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SubjectRe: [PATCH v8 1/3] Runtime Interpreted Power Sequences
Hi Alex,
I am looking forward for this feature to be mainlined, but I have
comment on the way the types are tied up to power seq infrastructure.
I know your use case are limited to using type "delay", "pwm" and "gpio"
and "regulator", However there are instances where the devices can be
powered up or reset by writing to special registers or sysconfs or
something else.
So My suggestion would be to make these type register them selfs
dynamically with the power_seq infrastructure so that in future this can
be extended to other types as-well.
This trivial change can make a lot of difference for the future chips
which do thing bit differently.
ST Microelectronics chips fit it in these category and I guess other
Vendors have this similar chips.

What do you think?


Thanks,
srini

On 16/11/12 06:38, Alexandre Courbot wrote:
> Some device drivers (e.g. panel or backlights) need to follow precise
> sequences for powering on and off, involving GPIOs, regulators, PWMs
> with a precise powering order and delays to respect between steps.
> These sequences are device-specific, and do not belong to a particular
> driver - therefore they have been performed by board-specific hook
> functions to far.
>
> With the advent of the device tree and of ARM kernels that are not
> board-tied, we cannot rely on these board-specific hooks anymore but
> need a way to implement these sequences in a portable manner. This patch
> introduces a simple interpreter that can execute such power sequences
> encoded either as platform data or within the device tree.
>
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
> Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
> Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
> ---
> .../devicetree/bindings/power/power_seq.txt | 121 +++++++
> Documentation/power/power_seq.txt | 253 ++++++++++++++
> drivers/power/Kconfig | 1 +
> drivers/power/Makefile | 1 +
> drivers/power/power_seq/Kconfig | 2 +
> drivers/power/power_seq/Makefile | 1 +
> drivers/power/power_seq/power_seq.c | 376 +++++++++++++++++++++
> drivers/power/power_seq/power_seq_delay.c | 65 ++++
> drivers/power/power_seq/power_seq_gpio.c | 94 ++++++
> drivers/power/power_seq/power_seq_pwm.c | 82 +++++
> drivers/power/power_seq/power_seq_regulator.c | 83 +++++
> include/linux/power_seq.h | 203 +++++++++++
> 12 files changed, 1282 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/power/power_seq.txt
> create mode 100644 Documentation/power/power_seq.txt
> create mode 100644 drivers/power/power_seq/Kconfig
> create mode 100644 drivers/power/power_seq/Makefile
> create mode 100644 drivers/power/power_seq/power_seq.c
> create mode 100644 drivers/power/power_seq/power_seq_delay.c
> create mode 100644 drivers/power/power_seq/power_seq_gpio.c
> create mode 100644 drivers/power/power_seq/power_seq_pwm.c
> create mode 100644 drivers/power/power_seq/power_seq_regulator.c
> create mode 100644 include/linux/power_seq.h
>
> diff --git a/Documentation/devicetree/bindings/power/power_seq.txt b/Documentation/devicetree/bindings/power/power_seq.txt
> new file mode 100644
> index 0000000..7880a6c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/power/power_seq.txt
> @@ -0,0 +1,121 @@
> +Runtime Interpreted Power Sequences
> +===================================
> +
> +Power sequences are sequential descriptions of actions to be performed on
> +power-related resources. Having these descriptions in a well-defined data format
> +allows us to take much of the board- or device- specific power control code out
> +of the kernel and place it into the device tree instead, making kernels less
> +board-dependant.
> +
> +A device typically makes use of multiple power sequences, for different purposes
> +such as powering on and off. All the power sequences of a given device are
> +grouped into a set. In the device tree, this set is a sub-node of the device
> +node named "power-sequences".
> +
> +Power Sequences Structure
> +-------------------------
> +Every device that makes use of power sequences must have a "power-sequences"
> +node into which individual power sequences are declared as sub-nodes. The name
> +of the node becomes the name of the sequence within the power sequences
> +framework.
> +
> +Similarly, each power sequence declares its steps as sub-nodes of itself. Steps
> +must be named sequentially, with the first step named step0, the second step1,
> +etc. Failure to follow this rule will result in a parsing error.
> +
> +Power Sequences Steps
> +---------------------
> +Steps of a sequence describe an action to be performed on a resource. They
> +always include a "type" property which indicates what kind of resource this
> +step works on. Depending on the resource type, additional properties are defined
> +to control the action to be performed.
> +
> +"delay" type required properties:
> + - delay: delay to wait (in microseconds)
> +
> +"regulator" type required properties:
> + - id: name of the regulator to use.
> + - enable / disable: one of these two empty properties must be present to
> + enable or disable the resource
> +
> +"pwm" type required properties:
> + - id: name of the PWM to use.
> + - enable / disable: one of these two empty properties must be present to
> + enable or disable the resource
> +
> +"gpio" type required properties:
> + - gpio: phandle of the GPIO to use.
> + - value: value this GPIO should take. Must be 0 or 1.
> +
> +Example
> +-------
> +Here are example sequences declared within a backlight device that use all the
> +supported resources types:
> +
> + backlight {
> + compatible = "pwm-backlight";
> + ...
> +
> + /* resources used by the power sequences */
> + pwms = <&pwm 2 5000000>;
> + pwm-names = "backlight";
> + power-supply = <&backlight_reg>;
> +
> + power-sequences {
> + power-on {
> + step0 {
> + type = "regulator";
> + id = "power";
> + enable;
> + };
> + step1 {
> + type = "delay";
> + delay = <10000>;
> + };
> + step2 {
> + type = "pwm";
> + id = "backlight";
> + enable;
> + };
> + step3 {
> + type = "gpio";
> + gpio = <&gpio 28 0>;
> + value = <1>;
> + };
> + };
> +
> + power-off {
> + step0 {
> + type = "gpio";
> + gpio = <&gpio 28 0>;
> + value = <0>;
> + };
> + step1 {
> + type = "pwm";
> + id = "backlight";
> + disable;
> + };
> + step2 {
> + type = "delay";
> + delay = <10000>;
> + };
> + step3 {
> + type = "regulator";
> + id = "power";
> + disable;
> + };
> + };
> + };
> + };
> +
> +The first part lists the PWM and regulator resources used by the sequences.
> +These resources will be requested on behalf of the backlight device when the
> +sequences are built and are declared according to their own bindings (for
> +instance, regulators and pwms are resolved by name - note though that name
> +declaration is done differently by the two frameworks).
> +
> +After the resources declaration, two sequences follow for powering the backlight
> +on and off. Their names are specified by the pwm-backlight device bindings. Once
> +the sequences are built by calling devm_of_parse_power_seq_set() on the
> +backlight device, they can be added to a set using
> +power_seq_set_add_sequences().
> diff --git a/Documentation/power/power_seq.txt b/Documentation/power/power_seq.txt
> new file mode 100644
> index 0000000..8be0570
> --- /dev/null
> +++ b/Documentation/power/power_seq.txt
> @@ -0,0 +1,253 @@
> +Runtime Interpreted Power Sequences
> +===================================
> +
> +Problem
> +-------
> +Very commonly, boards need the help of out-of-driver code to turn some of their
> +devices on and off. For instance, SoC boards might use a GPIO (abstracted to a
> +regulator or not) to control the power supply of a backlight. The GPIO that
> +should be used, however, as well as the exact power sequence that may also
> +involve other resources, is board-dependent and thus unknown to the driver.
> +
> +This was previously addressed by having hooks in the device's platform data that
> +are called whenever the state of the device might need a power status change.
> +This approach, however, introduces board-dependant code into the kernel and is
> +not compatible with the device tree.
> +
> +The Runtime Interpreted Power Sequences (or power sequences for short) aim at
> +turning this code into platform data or device tree nodes. Power sequences are
> +described using a simple format and run by a lightweight interpreter whenever
> +needed. This allows device drivers to work without power callbacks and makes the
> +kernel less board-dependant.
> +
> +What are Power Sequences?
> +-------------------------
> +A power sequence is an array of sequential steps describing an action to be
> +performed on a resource. The supported resources and actions operations are:
> +- delay (just wait for a given number of microseconds)
> +- GPIO (set to 0 or 1)
> +- regulator (enable or disable)
> +- PWM (enable or disable)
> +
> +When a power sequence is run, its steps is executed one after the other until
> +one step fails or the end of the sequence is reached.
> +
> +Power sequences are named, and grouped into "sets" which contain all the
> +sequences of a device as well as the resources they use.
> +
> +Power sequences can be declared as platform data or in the device tree.
> +
> +Platform Data Format
> +--------------------
> +All relevant data structures for declaring power sequences are located in
> +include/linux/power_seq.h.
> +
> +The platform data for a device may include an instance of platform_power_seq_set
> +which references all the power sequences used for a device. The power sequences
> +reference resources in their steps, and setup the union member that corresponds
> +to the resource's type. Resources, similarly, have a union which relevant member
> +depends on their type.
> +
> +Note that the only "platform data" per se here is platform_power_seq_set. Other
> +structures (power_seq and power_seq_resource) will be used at runtime and thus
> +*must* survive initialization, so do not declare them with the __initdata
> +attribute.
> +
> +The following example should make it clear how the platform data for power
> +sequences is defined. It declares two power sequences named "power-on" and
> +"power-off" for a backlight device. The "power-on" sequence enables the "power"
> +regulator of the device, waits for 10ms, and then enables PWM "backlight" and
> +set GPIO 28 to 1. "power-off" does the opposite.
> +
> +struct power_seq_resource reg_res = {
> + .type = POWER_SEQ_REGULATOR,
> + .regulator.id = "power",
> +};
> +
> +struct power_seq_resource gpio_res = {
> + .type = POWER_SEQ_GPIO,
> + .gpio.gpio = 28,
> +};
> +
> +struct power_seq_resource pwm_res = {
> + .type = POWER_SEQ_PWM,
> + .pwm.id = "backlight",
> +};
> +
> +struct power_seq_resource delay_res = {
> + .type = POWER_SEQ_DELAY,
> +};
> +
> +struct power_seq power_on_seq = {
> + .id = "power-on",
> + .num_steps = 4,
> + .steps = {
> + {
> + .resource = &reg_res,
> + .regulator.enable = true,
> + }, {
> + .resource = &delay_res,
> + .delay.delay = 10000,
> + }, {
> + .resource = &pwm_res,
> + .pwm.enable = true,
> + }, {
> + .resource = &gpio_res,
> + .gpio.value = 1,
> + },
> + },
> +};
> +
> +struct power_seq power_off_seq = {
> + .id = "power-off",
> + .num_steps = 4,
> + .steps = {
> + {
> + .resource = &gpio_res,
> + .gpio.value = 0,
> + }, {
> + .resource = &pwm_res,
> + .pwm.enable = false,
> + }, {
> + .resource = &delay_res,
> + .delay.delay = 10000,
> + }, {
> + .resource = &reg_res,
> + .regulator.enable = false,
> + },
> + },
> +};
> +
> +struct platform_power_seq_set backlight_power_seqs __initdata = {
> + .num_seqs = 2,
> + .seqs = {
> + &power_on_seq,
> + &power_off_seq,
> + },
> +};
> +
> +"backlight_power_seqs" can then be passed to power_seq_set_add_sequences() in
> +order to add the sequences to a set and allocate all the necessary resources.
> +More on this later in this document.
> +
> +Device Tree
> +-----------
> +Power sequences can also be encoded as device tree nodes. The following
> +properties and nodes are equivalent to the platform data defined previously:
> +
> +pwms = <&pwm 2 5000000>;
> +pwm-names = "backlight";
> +power-supply = <&vdd_bl_reg>;
> +
> +power-sequences {
> + power-on {
> + step0 {
> + type = "regulator";
> + id = "power";
> + enable;
> + };
> + step1 {
> + type = "delay";
> + delay = <10000>;
> + };
> + step2 {
> + type = "pwm";
> + id = "backlight";
> + enable;
> + };
> + step3 {
> + type = "gpio";
> + gpio = <&gpio 28 0>;
> + value = <1>;
> + };
> + };
> +
> + power-off {
> + step0 {
> + type = "gpio";
> + gpio = <&gpio 28 0>;
> + value = <0>;
> + };
> + step1 {
> + type = "pwm";
> + id = "backlight";
> + disable;
> + };
> + step2 {
> + type = "delay";
> + delay = <10000>;
> + };
> + step3 {
> + type = "regulator";
> + id = "power";
> + disable;
> + };
> + };
> +};
> +
> +See Documentation/devicetree/bindings/power/power_seq.txt for the complete
> +syntax of the DT bindings.
> +
> +Use by Drivers and Resources Management
> +---------------------------------------
> +Power sequences make use of resources that must be properly allocated and
> +managed. The power_seq_set structure manages the sequences and resources for a
> +particular device. A driver willing to use power sequences will thus declare one
> +instance of power_seq_set per device and initialize it at probe time:
> +
> +struct my_device_data {
> + struct device *dev;
> + ...
> + struct power_set_set power_seqs;
> + ...
> +};
> +
> +power_seq_set_init(&my_device->power_seqs, my_device->dev);
> +
> +The power_seq_set_add_sequence() and power_seq_set_add_sequences() functions are
> +then used to add one or several sequences to a set. These functions will also
> +allocate all the resources used by the sequence(s) and make sure they are ready
> +to be run. All resources are allocated through devm and will thus be freed when
> +the set's device is removed.
> +
> + int power_seq_set_add_sequence(struct power_seq_set *set,
> + struct power_seq *seq);
> + int power_seq_set_add_sequences(struct power_seq_set *set,
> + struct platform_power_seq_set *seqs);
> +
> +Power sequences added to a set can then be resolved by their name using
> +power_seq_lookup():
> +
> + struct power_seq *power_seq_lookup(struct power_seq_set *seqs,
> + const char *id);
> +
> +power_seq_lookup() returns a ready-to-run pointer to the power sequence which
> +name matches the id parameter.
> +
> +A retrieved power sequence can then be executed by power_seq_run:
> +
> + int power_seq_run(struct power_seq *seq);
> +
> +It returns 0 if the sequence has successfully been run, or an error code if a
> +problem occurred.
> +
> +Sometimes, you may want to browse the list of resources allocated for the
> +sequences of a device, for instance to ensure that a resource of a given type is
> +present. The power_seq_for_each_resource() macro does this:
> +
> + power_seq_for_each_resource(pos, seqs)
> +
> +Here "pos" will be a pointer to a struct power_seq_resource. This structure
> +contains the type of the resource, the information used for identifying it, and
> +the resolved resource itself.
> +
> +Finally, users of the device tree can obtain a platform_power_seq_set structure
> +built from the device's node using devm_of_parse_power_seq_set:
> +
> + struct platform_power_seq_set *devm_of_parse_power_seq_set(struct device *dev);
> +
> +The power sequences must be declared under a "power-sequences" node directly
> +declared under the device's node. Detailed syntax contained in Documentation/devicetree/bindings/power/power_seq.txt. As the function name
> +states, all memory is allocated through devm. The returned
> +platform_power_seq_set can be freed after being added to a set, but the
> +sequences themselves must be preserved until they are freed by devm.
> \ No newline at end of file
> diff --git a/drivers/power/Kconfig b/drivers/power/Kconfig
> index 49a8939..f20d449 100644
> --- a/drivers/power/Kconfig
> +++ b/drivers/power/Kconfig
> @@ -338,3 +338,4 @@ config AB8500_BATTERY_THERM_ON_BATCTRL
> endif # POWER_SUPPLY
>
> source "drivers/power/avs/Kconfig"
> +source "drivers/power/power_seq/Kconfig"
> diff --git a/drivers/power/Makefile b/drivers/power/Makefile
> index b949cf8..883ad4d 100644
> --- a/drivers/power/Makefile
> +++ b/drivers/power/Makefile
> @@ -49,3 +49,4 @@ obj-$(CONFIG_CHARGER_MAX8997) += max8997_charger.o
> obj-$(CONFIG_CHARGER_MAX8998) += max8998_charger.o
> obj-$(CONFIG_POWER_AVS) += avs/
> obj-$(CONFIG_CHARGER_SMB347) += smb347-charger.o
> +obj-$(CONFIG_POWER_SEQ) += power_seq/
> diff --git a/drivers/power/power_seq/Kconfig b/drivers/power/power_seq/Kconfig
> new file mode 100644
> index 0000000..3bff26e
> --- /dev/null
> +++ b/drivers/power/power_seq/Kconfig
> @@ -0,0 +1,2 @@
> +config POWER_SEQ
> + bool
> diff --git a/drivers/power/power_seq/Makefile b/drivers/power/power_seq/Makefile
> new file mode 100644
> index 0000000..f77a359
> --- /dev/null
> +++ b/drivers/power/power_seq/Makefile
> @@ -0,0 +1 @@
> +obj-$(CONFIG_POWER_SEQ) += power_seq.o
> diff --git a/drivers/power/power_seq/power_seq.c b/drivers/power/power_seq/power_seq.c
> new file mode 100644
> index 0000000..255b1a0
> --- /dev/null
> +++ b/drivers/power/power_seq/power_seq.c
> @@ -0,0 +1,376 @@
> +/*
> + * power_seq.c - power sequence interpreter for platform devices and device tree
> + *
> + * Author: Alexandre Courbot <acourbot@nvidia.com>
> + *
> + * Copyright (c) 2012 NVIDIA Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; version 2 of the License.
> + *
> + * 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.
> + *
> + */
> +
> +#include <linux/power_seq.h>
> +#include <linux/module.h>
> +#include <linux/err.h>
> +#include <linux/device.h>
> +
> +#include <linux/of.h>
> +
> +#define power_seq_err(seq, step_nbr, format, ...) \
> + dev_err(seq->set->dev, "%s[%d]: " format, seq->id, step_nbr, \
> + ##__VA_ARGS__);
> +
> +/**
> + * struct power_seq_res_ops - operators for power sequences resources
> + * @name: Name of the resource type. Set to null when a resource
> + * type support is not compiled in
> + * @of_parse: Parse a step for this kind of resource from a device
> + * tree node. The result of parsing must be written into
> + * step step_nbr of seq
> + * @step_run: Run a step for this kind of resource
> + * @res_compare: Return true if the resource used by the resource is the
> + * same as the one referenced by the step, false otherwise.
> + * @res_alloc: Resolve and allocate a resource. Return error code if
> + * the resource cannot be allocated, 0 otherwise
> + */
> +struct power_seq_res_ops {
> + const char *name;
> + int (*of_parse)(struct device_node *node, struct power_seq *seq,
> + unsigned int step_nbr, struct power_seq_resource *res);
> + int (*step_run)(struct power_seq_step *step);
> + bool (*res_compare)(struct power_seq_resource *res,
> + struct power_seq_resource *res2);
> + int (*res_alloc)(struct device *dev,
> + struct power_seq_resource *res);
> +};
> +
> +static const struct power_seq_res_ops power_seq_ops[POWER_SEQ_NUM_TYPES];
> +
> +#ifdef CONFIG_OF
> +static int of_power_seq_parse_enable_properties(struct device_node *node,
> + struct power_seq *seq,
> + unsigned int step_nbr,
> + bool *enable)
> +{
> + if (of_find_property(node, "enable", NULL)) {
> + *enable = true;
> + } else if (of_find_property(node, "disable", NULL)) {
> + *enable = false;
> + } else {
> + power_seq_err(seq, step_nbr,
> + "missing enable or disable property\n");
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +static int of_power_seq_parse_step(struct device *dev,
> + struct device_node *node,
> + struct power_seq *seq,
> + unsigned int step_nbr,
> + struct list_head *resources)
> +{
> + struct power_seq_step *step = &seq->steps[step_nbr];
> + struct power_seq_resource res, *res2;
> + const char *type;
> + int i, err;
> +
> + err = of_property_read_string(node, "type", &type);
> + if (err < 0) {
> + power_seq_err(seq, step_nbr, "cannot read type property\n");
> + return err;
> + }
> + for (i = 0; i < POWER_SEQ_NUM_TYPES; i++) {
> + if (power_seq_ops[i].name == NULL)
> + continue;
> + if (!strcmp(type, power_seq_ops[i].name))
> + break;
> + }
> + if (i >= POWER_SEQ_NUM_TYPES) {
> + power_seq_err(seq, step_nbr, "unknown type %s\n", type);
> + return -EINVAL;
> + }
> + memset(&res, 0, sizeof(res));
> + res.type = i;
> + err = power_seq_ops[res.type].of_parse(node, seq, step_nbr, &res);
> + if (err < 0)
> + return err;
> +
> + /* Use the same instance of the resource if met before */
> + list_for_each_entry(res2, resources, list) {
> + if (res.type == res2->type &&
> + power_seq_ops[res.type].res_compare(&res, res2))
> + break;
> + }
> + /* Resource never met before, create it */
> + if (&res2->list == resources) {
> + res2 = devm_kzalloc(dev, sizeof(*res2), GFP_KERNEL);
> + if (!res2)
> + return -ENOMEM;
> + memcpy(res2, &res, sizeof(res));
> + list_add_tail(&res2->list, resources);
> + }
> + step->resource = res2;
> +
> + return 0;
> +}
> +
> +static struct power_seq *of_parse_power_seq(struct device *dev,
> + struct device_node *node,
> + struct list_head *resources)
> +{
> + struct device_node *child = NULL;
> + struct power_seq *pseq;
> + int num_steps, sz;
> + int err;
> +
> + if (!node)
> + return ERR_PTR(-EINVAL);
> +
> + num_steps = of_get_child_count(node);
> + sz = sizeof(*pseq) + sizeof(pseq->steps[0]) * num_steps;
> + pseq = devm_kzalloc(dev, sz, GFP_KERNEL);
> + if (!pseq)
> + return ERR_PTR(-ENOMEM);
> + pseq->id = node->name;
> + pseq->num_steps = num_steps;
> +
> + for_each_child_of_node(node, child) {
> + unsigned int pos;
> +
> + /* Check that the name's format is correct and within bounds */
> + if (strncmp("step", child->name, 4)) {
> + err = -EINVAL;
> + goto parse_error;
> + }
> +
> + err = kstrtouint(child->name + 4, 10, &pos);
> + if (err < 0)
> + goto parse_error;
> +
> + /* Invalid step index or step already parsed? */
> + if (pos >= num_steps || pseq->steps[pos].resource != NULL) {
> + err = -EINVAL;
> + goto parse_error;
> + }
> +
> + err = of_power_seq_parse_step(dev, child, pseq, pos, resources);
> + if (err)
> + return ERR_PTR(err);
> + }
> +
> + return pseq;
> +
> +parse_error:
> + dev_err(dev, "%s: invalid power step name %s!\n", pseq->id,
> + child->name);
> + return ERR_PTR(err);
> +}
> +
> +/**
> + * devm_of_parse_power_seq_set - build a power_seq_set from the device tree
> + * @dev: Device to parse the power sequences of
> + *
> + * Sequences must be contained into a subnode named "power-sequences" of the
> + * device root node.
> + *
> + * Memory for the sequence is allocated using devm_kzalloc on dev. The returned
> + * platform_power_seq_set can be freed by devm_kfree after the sequences have
> + * been added, but the sequences themselves must be preserved.
> + *
> + * Returns the built set on success, or an error code in case of failure.
> + */
> +struct platform_power_seq_set *devm_of_parse_power_seq_set(struct device *dev)
> +{
> + struct platform_power_seq_set *set;
> + struct device_node *root = dev->of_node;
> + struct device_node *seq;
> + struct list_head resources;
> + int n, sz;
> +
> + if (!root)
> + return NULL;
> +
> + root = of_find_node_by_name(root, "power-sequences");
> + if (!root)
> + return NULL;
> +
> + n = of_get_child_count(root);
> + sz = sizeof(*set) + sizeof(struct power_seq *) * n;
> + set = devm_kzalloc(dev, sz, GFP_KERNEL);
> + if (!set)
> + return ERR_PTR(-ENOMEM);
> + set->num_seqs = n;
> +
> + n = 0;
> + INIT_LIST_HEAD(&resources);
> + for_each_child_of_node(root, seq) {
> + struct power_seq *pseq;
> +
> + pseq = of_parse_power_seq(dev, seq, &resources);
> + if (IS_ERR(pseq))
> + return (void *)pseq;
> +
> + set->seqs[n++] = pseq;
> + }
> +
> + return set;
> +}
> +EXPORT_SYMBOL_GPL(devm_of_parse_power_seq_set);
> +#endif /* CONFIG_OF */
> +
> +/**
> + * power_seq_set_init - initialize a power_seq_set
> + * @set: Set to initialize
> + * @dev: Device this set is going to belong to
> + */
> +void power_seq_set_init(struct power_seq_set *set, struct device *dev)
> +{
> + set->dev = dev;
> + INIT_LIST_HEAD(&set->resources);
> + INIT_LIST_HEAD(&set->seqs);
> +}
> +EXPORT_SYMBOL_GPL(power_seq_set_init);
> +
> +/**
> + * power_seq_add_sequence - add a power sequence to a set
> + * @set: Set to add the sequence to
> + * @seq: Sequence to add
> + *
> + * This step will check that all the resources used by the sequence are
> + * allocated. If they are not, an attempt to allocate them is made. This
> + * operation can fail and and return an error code.
> + *
> + * Returns 0 on success, error code if a resource initialization failed.
> + */
> +int power_seq_add_sequence(struct power_seq_set *set, struct power_seq *seq)
> +{
> + struct power_seq_resource *res;
> + int i, err;
> +
> + for (i = 0; i < seq->num_steps; i++) {
> + struct power_seq_step *step = &seq->steps[i];
> + struct power_seq_resource *step_res = step->resource;
> + list_for_each_entry(res, &set->resources, list) {
> + if (res == step_res)
> + break;
> + }
> + /* resource not allocated yet, allocate and add it */
> + if (&res->list == &set->resources) {
> + err = power_seq_ops[step_res->type].res_alloc(set->dev,
> + step_res);
> + if (err)
> + return err;
> + list_add_tail(&step->resource->list, &set->resources);
> + }
> + }
> +
> + list_add_tail(&seq->list, &set->seqs);
> + seq->set = set;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(power_seq_add_sequence);
> +
> +/**
> + * power_seq_add_sequences - add power sequences defined as platform data
> + * @set: Set to add the sequences to
> + * @seqs: Sequences to add
> + *
> + * See power_seq_add_sequence for more details.
> + *
> + * Returns 0 on success, error code if a resource initialization failed.
> + */
> +int power_seq_set_add_sequences(struct power_seq_set *set,
> + struct platform_power_seq_set *seqs)
> +{
> + int i, ret;
> +
> + for (i = 0; i < seqs->num_seqs; i++) {
> + ret = power_seq_add_sequence(set, seqs->seqs[i]);
> + if (ret < 0)
> + return ret;
> + }
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(power_seq_set_add_sequences);
> +
> +/**
> + * power_seq_lookup - Lookup a power sequence by name from a set
> + * @seqs: The set to look in
> + * @id: Name to look after
> + *
> + * Returns a matching power sequence if it exists, NULL if it does not.
> + */
> +struct power_seq *power_seq_lookup(struct power_seq_set *set, const char *id)
> +{
> + struct power_seq *seq;
> +
> + list_for_each_entry(seq, &set->seqs, list) {
> + if (!strcmp(seq->id, id))
> + return seq;
> + }
> +
> + return NULL;
> +}
> +EXPORT_SYMBOL_GPL(power_seq_lookup);
> +
> +/**
> + * power_seq_run() - run a power sequence
> + * @seq: The power sequence to run
> + *
> + * Returns 0 on success, error code in case of failure.
> + */
> +int power_seq_run(struct power_seq *seq)
> +{
> + unsigned int i;
> + int err;
> +
> + if (!seq)
> + return 0;
> +
> + if (!seq->set) {
> + pr_err("cannot run a sequence not added to a set");
> + return -EINVAL;
> + }
> +
> + for (i = 0; i < seq->num_steps; i++) {
> + unsigned int type = seq->steps[i].resource->type;
> +
> + err = power_seq_ops[type].step_run(&seq->steps[i]);
> + if (err) {
> + power_seq_err(seq, i,
> + "error %d while running power sequence step\n",
> + err);
> + return err;
> + }
> + }
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(power_seq_run);
> +
> +#include "power_seq_delay.c"
> +#include "power_seq_regulator.c"
> +#include "power_seq_pwm.c"
> +#include "power_seq_gpio.c"
> +
> +static const struct power_seq_res_ops power_seq_ops[POWER_SEQ_NUM_TYPES] = {
> + [POWER_SEQ_DELAY] = POWER_SEQ_DELAY_TYPE,
> + [POWER_SEQ_REGULATOR] = POWER_SEQ_REGULATOR_TYPE,
> + [POWER_SEQ_PWM] = POWER_SEQ_PWM_TYPE,
> + [POWER_SEQ_GPIO] = POWER_SEQ_GPIO_TYPE,
> +};
> +
> +MODULE_AUTHOR("Alexandre Courbot <acourbot@nvidia.com>");
> +MODULE_DESCRIPTION("Runtime Interpreted Power Sequences");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/power/power_seq/power_seq_delay.c b/drivers/power/power_seq/power_seq_delay.c
> new file mode 100644
> index 0000000..5bb0a46
> --- /dev/null
> +++ b/drivers/power/power_seq/power_seq_delay.c
> @@ -0,0 +1,65 @@
> +/*
> + * Copyright (c) 2012 NVIDIA Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; version 2 of the License.
> + *
> + * 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.
> + *
> + */
> +
> +#include <linux/delay.h>
> +
> +#ifdef CONFIG_OF
> +static int of_power_seq_parse_delay(struct device_node *node,
> + struct power_seq *seq,
> + unsigned int step_nbr,
> + struct power_seq_resource *res)
> +{
> + struct power_seq_step *step = &seq->steps[step_nbr];
> + int err;
> +
> + err = of_property_read_u32(node, "delay",
> + &step->delay.delay);
> + if (err < 0)
> + power_seq_err(seq, step_nbr, "error reading delay property\n");
> +
> + return err;
> +}
> +#else
> +#define of_power_seq_parse_delay NULL
> +#endif
> +
> +static bool power_seq_res_compare_delay(struct power_seq_resource *res,
> + struct power_seq_resource *res2)
> +{
> + /* Delay resources are just here to hold the type of steps, so they are
> + * all equivalent. */
> + return true;
> +}
> +
> +static int power_seq_res_alloc_delay(struct device *dev,
> + struct power_seq_resource *res)
> +{
> + return 0;
> +}
> +
> +static int power_seq_step_run_delay(struct power_seq_step *step)
> +{
> + usleep_range(step->delay.delay,
> + step->delay.delay + 1000);
> +
> + return 0;
> +}
> +
> +#define POWER_SEQ_DELAY_TYPE { \
> + .name = "delay", \
> + .of_parse = of_power_seq_parse_delay, \
> + .step_run = power_seq_step_run_delay, \
> + .res_compare = power_seq_res_compare_delay, \
> + .res_alloc = power_seq_res_alloc_delay, \
> +}
> diff --git a/drivers/power/power_seq/power_seq_gpio.c b/drivers/power/power_seq/power_seq_gpio.c
> new file mode 100644
> index 0000000..028a4cc
> --- /dev/null
> +++ b/drivers/power/power_seq/power_seq_gpio.c
> @@ -0,0 +1,94 @@
> +/*
> + * Copyright (c) 2012 NVIDIA Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; version 2 of the License.
> + *
> + * 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.
> + *
> + */
> +
> +#include <linux/gpio.h>
> +#include <linux/of_gpio.h>
> +
> +#ifdef CONFIG_OF
> +static int of_power_seq_parse_gpio(struct device_node *node,
> + struct power_seq *seq,
> + unsigned int step_nbr,
> + struct power_seq_resource *res)
> +{
> + struct power_seq_step *step = &seq->steps[step_nbr];
> + int gpio;
> + int err;
> +
> + gpio = of_get_named_gpio(node, "gpio", 0);
> + if (gpio < 0) {
> + power_seq_err(seq, step_nbr, "error reading gpio property\n");
> + return gpio;
> + }
> + res->gpio.gpio = gpio;
> +
> + err = of_property_read_u32(node, "value", &step->gpio.value);
> + if (err < 0) {
> + power_seq_err(seq, step_nbr, "error reading value property\n");
> + } else if (step->gpio.value < 0 || step->gpio.value > 1) {
> + power_seq_err(seq, step_nbr,
> + "value out of range (must be 0 or 1)\n");
> + err = -EINVAL;
> + }
> +
> + return err;
> +}
> +#else
> +#define of_power_seq_parse_gpio NULL
> +#endif
> +
> +static bool power_seq_res_compare_gpio(struct power_seq_resource *res,
> + struct power_seq_resource *res2)
> +{
> + return res->gpio.gpio == res2->gpio.gpio;
> +}
> +
> +static int power_seq_res_alloc_gpio(struct device *dev,
> + struct power_seq_resource *res)
> +{
> + int err;
> +
> + err = devm_gpio_request(dev, res->gpio.gpio, dev_name(dev));
> + if (err) {
> + dev_err(dev, "cannot get gpio %d\n", res->gpio.gpio);
> + return err;
> + }
> +
> + return 0;
> +}
> +
> +static int power_seq_step_run_gpio(struct power_seq_step *step)
> +{
> + struct power_seq_resource *res = step->resource;
> +
> + /* set the GPIO direction at first use */
> + if (!res->gpio.is_set) {
> + int err = gpio_direction_output(res->gpio.gpio,
> + step->gpio.value);
> + if (err)
> + return err;
> + res->gpio.is_set = true;
> + } else {
> + gpio_set_value_cansleep(res->gpio.gpio, step->gpio.value);
> + }
> +
> + return 0;
> +}
> +
> +#define POWER_SEQ_GPIO_TYPE { \
> + .name = "gpio", \
> + .of_parse = of_power_seq_parse_gpio, \
> + .step_run = power_seq_step_run_gpio, \
> + .res_compare = power_seq_res_compare_gpio, \
> + .res_alloc = power_seq_res_alloc_gpio, \
> +}
> diff --git a/drivers/power/power_seq/power_seq_pwm.c b/drivers/power/power_seq/power_seq_pwm.c
> new file mode 100644
> index 0000000..e61acdd
> --- /dev/null
> +++ b/drivers/power/power_seq/power_seq_pwm.c
> @@ -0,0 +1,82 @@
> +/*
> + * Copyright (c) 2012 NVIDIA Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; version 2 of the License.
> + *
> + * 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.
> + *
> + */
> +
> +#ifdef CONFIG_PWM
> +
> +#include <linux/pwm.h>
> +
> +#ifdef CONFIG_OF
> +static int of_power_seq_parse_pwm(struct device_node *node,
> + struct power_seq *seq,
> + unsigned int step_nbr,
> + struct power_seq_resource *res)
> +{
> + struct power_seq_step *step = &seq->steps[step_nbr];
> + int err;
> +
> + err = of_property_read_string(node, "id", &res->pwm.id);
> + if (err) {
> + power_seq_err(seq, step_nbr, "error reading id property\n");
> + return err;
> + }
> +
> + err = of_power_seq_parse_enable_properties(node, seq, step_nbr,
> + &step->pwm.enable);
> + return err;
> +}
> +#else
> +#define of_power_seq_parse_pwm NULL
> +#endif
> +
> +static bool power_seq_res_compare_pwm(struct power_seq_resource *res,
> + struct power_seq_resource *res2)
> +{
> + return !strcmp(res->pwm.id, res2->pwm.id);
> +}
> +
> +static int power_seq_res_alloc_pwm(struct device *dev,
> + struct power_seq_resource *res)
> +{
> + res->pwm.pwm = devm_pwm_get(dev, res->pwm.id);
> + if (IS_ERR(res->pwm.pwm)) {
> + dev_err(dev, "cannot get pwm \"%s\"\n", res->pwm.id);
> + return PTR_ERR(res->pwm.pwm);
> + }
> +
> + return 0;
> +}
> +
> +static int power_seq_step_run_pwm(struct power_seq_step *step)
> +{
> + if (step->pwm.enable) {
> + return pwm_enable(step->resource->pwm.pwm);
> + } else {
> + pwm_disable(step->resource->pwm.pwm);
> + return 0;
> + }
> +}
> +
> +#define POWER_SEQ_PWM_TYPE { \
> + .name = "pwm", \
> + .of_parse = of_power_seq_parse_pwm, \
> + .step_run = power_seq_step_run_pwm, \
> + .res_compare = power_seq_res_compare_pwm, \
> + .res_alloc = power_seq_res_alloc_pwm, \
> +}
> +
> +#else
> +
> +#define POWER_SEQ_PWM_TYPE {}
> +
> +#endif
> diff --git a/drivers/power/power_seq/power_seq_regulator.c b/drivers/power/power_seq/power_seq_regulator.c
> new file mode 100644
> index 0000000..2025155
> --- /dev/null
> +++ b/drivers/power/power_seq/power_seq_regulator.c
> @@ -0,0 +1,83 @@
> +/*
> + * Copyright (c) 2012 NVIDIA Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; version 2 of the License.
> + *
> + * 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.
> + *
> + */
> +
> +#ifdef CONFIG_REGULATOR
> +
> +#include <linux/regulator/consumer.h>
> +
> +#ifdef CONFIG_OF
> +static int of_power_seq_parse_regulator(struct device_node *node,
> + struct power_seq *seq,
> + unsigned int step_nbr,
> + struct power_seq_resource *res)
> +{
> + struct power_seq_step *step = &seq->steps[step_nbr];
> + int err;
> +
> + err = of_property_read_string(node, "id",
> + &res->regulator.id);
> + if (err) {
> + power_seq_err(seq, step_nbr, "error reading id property\n");
> + return err;
> + }
> +
> + err = of_power_seq_parse_enable_properties(node, seq, step_nbr,
> + &step->regulator.enable);
> + return err;
> +}
> +#else
> +#define of_power_seq_parse_regulator NULL
> +#endif
> +
> +static bool
> +power_seq_res_compare_regulator(struct power_seq_resource *res,
> + struct power_seq_resource *res2)
> +{
> + return !strcmp(res->regulator.id, res2->regulator.id);
> +}
> +
> +static int power_seq_res_alloc_regulator(struct device *dev,
> + struct power_seq_resource *res)
> +{
> + res->regulator.regulator = devm_regulator_get(dev, res->regulator.id);
> + if (IS_ERR(res->regulator.regulator)) {
> + dev_err(dev, "cannot get regulator \"%s\"\n",
> + res->regulator.id);
> + return PTR_ERR(res->regulator.regulator);
> + }
> +
> + return 0;
> +}
> +
> +static int power_seq_step_run_regulator(struct power_seq_step *step)
> +{
> + if (step->regulator.enable)
> + return regulator_enable(step->resource->regulator.regulator);
> + else
> + return regulator_disable(step->resource->regulator.regulator);
> +}
> +
> +#define POWER_SEQ_REGULATOR_TYPE { \
> + .name = "regulator", \
> + .of_parse = of_power_seq_parse_regulator, \
> + .step_run = power_seq_step_run_regulator, \
> + .res_compare = power_seq_res_compare_regulator, \
> + .res_alloc = power_seq_res_alloc_regulator, \
> +}
> +
> +#else
> +
> +#define POWER_SEQ_REGULATOR_TYPE {}
> +
> +#endif
> diff --git a/include/linux/power_seq.h b/include/linux/power_seq.h
> new file mode 100644
> index 0000000..21b95b6
> --- /dev/null
> +++ b/include/linux/power_seq.h
> @@ -0,0 +1,203 @@
> +/*
> + * power_seq.h
> + *
> + * Simple interpreter for power sequences defined as platform data or device
> + * tree properties.
> + *
> + * Power sequences are designed to replace the callbacks typically used in
> + * board-specific files that implement board- or device- specific power
> + * sequences (such as those of backlights). A power sequence is an array of
> + * steps referencing resources (regulators, GPIOs, PWMs, ...) with an action to
> + * perform on them. By having the power sequences interpreted, it becomes
> + * possible to describe them in the device tree and thus to remove
> + * board-specific files from the kernel.
> + *
> + * See Documentation/power/power_seqs.txt for detailed information.
> + *
> + * Author: Alexandre Courbot <acourbot@nvidia.com>
> + *
> + * Copyright (c) 2012 NVIDIA Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; version 2 of the License.
> + *
> + * 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.
> + *
> + */
> +
> +#ifndef __LINUX_POWER_SEQ_H
> +#define __LINUX_POWER_SEQ_H
> +
> +#include <linux/types.h>
> +#include <linux/list.h>
> +
> +struct device;
> +struct regulator;
> +struct pwm_device;
> +
> +/**
> + * The different kinds of resources that can be controlled by the sequences
> + */
> +enum power_seq_res_type {
> + POWER_SEQ_DELAY,
> + POWER_SEQ_REGULATOR,
> + POWER_SEQ_PWM,
> + POWER_SEQ_GPIO,
> + POWER_SEQ_NUM_TYPES,
> +};
> +
> +/**
> + * struct power_seq_regulator_resource
> + * @id: name of the regulator
> + * @regulator: resolved regulator. Written during resource resolution.
> + */
> +struct power_seq_regulator_resource {
> + const char *id;
> + struct regulator *regulator;
> +};
> +
> +/**
> + * struct power_seq_pwm_resource
> + * @id: name of the PWM
> + * @regulator: resolved PWM. Written during resource resolution.
> + */
> +struct power_seq_pwm_resource {
> + const char *id;
> + struct pwm_device *pwm;
> +};
> +
> +/**
> + * struct power_seq_gpio_resource
> + * @gpio: number of the GPIO
> + * @is_set: track GPIO state to set its direction at first use
> + */
> +struct power_seq_gpio_resource {
> + int gpio;
> + bool is_set;
> +};
> +
> +/**
> + * struct power_seq_resource - resource used by power sequences
> + * @type: type of the resource. This decides which member of the union is
> + * used for this resource
> + * @list: link resources together in power_seq_set
> + * @regulator: used if @type == POWER_SEQ_REGULATOR
> + * @pwm: used if @type == POWER_SEQ_PWM
> + * @gpio: used if @type == POWER_SEQ_GPIO
> + */
> +struct power_seq_resource {
> + enum power_seq_res_type type;
> + struct list_head list;
> + union {
> + struct power_seq_regulator_resource regulator;
> + struct power_seq_pwm_resource pwm;
> + struct power_seq_gpio_resource gpio;
> + };
> +};
> +#define power_seq_for_each_resource(pos, set) \
> + list_for_each_entry(pos, &(set)->resources, list)
> +
> +/**
> + * struct power_seq_delay_step - action data for delay steps
> + * @delay: amount of time to wait, in microseconds
> + */
> +struct power_seq_delay_step {
> + unsigned int delay;
> +};
> +
> +/**
> + * struct power_seq_regulator_step - platform data for regulator steps
> + * @enable: whether to enable or disable the regulator during this step
> + */
> +struct power_seq_regulator_step {
> + bool enable;
> +};
> +
> +/**
> + * struct power_seq_pwm_step - action data for PWM steps
> + * @enable: whether to enable or disable the PWM during this step
> + */
> +struct power_seq_pwm_step {
> + bool enable;
> +};
> +
> +/**
> + * struct power_seq_gpio_step - action data for GPIO steps
> + * @enable: whether to enable or disable the GPIO during this step
> + */
> +struct power_seq_gpio_step {
> + int value;
> +};
> +
> +/**
> + * struct power_seq_step - data for power sequences steps
> + * @resource: resource used by this step
> + * @delay: used if resource->type == POWER_SEQ_DELAY
> + * @regulator: used if resource->type == POWER_SEQ_REGULATOR
> + * @pwm: used if resource->type == POWER_SEQ_PWN
> + * @gpio: used if resource->type == POWER_SEQ_GPIO
> + */
> +struct power_seq_step {
> + struct power_seq_resource *resource;
> + union {
> + struct power_seq_delay_step delay;
> + struct power_seq_regulator_step regulator;
> + struct power_seq_pwm_step pwm;
> + struct power_seq_gpio_step gpio;
> + };
> +};
> +
> +struct power_seq_set;
> +
> +/**
> + * struct power_seq - single power sequence
> + * @id: name of this sequence
> + * @list: link sequences together in power_seq_set. Leave as-is
> + * @set: set this sequence belongs to. Written when added to a set
> + * @num_steps: number of steps in the sequence
> + * @steps: array of steps that make the sequence
> + */
> +struct power_seq {
> + const char *id;
> + struct list_head list;
> + struct power_seq_set *set;
> + unsigned int num_steps;
> + struct power_seq_step steps[];
> +};
> +
> +/**
> + * struct power_seq_set - power sequences and resources used by a device
> + * @dev: device this set belongs to
> + * @resources: list of resources used by power sequences
> + * @seqs: list of power sequences
> + */
> +struct power_seq_set {
> + struct device *dev;
> + struct list_head resources;
> + struct list_head seqs;
> +};
> +
> +/**
> + * struct platform_power_seq_set - define power sequences as platform data
> + * @num_seqs: number of sequences defined
> + * @seqs: array of num_seqs power sequences
> + */
> +struct platform_power_seq_set {
> + unsigned int num_seqs;
> + struct power_seq *seqs[];
> +};
> +
> +struct platform_power_seq_set *devm_of_parse_power_seq_set(struct device *dev);
> +void power_seq_set_init(struct power_seq_set *set, struct device *dev);
> +int power_seq_set_add_sequence(struct power_seq_set *set,
> + struct power_seq *seq);
> +int power_seq_set_add_sequences(struct power_seq_set *set,
> + struct platform_power_seq_set *seqs);
> +struct power_seq *power_seq_lookup(struct power_seq_set *seqs, const char *id);
> +int power_seq_run(struct power_seq *seq);
> +
> +#endif



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