drivers/rtc/rtc-pcf85063.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * An I2C driver for the PCF85063 RTC
   4  * Copyright 2014 Rose Technology
   5  *
   6  * Author: Søren Andersen <san@rosetechnology.dk>
   7  * Maintainers: http://www.nslu2-linux.org/
   8  */
   9 #include <linux/i2c.h>
  10 #include <linux/bcd.h>
  11 #include <linux/rtc.h>
  12 #include <linux/module.h>
  13
  14 /*
  15  * Information for this driver was pulled from the following datasheets.
  16  *
  17  *  http://www.nxp.com/documents/data_sheet/PCF85063A.pdf
  18  *  http://www.nxp.com/documents/data_sheet/PCF85063TP.pdf
  19  *
  20  *  PCF85063A -- Rev. 6 — 18 November 2015
  21  *  PCF85063TP -- Rev. 4 — 6 May 2015
  22 */
  23
  24 #define PCF85063_REG_CTRL1              0x00 /* status */
  25 #define PCF85063_REG_CTRL1_CAP_SEL      BIT(0)
  26 #define PCF85063_REG_CTRL1_STOP         BIT(5)
  27
  28 #define PCF85063_REG_SC                 0x04 /* datetime */
  29 #define PCF85063_REG_SC_OS              0x80
  30
  31 static struct i2c_driver pcf85063_driver;
  32
  33 static int pcf85063_stop_clock(struct i2c_client *client, u8 *ctrl1)
  34 {
  35         int rc;
  36         u8 reg;
  37
  38         rc = i2c_smbus_read_byte_data(client, PCF85063_REG_CTRL1);
  39         if (rc < 0) {
  40                 dev_err(&client->dev, "Failing to stop the clock\n");
  41                 return -EIO;
  42         }
  43
  44         /* stop the clock */
  45         reg = rc | PCF85063_REG_CTRL1_STOP;
  46
  47         rc = i2c_smbus_write_byte_data(client, PCF85063_REG_CTRL1, reg);
  48         if (rc < 0) {
  49                 dev_err(&client->dev, "Failing to stop the clock\n");
  50                 return -EIO;
  51         }
  52
  53         *ctrl1 = reg;
  54
  55         return 0;
  56 }
  57
  58 static int pcf85063_start_clock(struct i2c_client *client, u8 ctrl1)
  59 {
  60         int rc;
  61
  62         /* start the clock */
  63         ctrl1 &= ~PCF85063_REG_CTRL1_STOP;
  64
  65         rc = i2c_smbus_write_byte_data(client, PCF85063_REG_CTRL1, ctrl1);
  66         if (rc < 0) {
  67                 dev_err(&client->dev, "Failing to start the clock\n");
  68                 return -EIO;
  69         }
  70
  71         return 0;
  72 }
  73
  74 static int pcf85063_rtc_read_time(struct device *dev, struct rtc_time *tm)
  75 {
  76         struct i2c_client *client = to_i2c_client(dev);
  77         int rc;
  78         u8 regs[7];
  79
  80         /*
  81          * while reading, the time/date registers are blocked and not updated
  82          * anymore until the access is finished. To not lose a second
  83          * event, the access must be finished within one second. So, read all
  84          * time/date registers in one turn.
  85          */
  86         rc = i2c_smbus_read_i2c_block_data(client, PCF85063_REG_SC,
  87                                            sizeof(regs), regs);
  88         if (rc != sizeof(regs)) {
  89                 dev_err(&client->dev, "date/time register read error\n");
  90                 return -EIO;
  91         }
  92
  93         /* if the clock has lost its power it makes no sense to use its time */
  94         if (regs[0] & PCF85063_REG_SC_OS) {
  95                 dev_warn(&client->dev, "Power loss detected, invalid time\n");
  96                 return -EINVAL;
  97         }
  98
  99         tm->tm_sec = bcd2bin(regs[0] & 0x7F);
 100         tm->tm_min = bcd2bin(regs[1] & 0x7F);
 101         tm->tm_hour = bcd2bin(regs[2] & 0x3F); /* rtc hr 0-23 */
 102         tm->tm_mday = bcd2bin(regs[3] & 0x3F);
 103         tm->tm_wday = regs[4] & 0x07;
 104         tm->tm_mon = bcd2bin(regs[5] & 0x1F) - 1; /* rtc mn 1-12 */
 105         tm->tm_year = bcd2bin(regs[6]);
 106         tm->tm_year += 100;
 107
 108         return 0;
 109 }
 110
 111 static int pcf85063_rtc_set_time(struct device *dev, struct rtc_time *tm)
 112 {
 113         struct i2c_client *client = to_i2c_client(dev);
 114         int rc;
 115         u8 regs[7];
 116         u8 ctrl1;
 117
 118         if ((tm->tm_year < 100) || (tm->tm_year > 199))
 119                 return -EINVAL;
 120
 121         /*
 122          * to accurately set the time, reset the divider chain and keep it in
 123          * reset state until all time/date registers are written
 124          */
 125         rc = pcf85063_stop_clock(client, &ctrl1);
 126         if (rc != 0)
 127                 return rc;
 128
 129         /* hours, minutes and seconds */
 130         regs[0] = bin2bcd(tm->tm_sec) & 0x7F; /* clear OS flag */
 131
 132         regs[1] = bin2bcd(tm->tm_min);
 133         regs[2] = bin2bcd(tm->tm_hour);
 134
 135         /* Day of month, 1 - 31 */
 136         regs[3] = bin2bcd(tm->tm_mday);
 137
 138         /* Day, 0 - 6 */
 139         regs[4] = tm->tm_wday & 0x07;
 140
 141         /* month, 1 - 12 */
 142         regs[5] = bin2bcd(tm->tm_mon + 1);
 143
 144         /* year and century */
 145         regs[6] = bin2bcd(tm->tm_year - 100);
 146
 147         /* write all registers at once */
 148         rc = i2c_smbus_write_i2c_block_data(client, PCF85063_REG_SC,
 149                                             sizeof(regs), regs);
 150         if (rc < 0) {
 151                 dev_err(&client->dev, "date/time register write error\n");
 152                 return rc;
 153         }
 154
 155         /*
 156          * Write the control register as a separate action since the size of
 157          * the register space is different between the PCF85063TP and
 158          * PCF85063A devices.  The rollover point can not be used.
 159          */
 160         rc = pcf85063_start_clock(client, ctrl1);
 161         if (rc != 0)
 162                 return rc;
 163
 164         return 0;
 165 }
 166
 167 static const struct rtc_class_ops pcf85063_rtc_ops = {
 168         .read_time      = pcf85063_rtc_read_time,
 169         .set_time       = pcf85063_rtc_set_time
 170 };
 171
 172 static int pcf85063_load_capacitance(struct i2c_client *client)
 173 {
 174         u32 load;
 175         int rc;
 176         u8 reg;
 177
 178         rc = i2c_smbus_read_byte_data(client, PCF85063_REG_CTRL1);
 179         if (rc < 0)
 180                 return rc;
 181
 182         reg = rc;
 183         load = 7000;
 184         of_property_read_u32(client->dev.of_node, "quartz-load-femtofarads",
 185                              &load);
 186
 187         switch (load) {
 188         default:
 189                 dev_warn(&client->dev, "Unknown quartz-load-femtofarads value: %d. Assuming 7000",
 190                          load);
 191                 /* fall through */
 192         case 7000:
 193                 reg &= ~PCF85063_REG_CTRL1_CAP_SEL;
 194                 break;
 195         case 12500:
 196                 reg |= PCF85063_REG_CTRL1_CAP_SEL;
 197                 break;
 198         }
 199
 200         rc = i2c_smbus_write_byte_data(client, PCF85063_REG_CTRL1, reg);
 201
 202         return rc;
 203 }
 204
 205 static int pcf85063_probe(struct i2c_client *client)
 206 {
 207         struct rtc_device *rtc;
 208         int err;
 209
 210         dev_dbg(&client->dev, "%s\n", __func__);
 211
 212         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 213                 return -ENODEV;
 214
 215         err = i2c_smbus_read_byte_data(client, PCF85063_REG_CTRL1);
 216         if (err < 0) {
 217                 dev_err(&client->dev, "RTC chip is not present\n");
 218                 return err;
 219         }
 220
 221         err = pcf85063_load_capacitance(client);
 222         if (err < 0)
 223                 dev_warn(&client->dev, "failed to set xtal load capacitance: %d",
 224                          err);
 225
 226         rtc = devm_rtc_device_register(&client->dev,
 227                                        pcf85063_driver.driver.name,
 228                                        &pcf85063_rtc_ops, THIS_MODULE);
 229
 230         return PTR_ERR_OR_ZERO(rtc);
 231 }
 232
 233 #ifdef CONFIG_OF
 234 static const struct of_device_id pcf85063_of_match[] = {
 235         { .compatible = "nxp,pcf85063" },
 236         {}
 237 };
 238 MODULE_DEVICE_TABLE(of, pcf85063_of_match);
 239 #endif
 240
 241 static struct i2c_driver pcf85063_driver = {
 242         .driver         = {
 243                 .name   = "rtc-pcf85063",
 244                 .of_match_table = of_match_ptr(pcf85063_of_match),
 245         },
 246         .probe_new      = pcf85063_probe,
 247 };
 248
 249 module_i2c_driver(pcf85063_driver);
 250
 251 MODULE_AUTHOR("Søren Andersen <san@rosetechnology.dk>");
 252 MODULE_DESCRIPTION("PCF85063 RTC driver");
 253 MODULE_LICENSE("GPL");