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