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// 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;
struct rtc_device *rtc;
};
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;
int retval = -EBUSY;
chip = devm_kzalloc(&pdev->dev, sizeof(struct ds2404), GFP_KERNEL);
if (!chip)
return -ENOMEM;
chip->dev = &pdev->dev;
chip->rtc = devm_rtc_allocate_device(&pdev->dev);
if (IS_ERR(chip->rtc))
return PTR_ERR(chip->rtc);
retval = ds2404_gpio_map(chip, pdev);
if (retval)
return retval;
platform_set_drvdata(pdev, chip);
chip->rtc->ops = &ds2404_rtc_ops;
chip->rtc->range_max = U32_MAX;
retval = devm_rtc_register_device(chip->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");
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