xref: /openbmc/linux/drivers/rtc/rtc-ds2404.c (revision d890cfc2)
1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (C) 2012 Sven Schnelle <svens@stackframe.org>
3 
4 #include <linux/platform_device.h>
5 #include <linux/module.h>
6 #include <linux/init.h>
7 #include <linux/rtc.h>
8 #include <linux/types.h>
9 #include <linux/bcd.h>
10 #include <linux/delay.h>
11 #include <linux/gpio/consumer.h>
12 #include <linux/slab.h>
13 
14 #include <linux/io.h>
15 
16 #define DS2404_STATUS_REG 0x200
17 #define DS2404_CONTROL_REG 0x201
18 #define DS2404_RTC_REG 0x202
19 
20 #define DS2404_WRITE_SCRATCHPAD_CMD 0x0f
21 #define DS2404_READ_SCRATCHPAD_CMD 0xaa
22 #define DS2404_COPY_SCRATCHPAD_CMD 0x55
23 #define DS2404_READ_MEMORY_CMD 0xf0
24 
25 #define DS2404_RST	0
26 #define DS2404_CLK	1
27 #define DS2404_DQ	2
28 
29 struct ds2404 {
30 	struct device *dev;
31 	struct gpio_desc *rst_gpiod;
32 	struct gpio_desc *clk_gpiod;
33 	struct gpio_desc *dq_gpiod;
34 	struct rtc_device *rtc;
35 };
36 
ds2404_gpio_map(struct ds2404 * chip,struct platform_device * pdev)37 static int ds2404_gpio_map(struct ds2404 *chip, struct platform_device *pdev)
38 {
39 	struct device *dev = &pdev->dev;
40 
41 	/* This will de-assert RESET, declare this GPIO as GPIOD_ACTIVE_LOW */
42 	chip->rst_gpiod = devm_gpiod_get(dev, "rst", GPIOD_OUT_LOW);
43 	if (IS_ERR(chip->rst_gpiod))
44 		return PTR_ERR(chip->rst_gpiod);
45 
46 	chip->clk_gpiod = devm_gpiod_get(dev, "clk", GPIOD_OUT_HIGH);
47 	if (IS_ERR(chip->clk_gpiod))
48 		return PTR_ERR(chip->clk_gpiod);
49 
50 	chip->dq_gpiod = devm_gpiod_get(dev, "dq", GPIOD_ASIS);
51 	if (IS_ERR(chip->dq_gpiod))
52 		return PTR_ERR(chip->dq_gpiod);
53 
54 	return 0;
55 }
56 
ds2404_reset(struct ds2404 * chip)57 static void ds2404_reset(struct ds2404 *chip)
58 {
59 	gpiod_set_value(chip->rst_gpiod, 1);
60 	udelay(1000);
61 	gpiod_set_value(chip->rst_gpiod, 0);
62 	gpiod_set_value(chip->clk_gpiod, 0);
63 	gpiod_direction_output(chip->dq_gpiod, 0);
64 	udelay(10);
65 }
66 
ds2404_write_byte(struct ds2404 * chip,u8 byte)67 static void ds2404_write_byte(struct ds2404 *chip, u8 byte)
68 {
69 	int i;
70 
71 	gpiod_direction_output(chip->dq_gpiod, 1);
72 	for (i = 0; i < 8; i++) {
73 		gpiod_set_value(chip->dq_gpiod, byte & (1 << i));
74 		udelay(10);
75 		gpiod_set_value(chip->clk_gpiod, 1);
76 		udelay(10);
77 		gpiod_set_value(chip->clk_gpiod, 0);
78 		udelay(10);
79 	}
80 }
81 
ds2404_read_byte(struct ds2404 * chip)82 static u8 ds2404_read_byte(struct ds2404 *chip)
83 {
84 	int i;
85 	u8 ret = 0;
86 
87 	gpiod_direction_input(chip->dq_gpiod);
88 
89 	for (i = 0; i < 8; i++) {
90 		gpiod_set_value(chip->clk_gpiod, 0);
91 		udelay(10);
92 		if (gpiod_get_value(chip->dq_gpiod))
93 			ret |= 1 << i;
94 		gpiod_set_value(chip->clk_gpiod, 1);
95 		udelay(10);
96 	}
97 	return ret;
98 }
99 
ds2404_read_memory(struct ds2404 * chip,u16 offset,int length,u8 * out)100 static void ds2404_read_memory(struct ds2404 *chip, u16 offset,
101 			       int length, u8 *out)
102 {
103 	ds2404_reset(chip);
104 	ds2404_write_byte(chip, DS2404_READ_MEMORY_CMD);
105 	ds2404_write_byte(chip, offset & 0xff);
106 	ds2404_write_byte(chip, (offset >> 8) & 0xff);
107 	while (length--)
108 		*out++ = ds2404_read_byte(chip);
109 }
110 
ds2404_write_memory(struct ds2404 * chip,u16 offset,int length,u8 * out)111 static void ds2404_write_memory(struct ds2404 *chip, u16 offset,
112 				int length, u8 *out)
113 {
114 	int i;
115 	u8 ta01, ta02, es;
116 
117 	ds2404_reset(chip);
118 	ds2404_write_byte(chip, DS2404_WRITE_SCRATCHPAD_CMD);
119 	ds2404_write_byte(chip, offset & 0xff);
120 	ds2404_write_byte(chip, (offset >> 8) & 0xff);
121 
122 	for (i = 0; i < length; i++)
123 		ds2404_write_byte(chip, out[i]);
124 
125 	ds2404_reset(chip);
126 	ds2404_write_byte(chip, DS2404_READ_SCRATCHPAD_CMD);
127 
128 	ta01 = ds2404_read_byte(chip);
129 	ta02 = ds2404_read_byte(chip);
130 	es = ds2404_read_byte(chip);
131 
132 	for (i = 0; i < length; i++) {
133 		if (out[i] != ds2404_read_byte(chip)) {
134 			dev_err(chip->dev, "read invalid data\n");
135 			return;
136 		}
137 	}
138 
139 	ds2404_reset(chip);
140 	ds2404_write_byte(chip, DS2404_COPY_SCRATCHPAD_CMD);
141 	ds2404_write_byte(chip, ta01);
142 	ds2404_write_byte(chip, ta02);
143 	ds2404_write_byte(chip, es);
144 
145 	while (gpiod_get_value(chip->dq_gpiod))
146 		;
147 }
148 
ds2404_enable_osc(struct ds2404 * chip)149 static void ds2404_enable_osc(struct ds2404 *chip)
150 {
151 	u8 in[1] = { 0x10 }; /* enable oscillator */
152 
153 	ds2404_write_memory(chip, 0x201, 1, in);
154 }
155 
ds2404_read_time(struct device * dev,struct rtc_time * dt)156 static int ds2404_read_time(struct device *dev, struct rtc_time *dt)
157 {
158 	struct ds2404 *chip = dev_get_drvdata(dev);
159 	unsigned long time = 0;
160 	__le32 hw_time = 0;
161 
162 	ds2404_read_memory(chip, 0x203, 4, (u8 *)&hw_time);
163 	time = le32_to_cpu(hw_time);
164 
165 	rtc_time64_to_tm(time, dt);
166 	return 0;
167 }
168 
ds2404_set_time(struct device * dev,struct rtc_time * dt)169 static int ds2404_set_time(struct device *dev, struct rtc_time *dt)
170 {
171 	struct ds2404 *chip = dev_get_drvdata(dev);
172 	u32 time = cpu_to_le32(rtc_tm_to_time64(dt));
173 	ds2404_write_memory(chip, 0x203, 4, (u8 *)&time);
174 	return 0;
175 }
176 
177 static const struct rtc_class_ops ds2404_rtc_ops = {
178 	.read_time	= ds2404_read_time,
179 	.set_time	= ds2404_set_time,
180 };
181 
rtc_probe(struct platform_device * pdev)182 static int rtc_probe(struct platform_device *pdev)
183 {
184 	struct ds2404 *chip;
185 	int retval = -EBUSY;
186 
187 	chip = devm_kzalloc(&pdev->dev, sizeof(struct ds2404), GFP_KERNEL);
188 	if (!chip)
189 		return -ENOMEM;
190 
191 	chip->dev = &pdev->dev;
192 
193 	chip->rtc = devm_rtc_allocate_device(&pdev->dev);
194 	if (IS_ERR(chip->rtc))
195 		return PTR_ERR(chip->rtc);
196 
197 	retval = ds2404_gpio_map(chip, pdev);
198 	if (retval)
199 		return retval;
200 
201 	platform_set_drvdata(pdev, chip);
202 
203 	chip->rtc->ops = &ds2404_rtc_ops;
204 	chip->rtc->range_max = U32_MAX;
205 
206 	retval = devm_rtc_register_device(chip->rtc);
207 	if (retval)
208 		return retval;
209 
210 	ds2404_enable_osc(chip);
211 	return 0;
212 }
213 
214 static struct platform_driver rtc_device_driver = {
215 	.probe	= rtc_probe,
216 	.driver = {
217 		.name	= "ds2404",
218 	},
219 };
220 module_platform_driver(rtc_device_driver);
221 
222 MODULE_DESCRIPTION("DS2404 RTC");
223 MODULE_AUTHOR("Sven Schnelle");
224 MODULE_LICENSE("GPL");
225 MODULE_ALIAS("platform:ds2404");
226