drivers/rtc/rtc-bq32k.c

   1 /*
   2  * Driver for TI BQ32000 RTC.
   3  *
   4  * Copyright (C) 2009 Semihalf.
   5  * Copyright (C) 2014 Pavel Machek <pavel@denx.de>
   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  * You can get hardware description at
  12  * http://www.ti.com/lit/ds/symlink/bq32000.pdf
  13  */
  14
  15 #include <linux/module.h>
  16 #include <linux/i2c.h>
  17 #include <linux/rtc.h>
  18 #include <linux/init.h>
  19 #include <linux/errno.h>
  20 #include <linux/bcd.h>
  21
  22 #define BQ32K_SECONDS           0x00    /* Seconds register address */
  23 #define BQ32K_SECONDS_MASK      0x7F    /* Mask over seconds value */
  24 #define BQ32K_STOP              0x80    /* Oscillator Stop flat */
  25
  26 #define BQ32K_MINUTES           0x01    /* Minutes register address */
  27 #define BQ32K_MINUTES_MASK      0x7F    /* Mask over minutes value */
  28 #define BQ32K_OF                0x80    /* Oscillator Failure flag */
  29
  30 #define BQ32K_HOURS_MASK        0x3F    /* Mask over hours value */
  31 #define BQ32K_CENT              0x40    /* Century flag */
  32 #define BQ32K_CENT_EN           0x80    /* Century flag enable bit */
  33
  34 #define BQ32K_CALIBRATION       0x07    /* CAL_CFG1, calibration and control */
  35 #define BQ32K_TCH2              0x08    /* Trickle charge enable */
  36 #define BQ32K_CFG2              0x09    /* Trickle charger control */
  37
  38 struct bq32k_regs {
  39         uint8_t         seconds;
  40         uint8_t         minutes;
  41         uint8_t         cent_hours;
  42         uint8_t         day;
  43         uint8_t         date;
  44         uint8_t         month;
  45         uint8_t         years;
  46 };
  47
  48 static struct i2c_driver bq32k_driver;
  49
  50 static int bq32k_read(struct device *dev, void *data, uint8_t off, uint8_t len)
  51 {
  52         struct i2c_client *client = to_i2c_client(dev);
  53         struct i2c_msg msgs[] = {
  54                 {
  55                         .addr = client->addr,
  56                         .flags = 0,
  57                         .len = 1,
  58                         .buf = &off,
  59                 }, {
  60                         .addr = client->addr,
  61                         .flags = I2C_M_RD,
  62                         .len = len,
  63                         .buf = data,
  64                 }
  65         };
  66
  67         if (i2c_transfer(client->adapter, msgs, 2) == 2)
  68                 return 0;
  69
  70         return -EIO;
  71 }
  72
  73 static int bq32k_write(struct device *dev, void *data, uint8_t off, uint8_t len)
  74 {
  75         struct i2c_client *client = to_i2c_client(dev);
  76         uint8_t buffer[len + 1];
  77
  78         buffer[0] = off;
  79         memcpy(&buffer[1], data, len);
  80
  81         if (i2c_master_send(client, buffer, len + 1) == len + 1)
  82                 return 0;
  83
  84         return -EIO;
  85 }
  86
  87 static int bq32k_rtc_read_time(struct device *dev, struct rtc_time *tm)
  88 {
  89         struct bq32k_regs regs;
  90         int error;
  91
  92         error = bq32k_read(dev, &regs, 0, sizeof(regs));
  93         if (error)
  94                 return error;
  95
  96         /*
  97          * In case of oscillator failure, the register contents should be
  98          * considered invalid. The flag is cleared the next time the RTC is set.
  99          */
 100         if (regs.minutes & BQ32K_OF)
 101                 return -EINVAL;
 102
 103         tm->tm_sec = bcd2bin(regs.seconds & BQ32K_SECONDS_MASK);
 104         tm->tm_min = bcd2bin(regs.minutes & BQ32K_MINUTES_MASK);
 105         tm->tm_hour = bcd2bin(regs.cent_hours & BQ32K_HOURS_MASK);
 106         tm->tm_mday = bcd2bin(regs.date);
 107         tm->tm_wday = bcd2bin(regs.day) - 1;
 108         tm->tm_mon = bcd2bin(regs.month) - 1;
 109         tm->tm_year = bcd2bin(regs.years) +
 110                                 ((regs.cent_hours & BQ32K_CENT) ? 100 : 0);
 111
 112         return rtc_valid_tm(tm);
 113 }
 114
 115 static int bq32k_rtc_set_time(struct device *dev, struct rtc_time *tm)
 116 {
 117         struct bq32k_regs regs;
 118
 119         regs.seconds = bin2bcd(tm->tm_sec);
 120         regs.minutes = bin2bcd(tm->tm_min);
 121         regs.cent_hours = bin2bcd(tm->tm_hour) | BQ32K_CENT_EN;
 122         regs.day = bin2bcd(tm->tm_wday + 1);
 123         regs.date = bin2bcd(tm->tm_mday);
 124         regs.month = bin2bcd(tm->tm_mon + 1);
 125
 126         if (tm->tm_year >= 100) {
 127                 regs.cent_hours |= BQ32K_CENT;
 128                 regs.years = bin2bcd(tm->tm_year - 100);
 129         } else
 130                 regs.years = bin2bcd(tm->tm_year);
 131
 132         return bq32k_write(dev, &regs, 0, sizeof(regs));
 133 }
 134
 135 static const struct rtc_class_ops bq32k_rtc_ops = {
 136         .read_time      = bq32k_rtc_read_time,
 137         .set_time       = bq32k_rtc_set_time,
 138 };
 139
 140 static int trickle_charger_of_init(struct device *dev, struct device_node *node)
 141 {
 142         unsigned char reg;
 143         int error;
 144         u32 ohms = 0;
 145
 146         if (of_property_read_u32(node, "trickle-resistor-ohms" , &ohms))
 147                 return 0;
 148
 149         switch (ohms) {
 150         case 180+940:
 151                 /*
 152                  * TCHE[3:0] == 0x05, TCH2 == 1, TCFE == 0 (charging
 153                  * over diode and 940ohm resistor)
 154                  */
 155
 156                 if (of_property_read_bool(node, "trickle-diode-disable")) {
 157                         dev_err(dev, "diode and resistor mismatch\n");
 158                         return -EINVAL;
 159                 }
 160                 reg = 0x05;
 161                 break;
 162
 163         case 180+20000:
 164                 /* diode disabled */
 165
 166                 if (!of_property_read_bool(node, "trickle-diode-disable")) {
 167                         dev_err(dev, "bq32k: diode and resistor mismatch\n");
 168                         return -EINVAL;
 169                 }
 170                 reg = 0x45;
 171                 break;
 172
 173         default:
 174                 dev_err(dev, "invalid resistor value (%d)\n", ohms);
 175                 return -EINVAL;
 176         }
 177
 178         error = bq32k_write(dev, &reg, BQ32K_CFG2, 1);
 179         if (error)
 180                 return error;
 181
 182         reg = 0x20;
 183         error = bq32k_write(dev, &reg, BQ32K_TCH2, 1);
 184         if (error)
 185                 return error;
 186
 187         dev_info(dev, "Enabled trickle RTC battery charge.\n");
 188         return 0;
 189 }
 190
 191 static int bq32k_probe(struct i2c_client *client,
 192                                 const struct i2c_device_id *id)
 193 {
 194         struct device *dev = &client->dev;
 195         struct rtc_device *rtc;
 196         uint8_t reg;
 197         int error;
 198
 199         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 200                 return -ENODEV;
 201
 202         /* Check Oscillator Stop flag */
 203         error = bq32k_read(dev, &reg, BQ32K_SECONDS, 1);
 204         if (!error && (reg & BQ32K_STOP)) {
 205                 dev_warn(dev, "Oscillator was halted. Restarting...\n");
 206                 reg &= ~BQ32K_STOP;
 207                 error = bq32k_write(dev, &reg, BQ32K_SECONDS, 1);
 208         }
 209         if (error)
 210                 return error;
 211
 212         /* Check Oscillator Failure flag */
 213         error = bq32k_read(dev, &reg, BQ32K_MINUTES, 1);
 214         if (error)
 215                 return error;
 216         if (reg & BQ32K_OF)
 217                 dev_warn(dev, "Oscillator Failure. Check RTC battery.\n");
 218
 219         if (client->dev.of_node)
 220                 trickle_charger_of_init(dev, client->dev.of_node);
 221
 222         rtc = devm_rtc_device_register(&client->dev, bq32k_driver.driver.name,
 223                                                 &bq32k_rtc_ops, THIS_MODULE);
 224         if (IS_ERR(rtc))
 225                 return PTR_ERR(rtc);
 226
 227         i2c_set_clientdata(client, rtc);
 228
 229         return 0;
 230 }
 231
 232 static const struct i2c_device_id bq32k_id[] = {
 233         { "bq32000", 0 },
 234         { }
 235 };
 236 MODULE_DEVICE_TABLE(i2c, bq32k_id);
 237
 238 static struct i2c_driver bq32k_driver = {
 239         .driver = {
 240                 .name   = "bq32k",
 241         },
 242         .probe          = bq32k_probe,
 243         .id_table       = bq32k_id,
 244 };
 245
 246 module_i2c_driver(bq32k_driver);
 247
 248 MODULE_AUTHOR("Semihalf, Piotr Ziecik <kosmo@semihalf.com>");
 249 MODULE_DESCRIPTION("TI BQ32000 I2C RTC driver");
 250 MODULE_LICENSE("GPL");