drivers/rtc/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
  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");