// SPDX-License-Identifier: GPL-2.0// Copyright (C) 2012 Sven Schnelle <svens@stackframe.org> #include <linux/platform_device.h>#include <linux/module.h>#include <linux/init.h>#include <linux/rtc.h>#include <linux/types.h>#include <linux/bcd.h>#include <linux/delay.h>#include <linux/gpio/consumer.h>#include <linux/slab.h> #include <linux/io.h> #define DS2404_STATUS_REG 0x200#define DS2404_CONTROL_REG 0x201#define DS2404_RTC_REG 0x202 #define DS2404_WRITE_SCRATCHPAD_CMD 0x0f#define DS2404_READ_SCRATCHPAD_CMD 0xaa#define DS2404_COPY_SCRATCHPAD_CMD 0x55#define DS2404_READ_MEMORY_CMD 0xf0 #define DS2404_RST	0#define DS2404_CLK	1#define DS2404_DQ	2 struct ds2404 {	struct device *dev;	struct gpio_desc *rst_gpiod;	struct gpio_desc *clk_gpiod;	struct gpio_desc *dq_gpiod;}; static int ds2404_gpio_map(struct ds2404 *chip, struct platform_device *pdev){	struct device *dev = &pdev->dev; 	/* This will de-assert RESET, declare this GPIO as GPIOD_ACTIVE_LOW */	chip->rst_gpiod = devm_gpiod_get(dev, "rst", GPIOD_OUT_LOW);	if (IS_ERR(chip->rst_gpiod))		return PTR_ERR(chip->rst_gpiod); 	chip->clk_gpiod = devm_gpiod_get(dev, "clk", GPIOD_OUT_HIGH);	if (IS_ERR(chip->clk_gpiod))		return PTR_ERR(chip->clk_gpiod); 	chip->dq_gpiod = devm_gpiod_get(dev, "dq", GPIOD_ASIS);	if (IS_ERR(chip->dq_gpiod))		return PTR_ERR(chip->dq_gpiod); 	return 0;} static void ds2404_reset(struct ds2404 *chip){	gpiod_set_value(chip->rst_gpiod, 1);	udelay(1000);	gpiod_set_value(chip->rst_gpiod, 0);	gpiod_set_value(chip->clk_gpiod, 0);	gpiod_direction_output(chip->dq_gpiod, 0);	udelay(10);} static void ds2404_write_byte(struct ds2404 *chip, u8 byte){	int i; 	gpiod_direction_output(chip->dq_gpiod, 1);	for (i = 0; i < 8; i++) {		gpiod_set_value(chip->dq_gpiod, byte & (1 << i));		udelay(10);		gpiod_set_value(chip->clk_gpiod, 1);		udelay(10);		gpiod_set_value(chip->clk_gpiod, 0);		udelay(10);	}} static u8 ds2404_read_byte(struct ds2404 *chip){	int i;	u8 ret = 0; 	gpiod_direction_input(chip->dq_gpiod); 	for (i = 0; i < 8; i++) {		gpiod_set_value(chip->clk_gpiod, 0);		udelay(10);		if (gpiod_get_value(chip->dq_gpiod))			ret |= 1 << i;		gpiod_set_value(chip->clk_gpiod, 1);		udelay(10);	}	return ret;} static void ds2404_read_memory(struct ds2404 *chip, u16 offset,			       int length, u8 *out){	ds2404_reset(chip);	ds2404_write_byte(chip, DS2404_READ_MEMORY_CMD);	ds2404_write_byte(chip, offset & 0xff);	ds2404_write_byte(chip, (offset >> 8) & 0xff);	while (length--)		*out++ = ds2404_read_byte(chip);} static void ds2404_write_memory(struct ds2404 *chip, u16 offset,				int length, u8 *out){	int i;	u8 ta01, ta02, es; 	ds2404_reset(chip);	ds2404_write_byte(chip, DS2404_WRITE_SCRATCHPAD_CMD);	ds2404_write_byte(chip, offset & 0xff);	ds2404_write_byte(chip, (offset >> 8) & 0xff); 	for (i = 0; i < length; i++)		ds2404_write_byte(chip, out[i]); 	ds2404_reset(chip);	ds2404_write_byte(chip, DS2404_READ_SCRATCHPAD_CMD); 	ta01 = ds2404_read_byte(chip);	ta02 = ds2404_read_byte(chip);	es = ds2404_read_byte(chip); 	for (i = 0; i < length; i++) {		if (out[i] != ds2404_read_byte(chip)) {			dev_err(chip->dev, "read invalid data\n");			return;		}	} 	ds2404_reset(chip);	ds2404_write_byte(chip, DS2404_COPY_SCRATCHPAD_CMD);	ds2404_write_byte(chip, ta01);	ds2404_write_byte(chip, ta02);	ds2404_write_byte(chip, es); 	while (gpiod_get_value(chip->dq_gpiod))		;} static void ds2404_enable_osc(struct ds2404 *chip){	u8 in[1] = { 0x10 }; /* enable oscillator */ 	ds2404_write_memory(chip, 0x201, 1, in);} static int ds2404_read_time(struct device *dev, struct rtc_time *dt){	struct ds2404 *chip = dev_get_drvdata(dev);	unsigned long time = 0;	__le32 hw_time = 0; 	ds2404_read_memory(chip, 0x203, 4, (u8 *)&hw_time);	time = le32_to_cpu(hw_time); 	rtc_time64_to_tm(time, dt);	return 0;} static int ds2404_set_time(struct device *dev, struct rtc_time *dt){	struct ds2404 *chip = dev_get_drvdata(dev);	u32 time = cpu_to_le32(rtc_tm_to_time64(dt));	ds2404_write_memory(chip, 0x203, 4, (u8 *)&time);	return 0;} static const struct rtc_class_ops ds2404_rtc_ops = {	.read_time	= ds2404_read_time,	.set_time	= ds2404_set_time,}; static int rtc_probe(struct platform_device *pdev){	struct ds2404 *chip;	struct rtc_device *rtc;	int retval = -EBUSY; 	chip = devm_kzalloc(&pdev->dev, sizeof(struct ds2404), GFP_KERNEL);	if (!chip)		return -ENOMEM; 	chip->dev = &pdev->dev; 	rtc = devm_rtc_allocate_device(&pdev->dev);	if (IS_ERR(rtc))		return PTR_ERR(rtc); 	retval = ds2404_gpio_map(chip, pdev);	if (retval)		return retval; 	platform_set_drvdata(pdev, chip); 	rtc->ops = &ds2404_rtc_ops;	rtc->range_max = U32_MAX; 	retval = devm_rtc_register_device(rtc);	if (retval)		return retval; 	ds2404_enable_osc(chip);	return 0;} static struct platform_driver rtc_device_driver = {	.probe	= rtc_probe,	.driver = {		.name	= "ds2404",	},};module_platform_driver(rtc_device_driver); MODULE_DESCRIPTION("DS2404 RTC");MODULE_AUTHOR("Sven Schnelle");MODULE_LICENSE("GPL");MODULE_ALIAS("platform:ds2404");