drivers/rtc/rtc-m48t86.c

   1 /*
   2  * ST M48T86 / Dallas DS12887 RTC driver
   3  * Copyright (c) 2006 Tower Technologies
   4  *
   5  * Author: Alessandro Zummo <a.zummo@towertech.it>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * This drivers only supports the clock running in BCD and 24H mode.
  12  * If it will be ever adapted to binary and 12H mode, care must be taken
  13  * to not introduce bugs.
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/rtc.h>
  18 #include <linux/platform_device.h>
  19 #include <linux/bcd.h>
  20 #include <linux/io.h>
  21
  22 #define M48T86_SEC              0x00
  23 #define M48T86_SECALRM          0x01
  24 #define M48T86_MIN              0x02
  25 #define M48T86_MINALRM          0x03
  26 #define M48T86_HOUR             0x04
  27 #define M48T86_HOURALRM         0x05
  28 #define M48T86_DOW              0x06 /* 1 = sunday */
  29 #define M48T86_DOM              0x07
  30 #define M48T86_MONTH            0x08 /* 1 - 12 */
  31 #define M48T86_YEAR             0x09 /* 0 - 99 */
  32 #define M48T86_A                0x0a
  33 #define M48T86_B                0x0b
  34 #define M48T86_B_SET            BIT(7)
  35 #define M48T86_B_DM             BIT(2)
  36 #define M48T86_B_H24            BIT(1)
  37 #define M48T86_C                0x0c
  38 #define M48T86_D                0x0d
  39 #define M48T86_D_VRT            BIT(7)
  40 #define M48T86_NVRAM(x)         (0x0e + (x))
  41 #define M48T86_NVRAM_LEN        114
  42
  43 struct m48t86_rtc_info {
  44         void __iomem *index_reg;
  45         void __iomem *data_reg;
  46         struct rtc_device *rtc;
  47 };
  48
  49 static unsigned char m48t86_readb(struct device *dev, unsigned long addr)
  50 {
  51         struct m48t86_rtc_info *info = dev_get_drvdata(dev);
  52         unsigned char value;
  53
  54         writeb(addr, info->index_reg);
  55         value = readb(info->data_reg);
  56
  57         return value;
  58 }
  59
  60 static void m48t86_writeb(struct device *dev,
  61                           unsigned char value, unsigned long addr)
  62 {
  63         struct m48t86_rtc_info *info = dev_get_drvdata(dev);
  64
  65         writeb(addr, info->index_reg);
  66         writeb(value, info->data_reg);
  67 }
  68
  69 static int m48t86_rtc_read_time(struct device *dev, struct rtc_time *tm)
  70 {
  71         unsigned char reg;
  72
  73         reg = m48t86_readb(dev, M48T86_B);
  74
  75         if (reg & M48T86_B_DM) {
  76                 /* data (binary) mode */
  77                 tm->tm_sec      = m48t86_readb(dev, M48T86_SEC);
  78                 tm->tm_min      = m48t86_readb(dev, M48T86_MIN);
  79                 tm->tm_hour     = m48t86_readb(dev, M48T86_HOUR) & 0x3f;
  80                 tm->tm_mday     = m48t86_readb(dev, M48T86_DOM);
  81                 /* tm_mon is 0-11 */
  82                 tm->tm_mon      = m48t86_readb(dev, M48T86_MONTH) - 1;
  83                 tm->tm_year     = m48t86_readb(dev, M48T86_YEAR) + 100;
  84                 tm->tm_wday     = m48t86_readb(dev, M48T86_DOW);
  85         } else {
  86                 /* bcd mode */
  87                 tm->tm_sec      = bcd2bin(m48t86_readb(dev, M48T86_SEC));
  88                 tm->tm_min      = bcd2bin(m48t86_readb(dev, M48T86_MIN));
  89                 tm->tm_hour     = bcd2bin(m48t86_readb(dev, M48T86_HOUR) &
  90                                           0x3f);
  91                 tm->tm_mday     = bcd2bin(m48t86_readb(dev, M48T86_DOM));
  92                 /* tm_mon is 0-11 */
  93                 tm->tm_mon      = bcd2bin(m48t86_readb(dev, M48T86_MONTH)) - 1;
  94                 tm->tm_year     = bcd2bin(m48t86_readb(dev, M48T86_YEAR)) + 100;
  95                 tm->tm_wday     = bcd2bin(m48t86_readb(dev, M48T86_DOW));
  96         }
  97
  98         /* correct the hour if the clock is in 12h mode */
  99         if (!(reg & M48T86_B_H24))
 100                 if (m48t86_readb(dev, M48T86_HOUR) & 0x80)
 101                         tm->tm_hour += 12;
 102
 103         return rtc_valid_tm(tm);
 104 }
 105
 106 static int m48t86_rtc_set_time(struct device *dev, struct rtc_time *tm)
 107 {
 108         unsigned char reg;
 109
 110         reg = m48t86_readb(dev, M48T86_B);
 111
 112         /* update flag and 24h mode */
 113         reg |= M48T86_B_SET | M48T86_B_H24;
 114         m48t86_writeb(dev, reg, M48T86_B);
 115
 116         if (reg & M48T86_B_DM) {
 117                 /* data (binary) mode */
 118                 m48t86_writeb(dev, tm->tm_sec, M48T86_SEC);
 119                 m48t86_writeb(dev, tm->tm_min, M48T86_MIN);
 120                 m48t86_writeb(dev, tm->tm_hour, M48T86_HOUR);
 121                 m48t86_writeb(dev, tm->tm_mday, M48T86_DOM);
 122                 m48t86_writeb(dev, tm->tm_mon + 1, M48T86_MONTH);
 123                 m48t86_writeb(dev, tm->tm_year % 100, M48T86_YEAR);
 124                 m48t86_writeb(dev, tm->tm_wday, M48T86_DOW);
 125         } else {
 126                 /* bcd mode */
 127                 m48t86_writeb(dev, bin2bcd(tm->tm_sec), M48T86_SEC);
 128                 m48t86_writeb(dev, bin2bcd(tm->tm_min), M48T86_MIN);
 129                 m48t86_writeb(dev, bin2bcd(tm->tm_hour), M48T86_HOUR);
 130                 m48t86_writeb(dev, bin2bcd(tm->tm_mday), M48T86_DOM);
 131                 m48t86_writeb(dev, bin2bcd(tm->tm_mon + 1), M48T86_MONTH);
 132                 m48t86_writeb(dev, bin2bcd(tm->tm_year % 100), M48T86_YEAR);
 133                 m48t86_writeb(dev, bin2bcd(tm->tm_wday), M48T86_DOW);
 134         }
 135
 136         /* update ended */
 137         reg &= ~M48T86_B_SET;
 138         m48t86_writeb(dev, reg, M48T86_B);
 139
 140         return 0;
 141 }
 142
 143 static int m48t86_rtc_proc(struct device *dev, struct seq_file *seq)
 144 {
 145         unsigned char reg;
 146
 147         reg = m48t86_readb(dev, M48T86_B);
 148
 149         seq_printf(seq, "mode\t\t: %s\n",
 150                    (reg & M48T86_B_DM) ? "binary" : "bcd");
 151
 152         reg = m48t86_readb(dev, M48T86_D);
 153
 154         seq_printf(seq, "battery\t\t: %s\n",
 155                    (reg & M48T86_D_VRT) ? "ok" : "exhausted");
 156
 157         return 0;
 158 }
 159
 160 static const struct rtc_class_ops m48t86_rtc_ops = {
 161         .read_time      = m48t86_rtc_read_time,
 162         .set_time       = m48t86_rtc_set_time,
 163         .proc           = m48t86_rtc_proc,
 164 };
 165
 166 static ssize_t m48t86_nvram_read(struct file *filp, struct kobject *kobj,
 167                                  struct bin_attribute *attr,
 168                                  char *buf, loff_t off, size_t count)
 169 {
 170         struct device *dev = kobj_to_dev(kobj);
 171         unsigned int i;
 172
 173         for (i = 0; i < count; i++)
 174                 buf[i] = m48t86_readb(dev, M48T86_NVRAM(off + i));
 175
 176         return count;
 177 }
 178
 179 static ssize_t m48t86_nvram_write(struct file *filp, struct kobject *kobj,
 180                                   struct bin_attribute *attr,
 181                                   char *buf, loff_t off, size_t count)
 182 {
 183         struct device *dev = kobj_to_dev(kobj);
 184         unsigned int i;
 185
 186         for (i = 0; i < count; i++)
 187                 m48t86_writeb(dev, buf[i], M48T86_NVRAM(off + i));
 188
 189         return count;
 190 }
 191
 192 static BIN_ATTR(nvram, 0644, m48t86_nvram_read, m48t86_nvram_write,
 193                 M48T86_NVRAM_LEN);
 194
 195 /*
 196  * The RTC is an optional feature at purchase time on some Technologic Systems
 197  * boards. Verify that it actually exists by checking if the last two bytes
 198  * of the NVRAM can be changed.
 199  *
 200  * This is based on the method used in their rtc7800.c example.
 201  */
 202 static bool m48t86_verify_chip(struct platform_device *pdev)
 203 {
 204         unsigned int offset0 = M48T86_NVRAM(M48T86_NVRAM_LEN - 2);
 205         unsigned int offset1 = M48T86_NVRAM(M48T86_NVRAM_LEN - 1);
 206         unsigned char tmp0, tmp1;
 207
 208         tmp0 = m48t86_readb(&pdev->dev, offset0);
 209         tmp1 = m48t86_readb(&pdev->dev, offset1);
 210
 211         m48t86_writeb(&pdev->dev, 0x00, offset0);
 212         m48t86_writeb(&pdev->dev, 0x55, offset1);
 213         if (m48t86_readb(&pdev->dev, offset1) == 0x55) {
 214                 m48t86_writeb(&pdev->dev, 0xaa, offset1);
 215                 if (m48t86_readb(&pdev->dev, offset1) == 0xaa &&
 216                     m48t86_readb(&pdev->dev, offset0) == 0x00) {
 217                         m48t86_writeb(&pdev->dev, tmp0, offset0);
 218                         m48t86_writeb(&pdev->dev, tmp1, offset1);
 219
 220                         return true;
 221                 }
 222         }
 223         return false;
 224 }
 225
 226 static int m48t86_rtc_probe(struct platform_device *pdev)
 227 {
 228         struct m48t86_rtc_info *info;
 229         struct resource *res;
 230         unsigned char reg;
 231
 232         info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
 233         if (!info)
 234                 return -ENOMEM;
 235
 236         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 237         if (!res)
 238                 return -ENODEV;
 239         info->index_reg = devm_ioremap_resource(&pdev->dev, res);
 240         if (IS_ERR(info->index_reg))
 241                 return PTR_ERR(info->index_reg);
 242
 243         res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
 244         if (!res)
 245                 return -ENODEV;
 246         info->data_reg = devm_ioremap_resource(&pdev->dev, res);
 247         if (IS_ERR(info->data_reg))
 248                 return PTR_ERR(info->data_reg);
 249
 250         dev_set_drvdata(&pdev->dev, info);
 251
 252         if (!m48t86_verify_chip(pdev)) {
 253                 dev_info(&pdev->dev, "RTC not present\n");
 254                 return -ENODEV;
 255         }
 256
 257         info->rtc = devm_rtc_device_register(&pdev->dev, "m48t86",
 258                                              &m48t86_rtc_ops, THIS_MODULE);
 259         if (IS_ERR(info->rtc))
 260                 return PTR_ERR(info->rtc);
 261
 262         /* read battery status */
 263         reg = m48t86_readb(&pdev->dev, M48T86_D);
 264         dev_info(&pdev->dev, "battery %s\n",
 265                  (reg & M48T86_D_VRT) ? "ok" : "exhausted");
 266
 267         if (device_create_bin_file(&pdev->dev, &bin_attr_nvram))
 268                 dev_err(&pdev->dev, "failed to create nvram sysfs entry\n");
 269
 270         return 0;
 271 }
 272
 273 static int m48t86_rtc_remove(struct platform_device *pdev)
 274 {
 275         device_remove_bin_file(&pdev->dev, &bin_attr_nvram);
 276         return 0;
 277 }
 278
 279 static struct platform_driver m48t86_rtc_platform_driver = {
 280         .driver         = {
 281                 .name   = "rtc-m48t86",
 282         },
 283         .probe          = m48t86_rtc_probe,
 284         .remove         = m48t86_rtc_remove,
 285 };
 286
 287 module_platform_driver(m48t86_rtc_platform_driver);
 288
 289 MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
 290 MODULE_DESCRIPTION("M48T86 RTC driver");
 291 MODULE_LICENSE("GPL");
 292 MODULE_ALIAS("platform:rtc-m48t86");