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 0;
 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 int m48t86_nvram_read(void *priv, unsigned int off, void *buf,
 167                              size_t count)
 168 {
 169         struct device *dev = priv;
 170         unsigned int i;
 171
 172         for (i = 0; i < count; i++)
 173                 ((u8 *)buf)[i] = m48t86_readb(dev, M48T86_NVRAM(off + i));
 174
 175         return 0;
 176 }
 177
 178 static int m48t86_nvram_write(void *priv, unsigned int off, void *buf,
 179                               size_t count)
 180 {
 181         struct device *dev = priv;
 182         unsigned int i;
 183
 184         for (i = 0; i < count; i++)
 185                 m48t86_writeb(dev, ((u8 *)buf)[i], M48T86_NVRAM(off + i));
 186
 187         return 0;
 188 }
 189
 190 /*
 191  * The RTC is an optional feature at purchase time on some Technologic Systems
 192  * boards. Verify that it actually exists by checking if the last two bytes
 193  * of the NVRAM can be changed.
 194  *
 195  * This is based on the method used in their rtc7800.c example.
 196  */
 197 static bool m48t86_verify_chip(struct platform_device *pdev)
 198 {
 199         unsigned int offset0 = M48T86_NVRAM(M48T86_NVRAM_LEN - 2);
 200         unsigned int offset1 = M48T86_NVRAM(M48T86_NVRAM_LEN - 1);
 201         unsigned char tmp0, tmp1;
 202
 203         tmp0 = m48t86_readb(&pdev->dev, offset0);
 204         tmp1 = m48t86_readb(&pdev->dev, offset1);
 205
 206         m48t86_writeb(&pdev->dev, 0x00, offset0);
 207         m48t86_writeb(&pdev->dev, 0x55, offset1);
 208         if (m48t86_readb(&pdev->dev, offset1) == 0x55) {
 209                 m48t86_writeb(&pdev->dev, 0xaa, offset1);
 210                 if (m48t86_readb(&pdev->dev, offset1) == 0xaa &&
 211                     m48t86_readb(&pdev->dev, offset0) == 0x00) {
 212                         m48t86_writeb(&pdev->dev, tmp0, offset0);
 213                         m48t86_writeb(&pdev->dev, tmp1, offset1);
 214
 215                         return true;
 216                 }
 217         }
 218         return false;
 219 }
 220
 221 static int m48t86_rtc_probe(struct platform_device *pdev)
 222 {
 223         struct m48t86_rtc_info *info;
 224         struct resource *res;
 225         unsigned char reg;
 226         int err;
 227         struct nvmem_config m48t86_nvmem_cfg = {
 228                 .name = "m48t86_nvram",
 229                 .word_size = 1,
 230                 .stride = 1,
 231                 .size = M48T86_NVRAM_LEN,
 232                 .reg_read = m48t86_nvram_read,
 233                 .reg_write = m48t86_nvram_write,
 234                 .priv = &pdev->dev,
 235         };
 236
 237         info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
 238         if (!info)
 239                 return -ENOMEM;
 240
 241         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 242         if (!res)
 243                 return -ENODEV;
 244         info->index_reg = devm_ioremap_resource(&pdev->dev, res);
 245         if (IS_ERR(info->index_reg))
 246                 return PTR_ERR(info->index_reg);
 247
 248         res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
 249         if (!res)
 250                 return -ENODEV;
 251         info->data_reg = devm_ioremap_resource(&pdev->dev, res);
 252         if (IS_ERR(info->data_reg))
 253                 return PTR_ERR(info->data_reg);
 254
 255         dev_set_drvdata(&pdev->dev, info);
 256
 257         if (!m48t86_verify_chip(pdev)) {
 258                 dev_info(&pdev->dev, "RTC not present\n");
 259                 return -ENODEV;
 260         }
 261
 262         info->rtc = devm_rtc_allocate_device(&pdev->dev);
 263         if (IS_ERR(info->rtc))
 264                 return PTR_ERR(info->rtc);
 265
 266         info->rtc->ops = &m48t86_rtc_ops;
 267         info->rtc->nvram_old_abi = true;
 268
 269         err = rtc_register_device(info->rtc);
 270         if (err)
 271                 return err;
 272
 273         rtc_nvmem_register(info->rtc, &m48t86_nvmem_cfg);
 274
 275         /* read battery status */
 276         reg = m48t86_readb(&pdev->dev, M48T86_D);
 277         dev_info(&pdev->dev, "battery %s\n",
 278                  (reg & M48T86_D_VRT) ? "ok" : "exhausted");
 279
 280         return 0;
 281 }
 282
 283 static struct platform_driver m48t86_rtc_platform_driver = {
 284         .driver         = {
 285                 .name   = "rtc-m48t86",
 286         },
 287         .probe          = m48t86_rtc_probe,
 288 };
 289
 290 module_platform_driver(m48t86_rtc_platform_driver);
 291
 292 MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
 293 MODULE_DESCRIPTION("M48T86 RTC driver");
 294 MODULE_LICENSE("GPL");
 295 MODULE_ALIAS("platform:rtc-m48t86");