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/platform_data/rtc-ds2404.h>
  11 #include <linux/delay.h>
  12 #include <linux/gpio.h>
  13 #include <linux/slab.h>
  14
  15 #include <linux/io.h>
  16
  17 #define DS2404_STATUS_REG 0x200
  18 #define DS2404_CONTROL_REG 0x201
  19 #define DS2404_RTC_REG 0x202
  20
  21 #define DS2404_WRITE_SCRATCHPAD_CMD 0x0f
  22 #define DS2404_READ_SCRATCHPAD_CMD 0xaa
  23 #define DS2404_COPY_SCRATCHPAD_CMD 0x55
  24 #define DS2404_READ_MEMORY_CMD 0xf0
  25
  26 #define DS2404_RST      0
  27 #define DS2404_CLK      1
  28 #define DS2404_DQ       2
  29
  30 struct ds2404_gpio {
  31         const char *name;
  32         unsigned int gpio;
  33 };
  34
  35 struct ds2404 {
  36         struct ds2404_gpio *gpio;
  37         struct rtc_device *rtc;
  38 };
  39
  40 static struct ds2404_gpio ds2404_gpio[] = {
  41         { "RTC RST", 0 },
  42         { "RTC CLK", 0 },
  43         { "RTC DQ", 0 },
  44 };
  45
  46 static int ds2404_gpio_map(struct ds2404 *chip, struct platform_device *pdev,
  47                           struct ds2404_platform_data *pdata)
  48 {
  49         int i, err;
  50
  51         ds2404_gpio[DS2404_RST].gpio = pdata->gpio_rst;
  52         ds2404_gpio[DS2404_CLK].gpio = pdata->gpio_clk;
  53         ds2404_gpio[DS2404_DQ].gpio = pdata->gpio_dq;
  54
  55         for (i = 0; i < ARRAY_SIZE(ds2404_gpio); i++) {
  56                 err = gpio_request(ds2404_gpio[i].gpio, ds2404_gpio[i].name);
  57                 if (err) {
  58                         dev_err(&pdev->dev, "error mapping gpio %s: %d\n",
  59                                 ds2404_gpio[i].name, err);
  60                         goto err_request;
  61                 }
  62                 if (i != DS2404_DQ)
  63                         gpio_direction_output(ds2404_gpio[i].gpio, 1);
  64         }
  65
  66         chip->gpio = ds2404_gpio;
  67         return 0;
  68
  69 err_request:
  70         while (--i >= 0)
  71                 gpio_free(ds2404_gpio[i].gpio);
  72         return err;
  73 }
  74
  75 static void ds2404_gpio_unmap(void *data)
  76 {
  77         int i;
  78
  79         for (i = 0; i < ARRAY_SIZE(ds2404_gpio); i++)
  80                 gpio_free(ds2404_gpio[i].gpio);
  81 }
  82
  83 static void ds2404_reset(struct device *dev)
  84 {
  85         gpio_set_value(ds2404_gpio[DS2404_RST].gpio, 0);
  86         udelay(1000);
  87         gpio_set_value(ds2404_gpio[DS2404_RST].gpio, 1);
  88         gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
  89         gpio_direction_output(ds2404_gpio[DS2404_DQ].gpio, 0);
  90         udelay(10);
  91 }
  92
  93 static void ds2404_write_byte(struct device *dev, u8 byte)
  94 {
  95         int i;
  96
  97         gpio_direction_output(ds2404_gpio[DS2404_DQ].gpio, 1);
  98         for (i = 0; i < 8; i++) {
  99                 gpio_set_value(ds2404_gpio[DS2404_DQ].gpio, byte & (1 << i));
 100                 udelay(10);
 101                 gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 1);
 102                 udelay(10);
 103                 gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
 104                 udelay(10);
 105         }
 106 }
 107
 108 static u8 ds2404_read_byte(struct device *dev)
 109 {
 110         int i;
 111         u8 ret = 0;
 112
 113         gpio_direction_input(ds2404_gpio[DS2404_DQ].gpio);
 114
 115         for (i = 0; i < 8; i++) {
 116                 gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
 117                 udelay(10);
 118                 if (gpio_get_value(ds2404_gpio[DS2404_DQ].gpio))
 119                         ret |= 1 << i;
 120                 gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 1);
 121                 udelay(10);
 122         }
 123         return ret;
 124 }
 125
 126 static void ds2404_read_memory(struct device *dev, u16 offset,
 127                                int length, u8 *out)
 128 {
 129         ds2404_reset(dev);
 130         ds2404_write_byte(dev, DS2404_READ_MEMORY_CMD);
 131         ds2404_write_byte(dev, offset & 0xff);
 132         ds2404_write_byte(dev, (offset >> 8) & 0xff);
 133         while (length--)
 134                 *out++ = ds2404_read_byte(dev);
 135 }
 136
 137 static void ds2404_write_memory(struct device *dev, u16 offset,
 138                                 int length, u8 *out)
 139 {
 140         int i;
 141         u8 ta01, ta02, es;
 142
 143         ds2404_reset(dev);
 144         ds2404_write_byte(dev, DS2404_WRITE_SCRATCHPAD_CMD);
 145         ds2404_write_byte(dev, offset & 0xff);
 146         ds2404_write_byte(dev, (offset >> 8) & 0xff);
 147
 148         for (i = 0; i < length; i++)
 149                 ds2404_write_byte(dev, out[i]);
 150
 151         ds2404_reset(dev);
 152         ds2404_write_byte(dev, DS2404_READ_SCRATCHPAD_CMD);
 153
 154         ta01 = ds2404_read_byte(dev);
 155         ta02 = ds2404_read_byte(dev);
 156         es = ds2404_read_byte(dev);
 157
 158         for (i = 0; i < length; i++) {
 159                 if (out[i] != ds2404_read_byte(dev)) {
 160                         dev_err(dev, "read invalid data\n");
 161                         return;
 162                 }
 163         }
 164
 165         ds2404_reset(dev);
 166         ds2404_write_byte(dev, DS2404_COPY_SCRATCHPAD_CMD);
 167         ds2404_write_byte(dev, ta01);
 168         ds2404_write_byte(dev, ta02);
 169         ds2404_write_byte(dev, es);
 170
 171         gpio_direction_input(ds2404_gpio[DS2404_DQ].gpio);
 172         while (gpio_get_value(ds2404_gpio[DS2404_DQ].gpio))
 173                 ;
 174 }
 175
 176 static void ds2404_enable_osc(struct device *dev)
 177 {
 178         u8 in[1] = { 0x10 }; /* enable oscillator */
 179         ds2404_write_memory(dev, 0x201, 1, in);
 180 }
 181
 182 static int ds2404_read_time(struct device *dev, struct rtc_time *dt)
 183 {
 184         unsigned long time = 0;
 185         __le32 hw_time = 0;
 186
 187         ds2404_read_memory(dev, 0x203, 4, (u8 *)&hw_time);
 188         time = le32_to_cpu(hw_time);
 189
 190         rtc_time64_to_tm(time, dt);
 191         return 0;
 192 }
 193
 194 static int ds2404_set_time(struct device *dev, struct rtc_time *dt)
 195 {
 196         u32 time = cpu_to_le32(rtc_tm_to_time64(dt));
 197         ds2404_write_memory(dev, 0x203, 4, (u8 *)&time);
 198         return 0;
 199 }
 200
 201 static const struct rtc_class_ops ds2404_rtc_ops = {
 202         .read_time      = ds2404_read_time,
 203         .set_time       = ds2404_set_time,
 204 };
 205
 206 static int rtc_probe(struct platform_device *pdev)
 207 {
 208         struct ds2404_platform_data *pdata = dev_get_platdata(&pdev->dev);
 209         struct ds2404 *chip;
 210         int retval = -EBUSY;
 211
 212         chip = devm_kzalloc(&pdev->dev, sizeof(struct ds2404), GFP_KERNEL);
 213         if (!chip)
 214                 return -ENOMEM;
 215
 216         chip->rtc = devm_rtc_allocate_device(&pdev->dev);
 217         if (IS_ERR(chip->rtc))
 218                 return PTR_ERR(chip->rtc);
 219
 220         retval = ds2404_gpio_map(chip, pdev, pdata);
 221         if (retval)
 222                 return retval;
 223
 224         retval = devm_add_action_or_reset(&pdev->dev, ds2404_gpio_unmap, chip);
 225         if (retval)
 226                 return retval;
 227
 228         dev_info(&pdev->dev, "using GPIOs RST:%d, CLK:%d, DQ:%d\n",
 229                  chip->gpio[DS2404_RST].gpio, chip->gpio[DS2404_CLK].gpio,
 230                  chip->gpio[DS2404_DQ].gpio);
 231
 232         platform_set_drvdata(pdev, chip);
 233
 234         chip->rtc->ops = &ds2404_rtc_ops;
 235         chip->rtc->range_max = U32_MAX;
 236
 237         retval = devm_rtc_register_device(chip->rtc);
 238         if (retval)
 239                 return retval;
 240
 241         ds2404_enable_osc(&pdev->dev);
 242         return 0;
 243 }
 244
 245 static struct platform_driver rtc_device_driver = {
 246         .probe  = rtc_probe,
 247         .driver = {
 248                 .name   = "ds2404",
 249         },
 250 };
 251 module_platform_driver(rtc_device_driver);
 252
 253 MODULE_DESCRIPTION("DS2404 RTC");
 254 MODULE_AUTHOR("Sven Schnelle");
 255 MODULE_LICENSE("GPL");
 256 MODULE_ALIAS("platform:ds2404");