1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Power Management and GPIO expander driver for MPC8349E-mITX-compatible MCU
4  *
5  * Copyright (c) 2008  MontaVista Software, Inc.
6  *
7  * Author: Anton Vorontsov <avorontsov@ru.mvista.com>
8  */
9 
10 #include <linux/kernel.h>
11 #include <linux/mod_devicetable.h>
12 #include <linux/module.h>
13 #include <linux/device.h>
14 #include <linux/mutex.h>
15 #include <linux/i2c.h>
16 #include <linux/gpio/driver.h>
17 #include <linux/slab.h>
18 #include <linux/kthread.h>
19 #include <linux/property.h>
20 #include <linux/reboot.h>
21 #include <asm/machdep.h>
22 
23 /*
24  * I don't have specifications for the MCU firmware, I found this register
25  * and bits positions by the trial&error method.
26  */
27 #define MCU_REG_CTRL	0x20
28 #define MCU_CTRL_POFF	0x40
29 #define MCU_CTRL_BTN	0x80
30 
31 #define MCU_NUM_GPIO	2
32 
33 struct mcu {
34 	struct mutex lock;
35 	struct i2c_client *client;
36 	struct gpio_chip gc;
37 	u8 reg_ctrl;
38 };
39 
40 static struct mcu *glob_mcu;
41 
42 struct task_struct *shutdown_thread;
43 static int shutdown_thread_fn(void *data)
44 {
45 	int ret;
46 	struct mcu *mcu = glob_mcu;
47 
48 	while (!kthread_should_stop()) {
49 		ret = i2c_smbus_read_byte_data(mcu->client, MCU_REG_CTRL);
50 		if (ret < 0)
51 			pr_err("MCU status reg read failed.\n");
52 		mcu->reg_ctrl = ret;
53 
54 
55 		if (mcu->reg_ctrl & MCU_CTRL_BTN) {
56 			i2c_smbus_write_byte_data(mcu->client, MCU_REG_CTRL,
57 						  mcu->reg_ctrl & ~MCU_CTRL_BTN);
58 
59 			ctrl_alt_del();
60 		}
61 
62 		set_current_state(TASK_INTERRUPTIBLE);
63 		schedule_timeout(HZ);
64 	}
65 
66 	return 0;
67 }
68 
69 static ssize_t show_status(struct device *d,
70 			   struct device_attribute *attr, char *buf)
71 {
72 	int ret;
73 	struct mcu *mcu = glob_mcu;
74 
75 	ret = i2c_smbus_read_byte_data(mcu->client, MCU_REG_CTRL);
76 	if (ret < 0)
77 		return -ENODEV;
78 	mcu->reg_ctrl = ret;
79 
80 	return sprintf(buf, "%02x\n", ret);
81 }
82 static DEVICE_ATTR(status, 0444, show_status, NULL);
83 
84 static void mcu_power_off(void)
85 {
86 	struct mcu *mcu = glob_mcu;
87 
88 	pr_info("Sending power-off request to the MCU...\n");
89 	mutex_lock(&mcu->lock);
90 	i2c_smbus_write_byte_data(mcu->client, MCU_REG_CTRL,
91 				  mcu->reg_ctrl | MCU_CTRL_POFF);
92 	mutex_unlock(&mcu->lock);
93 }
94 
95 static void mcu_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
96 {
97 	struct mcu *mcu = gpiochip_get_data(gc);
98 	u8 bit = 1 << (4 + gpio);
99 
100 	mutex_lock(&mcu->lock);
101 	if (val)
102 		mcu->reg_ctrl &= ~bit;
103 	else
104 		mcu->reg_ctrl |= bit;
105 
106 	i2c_smbus_write_byte_data(mcu->client, MCU_REG_CTRL, mcu->reg_ctrl);
107 	mutex_unlock(&mcu->lock);
108 }
109 
110 static int mcu_gpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
111 {
112 	mcu_gpio_set(gc, gpio, val);
113 	return 0;
114 }
115 
116 static int mcu_gpiochip_add(struct mcu *mcu)
117 {
118 	struct device *dev = &mcu->client->dev;
119 	struct gpio_chip *gc = &mcu->gc;
120 
121 	gc->owner = THIS_MODULE;
122 	gc->label = kasprintf(GFP_KERNEL, "%pfw", dev_fwnode(dev));
123 	gc->can_sleep = 1;
124 	gc->ngpio = MCU_NUM_GPIO;
125 	gc->base = -1;
126 	gc->set = mcu_gpio_set;
127 	gc->direction_output = mcu_gpio_dir_out;
128 	gc->parent = dev;
129 
130 	return gpiochip_add_data(gc, mcu);
131 }
132 
133 static void mcu_gpiochip_remove(struct mcu *mcu)
134 {
135 	kfree(mcu->gc.label);
136 	gpiochip_remove(&mcu->gc);
137 }
138 
139 static int mcu_probe(struct i2c_client *client)
140 {
141 	struct mcu *mcu;
142 	int ret;
143 
144 	mcu = kzalloc(sizeof(*mcu), GFP_KERNEL);
145 	if (!mcu)
146 		return -ENOMEM;
147 
148 	mutex_init(&mcu->lock);
149 	mcu->client = client;
150 	i2c_set_clientdata(client, mcu);
151 
152 	ret = i2c_smbus_read_byte_data(mcu->client, MCU_REG_CTRL);
153 	if (ret < 0)
154 		goto err;
155 	mcu->reg_ctrl = ret;
156 
157 	ret = mcu_gpiochip_add(mcu);
158 	if (ret)
159 		goto err;
160 
161 	/* XXX: this is potentially racy, but there is no lock for pm_power_off */
162 	if (!pm_power_off) {
163 		glob_mcu = mcu;
164 		pm_power_off = mcu_power_off;
165 		dev_info(&client->dev, "will provide power-off service\n");
166 	}
167 
168 	if (device_create_file(&client->dev, &dev_attr_status))
169 		dev_err(&client->dev,
170 			"couldn't create device file for status\n");
171 
172 	shutdown_thread = kthread_run(shutdown_thread_fn, NULL,
173 				      "mcu-i2c-shdn");
174 
175 	return 0;
176 err:
177 	kfree(mcu);
178 	return ret;
179 }
180 
181 static void mcu_remove(struct i2c_client *client)
182 {
183 	struct mcu *mcu = i2c_get_clientdata(client);
184 
185 	kthread_stop(shutdown_thread);
186 
187 	device_remove_file(&client->dev, &dev_attr_status);
188 
189 	if (glob_mcu == mcu) {
190 		pm_power_off = NULL;
191 		glob_mcu = NULL;
192 	}
193 
194 	mcu_gpiochip_remove(mcu);
195 	kfree(mcu);
196 }
197 
198 static const struct i2c_device_id mcu_ids[] = {
199 	{ "mcu-mpc8349emitx", },
200 	{},
201 };
202 MODULE_DEVICE_TABLE(i2c, mcu_ids);
203 
204 static const struct of_device_id mcu_of_match_table[] = {
205 	{ .compatible = "fsl,mcu-mpc8349emitx", },
206 	{ },
207 };
208 
209 static struct i2c_driver mcu_driver = {
210 	.driver = {
211 		.name = "mcu-mpc8349emitx",
212 		.of_match_table = mcu_of_match_table,
213 	},
214 	.probe = mcu_probe,
215 	.remove	= mcu_remove,
216 	.id_table = mcu_ids,
217 };
218 
219 module_i2c_driver(mcu_driver);
220 
221 MODULE_DESCRIPTION("Power Management and GPIO expander driver for "
222 		   "MPC8349E-mITX-compatible MCU");
223 MODULE_AUTHOR("Anton Vorontsov <avorontsov@ru.mvista.com>");
224 MODULE_LICENSE("GPL");
225