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/module.h>
12 #include <linux/device.h>
13 #include <linux/mutex.h>
14 #include <linux/i2c.h>
15 #include <linux/gpio/driver.h>
16 #include <linux/of.h>
17 #include <linux/of_gpio.h>
18 #include <linux/slab.h>
19 #include <linux/kthread.h>
20 #include <linux/reboot.h>
21 #include <asm/prom.h>
22 #include <asm/machdep.h>
23 
24 /*
25  * I don't have specifications for the MCU firmware, I found this register
26  * and bits positions by the trial&error method.
27  */
28 #define MCU_REG_CTRL	0x20
29 #define MCU_CTRL_POFF	0x40
30 #define MCU_CTRL_BTN	0x80
31 
32 #define MCU_NUM_GPIO	2
33 
34 struct mcu {
35 	struct mutex lock;
36 	struct i2c_client *client;
37 	struct gpio_chip gc;
38 	u8 reg_ctrl;
39 };
40 
41 static struct mcu *glob_mcu;
42 
43 struct task_struct *shutdown_thread;
44 static int shutdown_thread_fn(void *data)
45 {
46 	int ret;
47 	struct mcu *mcu = glob_mcu;
48 
49 	while (!kthread_should_stop()) {
50 		ret = i2c_smbus_read_byte_data(mcu->client, MCU_REG_CTRL);
51 		if (ret < 0)
52 			pr_err("MCU status reg read failed.\n");
53 		mcu->reg_ctrl = ret;
54 
55 
56 		if (mcu->reg_ctrl & MCU_CTRL_BTN) {
57 			i2c_smbus_write_byte_data(mcu->client, MCU_REG_CTRL,
58 						  mcu->reg_ctrl & ~MCU_CTRL_BTN);
59 
60 			ctrl_alt_del();
61 		}
62 
63 		set_current_state(TASK_INTERRUPTIBLE);
64 		schedule_timeout(HZ);
65 	}
66 
67 	return 0;
68 }
69 
70 static ssize_t show_status(struct device *d,
71 			   struct device_attribute *attr, char *buf)
72 {
73 	int ret;
74 	struct mcu *mcu = glob_mcu;
75 
76 	ret = i2c_smbus_read_byte_data(mcu->client, MCU_REG_CTRL);
77 	if (ret < 0)
78 		return -ENODEV;
79 	mcu->reg_ctrl = ret;
80 
81 	return sprintf(buf, "%02x\n", ret);
82 }
83 static DEVICE_ATTR(status, 0444, show_status, NULL);
84 
85 static void mcu_power_off(void)
86 {
87 	struct mcu *mcu = glob_mcu;
88 
89 	pr_info("Sending power-off request to the MCU...\n");
90 	mutex_lock(&mcu->lock);
91 	i2c_smbus_write_byte_data(mcu->client, MCU_REG_CTRL,
92 				  mcu->reg_ctrl | MCU_CTRL_POFF);
93 	mutex_unlock(&mcu->lock);
94 }
95 
96 static void mcu_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
97 {
98 	struct mcu *mcu = gpiochip_get_data(gc);
99 	u8 bit = 1 << (4 + gpio);
100 
101 	mutex_lock(&mcu->lock);
102 	if (val)
103 		mcu->reg_ctrl &= ~bit;
104 	else
105 		mcu->reg_ctrl |= bit;
106 
107 	i2c_smbus_write_byte_data(mcu->client, MCU_REG_CTRL, mcu->reg_ctrl);
108 	mutex_unlock(&mcu->lock);
109 }
110 
111 static int mcu_gpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
112 {
113 	mcu_gpio_set(gc, gpio, val);
114 	return 0;
115 }
116 
117 static int mcu_gpiochip_add(struct mcu *mcu)
118 {
119 	struct device_node *np;
120 	struct gpio_chip *gc = &mcu->gc;
121 
122 	np = of_find_compatible_node(NULL, NULL, "fsl,mcu-mpc8349emitx");
123 	if (!np)
124 		return -ENODEV;
125 
126 	gc->owner = THIS_MODULE;
127 	gc->label = kasprintf(GFP_KERNEL, "%pOF", np);
128 	gc->can_sleep = 1;
129 	gc->ngpio = MCU_NUM_GPIO;
130 	gc->base = -1;
131 	gc->set = mcu_gpio_set;
132 	gc->direction_output = mcu_gpio_dir_out;
133 	gc->of_node = np;
134 
135 	return gpiochip_add_data(gc, mcu);
136 }
137 
138 static int mcu_gpiochip_remove(struct mcu *mcu)
139 {
140 	kfree(mcu->gc.label);
141 	gpiochip_remove(&mcu->gc);
142 	return 0;
143 }
144 
145 static int mcu_probe(struct i2c_client *client)
146 {
147 	struct mcu *mcu;
148 	int ret;
149 
150 	mcu = kzalloc(sizeof(*mcu), GFP_KERNEL);
151 	if (!mcu)
152 		return -ENOMEM;
153 
154 	mutex_init(&mcu->lock);
155 	mcu->client = client;
156 	i2c_set_clientdata(client, mcu);
157 
158 	ret = i2c_smbus_read_byte_data(mcu->client, MCU_REG_CTRL);
159 	if (ret < 0)
160 		goto err;
161 	mcu->reg_ctrl = ret;
162 
163 	ret = mcu_gpiochip_add(mcu);
164 	if (ret)
165 		goto err;
166 
167 	/* XXX: this is potentially racy, but there is no lock for pm_power_off */
168 	if (!pm_power_off) {
169 		glob_mcu = mcu;
170 		pm_power_off = mcu_power_off;
171 		dev_info(&client->dev, "will provide power-off service\n");
172 	}
173 
174 	if (device_create_file(&client->dev, &dev_attr_status))
175 		dev_err(&client->dev,
176 			"couldn't create device file for status\n");
177 
178 	shutdown_thread = kthread_run(shutdown_thread_fn, NULL,
179 				      "mcu-i2c-shdn");
180 
181 	return 0;
182 err:
183 	kfree(mcu);
184 	return ret;
185 }
186 
187 static int mcu_remove(struct i2c_client *client)
188 {
189 	struct mcu *mcu = i2c_get_clientdata(client);
190 	int ret;
191 
192 	kthread_stop(shutdown_thread);
193 
194 	device_remove_file(&client->dev, &dev_attr_status);
195 
196 	if (glob_mcu == mcu) {
197 		pm_power_off = NULL;
198 		glob_mcu = NULL;
199 	}
200 
201 	ret = mcu_gpiochip_remove(mcu);
202 	if (ret)
203 		return ret;
204 	kfree(mcu);
205 	return 0;
206 }
207 
208 static const struct i2c_device_id mcu_ids[] = {
209 	{ "mcu-mpc8349emitx", },
210 	{},
211 };
212 MODULE_DEVICE_TABLE(i2c, mcu_ids);
213 
214 static const struct of_device_id mcu_of_match_table[] = {
215 	{ .compatible = "fsl,mcu-mpc8349emitx", },
216 	{ },
217 };
218 
219 static struct i2c_driver mcu_driver = {
220 	.driver = {
221 		.name = "mcu-mpc8349emitx",
222 		.of_match_table = mcu_of_match_table,
223 	},
224 	.probe_new = mcu_probe,
225 	.remove	= mcu_remove,
226 	.id_table = mcu_ids,
227 };
228 
229 module_i2c_driver(mcu_driver);
230 
231 MODULE_DESCRIPTION("Power Management and GPIO expander driver for "
232 		   "MPC8349E-mITX-compatible MCU");
233 MODULE_AUTHOR("Anton Vorontsov <avorontsov@ru.mvista.com>");
234 MODULE_LICENSE("GPL");
235