drivers/i2c/busses/i2c-cgbc.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Congatec Board Controller I2C busses driver
   4  *
   5  * Copyright (C) 2024 Bootlin
   6  * Author: Thomas Richard <thomas.richard@bootlin.com>
   7  */
   8
   9 #include <linux/i2c.h>
  10 #include <linux/iopoll.h>
  11 #include <linux/mfd/cgbc.h>
  12 #include <linux/module.h>
  13 #include <linux/platform_device.h>
  14
  15 #define CGBC_I2C_PRIMARY_BUS_ID 0
  16 #define CGBC_I2C_PM_BUS_ID      4
  17
  18 #define CGBC_I2C_CMD_START      0x40
  19 #define CGBC_I2C_CMD_STAT       0x48
  20 #define CGBC_I2C_CMD_DATA       0x50
  21 #define CGBC_I2C_CMD_SPEED      0x58
  22
  23 #define CGBC_I2C_STAT_IDL       0x00
  24 #define CGBC_I2C_STAT_DAT       0x01
  25 #define CGBC_I2C_STAT_BUSY      0x02
  26
  27 #define CGBC_I2C_START  0x80
  28 #define CGBC_I2C_STOP   0x40
  29
  30 #define CGBC_I2C_LAST_ACK  0x80    /* send ACK on last read byte */
  31
  32 /*
  33  * Reference code defines 1kHz as min freq and 6.1MHz as max freq.
  34  * But in practice, the board controller limits the frequency to 1MHz, and the
  35  * 1kHz is not functional (minimal working freq is 50kHz).
  36  * So use these values as limits.
  37  */
  38 #define CGBC_I2C_FREQ_MIN_HZ    50000   /* 50 kHz */
  39 #define CGBC_I2C_FREQ_MAX_HZ    1000000 /* 1 MHz */
  40
  41 #define CGBC_I2C_FREQ_UNIT_1KHZ         0x40
  42 #define CGBC_I2C_FREQ_UNIT_10KHZ        0x80
  43 #define CGBC_I2C_FREQ_UNIT_100KHZ       0xC0
  44
  45 #define CGBC_I2C_FREQ_UNIT_MASK         0xC0
  46 #define CGBC_I2C_FREQ_VALUE_MASK        0x3F
  47
  48 #define CGBC_I2C_READ_MAX_LEN   31
  49 #define CGBC_I2C_WRITE_MAX_LEN  32
  50
  51 #define CGBC_I2C_CMD_HEADER_SIZE        4
  52 #define CGBC_I2C_CMD_SIZE               (CGBC_I2C_CMD_HEADER_SIZE + CGBC_I2C_WRITE_MAX_LEN)
  53
  54 enum cgbc_i2c_state {
  55         CGBC_I2C_STATE_DONE = 0,
  56         CGBC_I2C_STATE_INIT,
  57         CGBC_I2C_STATE_START,
  58         CGBC_I2C_STATE_READ,
  59         CGBC_I2C_STATE_WRITE,
  60         CGBC_I2C_STATE_ERROR,
  61 };
  62
  63 struct i2c_algo_cgbc_data {
  64         u8              bus_id;
  65         unsigned long   read_maxtime_us;
  66 };
  67
  68 struct cgbc_i2c_data {
  69         struct device           *dev;
  70         struct cgbc_device_data *cgbc;
  71         struct i2c_adapter      adap;
  72         struct i2c_msg          *msg;
  73         int                     nmsgs;
  74         int                     pos;
  75         enum cgbc_i2c_state     state;
  76 };
  77
  78 struct cgbc_i2c_transfer {
  79         u8 bus_id;
  80         bool start;
  81         bool stop;
  82         bool last_ack;
  83         u8 read;
  84         u8 write;
  85         u8 addr;
  86         u8 data[CGBC_I2C_WRITE_MAX_LEN];
  87 };
  88
  89 static u8 cgbc_i2c_freq_to_reg(unsigned int bus_frequency)
  90 {
  91         u8 reg;
  92
  93         if (bus_frequency <= 10000)
  94                 reg = CGBC_I2C_FREQ_UNIT_1KHZ | (bus_frequency / 1000);
  95         else if (bus_frequency <= 100000)
  96                 reg = CGBC_I2C_FREQ_UNIT_10KHZ | (bus_frequency / 10000);
  97         else
  98                 reg = CGBC_I2C_FREQ_UNIT_100KHZ | (bus_frequency / 100000);
  99
 100         return reg;
 101 }
 102
 103 static unsigned int cgbc_i2c_reg_to_freq(u8 reg)
 104 {
 105         unsigned int freq = reg & CGBC_I2C_FREQ_VALUE_MASK;
 106         u8 unit = reg & CGBC_I2C_FREQ_UNIT_MASK;
 107
 108         if (unit == CGBC_I2C_FREQ_UNIT_100KHZ)
 109                 return freq * 100000;
 110         else if (unit == CGBC_I2C_FREQ_UNIT_10KHZ)
 111                 return freq * 10000;
 112         else
 113                 return freq * 1000;
 114 }
 115
 116 static int cgbc_i2c_get_status(struct i2c_adapter *adap)
 117 {
 118         struct i2c_algo_cgbc_data *algo_data = adap->algo_data;
 119         struct cgbc_i2c_data *i2c = i2c_get_adapdata(adap);
 120         struct cgbc_device_data *cgbc = i2c->cgbc;
 121         u8 cmd = CGBC_I2C_CMD_STAT | algo_data->bus_id;
 122         u8 status;
 123         int ret;
 124
 125         ret = cgbc_command(cgbc, &cmd, sizeof(cmd), NULL, 0, &status);
 126         if (ret)
 127                 return ret;
 128
 129         return status;
 130 }
 131
 132 static int cgbc_i2c_set_frequency(struct i2c_adapter *adap,
 133                                   unsigned int bus_frequency)
 134 {
 135         struct i2c_algo_cgbc_data *algo_data = adap->algo_data;
 136         struct cgbc_i2c_data *i2c = i2c_get_adapdata(adap);
 137         struct cgbc_device_data *cgbc = i2c->cgbc;
 138         u8 cmd[2], data;
 139         int ret;
 140
 141         if (bus_frequency > CGBC_I2C_FREQ_MAX_HZ ||
 142             bus_frequency < CGBC_I2C_FREQ_MIN_HZ) {
 143                 dev_info(i2c->dev, "invalid frequency %u, using default\n", bus_frequency);
 144                 bus_frequency = I2C_MAX_STANDARD_MODE_FREQ;
 145         }
 146
 147         cmd[0] = CGBC_I2C_CMD_SPEED | algo_data->bus_id;
 148         cmd[1] = cgbc_i2c_freq_to_reg(bus_frequency);
 149
 150         ret = cgbc_command(cgbc, &cmd, sizeof(cmd), &data, 1, NULL);
 151         if (ret)
 152                 return dev_err_probe(i2c->dev, ret,
 153                                      "Failed to initialize I2C bus %s",
 154                                      adap->name);
 155
 156         cmd[1] = 0x00;
 157
 158         ret = cgbc_command(cgbc, &cmd, sizeof(cmd), &data, 1, NULL);
 159         if (ret)
 160                 return dev_err_probe(i2c->dev, ret,
 161                                      "Failed to get I2C bus frequency");
 162
 163         bus_frequency = cgbc_i2c_reg_to_freq(data);
 164
 165         dev_dbg(i2c->dev, "%s is running at %d Hz\n", adap->name, bus_frequency);
 166
 167         /*
 168          * The read_maxtime_us variable represents the maximum time to wait
 169          * for data during a read operation. The maximum amount of data that
 170          * can be read by a command is CGBC_I2C_READ_MAX_LEN.
 171          * Therefore, calculate the max time to properly size the timeout.
 172          */
 173         algo_data->read_maxtime_us = (BITS_PER_BYTE + 1) * CGBC_I2C_READ_MAX_LEN
 174                 * USEC_PER_SEC / bus_frequency;
 175
 176         return 0;
 177 }
 178
 179 static unsigned int cgbc_i2c_xfer_to_cmd(struct cgbc_i2c_transfer xfer, u8 *cmd)
 180 {
 181         int i = 0;
 182
 183         cmd[i++] = CGBC_I2C_CMD_START | xfer.bus_id;
 184
 185         cmd[i] = (xfer.start) ? CGBC_I2C_START : 0x00;
 186         if (xfer.stop)
 187                 cmd[i] |= CGBC_I2C_STOP;
 188         cmd[i++] |= (xfer.start) ? xfer.write + 1 : xfer.write;
 189
 190         cmd[i++] = (xfer.last_ack) ? (xfer.read | CGBC_I2C_LAST_ACK) : xfer.read;
 191
 192         if (xfer.start)
 193                 cmd[i++] = xfer.addr;
 194
 195         if (xfer.write > 0)
 196                 memcpy(&cmd[i], &xfer.data, xfer.write);
 197
 198         return i + xfer.write;
 199 }
 200
 201 static int cgbc_i2c_xfer_msg(struct i2c_adapter *adap)
 202 {
 203         struct i2c_algo_cgbc_data *algo_data = adap->algo_data;
 204         struct cgbc_i2c_data *i2c = i2c_get_adapdata(adap);
 205         struct cgbc_device_data *cgbc = i2c->cgbc;
 206         struct i2c_msg *msg = i2c->msg;
 207         u8 cmd[CGBC_I2C_CMD_SIZE];
 208         int ret, max_len, len, i;
 209         unsigned int cmd_len;
 210         u8 cmd_data;
 211
 212         struct cgbc_i2c_transfer xfer = {
 213                 .bus_id = algo_data->bus_id,
 214                 .addr = i2c_8bit_addr_from_msg(msg),
 215         };
 216
 217         if (i2c->state == CGBC_I2C_STATE_DONE)
 218                 return 0;
 219
 220         ret = cgbc_i2c_get_status(adap);
 221
 222         if (ret == CGBC_I2C_STAT_BUSY)
 223                 return -EBUSY;
 224         else if (ret < 0)
 225                 goto err;
 226
 227         if (i2c->state == CGBC_I2C_STATE_INIT ||
 228             (i2c->state == CGBC_I2C_STATE_WRITE && msg->flags & I2C_M_RD))
 229                 xfer.start = true;
 230
 231         i2c->state = (msg->flags & I2C_M_RD) ? CGBC_I2C_STATE_READ : CGBC_I2C_STATE_WRITE;
 232
 233         max_len = (i2c->state == CGBC_I2C_STATE_READ) ?
 234                 CGBC_I2C_READ_MAX_LEN : CGBC_I2C_WRITE_MAX_LEN;
 235
 236         if (msg->len - i2c->pos > max_len) {
 237                 len = max_len;
 238         } else {
 239                 len = msg->len - i2c->pos;
 240
 241                 if (i2c->nmsgs == 1)
 242                         xfer.stop = true;
 243         }
 244
 245         if (i2c->state == CGBC_I2C_STATE_WRITE) {
 246                 xfer.write = len;
 247                 xfer.read = 0;
 248
 249                 for (i = 0; i < len; i++)
 250                         xfer.data[i] = msg->buf[i2c->pos + i];
 251
 252                 cmd_len = cgbc_i2c_xfer_to_cmd(xfer, &cmd[0]);
 253
 254                 ret = cgbc_command(cgbc, &cmd, cmd_len, NULL, 0, NULL);
 255                 if (ret)
 256                         goto err;
 257         } else if (i2c->state == CGBC_I2C_STATE_READ) {
 258                 xfer.write = 0;
 259                 xfer.read = len;
 260
 261                 if (i2c->nmsgs > 1 || msg->len - i2c->pos > max_len)
 262                         xfer.read |= CGBC_I2C_LAST_ACK;
 263
 264                 cmd_len = cgbc_i2c_xfer_to_cmd(xfer, &cmd[0]);
 265                 ret = cgbc_command(cgbc, &cmd, cmd_len, NULL, 0, NULL);
 266                 if (ret)
 267                         goto err;
 268
 269                 ret = read_poll_timeout(cgbc_i2c_get_status, ret,
 270                                         ret != CGBC_I2C_STAT_BUSY, 0,
 271                                         2 * algo_data->read_maxtime_us, false, adap);
 272                 if (ret < 0)
 273                         goto err;
 274
 275                 cmd_data = CGBC_I2C_CMD_DATA | algo_data->bus_id;
 276                 ret = cgbc_command(cgbc, &cmd_data, sizeof(cmd_data),
 277                                    msg->buf + i2c->pos, len, NULL);
 278                 if (ret)
 279                         goto err;
 280         }
 281
 282         if (len == (msg->len - i2c->pos)) {
 283                 i2c->msg++;
 284                 i2c->nmsgs--;
 285                 i2c->pos = 0;
 286         } else {
 287                 i2c->pos += len;
 288         }
 289
 290         if (i2c->nmsgs == 0)
 291                 i2c->state = CGBC_I2C_STATE_DONE;
 292
 293         return 0;
 294
 295 err:
 296         i2c->state = CGBC_I2C_STATE_ERROR;
 297         return ret;
 298 }
 299
 300 static int cgbc_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 301                          int num)
 302 {
 303         struct cgbc_i2c_data *i2c = i2c_get_adapdata(adap);
 304         unsigned long timeout = jiffies + HZ;
 305         int ret;
 306
 307         i2c->state = CGBC_I2C_STATE_INIT;
 308         i2c->msg = msgs;
 309         i2c->nmsgs = num;
 310         i2c->pos = 0;
 311
 312         while (time_before(jiffies, timeout)) {
 313                 ret = cgbc_i2c_xfer_msg(adap);
 314                 if (i2c->state == CGBC_I2C_STATE_DONE)
 315                         return num;
 316
 317                 if (i2c->state == CGBC_I2C_STATE_ERROR)
 318                         return ret;
 319
 320                 if (ret == 0)
 321                         timeout = jiffies + HZ;
 322         }
 323
 324         i2c->state = CGBC_I2C_STATE_ERROR;
 325         return -ETIMEDOUT;
 326 }
 327
 328 static u32 cgbc_i2c_func(struct i2c_adapter *adap)
 329 {
 330         return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~(I2C_FUNC_SMBUS_QUICK));
 331 }
 332
 333 static const struct i2c_algorithm cgbc_i2c_algorithm = {
 334         .master_xfer    = cgbc_i2c_xfer,
 335         .functionality  = cgbc_i2c_func,
 336 };
 337
 338 static struct i2c_algo_cgbc_data cgbc_i2c_algo_data[] = {
 339         { .bus_id = CGBC_I2C_PRIMARY_BUS_ID },
 340         { .bus_id = CGBC_I2C_PM_BUS_ID },
 341 };
 342
 343 static const struct i2c_adapter cgbc_i2c_adapter[] = {
 344         {
 345                 .owner          = THIS_MODULE,
 346                 .name           = "Congatec General Purpose I2C adapter",
 347                 .class          = I2C_CLASS_DEPRECATED,
 348                 .algo           = &cgbc_i2c_algorithm,
 349                 .algo_data      = &cgbc_i2c_algo_data[0],
 350                 .nr             = -1,
 351         },
 352         {
 353                 .owner          = THIS_MODULE,
 354                 .name           = "Congatec Power Management I2C adapter",
 355                 .class          = I2C_CLASS_DEPRECATED,
 356                 .algo           = &cgbc_i2c_algorithm,
 357                 .algo_data      = &cgbc_i2c_algo_data[1],
 358                 .nr             = -1,
 359         },
 360 };
 361
 362 static int cgbc_i2c_probe(struct platform_device *pdev)
 363 {
 364         struct cgbc_device_data *cgbc = dev_get_drvdata(pdev->dev.parent);
 365         struct cgbc_i2c_data *i2c;
 366         int ret;
 367
 368         i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
 369         if (!i2c)
 370                 return -ENOMEM;
 371
 372         i2c->cgbc = cgbc;
 373         i2c->dev = &pdev->dev;
 374         i2c->adap = cgbc_i2c_adapter[pdev->id];
 375         i2c->adap.dev.parent = i2c->dev;
 376         i2c_set_adapdata(&i2c->adap, i2c);
 377         platform_set_drvdata(pdev, i2c);
 378
 379         ret = cgbc_i2c_set_frequency(&i2c->adap, I2C_MAX_STANDARD_MODE_FREQ);
 380         if (ret)
 381                 return ret;
 382
 383         return i2c_add_numbered_adapter(&i2c->adap);
 384 }
 385
 386 static void cgbc_i2c_remove(struct platform_device *pdev)
 387 {
 388         struct cgbc_i2c_data *i2c = platform_get_drvdata(pdev);
 389
 390         i2c_del_adapter(&i2c->adap);
 391 }
 392
 393 static struct platform_driver cgbc_i2c_driver = {
 394         .driver = {
 395                 .name = "cgbc-i2c",
 396         },
 397         .probe          = cgbc_i2c_probe,
 398         .remove         = cgbc_i2c_remove,
 399 };
 400
 401 module_platform_driver(cgbc_i2c_driver);
 402
 403 MODULE_DESCRIPTION("Congatec Board Controller I2C Driver");
 404 MODULE_AUTHOR("Thomas Richard <thomas.richard@bootlin.com>");
 405 MODULE_LICENSE("GPL");
 406 MODULE_ALIAS("platform:cgbc_i2c");