrseq-reset-gpios");
+		if (ret)
+			goto err_put_clks;
+
+		pwrseq_gen->gpiod_reset = gpio_to_desc(reset_gpio);
+		of_property_read_u32(np, "reset-duration-us",
+				&pwrseq_gen->duration_us);
+	} else if (reset_gpio == -ENOENT) {
+		; /* no such gpio */
+	} else {
+		ret = reset_gpio;
+		pr_err("Failed to get reset gpio on %s, err = %d\n",
+				np->full_name, reset_gpio);
+		goto err_put_clks;
+	}
+
+	/* allocate new one for later pwrseq instance request */
+	ret = pwrseq_generic_alloc_instance();
+	if (ret)
+		goto err_put_gpio;
+
+	return 0;
+
+err_put_gpio:
+	if (pwrseq_gen->gpiod_reset)
+		gpiod_put(pwrseq_gen->gpiod_reset);
+err_put_clks:
+	while (--clk >= 0)
+		clk_put(pwrseq_gen->clks[clk]);
+	return ret;
+}
+
+/**
+ * pwrseq_generic_alloc_instance - power sequence instance allocation
+ *
+ * This function is used to allocate one generic power sequence instance,
+ * it is called when the system boots up and after one power sequence
+ * instance is got successfully.
+ *
+ * Return zero on success or an error code otherwise.
+ */
+static int pwrseq_generic_alloc_instance(void)
+{
+	struct pwrseq_generic *pwrseq_gen;
+
+	pwrseq_gen = kzalloc(sizeof(*pwrseq_gen), GFP_KERNEL);
+	if (!pwrseq_gen)
+		return -ENOMEM;
+
+	pwrseq_gen->pwrseq.pwrseq_of_match_table = generic_id_table;
+	pwrseq_gen->pwrseq.get = pwrseq_generic_get;
+	pwrseq_gen->pwrseq.on = pwrseq_generic_on;
+	pwrseq_gen->pwrseq.off = pwrseq_generic_off;
+	pwrseq_gen->pwrseq.put = pwrseq_generic_put;
+	pwrseq_gen->pwrseq.suspend = pwrseq_generic_suspend;
+	pwrseq_gen->pwrseq.resume = pwrseq_generic_resume;
+
+	pwrseq_register(&pwrseq_gen->pwrseq);
+	return 0;
+}
+
+/* Allocate one pwrseq instance during boots up */
+static int __init pwrseq_generic_register(void)
+{
+	return pwrseq_generic_alloc_instance();
+}
+postcore_initcall(pwrseq_generic_register)
diff --git a/include/linux/power/pwrseq.h b/include/linux/power/pwrseq.h
new file mode 100644
index 0000000..cbc344c
--- /dev/null
+++ b/include/linux/power/pwrseq.h
@@ -0,0 +1,81 @@
+#ifndef __LINUX_PWRSEQ_H
+#define __LINUX_PWRSEQ_H
+
+#include <linux/of.h>
+
+#define PWRSEQ_MAX_CLKS		3
+
+/**
+ * struct pwrseq - the power sequence structure
+ * @pwrseq_of_match_table: the OF device id table this pwrseq library supports
+ * @node: the list pointer to be added to pwrseq list
+ * @get: the API is used to get pwrseq instance from the device node
+ * @on: do power on for this pwrseq instance
+ * @off: do power off for this pwrseq instance
+ * @put: release the resources on this pwrseq instance
+ * @suspend: do suspend operation on this pwrseq instance
+ * @resume: do resume operation on this pwrseq instance
+ * @used: this pwrseq instance is used by device
+ */
+struct pwrseq {
+	const struct of_device_id *pwrseq_of_match_table;
+	struct list_head node;
+	int (*get)(struct device_node *np, struct pwrseq *p);
+	int (*on)(struct pwrseq *p);
+	void (*off)(struct pwrseq *p);
+	void (*put)(struct pwrseq *p);
+	int (*suspend)(struct pwrseq *p);
+	int (*resume)(struct pwrseq *p);
+	bool used;
+	bool suspended;
+};
+
+/* used for power sequence instance list in one driver */
+struct pwrseq_list_per_dev {
+	struct pwrseq *pwrseq;
+	struct list_head list;
+};
+
+#if IS_ENABLED(CONFIG_POWER_SEQUENCE)
+void pwrseq_register(struct pwrseq *pwrseq);
+void pwrseq_unregister(struct pwrseq *pwrseq);
+struct pwrseq *of_pwrseq_on(struct device_node *np);
+void of_pwrseq_off(struct pwrseq *pwrseq);
+int of_pwrseq_on_list(struct device_node *np, struct list_head *head);
+void of_pwrseq_off_list(struct list_head *head);
+int pwrseq_suspend(struct pwrseq *p);
+int pwrseq_resume(struct pwrseq *p);
+int pwrseq_suspend_list(struct list_head *head);
+int pwrseq_resume_list(struct list_head *head);
+#else
+static inline void pwrseq_register(struct pwrseq *pwrseq) {}
+static inline void pwrseq_unregister(struct pwrseq *pwrseq) {}
+static inline struct pwrseq *of_pwrseq_on(struct device_node *np)
+{
+	return NULL;
+}
+static void of_pwrseq_off(struct pwrseq *pwrseq) {}
+static int of_pwrseq_on_list(struct device_node *np, struct list_head *head)
+{
+	return 0;
+}
+static void of_pwrseq_off_list(struct list_head *head) {}
+static int pwrseq_suspend(struct pwrseq *p)
+{
+	return 0;
+}
+static int pwrseq_resume(struct pwrseq *p)
+{
+	return 0;
+}
+static int pwrseq_suspend_list(struct list_head *head)
+{
+	return 0;
+}
+static int pwrseq_resume_list(struct list_head *head)
+{
+	return 0;
+}
+#endif /* CONFIG_POWER_SEQUENCE */
+
+#endif  /* __LINUX_PWRSEQ_H */
-- 
2.7.4