rtc-ds2404.c

  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
 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");