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/platform_data/rtc-ds2404.h>
11#include <linux/delay.h>
12#include <linux/gpio.h>
13#include <linux/slab.h>
14
15#include <linux/io.h>
16
17#define DS2404_STATUS_REG 0x200
18#define DS2404_CONTROL_REG 0x201
19#define DS2404_RTC_REG 0x202
20
21#define DS2404_WRITE_SCRATCHPAD_CMD 0x0f
22#define DS2404_READ_SCRATCHPAD_CMD 0xaa
23#define DS2404_COPY_SCRATCHPAD_CMD 0x55
24#define DS2404_READ_MEMORY_CMD 0xf0
25
26#define DS2404_RST	0
27#define DS2404_CLK	1
28#define DS2404_DQ	2
29
30struct ds2404_gpio {
31	const char *name;
32	unsigned int gpio;
33};
34
35struct ds2404 {
36	struct ds2404_gpio *gpio;
37	struct rtc_device *rtc;
38};
39
40static struct ds2404_gpio ds2404_gpio[] = {
41	{ "RTC RST", 0 },
42	{ "RTC CLK", 0 },
43	{ "RTC DQ", 0 },
44};
45
46static int ds2404_gpio_map(struct ds2404 *chip, struct platform_device *pdev,
47			  struct ds2404_platform_data *pdata)
48{
49	int i, err;
50
51	ds2404_gpio[DS2404_RST].gpio = pdata->gpio_rst;
52	ds2404_gpio[DS2404_CLK].gpio = pdata->gpio_clk;
53	ds2404_gpio[DS2404_DQ].gpio = pdata->gpio_dq;
54
55	for (i = 0; i < ARRAY_SIZE(ds2404_gpio); i++) {
56		err = gpio_request(ds2404_gpio[i].gpio, ds2404_gpio[i].name);
57		if (err) {
58			dev_err(&pdev->dev, "error mapping gpio %s: %d\n",
59				ds2404_gpio[i].name, err);
60			goto err_request;
61		}
62		if (i != DS2404_DQ)
63			gpio_direction_output(ds2404_gpio[i].gpio, 1);
64	}
65
66	chip->gpio = ds2404_gpio;
67	return 0;
68
69err_request:
70	while (--i >= 0)
71		gpio_free(ds2404_gpio[i].gpio);
72	return err;
73}
74
75static void ds2404_gpio_unmap(void *data)
76{
77	int i;
78
79	for (i = 0; i < ARRAY_SIZE(ds2404_gpio); i++)
80		gpio_free(ds2404_gpio[i].gpio);
81}
82
83static void ds2404_reset(struct device *dev)
84{
85	gpio_set_value(ds2404_gpio[DS2404_RST].gpio, 0);
86	udelay(1000);
87	gpio_set_value(ds2404_gpio[DS2404_RST].gpio, 1);
88	gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
89	gpio_direction_output(ds2404_gpio[DS2404_DQ].gpio, 0);
90	udelay(10);
91}
92
93static void ds2404_write_byte(struct device *dev, u8 byte)
94{
95	int i;
96
97	gpio_direction_output(ds2404_gpio[DS2404_DQ].gpio, 1);
98	for (i = 0; i < 8; i++) {
99		gpio_set_value(ds2404_gpio[DS2404_DQ].gpio, byte & (1 << i));
100		udelay(10);
101		gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 1);
102		udelay(10);
103		gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
104		udelay(10);
105	}
106}
107
108static u8 ds2404_read_byte(struct device *dev)
109{
110	int i;
111	u8 ret = 0;
112
113	gpio_direction_input(ds2404_gpio[DS2404_DQ].gpio);
114
115	for (i = 0; i < 8; i++) {
116		gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
117		udelay(10);
118		if (gpio_get_value(ds2404_gpio[DS2404_DQ].gpio))
119			ret |= 1 << i;
120		gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 1);
121		udelay(10);
122	}
123	return ret;
124}
125
126static void ds2404_read_memory(struct device *dev, u16 offset,
127			       int length, u8 *out)
128{
129	ds2404_reset(dev);
130	ds2404_write_byte(dev, DS2404_READ_MEMORY_CMD);
131	ds2404_write_byte(dev, offset & 0xff);
132	ds2404_write_byte(dev, (offset >> 8) & 0xff);
133	while (length--)
134		*out++ = ds2404_read_byte(dev);
135}
136
137static void ds2404_write_memory(struct device *dev, u16 offset,
138				int length, u8 *out)
139{
140	int i;
141	u8 ta01, ta02, es;
142
143	ds2404_reset(dev);
144	ds2404_write_byte(dev, DS2404_WRITE_SCRATCHPAD_CMD);
145	ds2404_write_byte(dev, offset & 0xff);
146	ds2404_write_byte(dev, (offset >> 8) & 0xff);
147
148	for (i = 0; i < length; i++)
149		ds2404_write_byte(dev, out[i]);
150
151	ds2404_reset(dev);
152	ds2404_write_byte(dev, DS2404_READ_SCRATCHPAD_CMD);
153
154	ta01 = ds2404_read_byte(dev);
155	ta02 = ds2404_read_byte(dev);
156	es = ds2404_read_byte(dev);
157
158	for (i = 0; i < length; i++) {
159		if (out[i] != ds2404_read_byte(dev)) {
160			dev_err(dev, "read invalid data\n");
161			return;
162		}
163	}
164
165	ds2404_reset(dev);
166	ds2404_write_byte(dev, DS2404_COPY_SCRATCHPAD_CMD);
167	ds2404_write_byte(dev, ta01);
168	ds2404_write_byte(dev, ta02);
169	ds2404_write_byte(dev, es);
170
171	gpio_direction_input(ds2404_gpio[DS2404_DQ].gpio);
172	while (gpio_get_value(ds2404_gpio[DS2404_DQ].gpio))
173		;
174}
175
176static void ds2404_enable_osc(struct device *dev)
177{
178	u8 in[1] = { 0x10 }; /* enable oscillator */
179	ds2404_write_memory(dev, 0x201, 1, in);
180}
181
182static int ds2404_read_time(struct device *dev, struct rtc_time *dt)
183{
184	unsigned long time = 0;
185	__le32 hw_time = 0;
186
187	ds2404_read_memory(dev, 0x203, 4, (u8 *)&hw_time);
188	time = le32_to_cpu(hw_time);
189
190	rtc_time64_to_tm(time, dt);
191	return 0;
192}
193
194static int ds2404_set_time(struct device *dev, struct rtc_time *dt)
195{
196	u32 time = cpu_to_le32(rtc_tm_to_time64(dt));
197	ds2404_write_memory(dev, 0x203, 4, (u8 *)&time);
198	return 0;
199}
200
201static const struct rtc_class_ops ds2404_rtc_ops = {
202	.read_time	= ds2404_read_time,
203	.set_time	= ds2404_set_time,
204};
205
206static int rtc_probe(struct platform_device *pdev)
207{
208	struct ds2404_platform_data *pdata = dev_get_platdata(&pdev->dev);
209	struct ds2404 *chip;
210	int retval = -EBUSY;
211
212	chip = devm_kzalloc(&pdev->dev, sizeof(struct ds2404), GFP_KERNEL);
213	if (!chip)
214		return -ENOMEM;
215
216	chip->rtc = devm_rtc_allocate_device(&pdev->dev);
217	if (IS_ERR(chip->rtc))
218		return PTR_ERR(chip->rtc);
219
220	retval = ds2404_gpio_map(chip, pdev, pdata);
221	if (retval)
222		return retval;
223
224	retval = devm_add_action_or_reset(&pdev->dev, ds2404_gpio_unmap, chip);
225	if (retval)
226		return retval;
227
228	dev_info(&pdev->dev, "using GPIOs RST:%d, CLK:%d, DQ:%d\n",
229		 chip->gpio[DS2404_RST].gpio, chip->gpio[DS2404_CLK].gpio,
230		 chip->gpio[DS2404_DQ].gpio);
231
232	platform_set_drvdata(pdev, chip);
233
234	chip->rtc->ops = &ds2404_rtc_ops;
235	chip->rtc->range_max = U32_MAX;
236
237	retval = rtc_register_device(chip->rtc);
238	if (retval)
239		return retval;
240
241	ds2404_enable_osc(&pdev->dev);
242	return 0;
243}
244
245static struct platform_driver rtc_device_driver = {
246	.probe	= rtc_probe,
247	.driver = {
248		.name	= "ds2404",
249	},
250};
251module_platform_driver(rtc_device_driver);
252
253MODULE_DESCRIPTION("DS2404 RTC");
254MODULE_AUTHOR("Sven Schnelle");
255MODULE_LICENSE("GPL");
256MODULE_ALIAS("platform:ds2404");
257