drivers/rtc/rtc-m48t86.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * ST M48T86 / Dallas DS12887 RTC driver
   4  * Copyright (c) 2006 Tower Technologies
   5  *
   6  * Author: Alessandro Zummo <a.zummo@towertech.it>
   7  *
   8  * This drivers only supports the clock running in BCD and 24H mode.
   9  * If it will be ever adapted to binary and 12H mode, care must be taken
  10  * to not introduce bugs.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/mod_devicetable.h>
  15 #include <linux/rtc.h>
  16 #include <linux/platform_device.h>
  17 #include <linux/bcd.h>
  18 #include <linux/io.h>
  19
  20 #define M48T86_SEC              0x00
  21 #define M48T86_SECALRM          0x01
  22 #define M48T86_MIN              0x02
  23 #define M48T86_MINALRM          0x03
  24 #define M48T86_HOUR             0x04
  25 #define M48T86_HOURALRM         0x05
  26 #define M48T86_DOW              0x06 /* 1 = sunday */
  27 #define M48T86_DOM              0x07
  28 #define M48T86_MONTH            0x08 /* 1 - 12 */
  29 #define M48T86_YEAR             0x09 /* 0 - 99 */
  30 #define M48T86_A                0x0a
  31 #define M48T86_B                0x0b
  32 #define M48T86_B_SET            BIT(7)
  33 #define M48T86_B_DM             BIT(2)
  34 #define M48T86_B_H24            BIT(1)
  35 #define M48T86_C                0x0c
  36 #define M48T86_D                0x0d
  37 #define M48T86_D_VRT            BIT(7)
  38 #define M48T86_NVRAM(x)         (0x0e + (x))
  39 #define M48T86_NVRAM_LEN        114
  40
  41 struct m48t86_rtc_info {
  42         void __iomem *index_reg;
  43         void __iomem *data_reg;
  44         struct rtc_device *rtc;
  45 };
  46
  47 static unsigned char m48t86_readb(struct device *dev, unsigned long addr)
  48 {
  49         struct m48t86_rtc_info *info = dev_get_drvdata(dev);
  50         unsigned char value;
  51
  52         writeb(addr, info->index_reg);
  53         value = readb(info->data_reg);
  54
  55         return value;
  56 }
  57
  58 static void m48t86_writeb(struct device *dev,
  59                           unsigned char value, unsigned long addr)
  60 {
  61         struct m48t86_rtc_info *info = dev_get_drvdata(dev);
  62
  63         writeb(addr, info->index_reg);
  64         writeb(value, info->data_reg);
  65 }
  66
  67 static int m48t86_rtc_read_time(struct device *dev, struct rtc_time *tm)
  68 {
  69         unsigned char reg;
  70
  71         reg = m48t86_readb(dev, M48T86_B);
  72
  73         if (reg & M48T86_B_DM) {
  74                 /* data (binary) mode */
  75                 tm->tm_sec      = m48t86_readb(dev, M48T86_SEC);
  76                 tm->tm_min      = m48t86_readb(dev, M48T86_MIN);
  77                 tm->tm_hour     = m48t86_readb(dev, M48T86_HOUR) & 0x3f;
  78                 tm->tm_mday     = m48t86_readb(dev, M48T86_DOM);
  79                 /* tm_mon is 0-11 */
  80                 tm->tm_mon      = m48t86_readb(dev, M48T86_MONTH) - 1;
  81                 tm->tm_year     = m48t86_readb(dev, M48T86_YEAR) + 100;
  82                 tm->tm_wday     = m48t86_readb(dev, M48T86_DOW);
  83         } else {
  84                 /* bcd mode */
  85                 tm->tm_sec      = bcd2bin(m48t86_readb(dev, M48T86_SEC));
  86                 tm->tm_min      = bcd2bin(m48t86_readb(dev, M48T86_MIN));
  87                 tm->tm_hour     = bcd2bin(m48t86_readb(dev, M48T86_HOUR) &
  88                                           0x3f);
  89                 tm->tm_mday     = bcd2bin(m48t86_readb(dev, M48T86_DOM));
  90                 /* tm_mon is 0-11 */
  91                 tm->tm_mon      = bcd2bin(m48t86_readb(dev, M48T86_MONTH)) - 1;
  92                 tm->tm_year     = bcd2bin(m48t86_readb(dev, M48T86_YEAR)) + 100;
  93                 tm->tm_wday     = bcd2bin(m48t86_readb(dev, M48T86_DOW));
  94         }
  95
  96         /* correct the hour if the clock is in 12h mode */
  97         if (!(reg & M48T86_B_H24))
  98                 if (m48t86_readb(dev, M48T86_HOUR) & 0x80)
  99                         tm->tm_hour += 12;
 100
 101         return 0;
 102 }
 103
 104 static int m48t86_rtc_set_time(struct device *dev, struct rtc_time *tm)
 105 {
 106         unsigned char reg;
 107
 108         reg = m48t86_readb(dev, M48T86_B);
 109
 110         /* update flag and 24h mode */
 111         reg |= M48T86_B_SET | M48T86_B_H24;
 112         m48t86_writeb(dev, reg, M48T86_B);
 113
 114         if (reg & M48T86_B_DM) {
 115                 /* data (binary) mode */
 116                 m48t86_writeb(dev, tm->tm_sec, M48T86_SEC);
 117                 m48t86_writeb(dev, tm->tm_min, M48T86_MIN);
 118                 m48t86_writeb(dev, tm->tm_hour, M48T86_HOUR);
 119                 m48t86_writeb(dev, tm->tm_mday, M48T86_DOM);
 120                 m48t86_writeb(dev, tm->tm_mon + 1, M48T86_MONTH);
 121                 m48t86_writeb(dev, tm->tm_year % 100, M48T86_YEAR);
 122                 m48t86_writeb(dev, tm->tm_wday, M48T86_DOW);
 123         } else {
 124                 /* bcd mode */
 125                 m48t86_writeb(dev, bin2bcd(tm->tm_sec), M48T86_SEC);
 126                 m48t86_writeb(dev, bin2bcd(tm->tm_min), M48T86_MIN);
 127                 m48t86_writeb(dev, bin2bcd(tm->tm_hour), M48T86_HOUR);
 128                 m48t86_writeb(dev, bin2bcd(tm->tm_mday), M48T86_DOM);
 129                 m48t86_writeb(dev, bin2bcd(tm->tm_mon + 1), M48T86_MONTH);
 130                 m48t86_writeb(dev, bin2bcd(tm->tm_year % 100), M48T86_YEAR);
 131                 m48t86_writeb(dev, bin2bcd(tm->tm_wday), M48T86_DOW);
 132         }
 133
 134         /* update ended */
 135         reg &= ~M48T86_B_SET;
 136         m48t86_writeb(dev, reg, M48T86_B);
 137
 138         return 0;
 139 }
 140
 141 static int m48t86_rtc_proc(struct device *dev, struct seq_file *seq)
 142 {
 143         unsigned char reg;
 144
 145         reg = m48t86_readb(dev, M48T86_B);
 146
 147         seq_printf(seq, "mode\t\t: %s\n",
 148                    (reg & M48T86_B_DM) ? "binary" : "bcd");
 149
 150         reg = m48t86_readb(dev, M48T86_D);
 151
 152         seq_printf(seq, "battery\t\t: %s\n",
 153                    (reg & M48T86_D_VRT) ? "ok" : "exhausted");
 154
 155         return 0;
 156 }
 157
 158 static const struct rtc_class_ops m48t86_rtc_ops = {
 159         .read_time      = m48t86_rtc_read_time,
 160         .set_time       = m48t86_rtc_set_time,
 161         .proc           = m48t86_rtc_proc,
 162 };
 163
 164 static int m48t86_nvram_read(void *priv, unsigned int off, void *buf,
 165                              size_t count)
 166 {
 167         struct device *dev = priv;
 168         unsigned int i;
 169
 170         for (i = 0; i < count; i++)
 171                 ((u8 *)buf)[i] = m48t86_readb(dev, M48T86_NVRAM(off + i));
 172
 173         return 0;
 174 }
 175
 176 static int m48t86_nvram_write(void *priv, unsigned int off, void *buf,
 177                               size_t count)
 178 {
 179         struct device *dev = priv;
 180         unsigned int i;
 181
 182         for (i = 0; i < count; i++)
 183                 m48t86_writeb(dev, ((u8 *)buf)[i], M48T86_NVRAM(off + i));
 184
 185         return 0;
 186 }
 187
 188 /*
 189  * The RTC is an optional feature at purchase time on some Technologic Systems
 190  * boards. Verify that it actually exists by checking if the last two bytes
 191  * of the NVRAM can be changed.
 192  *
 193  * This is based on the method used in their rtc7800.c example.
 194  */
 195 static bool m48t86_verify_chip(struct platform_device *pdev)
 196 {
 197         unsigned int offset0 = M48T86_NVRAM(M48T86_NVRAM_LEN - 2);
 198         unsigned int offset1 = M48T86_NVRAM(M48T86_NVRAM_LEN - 1);
 199         unsigned char tmp0, tmp1;
 200
 201         tmp0 = m48t86_readb(&pdev->dev, offset0);
 202         tmp1 = m48t86_readb(&pdev->dev, offset1);
 203
 204         m48t86_writeb(&pdev->dev, 0x00, offset0);
 205         m48t86_writeb(&pdev->dev, 0x55, offset1);
 206         if (m48t86_readb(&pdev->dev, offset1) == 0x55) {
 207                 m48t86_writeb(&pdev->dev, 0xaa, offset1);
 208                 if (m48t86_readb(&pdev->dev, offset1) == 0xaa &&
 209                     m48t86_readb(&pdev->dev, offset0) == 0x00) {
 210                         m48t86_writeb(&pdev->dev, tmp0, offset0);
 211                         m48t86_writeb(&pdev->dev, tmp1, offset1);
 212
 213                         return true;
 214                 }
 215         }
 216         return false;
 217 }
 218
 219 static int m48t86_rtc_probe(struct platform_device *pdev)
 220 {
 221         struct m48t86_rtc_info *info;
 222         unsigned char reg;
 223         int err;
 224         struct nvmem_config m48t86_nvmem_cfg = {
 225                 .name = "m48t86_nvram",
 226                 .word_size = 1,
 227                 .stride = 1,
 228                 .size = M48T86_NVRAM_LEN,
 229                 .reg_read = m48t86_nvram_read,
 230                 .reg_write = m48t86_nvram_write,
 231                 .priv = &pdev->dev,
 232         };
 233
 234         info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
 235         if (!info)
 236                 return -ENOMEM;
 237
 238         info->index_reg = devm_platform_ioremap_resource(pdev, 0);
 239         if (IS_ERR(info->index_reg))
 240                 return PTR_ERR(info->index_reg);
 241
 242         info->data_reg = devm_platform_ioremap_resource(pdev, 1);
 243         if (IS_ERR(info->data_reg))
 244                 return PTR_ERR(info->data_reg);
 245
 246         dev_set_drvdata(&pdev->dev, info);
 247
 248         if (!m48t86_verify_chip(pdev)) {
 249                 dev_info(&pdev->dev, "RTC not present\n");
 250                 return -ENODEV;
 251         }
 252
 253         info->rtc = devm_rtc_allocate_device(&pdev->dev);
 254         if (IS_ERR(info->rtc))
 255                 return PTR_ERR(info->rtc);
 256
 257         info->rtc->ops = &m48t86_rtc_ops;
 258
 259         err = devm_rtc_register_device(info->rtc);
 260         if (err)
 261                 return err;
 262
 263         devm_rtc_nvmem_register(info->rtc, &m48t86_nvmem_cfg);
 264
 265         /* read battery status */
 266         reg = m48t86_readb(&pdev->dev, M48T86_D);
 267         dev_info(&pdev->dev, "battery %s\n",
 268                  (reg & M48T86_D_VRT) ? "ok" : "exhausted");
 269
 270         return 0;
 271 }
 272
 273 static const struct of_device_id m48t86_rtc_of_ids[] = {
 274         { .compatible = "st,m48t86" },
 275         { /* sentinel */ }
 276 };
 277 MODULE_DEVICE_TABLE(of, m48t86_rtc_of_ids);
 278
 279 static struct platform_driver m48t86_rtc_platform_driver = {
 280         .driver         = {
 281                 .name   = "rtc-m48t86",
 282                 .of_match_table = m48t86_rtc_of_ids,
 283         },
 284         .probe          = m48t86_rtc_probe,
 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");