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 29 struct ds2404 { 30 struct device *dev; 31 struct gpio_desc *rst_gpiod; 32 struct gpio_desc *clk_gpiod; 33 struct gpio_desc *dq_gpiod; 34 struct rtc_device *rtc; 35 }; 36 37 static int ds2404_gpio_map(struct ds2404 *chip, struct platform_device *pdev) 38 { 39 struct device *dev = &pdev->dev; 40 41 /* This will de-assert RESET, declare this GPIO as GPIOD_ACTIVE_LOW */ 42 chip->rst_gpiod = devm_gpiod_get(dev, "rst", GPIOD_OUT_LOW); 43 if (IS_ERR(chip->rst_gpiod)) 44 return PTR_ERR(chip->rst_gpiod); 45 46 chip->clk_gpiod = devm_gpiod_get(dev, "clk", GPIOD_OUT_HIGH); 47 if (IS_ERR(chip->clk_gpiod)) 48 return PTR_ERR(chip->clk_gpiod); 49 50 chip->dq_gpiod = devm_gpiod_get(dev, "dq", GPIOD_ASIS); 51 if (IS_ERR(chip->dq_gpiod)) 52 return PTR_ERR(chip->dq_gpiod); 53 54 return 0; 55 } 56 57 static void ds2404_reset(struct ds2404 *chip) 58 { 59 gpiod_set_value(chip->rst_gpiod, 1); 60 udelay(1000); 61 gpiod_set_value(chip->rst_gpiod, 0); 62 gpiod_set_value(chip->clk_gpiod, 0); 63 gpiod_direction_output(chip->dq_gpiod, 0); 64 udelay(10); 65 } 66 67 static void ds2404_write_byte(struct ds2404 *chip, u8 byte) 68 { 69 int i; 70 71 gpiod_direction_output(chip->dq_gpiod, 1); 72 for (i = 0; i < 8; i++) { 73 gpiod_set_value(chip->dq_gpiod, byte & (1 << i)); 74 udelay(10); 75 gpiod_set_value(chip->clk_gpiod, 1); 76 udelay(10); 77 gpiod_set_value(chip->clk_gpiod, 0); 78 udelay(10); 79 } 80 } 81 82 static u8 ds2404_read_byte(struct ds2404 *chip) 83 { 84 int i; 85 u8 ret = 0; 86 87 gpiod_direction_input(chip->dq_gpiod); 88 89 for (i = 0; i < 8; i++) { 90 gpiod_set_value(chip->clk_gpiod, 0); 91 udelay(10); 92 if (gpiod_get_value(chip->dq_gpiod)) 93 ret |= 1 << i; 94 gpiod_set_value(chip->clk_gpiod, 1); 95 udelay(10); 96 } 97 return ret; 98 } 99 100 static void ds2404_read_memory(struct ds2404 *chip, u16 offset, 101 int length, u8 *out) 102 { 103 ds2404_reset(chip); 104 ds2404_write_byte(chip, DS2404_READ_MEMORY_CMD); 105 ds2404_write_byte(chip, offset & 0xff); 106 ds2404_write_byte(chip, (offset >> 8) & 0xff); 107 while (length--) 108 *out++ = ds2404_read_byte(chip); 109 } 110 111 static void ds2404_write_memory(struct ds2404 *chip, u16 offset, 112 int length, u8 *out) 113 { 114 int i; 115 u8 ta01, ta02, es; 116 117 ds2404_reset(chip); 118 ds2404_write_byte(chip, DS2404_WRITE_SCRATCHPAD_CMD); 119 ds2404_write_byte(chip, offset & 0xff); 120 ds2404_write_byte(chip, (offset >> 8) & 0xff); 121 122 for (i = 0; i < length; i++) 123 ds2404_write_byte(chip, out[i]); 124 125 ds2404_reset(chip); 126 ds2404_write_byte(chip, DS2404_READ_SCRATCHPAD_CMD); 127 128 ta01 = ds2404_read_byte(chip); 129 ta02 = ds2404_read_byte(chip); 130 es = ds2404_read_byte(chip); 131 132 for (i = 0; i < length; i++) { 133 if (out[i] != ds2404_read_byte(chip)) { 134 dev_err(chip->dev, "read invalid data\n"); 135 return; 136 } 137 } 138 139 ds2404_reset(chip); 140 ds2404_write_byte(chip, DS2404_COPY_SCRATCHPAD_CMD); 141 ds2404_write_byte(chip, ta01); 142 ds2404_write_byte(chip, ta02); 143 ds2404_write_byte(chip, es); 144 145 while (gpiod_get_value(chip->dq_gpiod)) 146 ; 147 } 148 149 static void ds2404_enable_osc(struct ds2404 *chip) 150 { 151 u8 in[1] = { 0x10 }; /* enable oscillator */ 152 153 ds2404_write_memory(chip, 0x201, 1, in); 154 } 155 156 static int ds2404_read_time(struct device *dev, struct rtc_time *dt) 157 { 158 struct ds2404 *chip = dev_get_drvdata(dev); 159 unsigned long time = 0; 160 __le32 hw_time = 0; 161 162 ds2404_read_memory(chip, 0x203, 4, (u8 *)&hw_time); 163 time = le32_to_cpu(hw_time); 164 165 rtc_time64_to_tm(time, dt); 166 return 0; 167 } 168 169 static int ds2404_set_time(struct device *dev, struct rtc_time *dt) 170 { 171 struct ds2404 *chip = dev_get_drvdata(dev); 172 u32 time = cpu_to_le32(rtc_tm_to_time64(dt)); 173 ds2404_write_memory(chip, 0x203, 4, (u8 *)&time); 174 return 0; 175 } 176 177 static const struct rtc_class_ops ds2404_rtc_ops = { 178 .read_time = ds2404_read_time, 179 .set_time = ds2404_set_time, 180 }; 181 182 static int rtc_probe(struct platform_device *pdev) 183 { 184 struct ds2404 *chip; 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 chip->rtc = devm_rtc_allocate_device(&pdev->dev); 194 if (IS_ERR(chip->rtc)) 195 return PTR_ERR(chip->rtc); 196 197 retval = ds2404_gpio_map(chip, pdev); 198 if (retval) 199 return retval; 200 201 platform_set_drvdata(pdev, chip); 202 203 chip->rtc->ops = &ds2404_rtc_ops; 204 chip->rtc->range_max = U32_MAX; 205 206 retval = devm_rtc_register_device(chip->rtc); 207 if (retval) 208 return retval; 209 210 ds2404_enable_osc(chip); 211 return 0; 212 } 213 214 static struct platform_driver rtc_device_driver = { 215 .probe = rtc_probe, 216 .driver = { 217 .name = "ds2404", 218 }, 219 }; 220 module_platform_driver(rtc_device_driver); 221 222 MODULE_DESCRIPTION("DS2404 RTC"); 223 MODULE_AUTHOR("Sven Schnelle"); 224 MODULE_LICENSE("GPL"); 225 MODULE_ALIAS("platform:ds2404"); 226