1 /*
2  * Copyright (C) 2012 Sven Schnelle <svens@stackframe.org>
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation.
7  *
8  */
9 
10 #include <linux/platform_device.h>
11 #include <linux/module.h>
12 #include <linux/init.h>
13 #include <linux/rtc.h>
14 #include <linux/types.h>
15 #include <linux/bcd.h>
16 #include <linux/platform_data/rtc-ds2404.h>
17 #include <linux/delay.h>
18 #include <linux/gpio.h>
19 #include <linux/slab.h>
20 
21 #include <linux/io.h>
22 
23 #define DS2404_STATUS_REG 0x200
24 #define DS2404_CONTROL_REG 0x201
25 #define DS2404_RTC_REG 0x202
26 
27 #define DS2404_WRITE_SCRATCHPAD_CMD 0x0f
28 #define DS2404_READ_SCRATCHPAD_CMD 0xaa
29 #define DS2404_COPY_SCRATCHPAD_CMD 0x55
30 #define DS2404_READ_MEMORY_CMD 0xf0
31 
32 struct ds2404;
33 
34 struct ds2404_chip_ops {
35 	int (*map_io)(struct ds2404 *chip, struct platform_device *pdev,
36 		      struct ds2404_platform_data *pdata);
37 	void (*unmap_io)(struct ds2404 *chip);
38 };
39 
40 #define DS2404_RST	0
41 #define DS2404_CLK	1
42 #define DS2404_DQ	2
43 
44 struct ds2404_gpio {
45 	const char *name;
46 	unsigned int gpio;
47 };
48 
49 struct ds2404 {
50 	struct ds2404_gpio *gpio;
51 	const struct ds2404_chip_ops *ops;
52 	struct rtc_device *rtc;
53 };
54 
55 static struct ds2404_gpio ds2404_gpio[] = {
56 	{ "RTC RST", 0 },
57 	{ "RTC CLK", 0 },
58 	{ "RTC DQ", 0 },
59 };
60 
ds2404_gpio_map(struct ds2404 * chip,struct platform_device * pdev,struct ds2404_platform_data * pdata)61 static int ds2404_gpio_map(struct ds2404 *chip, struct platform_device *pdev,
62 			  struct ds2404_platform_data *pdata)
63 {
64 	int i, err;
65 
66 	ds2404_gpio[DS2404_RST].gpio = pdata->gpio_rst;
67 	ds2404_gpio[DS2404_CLK].gpio = pdata->gpio_clk;
68 	ds2404_gpio[DS2404_DQ].gpio = pdata->gpio_dq;
69 
70 	for (i = 0; i < ARRAY_SIZE(ds2404_gpio); i++) {
71 		err = gpio_request(ds2404_gpio[i].gpio, ds2404_gpio[i].name);
72 		if (err) {
73 			dev_err(&pdev->dev, "error mapping gpio %s: %d\n",
74 				ds2404_gpio[i].name, err);
75 			goto err_request;
76 		}
77 		if (i != DS2404_DQ)
78 			gpio_direction_output(ds2404_gpio[i].gpio, 1);
79 	}
80 
81 	chip->gpio = ds2404_gpio;
82 	return 0;
83 
84 err_request:
85 	while (--i >= 0)
86 		gpio_free(ds2404_gpio[i].gpio);
87 	return err;
88 }
89 
ds2404_gpio_unmap(struct ds2404 * chip)90 static void ds2404_gpio_unmap(struct ds2404 *chip)
91 {
92 	int i;
93 
94 	for (i = 0; i < ARRAY_SIZE(ds2404_gpio); i++)
95 		gpio_free(ds2404_gpio[i].gpio);
96 }
97 
98 static const struct ds2404_chip_ops ds2404_gpio_ops = {
99 	.map_io		= ds2404_gpio_map,
100 	.unmap_io	= ds2404_gpio_unmap,
101 };
102 
ds2404_reset(struct device * dev)103 static void ds2404_reset(struct device *dev)
104 {
105 	gpio_set_value(ds2404_gpio[DS2404_RST].gpio, 0);
106 	udelay(1000);
107 	gpio_set_value(ds2404_gpio[DS2404_RST].gpio, 1);
108 	gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
109 	gpio_direction_output(ds2404_gpio[DS2404_DQ].gpio, 0);
110 	udelay(10);
111 }
112 
ds2404_write_byte(struct device * dev,u8 byte)113 static void ds2404_write_byte(struct device *dev, u8 byte)
114 {
115 	int i;
116 
117 	gpio_direction_output(ds2404_gpio[DS2404_DQ].gpio, 1);
118 	for (i = 0; i < 8; i++) {
119 		gpio_set_value(ds2404_gpio[DS2404_DQ].gpio, byte & (1 << i));
120 		udelay(10);
121 		gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 1);
122 		udelay(10);
123 		gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
124 		udelay(10);
125 	}
126 }
127 
ds2404_read_byte(struct device * dev)128 static u8 ds2404_read_byte(struct device *dev)
129 {
130 	int i;
131 	u8 ret = 0;
132 
133 	gpio_direction_input(ds2404_gpio[DS2404_DQ].gpio);
134 
135 	for (i = 0; i < 8; i++) {
136 		gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
137 		udelay(10);
138 		if (gpio_get_value(ds2404_gpio[DS2404_DQ].gpio))
139 			ret |= 1 << i;
140 		gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 1);
141 		udelay(10);
142 	}
143 	return ret;
144 }
145 
ds2404_read_memory(struct device * dev,u16 offset,int length,u8 * out)146 static void ds2404_read_memory(struct device *dev, u16 offset,
147 			       int length, u8 *out)
148 {
149 	ds2404_reset(dev);
150 	ds2404_write_byte(dev, DS2404_READ_MEMORY_CMD);
151 	ds2404_write_byte(dev, offset & 0xff);
152 	ds2404_write_byte(dev, (offset >> 8) & 0xff);
153 	while (length--)
154 		*out++ = ds2404_read_byte(dev);
155 }
156 
ds2404_write_memory(struct device * dev,u16 offset,int length,u8 * out)157 static void ds2404_write_memory(struct device *dev, u16 offset,
158 				int length, u8 *out)
159 {
160 	int i;
161 	u8 ta01, ta02, es;
162 
163 	ds2404_reset(dev);
164 	ds2404_write_byte(dev, DS2404_WRITE_SCRATCHPAD_CMD);
165 	ds2404_write_byte(dev, offset & 0xff);
166 	ds2404_write_byte(dev, (offset >> 8) & 0xff);
167 
168 	for (i = 0; i < length; i++)
169 		ds2404_write_byte(dev, out[i]);
170 
171 	ds2404_reset(dev);
172 	ds2404_write_byte(dev, DS2404_READ_SCRATCHPAD_CMD);
173 
174 	ta01 = ds2404_read_byte(dev);
175 	ta02 = ds2404_read_byte(dev);
176 	es = ds2404_read_byte(dev);
177 
178 	for (i = 0; i < length; i++) {
179 		if (out[i] != ds2404_read_byte(dev)) {
180 			dev_err(dev, "read invalid data\n");
181 			return;
182 		}
183 	}
184 
185 	ds2404_reset(dev);
186 	ds2404_write_byte(dev, DS2404_COPY_SCRATCHPAD_CMD);
187 	ds2404_write_byte(dev, ta01);
188 	ds2404_write_byte(dev, ta02);
189 	ds2404_write_byte(dev, es);
190 
191 	gpio_direction_input(ds2404_gpio[DS2404_DQ].gpio);
192 	while (gpio_get_value(ds2404_gpio[DS2404_DQ].gpio))
193 		;
194 }
195 
ds2404_enable_osc(struct device * dev)196 static void ds2404_enable_osc(struct device *dev)
197 {
198 	u8 in[1] = { 0x10 }; /* enable oscillator */
199 	ds2404_write_memory(dev, 0x201, 1, in);
200 }
201 
ds2404_read_time(struct device * dev,struct rtc_time * dt)202 static int ds2404_read_time(struct device *dev, struct rtc_time *dt)
203 {
204 	unsigned long time = 0;
205 
206 	ds2404_read_memory(dev, 0x203, 4, (u8 *)&time);
207 	time = le32_to_cpu(time);
208 
209 	rtc_time_to_tm(time, dt);
210 	return 0;
211 }
212 
ds2404_set_mmss(struct device * dev,unsigned long secs)213 static int ds2404_set_mmss(struct device *dev, unsigned long secs)
214 {
215 	u32 time = cpu_to_le32(secs);
216 	ds2404_write_memory(dev, 0x203, 4, (u8 *)&time);
217 	return 0;
218 }
219 
220 static const struct rtc_class_ops ds2404_rtc_ops = {
221 	.read_time	= ds2404_read_time,
222 	.set_mmss	= ds2404_set_mmss,
223 };
224 
rtc_probe(struct platform_device * pdev)225 static int rtc_probe(struct platform_device *pdev)
226 {
227 	struct ds2404_platform_data *pdata = dev_get_platdata(&pdev->dev);
228 	struct ds2404 *chip;
229 	int retval = -EBUSY;
230 
231 	chip = devm_kzalloc(&pdev->dev, sizeof(struct ds2404), GFP_KERNEL);
232 	if (!chip)
233 		return -ENOMEM;
234 
235 	chip->ops = &ds2404_gpio_ops;
236 
237 	retval = chip->ops->map_io(chip, pdev, pdata);
238 	if (retval)
239 		goto err_chip;
240 
241 	dev_info(&pdev->dev, "using GPIOs RST:%d, CLK:%d, DQ:%d\n",
242 		 chip->gpio[DS2404_RST].gpio, chip->gpio[DS2404_CLK].gpio,
243 		 chip->gpio[DS2404_DQ].gpio);
244 
245 	platform_set_drvdata(pdev, chip);
246 
247 	chip->rtc = devm_rtc_device_register(&pdev->dev, "ds2404",
248 					&ds2404_rtc_ops, THIS_MODULE);
249 	if (IS_ERR(chip->rtc)) {
250 		retval = PTR_ERR(chip->rtc);
251 		goto err_io;
252 	}
253 
254 	ds2404_enable_osc(&pdev->dev);
255 	return 0;
256 
257 err_io:
258 	chip->ops->unmap_io(chip);
259 err_chip:
260 	return retval;
261 }
262 
rtc_remove(struct platform_device * dev)263 static int rtc_remove(struct platform_device *dev)
264 {
265 	struct ds2404 *chip = platform_get_drvdata(dev);
266 
267 	chip->ops->unmap_io(chip);
268 
269 	return 0;
270 }
271 
272 static struct platform_driver rtc_device_driver = {
273 	.probe	= rtc_probe,
274 	.remove = rtc_remove,
275 	.driver = {
276 		.name	= "ds2404",
277 	},
278 };
279 module_platform_driver(rtc_device_driver);
280 
281 MODULE_DESCRIPTION("DS2404 RTC");
282 MODULE_AUTHOR("Sven Schnelle");
283 MODULE_LICENSE("GPL");
284 MODULE_ALIAS("platform:ds2404");
285