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225 lines · 5.0 KiB

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