drivers/mfd/ntxec.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * The Netronix embedded controller is a microcontroller found in some
   4  * e-book readers designed by the original design manufacturer Netronix, Inc.
   5  * It contains RTC, battery monitoring, system power management, and PWM
   6  * functionality.
   7  *
   8  * This driver implements register access, version detection, and system
   9  * power-off/reset.
  10  *
  11  * Copyright 2020 Jonathan Neuschäfer <j.neuschaefer@gmx.net>
  12  */
  13
  14 #include <linux/delay.h>
  15 #include <linux/errno.h>
  16 #include <linux/i2c.h>
  17 #include <linux/mfd/core.h>
  18 #include <linux/mfd/ntxec.h>
  19 #include <linux/module.h>
  20 #include <linux/pm.h>
  21 #include <linux/reboot.h>
  22 #include <linux/regmap.h>
  23 #include <linux/types.h>
  24 #include <linux/unaligned.h>
  25
  26 #define NTXEC_REG_VERSION       0x00
  27 #define NTXEC_REG_POWEROFF      0x50
  28 #define NTXEC_REG_POWERKEEP     0x70
  29 #define NTXEC_REG_RESET         0x90
  30
  31 #define NTXEC_POWEROFF_VALUE    0x0100
  32 #define NTXEC_POWERKEEP_VALUE   0x0800
  33 #define NTXEC_RESET_VALUE       0xff00
  34
  35 static struct i2c_client *poweroff_restart_client;
  36
  37 static void ntxec_poweroff(void)
  38 {
  39         int res;
  40         u8 buf[3] = { NTXEC_REG_POWEROFF };
  41         struct i2c_msg msgs[] = {
  42                 {
  43                         .addr = poweroff_restart_client->addr,
  44                         .flags = 0,
  45                         .len = sizeof(buf),
  46                         .buf = buf,
  47                 },
  48         };
  49
  50         put_unaligned_be16(NTXEC_POWEROFF_VALUE, buf + 1);
  51
  52         res = i2c_transfer(poweroff_restart_client->adapter, msgs, ARRAY_SIZE(msgs));
  53         if (res < 0)
  54                 dev_warn(&poweroff_restart_client->dev,
  55                          "Failed to power off (err = %d)\n", res);
  56
  57         /*
  58          * The time from the register write until the host CPU is powered off
  59          * has been observed to be about 2.5 to 3 seconds. Sleep long enough to
  60          * safely avoid returning from the poweroff handler.
  61          */
  62         msleep(5000);
  63 }
  64
  65 static int ntxec_restart(struct notifier_block *nb,
  66                          unsigned long action, void *data)
  67 {
  68         int res;
  69         u8 buf[3] = { NTXEC_REG_RESET };
  70         /*
  71          * NOTE: The lower half of the reset value is not sent, because sending
  72          * it causes an I2C error. (The reset handler in the downstream driver
  73          * does send the full two-byte value, but doesn't check the result).
  74          */
  75         struct i2c_msg msgs[] = {
  76                 {
  77                         .addr = poweroff_restart_client->addr,
  78                         .flags = 0,
  79                         .len = sizeof(buf) - 1,
  80                         .buf = buf,
  81                 },
  82         };
  83
  84         put_unaligned_be16(NTXEC_RESET_VALUE, buf + 1);
  85
  86         res = i2c_transfer(poweroff_restart_client->adapter, msgs, ARRAY_SIZE(msgs));
  87         if (res < 0)
  88                 dev_warn(&poweroff_restart_client->dev,
  89                          "Failed to restart (err = %d)\n", res);
  90
  91         return NOTIFY_DONE;
  92 }
  93
  94 static struct notifier_block ntxec_restart_handler = {
  95         .notifier_call = ntxec_restart,
  96         .priority = 128,
  97 };
  98
  99 static int regmap_ignore_write(void *context,
 100                                unsigned int reg, unsigned int val)
 101
 102 {
 103         struct regmap *regmap = context;
 104
 105         regmap_write(regmap, reg, val);
 106
 107         return 0;
 108 }
 109
 110 static int regmap_wrap_read(void *context, unsigned int reg,
 111                             unsigned int *val)
 112 {
 113         struct regmap *regmap = context;
 114
 115         return regmap_read(regmap, reg, val);
 116 }
 117
 118 /*
 119  * Some firmware versions do not ack written data, add a wrapper. It
 120  * is used to stack another regmap on top.
 121  */
 122 static const struct regmap_config regmap_config_noack = {
 123         .name = "ntxec_noack",
 124         .reg_bits = 8,
 125         .val_bits = 16,
 126         .cache_type = REGCACHE_NONE,
 127         .reg_write = regmap_ignore_write,
 128         .reg_read = regmap_wrap_read
 129 };
 130
 131 static const struct regmap_config regmap_config = {
 132         .name = "ntxec",
 133         .reg_bits = 8,
 134         .val_bits = 16,
 135         .cache_type = REGCACHE_NONE,
 136         .val_format_endian = REGMAP_ENDIAN_BIG,
 137 };
 138
 139 static const struct mfd_cell ntxec_subdev[] = {
 140         { .name = "ntxec-rtc" },
 141         { .name = "ntxec-pwm" },
 142 };
 143
 144 static const struct mfd_cell ntxec_subdev_pwm[] = {
 145         { .name = "ntxec-pwm" },
 146 };
 147
 148 static int ntxec_probe(struct i2c_client *client)
 149 {
 150         struct ntxec *ec;
 151         unsigned int version;
 152         int res;
 153         const struct mfd_cell *subdevs;
 154         size_t n_subdevs;
 155
 156         ec = devm_kmalloc(&client->dev, sizeof(*ec), GFP_KERNEL);
 157         if (!ec)
 158                 return -ENOMEM;
 159
 160         ec->dev = &client->dev;
 161
 162         ec->regmap = devm_regmap_init_i2c(client, &regmap_config);
 163         if (IS_ERR(ec->regmap)) {
 164                 dev_err(ec->dev, "Failed to set up regmap for device\n");
 165                 return PTR_ERR(ec->regmap);
 166         }
 167
 168         /* Determine the firmware version */
 169         res = regmap_read(ec->regmap, NTXEC_REG_VERSION, &version);
 170         if (res < 0) {
 171                 dev_err(ec->dev, "Failed to read firmware version number\n");
 172                 return res;
 173         }
 174
 175         /* Bail out if we encounter an unknown firmware version */
 176         switch (version) {
 177         case NTXEC_VERSION_KOBO_AURA:
 178         case NTXEC_VERSION_TOLINO_VISION:
 179                 subdevs = ntxec_subdev;
 180                 n_subdevs = ARRAY_SIZE(ntxec_subdev);
 181                 break;
 182         case NTXEC_VERSION_TOLINO_SHINE2:
 183                 subdevs = ntxec_subdev_pwm;
 184                 n_subdevs = ARRAY_SIZE(ntxec_subdev_pwm);
 185                 /* Another regmap stacked on top of the other */
 186                 ec->regmap = devm_regmap_init(ec->dev, NULL,
 187                                               ec->regmap,
 188                                               &regmap_config_noack);
 189                 if (IS_ERR(ec->regmap))
 190                         return PTR_ERR(ec->regmap);
 191                 break;
 192         default:
 193                 dev_err(ec->dev,
 194                         "Netronix embedded controller version %04x is not supported.\n",
 195                         version);
 196                 return -ENODEV;
 197         }
 198
 199         dev_info(ec->dev,
 200                  "Netronix embedded controller version %04x detected.\n", version);
 201
 202         if (of_device_is_system_power_controller(ec->dev->of_node)) {
 203                 /*
 204                  * Set the 'powerkeep' bit. This is necessary on some boards
 205                  * in order to keep the system running.
 206                  */
 207                 res = regmap_write(ec->regmap, NTXEC_REG_POWERKEEP,
 208                                    NTXEC_POWERKEEP_VALUE);
 209                 if (res < 0)
 210                         return res;
 211
 212                 if (poweroff_restart_client)
 213                         /*
 214                          * Another instance of the driver already took
 215                          * poweroff/restart duties.
 216                          */
 217                         dev_err(ec->dev, "poweroff_restart_client already assigned\n");
 218                 else
 219                         poweroff_restart_client = client;
 220
 221                 if (pm_power_off)
 222                         /* Another driver already registered a poweroff handler. */
 223                         dev_err(ec->dev, "pm_power_off already assigned\n");
 224                 else
 225                         pm_power_off = ntxec_poweroff;
 226
 227                 res = register_restart_handler(&ntxec_restart_handler);
 228                 if (res)
 229                         dev_err(ec->dev,
 230                                 "Failed to register restart handler: %d\n", res);
 231         }
 232
 233         i2c_set_clientdata(client, ec);
 234
 235         res = devm_mfd_add_devices(ec->dev, PLATFORM_DEVID_NONE,
 236                                    subdevs, n_subdevs, NULL, 0, NULL);
 237         if (res)
 238                 dev_err(ec->dev, "Failed to add subdevices: %d\n", res);
 239
 240         return res;
 241 }
 242
 243 static void ntxec_remove(struct i2c_client *client)
 244 {
 245         if (client == poweroff_restart_client) {
 246                 poweroff_restart_client = NULL;
 247                 pm_power_off = NULL;
 248                 unregister_restart_handler(&ntxec_restart_handler);
 249         }
 250 }
 251
 252 static const struct of_device_id of_ntxec_match_table[] = {
 253         { .compatible = "netronix,ntxec", },
 254         {}
 255 };
 256 MODULE_DEVICE_TABLE(of, of_ntxec_match_table);
 257
 258 static struct i2c_driver ntxec_driver = {
 259         .driver = {
 260                 .name = "ntxec",
 261                 .of_match_table = of_ntxec_match_table,
 262         },
 263         .probe = ntxec_probe,
 264         .remove = ntxec_remove,
 265 };
 266 module_i2c_driver(ntxec_driver);
 267
 268 MODULE_AUTHOR("Jonathan Neuschäfer <j.neuschaefer@gmx.net>");
 269 MODULE_DESCRIPTION("Core driver for Netronix EC");
 270 MODULE_LICENSE("GPL");