drivers/rtc/rtc-ds2404.c

   1 /*
   2  * Copyright (C) 2012 Sven Schnelle <svens@stackframe.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  */
   9
  10 #include <linux/platform_device.h>
  11 #include <linux/module.h>
  12 #include <linux/init.h>
  13 #include <linux/rtc.h>
  14 #include <linux/types.h>
  15 #include <linux/bcd.h>
  16 #include <linux/rtc-ds2404.h>
  17 #include <linux/delay.h>
  18 #include <linux/gpio.h>
  19 #include <linux/slab.h>
  20
  21 #include <linux/io.h>
  22
  23 #define DS2404_STATUS_REG 0x200
  24 #define DS2404_CONTROL_REG 0x201
  25 #define DS2404_RTC_REG 0x202
  26
  27 #define DS2404_WRITE_SCRATCHPAD_CMD 0x0f
  28 #define DS2404_READ_SCRATCHPAD_CMD 0xaa
  29 #define DS2404_COPY_SCRATCHPAD_CMD 0x55
  30 #define DS2404_READ_MEMORY_CMD 0xf0
  31
  32 struct ds2404;
  33
  34 struct ds2404_chip_ops {
  35         int (*map_io)(struct ds2404 *chip, struct platform_device *pdev,
  36                       struct ds2404_platform_data *pdata);
  37         void (*unmap_io)(struct ds2404 *chip);
  38 };
  39
  40 #define DS2404_RST      0
  41 #define DS2404_CLK      1
  42 #define DS2404_DQ       2
  43
  44 struct ds2404_gpio {
  45         const char *name;
  46         unsigned int gpio;
  47 };
  48
  49 struct ds2404 {
  50         struct ds2404_gpio *gpio;
  51         struct ds2404_chip_ops *ops;
  52         struct rtc_device *rtc;
  53 };
  54
  55 static struct ds2404_gpio ds2404_gpio[] = {
  56         { "RTC RST", 0 },
  57         { "RTC CLK", 0 },
  58         { "RTC DQ", 0 },
  59 };
  60
  61 static int ds2404_gpio_map(struct ds2404 *chip, struct platform_device *pdev,
  62                           struct ds2404_platform_data *pdata)
  63 {
  64         int i, err;
  65
  66         ds2404_gpio[DS2404_RST].gpio = pdata->gpio_rst;
  67         ds2404_gpio[DS2404_CLK].gpio = pdata->gpio_clk;
  68         ds2404_gpio[DS2404_DQ].gpio = pdata->gpio_dq;
  69
  70         for (i = 0; i < ARRAY_SIZE(ds2404_gpio); i++) {
  71                 err = gpio_request(ds2404_gpio[i].gpio, ds2404_gpio[i].name);
  72                 if (err) {
  73                         dev_err(&pdev->dev, "error mapping gpio %s: %d\n",
  74                                 ds2404_gpio[i].name, err);
  75                         goto err_request;
  76                 }
  77                 if (i != DS2404_DQ)
  78                         gpio_direction_output(ds2404_gpio[i].gpio, 1);
  79         }
  80
  81         chip->gpio = ds2404_gpio;
  82         return 0;
  83
  84 err_request:
  85         while (--i >= 0)
  86                 gpio_free(ds2404_gpio[i].gpio);
  87         return err;
  88 }
  89
  90 static void ds2404_gpio_unmap(struct ds2404 *chip)
  91 {
  92         int i;
  93
  94         for (i = 0; i < ARRAY_SIZE(ds2404_gpio); i++)
  95                 gpio_free(ds2404_gpio[i].gpio);
  96 }
  97
  98 static struct ds2404_chip_ops ds2404_gpio_ops = {
  99         .map_io         = ds2404_gpio_map,
 100         .unmap_io       = ds2404_gpio_unmap,
 101 };
 102
 103 static void ds2404_reset(struct device *dev)
 104 {
 105         gpio_set_value(ds2404_gpio[DS2404_RST].gpio, 0);
 106         udelay(1000);
 107         gpio_set_value(ds2404_gpio[DS2404_RST].gpio, 1);
 108         gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
 109         gpio_direction_output(ds2404_gpio[DS2404_DQ].gpio, 0);
 110         udelay(10);
 111 }
 112
 113 static void ds2404_write_byte(struct device *dev, u8 byte)
 114 {
 115         int i;
 116
 117         gpio_direction_output(ds2404_gpio[DS2404_DQ].gpio, 1);
 118         for (i = 0; i < 8; i++) {
 119                 gpio_set_value(ds2404_gpio[DS2404_DQ].gpio, byte & (1 << i));
 120                 udelay(10);
 121                 gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 1);
 122                 udelay(10);
 123                 gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
 124                 udelay(10);
 125         }
 126 }
 127
 128 static u8 ds2404_read_byte(struct device *dev)
 129 {
 130         int i;
 131         u8 ret = 0;
 132
 133         gpio_direction_input(ds2404_gpio[DS2404_DQ].gpio);
 134
 135         for (i = 0; i < 8; i++) {
 136                 gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
 137                 udelay(10);
 138                 if (gpio_get_value(ds2404_gpio[DS2404_DQ].gpio))
 139                         ret |= 1 << i;
 140                 gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 1);
 141                 udelay(10);
 142         }
 143         return ret;
 144 }
 145
 146 static void ds2404_read_memory(struct device *dev, u16 offset,
 147                                int length, u8 *out)
 148 {
 149         ds2404_reset(dev);
 150         ds2404_write_byte(dev, DS2404_READ_MEMORY_CMD);
 151         ds2404_write_byte(dev, offset & 0xff);
 152         ds2404_write_byte(dev, (offset >> 8) & 0xff);
 153         while (length--)
 154                 *out++ = ds2404_read_byte(dev);
 155 }
 156
 157 static void ds2404_write_memory(struct device *dev, u16 offset,
 158                                 int length, u8 *out)
 159 {
 160         int i;
 161         u8 ta01, ta02, es;
 162
 163         ds2404_reset(dev);
 164         ds2404_write_byte(dev, DS2404_WRITE_SCRATCHPAD_CMD);
 165         ds2404_write_byte(dev, offset & 0xff);
 166         ds2404_write_byte(dev, (offset >> 8) & 0xff);
 167
 168         for (i = 0; i < length; i++)
 169                 ds2404_write_byte(dev, out[i]);
 170
 171         ds2404_reset(dev);
 172         ds2404_write_byte(dev, DS2404_READ_SCRATCHPAD_CMD);
 173
 174         ta01 = ds2404_read_byte(dev);
 175         ta02 = ds2404_read_byte(dev);
 176         es = ds2404_read_byte(dev);
 177
 178         for (i = 0; i < length; i++) {
 179                 if (out[i] != ds2404_read_byte(dev)) {
 180                         dev_err(dev, "read invalid data\n");
 181                         return;
 182                 }
 183         }
 184
 185         ds2404_reset(dev);
 186         ds2404_write_byte(dev, DS2404_COPY_SCRATCHPAD_CMD);
 187         ds2404_write_byte(dev, ta01);
 188         ds2404_write_byte(dev, ta02);
 189         ds2404_write_byte(dev, es);
 190
 191         gpio_direction_input(ds2404_gpio[DS2404_DQ].gpio);
 192         while (gpio_get_value(ds2404_gpio[DS2404_DQ].gpio))
 193                 ;
 194 }
 195
 196 static void ds2404_enable_osc(struct device *dev)
 197 {
 198         u8 in[1] = { 0x10 }; /* enable oscillator */
 199         ds2404_write_memory(dev, 0x201, 1, in);
 200 }
 201
 202 static int ds2404_read_time(struct device *dev, struct rtc_time *dt)
 203 {
 204         unsigned long time = 0;
 205
 206         ds2404_read_memory(dev, 0x203, 4, (u8 *)&time);
 207         time = le32_to_cpu(time);
 208
 209         rtc_time_to_tm(time, dt);
 210         return rtc_valid_tm(dt);
 211 }
 212
 213 static int ds2404_set_mmss(struct device *dev, unsigned long secs)
 214 {
 215         u32 time = cpu_to_le32(secs);
 216         ds2404_write_memory(dev, 0x203, 4, (u8 *)&time);
 217         return 0;
 218 }
 219
 220 static const struct rtc_class_ops ds2404_rtc_ops = {
 221         .read_time      = ds2404_read_time,
 222         .set_mmss       = ds2404_set_mmss,
 223 };
 224
 225 static int rtc_probe(struct platform_device *pdev)
 226 {
 227         struct ds2404_platform_data *pdata = pdev->dev.platform_data;
 228         struct ds2404 *chip;
 229         int retval = -EBUSY;
 230
 231         chip = devm_kzalloc(&pdev->dev, sizeof(struct ds2404), GFP_KERNEL);
 232         if (!chip)
 233                 return -ENOMEM;
 234
 235         chip->ops = &ds2404_gpio_ops;
 236
 237         retval = chip->ops->map_io(chip, pdev, pdata);
 238         if (retval)
 239                 goto err_chip;
 240
 241         dev_info(&pdev->dev, "using GPIOs RST:%d, CLK:%d, DQ:%d\n",
 242                  chip->gpio[DS2404_RST].gpio, chip->gpio[DS2404_CLK].gpio,
 243                  chip->gpio[DS2404_DQ].gpio);
 244
 245         platform_set_drvdata(pdev, chip);
 246
 247         chip->rtc = devm_rtc_device_register(&pdev->dev, "ds2404",
 248                                         &ds2404_rtc_ops, THIS_MODULE);
 249         if (IS_ERR(chip->rtc)) {
 250                 retval = PTR_ERR(chip->rtc);
 251                 goto err_io;
 252         }
 253
 254         ds2404_enable_osc(&pdev->dev);
 255         return 0;
 256
 257 err_io:
 258         chip->ops->unmap_io(chip);
 259 err_chip:
 260         return retval;
 261 }
 262
 263 static int rtc_remove(struct platform_device *dev)
 264 {
 265         struct ds2404 *chip = platform_get_drvdata(dev);
 266
 267         chip->ops->unmap_io(chip);
 268
 269         return 0;
 270 }
 271
 272 static struct platform_driver rtc_device_driver = {
 273         .probe  = rtc_probe,
 274         .remove = rtc_remove,
 275         .driver = {
 276                 .name   = "ds2404",
 277                 .owner  = THIS_MODULE,
 278         },
 279 };
 280 module_platform_driver(rtc_device_driver);
 281
 282 MODULE_DESCRIPTION("DS2404 RTC");
 283 MODULE_AUTHOR("Sven Schnelle");
 284 MODULE_LICENSE("GPL");
 285 MODULE_ALIAS("platform:ds2404");