1/*
2 * Copyright (C) 2013 - 2014 Texas Instruments Incorporated - http://www.ti.com
3 * Author: Jyri Sarha <jsarha@ti.com>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 *
9 * Gpio gated clock implementation
10 */
11
12#include <linux/clk-provider.h>
13#include <linux/module.h>
14#include <linux/slab.h>
15#include <linux/gpio.h>
16#include <linux/gpio/consumer.h>
17#include <linux/of_gpio.h>
18#include <linux/err.h>
19#include <linux/device.h>
20
21/**
22 * DOC: basic gpio gated clock which can be enabled and disabled
23 *      with gpio output
24 * Traits of this clock:
25 * prepare - clk_(un)prepare only ensures parent is (un)prepared
26 * enable - clk_enable and clk_disable are functional & control gpio
27 * rate - inherits rate from parent.  No clk_set_rate support
28 * parent - fixed parent.  No clk_set_parent support
29 */
30
31#define to_clk_gpio(_hw) container_of(_hw, struct clk_gpio, hw)
32
33static int clk_gpio_gate_enable(struct clk_hw *hw)
34{
35	struct clk_gpio *clk = to_clk_gpio(hw);
36
37	gpiod_set_value(clk->gpiod, 1);
38
39	return 0;
40}
41
42static void clk_gpio_gate_disable(struct clk_hw *hw)
43{
44	struct clk_gpio *clk = to_clk_gpio(hw);
45
46	gpiod_set_value(clk->gpiod, 0);
47}
48
49static int clk_gpio_gate_is_enabled(struct clk_hw *hw)
50{
51	struct clk_gpio *clk = to_clk_gpio(hw);
52
53	return gpiod_get_value(clk->gpiod);
54}
55
56const struct clk_ops clk_gpio_gate_ops = {
57	.enable = clk_gpio_gate_enable,
58	.disable = clk_gpio_gate_disable,
59	.is_enabled = clk_gpio_gate_is_enabled,
60};
61EXPORT_SYMBOL_GPL(clk_gpio_gate_ops);
62
63/**
64 * clk_register_gpio - register a gpip clock with the clock framework
65 * @dev: device that is registering this clock
66 * @name: name of this clock
67 * @parent_name: name of this clock's parent
68 * @gpio: gpio number to gate this clock
69 * @active_low: true if gpio should be set to 0 to enable clock
70 * @flags: clock flags
71 */
72struct clk *clk_register_gpio_gate(struct device *dev, const char *name,
73		const char *parent_name, unsigned gpio, bool active_low,
74		unsigned long flags)
75{
76	struct clk_gpio *clk_gpio = NULL;
77	struct clk *clk = ERR_PTR(-EINVAL);
78	struct clk_init_data init = { NULL };
79	unsigned long gpio_flags;
80	int err;
81
82	if (active_low)
83		gpio_flags = GPIOF_ACTIVE_LOW | GPIOF_OUT_INIT_HIGH;
84	else
85		gpio_flags = GPIOF_OUT_INIT_LOW;
86
87	if (dev)
88		err = devm_gpio_request_one(dev, gpio, gpio_flags, name);
89	else
90		err = gpio_request_one(gpio, gpio_flags, name);
91
92	if (err) {
93		pr_err("%s: %s: Error requesting clock control gpio %u\n",
94		       __func__, name, gpio);
95		return ERR_PTR(err);
96	}
97
98	if (dev)
99		clk_gpio = devm_kzalloc(dev, sizeof(struct clk_gpio),
100					GFP_KERNEL);
101	else
102		clk_gpio = kzalloc(sizeof(struct clk_gpio), GFP_KERNEL);
103
104	if (!clk_gpio) {
105		clk = ERR_PTR(-ENOMEM);
106		goto clk_register_gpio_gate_err;
107	}
108
109	init.name = name;
110	init.ops = &clk_gpio_gate_ops;
111	init.flags = flags | CLK_IS_BASIC;
112	init.parent_names = (parent_name ? &parent_name : NULL);
113	init.num_parents = (parent_name ? 1 : 0);
114
115	clk_gpio->gpiod = gpio_to_desc(gpio);
116	clk_gpio->hw.init = &init;
117
118	clk = clk_register(dev, &clk_gpio->hw);
119
120	if (!IS_ERR(clk))
121		return clk;
122
123	if (!dev)
124		kfree(clk_gpio);
125
126clk_register_gpio_gate_err:
127	if (!dev)
128		gpio_free(gpio);
129
130	return clk;
131}
132EXPORT_SYMBOL_GPL(clk_register_gpio_gate);
133
134#ifdef CONFIG_OF
135/**
136 * The clk_register_gpio_gate has to be delayed, because the EPROBE_DEFER
137 * can not be handled properly at of_clk_init() call time.
138 */
139
140struct clk_gpio_gate_delayed_register_data {
141	struct device_node *node;
142	struct mutex lock;
143	struct clk *clk;
144};
145
146static struct clk *of_clk_gpio_gate_delayed_register_get(
147		struct of_phandle_args *clkspec,
148		void *_data)
149{
150	struct clk_gpio_gate_delayed_register_data *data = _data;
151	struct clk *clk;
152	const char *clk_name = data->node->name;
153	const char *parent_name;
154	int gpio;
155	enum of_gpio_flags of_flags;
156
157	mutex_lock(&data->lock);
158
159	if (data->clk) {
160		mutex_unlock(&data->lock);
161		return data->clk;
162	}
163
164	gpio = of_get_named_gpio_flags(data->node, "enable-gpios", 0,
165						&of_flags);
166	if (gpio < 0) {
167		mutex_unlock(&data->lock);
168		if (gpio != -EPROBE_DEFER)
169			pr_err("%s: %s: Can't get 'enable-gpios' DT property\n",
170			       __func__, clk_name);
171		return ERR_PTR(gpio);
172	}
173
174	parent_name = of_clk_get_parent_name(data->node, 0);
175
176	clk = clk_register_gpio_gate(NULL, clk_name, parent_name, gpio,
177					of_flags & OF_GPIO_ACTIVE_LOW, 0);
178	if (IS_ERR(clk)) {
179		mutex_unlock(&data->lock);
180		return clk;
181	}
182
183	data->clk = clk;
184	mutex_unlock(&data->lock);
185
186	return clk;
187}
188
189/**
190 * of_gpio_gate_clk_setup() - Setup function for gpio controlled clock
191 */
192void __init of_gpio_gate_clk_setup(struct device_node *node)
193{
194	struct clk_gpio_gate_delayed_register_data *data;
195
196	data = kzalloc(sizeof(struct clk_gpio_gate_delayed_register_data),
197		       GFP_KERNEL);
198	if (!data)
199		return;
200
201	data->node = node;
202	mutex_init(&data->lock);
203
204	of_clk_add_provider(node, of_clk_gpio_gate_delayed_register_get, data);
205}
206EXPORT_SYMBOL_GPL(of_gpio_gate_clk_setup);
207CLK_OF_DECLARE(gpio_gate_clk, "gpio-gate-clock", of_gpio_gate_clk_setup);
208#endif
209