drivers/i2c/busses/i2c-lpc2k.c

   1 /*
   2  * Copyright (C) 2011 NXP Semiconductors
   3  *
   4  * Code portions referenced from the i2x-pxa and i2c-pnx drivers
   5  *
   6  * Make SMBus byte and word transactions work on LPC178x/7x
   7  * Copyright (c) 2012
   8  * Alexander Potashev, Emcraft Systems, [email protected]
   9  * Anton Protopopov, Emcraft Systems, [email protected]
  10  *
  11  * Copyright (C) 2015 Joachim Eastwood <[email protected]>
  12  *
  13  * This program is free software; you can redistribute it and/or modify
  14  * it under the terms of the GNU General Public License as published by
  15  * the Free Software Foundation; either version 2 of the License, or
  16  * (at your option) any later version.
  17  *
  18  */
  19
  20 #include <linux/clk.h>
  21 #include <linux/errno.h>
  22 #include <linux/i2c.h>
  23 #include <linux/interrupt.h>
  24 #include <linux/io.h>
  25 #include <linux/kernel.h>
  26 #include <linux/module.h>
  27 #include <linux/of.h>
  28 #include <linux/of_device.h>
  29 #include <linux/platform_device.h>
  30 #include <linux/sched.h>
  31 #include <linux/time.h>
  32
  33 /* LPC24xx register offsets and bits */
  34 #define LPC24XX_I2CONSET        0x00
  35 #define LPC24XX_I2STAT          0x04
  36 #define LPC24XX_I2DAT           0x08
  37 #define LPC24XX_I2ADDR          0x0c
  38 #define LPC24XX_I2SCLH          0x10
  39 #define LPC24XX_I2SCLL          0x14
  40 #define LPC24XX_I2CONCLR        0x18
  41
  42 #define LPC24XX_AA              BIT(2)
  43 #define LPC24XX_SI              BIT(3)
  44 #define LPC24XX_STO             BIT(4)
  45 #define LPC24XX_STA             BIT(5)
  46 #define LPC24XX_I2EN            BIT(6)
  47
  48 #define LPC24XX_STO_AA          (LPC24XX_STO | LPC24XX_AA)
  49 #define LPC24XX_CLEAR_ALL       (LPC24XX_AA | LPC24XX_SI | LPC24XX_STO | \
  50                                  LPC24XX_STA | LPC24XX_I2EN)
  51
  52 /* I2C SCL clock has different duty cycle depending on mode */
  53 #define I2C_STD_MODE_DUTY               46
  54 #define I2C_FAST_MODE_DUTY              36
  55 #define I2C_FAST_MODE_PLUS_DUTY         38
  56
  57 /*
  58  * 26 possible I2C status codes, but codes applicable only
  59  * to master are listed here and used in this driver
  60  */
  61 enum {
  62         M_BUS_ERROR             = 0x00,
  63         M_START                 = 0x08,
  64         M_REPSTART              = 0x10,
  65         MX_ADDR_W_ACK           = 0x18,
  66         MX_ADDR_W_NACK          = 0x20,
  67         MX_DATA_W_ACK           = 0x28,
  68         MX_DATA_W_NACK          = 0x30,
  69         M_DATA_ARB_LOST         = 0x38,
  70         MR_ADDR_R_ACK           = 0x40,
  71         MR_ADDR_R_NACK          = 0x48,
  72         MR_DATA_R_ACK           = 0x50,
  73         MR_DATA_R_NACK          = 0x58,
  74         M_I2C_IDLE              = 0xf8,
  75 };
  76
  77 struct lpc2k_i2c {
  78         void __iomem            *base;
  79         struct clk              *clk;
  80         int                     irq;
  81         wait_queue_head_t       wait;
  82         struct i2c_adapter      adap;
  83         struct i2c_msg          *msg;
  84         int                     msg_idx;
  85         int                     msg_status;
  86         int                     is_last;
  87 };
  88
  89 static void i2c_lpc2k_reset(struct lpc2k_i2c *i2c)
  90 {
  91         /* Will force clear all statuses */
  92         writel(LPC24XX_CLEAR_ALL, i2c->base + LPC24XX_I2CONCLR);
  93         writel(0, i2c->base + LPC24XX_I2ADDR);
  94         writel(LPC24XX_I2EN, i2c->base + LPC24XX_I2CONSET);
  95 }
  96
  97 static int i2c_lpc2k_clear_arb(struct lpc2k_i2c *i2c)
  98 {
  99         unsigned long timeout = jiffies + msecs_to_jiffies(1000);
 100
 101         /*
 102          * If the transfer needs to abort for some reason, we'll try to
 103          * force a stop condition to clear any pending bus conditions
 104          */
 105         writel(LPC24XX_STO, i2c->base + LPC24XX_I2CONSET);
 106
 107         /* Wait for status change */
 108         while (readl(i2c->base + LPC24XX_I2STAT) != M_I2C_IDLE) {
 109                 if (time_after(jiffies, timeout)) {
 110                         /* Bus was not idle, try to reset adapter */
 111                         i2c_lpc2k_reset(i2c);
 112                         return -EBUSY;
 113                 }
 114
 115                 cpu_relax();
 116         }
 117
 118         return 0;
 119 }
 120
 121 static void i2c_lpc2k_pump_msg(struct lpc2k_i2c *i2c)
 122 {
 123         unsigned char data;
 124         u32 status;
 125
 126         /*
 127          * I2C in the LPC2xxx series is basically a state machine.
 128          * Just run through the steps based on the current status.
 129          */
 130         status = readl(i2c->base + LPC24XX_I2STAT);
 131
 132         switch (status) {
 133         case M_START:
 134         case M_REPSTART:
 135                 /* Start bit was just sent out, send out addr and dir */
 136                 data = i2c_8bit_addr_from_msg(i2c->msg);
 137
 138                 writel(data, i2c->base + LPC24XX_I2DAT);
 139                 writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONCLR);
 140                 break;
 141
 142         case MX_ADDR_W_ACK:
 143         case MX_DATA_W_ACK:
 144                 /*
 145                  * Address or data was sent out with an ACK. If there is more
 146                  * data to send, send it now
 147                  */
 148                 if (i2c->msg_idx < i2c->msg->len) {
 149                         writel(i2c->msg->buf[i2c->msg_idx],
 150                                i2c->base + LPC24XX_I2DAT);
 151                 } else if (i2c->is_last) {
 152                         /* Last message, send stop */
 153                         writel(LPC24XX_STO_AA, i2c->base + LPC24XX_I2CONSET);
 154                         writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
 155                         i2c->msg_status = 0;
 156                         disable_irq_nosync(i2c->irq);
 157                 } else {
 158                         i2c->msg_status = 0;
 159                         disable_irq_nosync(i2c->irq);
 160                 }
 161
 162                 i2c->msg_idx++;
 163                 break;
 164
 165         case MR_ADDR_R_ACK:
 166                 /* Receive first byte from slave */
 167                 if (i2c->msg->len == 1) {
 168                         /* Last byte, return NACK */
 169                         writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONCLR);
 170                 } else {
 171                         /* Not last byte, return ACK */
 172                         writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONSET);
 173                 }
 174
 175                 writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONCLR);
 176                 break;
 177
 178         case MR_DATA_R_NACK:
 179                 /*
 180                  * The I2C shows NACK status on reads, so we need to accept
 181                  * the NACK as an ACK here. This should be ok, as the real
 182                  * BACK would of been caught on the address write.
 183                  */
 184         case MR_DATA_R_ACK:
 185                 /* Data was received */
 186                 if (i2c->msg_idx < i2c->msg->len) {
 187                         i2c->msg->buf[i2c->msg_idx] =
 188                                         readl(i2c->base + LPC24XX_I2DAT);
 189                 }
 190
 191                 /* If transfer is done, send STOP */
 192                 if (i2c->msg_idx >= i2c->msg->len - 1 && i2c->is_last) {
 193                         writel(LPC24XX_STO_AA, i2c->base + LPC24XX_I2CONSET);
 194                         writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
 195                         i2c->msg_status = 0;
 196                 }
 197
 198                 /* Message is done */
 199                 if (i2c->msg_idx >= i2c->msg->len - 1) {
 200                         i2c->msg_status = 0;
 201                         disable_irq_nosync(i2c->irq);
 202                 }
 203
 204                 /*
 205                  * One pre-last data input, send NACK to tell the slave that
 206                  * this is going to be the last data byte to be transferred.
 207                  */
 208                 if (i2c->msg_idx >= i2c->msg->len - 2) {
 209                         /* One byte left to receive - NACK */
 210                         writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONCLR);
 211                 } else {
 212                         /* More than one byte left to receive - ACK */
 213                         writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONSET);
 214                 }
 215
 216                 writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONCLR);
 217                 i2c->msg_idx++;
 218                 break;
 219
 220         case MX_ADDR_W_NACK:
 221         case MX_DATA_W_NACK:
 222         case MR_ADDR_R_NACK:
 223                 /* NACK processing is done */
 224                 writel(LPC24XX_STO_AA, i2c->base + LPC24XX_I2CONSET);
 225                 i2c->msg_status = -ENXIO;
 226                 disable_irq_nosync(i2c->irq);
 227                 break;
 228
 229         case M_DATA_ARB_LOST:
 230                 /* Arbitration lost */
 231                 i2c->msg_status = -EAGAIN;
 232
 233                 /* Release the I2C bus */
 234                 writel(LPC24XX_STA | LPC24XX_STO, i2c->base + LPC24XX_I2CONCLR);
 235                 disable_irq_nosync(i2c->irq);
 236                 break;
 237
 238         default:
 239                 /* Unexpected statuses */
 240                 i2c->msg_status = -EIO;
 241                 disable_irq_nosync(i2c->irq);
 242                 break;
 243         }
 244
 245         /* Exit on failure or all bytes transferred */
 246         if (i2c->msg_status != -EBUSY)
 247                 wake_up(&i2c->wait);
 248
 249         /*
 250          * If `msg_status` is zero, then `lpc2k_process_msg()`
 251          * is responsible for clearing the SI flag.
 252          */
 253         if (i2c->msg_status != 0)
 254                 writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
 255 }
 256
 257 static int lpc2k_process_msg(struct lpc2k_i2c *i2c, int msgidx)
 258 {
 259         /* A new transfer is kicked off by initiating a start condition */
 260         if (!msgidx) {
 261                 writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONSET);
 262         } else {
 263                 /*
 264                  * A multi-message I2C transfer continues where the
 265                  * previous I2C transfer left off and uses the
 266                  * current condition of the I2C adapter.
 267                  */
 268                 if (unlikely(i2c->msg->flags & I2C_M_NOSTART)) {
 269                         WARN_ON(i2c->msg->len == 0);
 270
 271                         if (!(i2c->msg->flags & I2C_M_RD)) {
 272                                 /* Start transmit of data */
 273                                 writel(i2c->msg->buf[0],
 274                                        i2c->base + LPC24XX_I2DAT);
 275                                 i2c->msg_idx++;
 276                         }
 277                 } else {
 278                         /* Start or repeated start */
 279                         writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONSET);
 280                 }
 281
 282                 writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
 283         }
 284
 285         enable_irq(i2c->irq);
 286
 287         /* Wait for transfer completion */
 288         if (wait_event_timeout(i2c->wait, i2c->msg_status != -EBUSY,
 289                                msecs_to_jiffies(1000)) == 0) {
 290                 disable_irq_nosync(i2c->irq);
 291
 292                 return -ETIMEDOUT;
 293         }
 294
 295         return i2c->msg_status;
 296 }
 297
 298 static int i2c_lpc2k_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 299                           int msg_num)
 300 {
 301         struct lpc2k_i2c *i2c = i2c_get_adapdata(adap);
 302         int ret, i;
 303         u32 stat;
 304
 305         /* Check for bus idle condition */
 306         stat = readl(i2c->base + LPC24XX_I2STAT);
 307         if (stat != M_I2C_IDLE) {
 308                 /* Something is holding the bus, try to clear it */
 309                 return i2c_lpc2k_clear_arb(i2c);
 310         }
 311
 312         /* Process a single message at a time */
 313         for (i = 0; i < msg_num; i++) {
 314                 /* Save message pointer and current message data index */
 315                 i2c->msg = &msgs[i];
 316                 i2c->msg_idx = 0;
 317                 i2c->msg_status = -EBUSY;
 318                 i2c->is_last = (i == (msg_num - 1));
 319
 320                 ret = lpc2k_process_msg(i2c, i);
 321                 if (ret)
 322                         return ret;
 323         }
 324
 325         return msg_num;
 326 }
 327
 328 static irqreturn_t i2c_lpc2k_handler(int irq, void *dev_id)
 329 {
 330         struct lpc2k_i2c *i2c = dev_id;
 331
 332         if (readl(i2c->base + LPC24XX_I2CONSET) & LPC24XX_SI) {
 333                 i2c_lpc2k_pump_msg(i2c);
 334                 return IRQ_HANDLED;
 335         }
 336
 337         return IRQ_NONE;
 338 }
 339
 340 static u32 i2c_lpc2k_functionality(struct i2c_adapter *adap)
 341 {
 342         /* Only emulated SMBus for now */
 343         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 344 }
 345
 346 static const struct i2c_algorithm i2c_lpc2k_algorithm = {
 347         .master_xfer    = i2c_lpc2k_xfer,
 348         .functionality  = i2c_lpc2k_functionality,
 349 };
 350
 351 static int i2c_lpc2k_probe(struct platform_device *pdev)
 352 {
 353         struct lpc2k_i2c *i2c;
 354         struct resource *res;
 355         u32 bus_clk_rate;
 356         u32 scl_high;
 357         u32 clkrate;
 358         int ret;
 359
 360         i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
 361         if (!i2c)
 362                 return -ENOMEM;
 363
 364         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 365         i2c->base = devm_ioremap_resource(&pdev->dev, res);
 366         if (IS_ERR(i2c->base))
 367                 return PTR_ERR(i2c->base);
 368
 369         i2c->irq = platform_get_irq(pdev, 0);
 370         if (i2c->irq < 0) {
 371                 dev_err(&pdev->dev, "can't get interrupt resource\n");
 372                 return i2c->irq;
 373         }
 374
 375         init_waitqueue_head(&i2c->wait);
 376
 377         i2c->clk = devm_clk_get(&pdev->dev, NULL);
 378         if (IS_ERR(i2c->clk)) {
 379                 dev_err(&pdev->dev, "error getting clock\n");
 380                 return PTR_ERR(i2c->clk);
 381         }
 382
 383         ret = clk_prepare_enable(i2c->clk);
 384         if (ret) {
 385                 dev_err(&pdev->dev, "unable to enable clock.\n");
 386                 return ret;
 387         }
 388
 389         ret = devm_request_irq(&pdev->dev, i2c->irq, i2c_lpc2k_handler, 0,
 390                                dev_name(&pdev->dev), i2c);
 391         if (ret < 0) {
 392                 dev_err(&pdev->dev, "can't request interrupt.\n");
 393                 goto fail_clk;
 394         }
 395
 396         disable_irq_nosync(i2c->irq);
 397
 398         /* Place controller is a known state */
 399         i2c_lpc2k_reset(i2c);
 400
 401         ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
 402                                    &bus_clk_rate);
 403         if (ret)
 404                 bus_clk_rate = 100000; /* 100 kHz default clock rate */
 405
 406         clkrate = clk_get_rate(i2c->clk);
 407         if (clkrate == 0) {
 408                 dev_err(&pdev->dev, "can't get I2C base clock\n");
 409                 ret = -EINVAL;
 410                 goto fail_clk;
 411         }
 412
 413         /* Setup I2C dividers to generate clock with proper duty cycle */
 414         clkrate = clkrate / bus_clk_rate;
 415         if (bus_clk_rate <= 100000)
 416                 scl_high = (clkrate * I2C_STD_MODE_DUTY) / 100;
 417         else if (bus_clk_rate <= 400000)
 418                 scl_high = (clkrate * I2C_FAST_MODE_DUTY) / 100;
 419         else
 420                 scl_high = (clkrate * I2C_FAST_MODE_PLUS_DUTY) / 100;
 421
 422         writel(scl_high, i2c->base + LPC24XX_I2SCLH);
 423         writel(clkrate - scl_high, i2c->base + LPC24XX_I2SCLL);
 424
 425         platform_set_drvdata(pdev, i2c);
 426
 427         i2c_set_adapdata(&i2c->adap, i2c);
 428         i2c->adap.owner = THIS_MODULE;
 429         strlcpy(i2c->adap.name, "LPC2K I2C adapter", sizeof(i2c->adap.name));
 430         i2c->adap.algo = &i2c_lpc2k_algorithm;
 431         i2c->adap.dev.parent = &pdev->dev;
 432         i2c->adap.dev.of_node = pdev->dev.of_node;
 433
 434         ret = i2c_add_adapter(&i2c->adap);
 435         if (ret < 0)
 436                 goto fail_clk;
 437
 438         dev_info(&pdev->dev, "LPC2K I2C adapter\n");
 439
 440         return 0;
 441
 442 fail_clk:
 443         clk_disable_unprepare(i2c->clk);
 444         return ret;
 445 }
 446
 447 static int i2c_lpc2k_remove(struct platform_device *dev)
 448 {
 449         struct lpc2k_i2c *i2c = platform_get_drvdata(dev);
 450
 451         i2c_del_adapter(&i2c->adap);
 452         clk_disable_unprepare(i2c->clk);
 453
 454         return 0;
 455 }
 456
 457 #ifdef CONFIG_PM
 458 static int i2c_lpc2k_suspend(struct device *dev)
 459 {
 460         struct lpc2k_i2c *i2c = dev_get_drvdata(dev);
 461
 462         clk_disable(i2c->clk);
 463
 464         return 0;
 465 }
 466
 467 static int i2c_lpc2k_resume(struct device *dev)
 468 {
 469         struct lpc2k_i2c *i2c = dev_get_drvdata(dev);
 470
 471         clk_enable(i2c->clk);
 472         i2c_lpc2k_reset(i2c);
 473
 474         return 0;
 475 }
 476
 477 static const struct dev_pm_ops i2c_lpc2k_dev_pm_ops = {
 478         .suspend_noirq = i2c_lpc2k_suspend,
 479         .resume_noirq = i2c_lpc2k_resume,
 480 };
 481
 482 #define I2C_LPC2K_DEV_PM_OPS (&i2c_lpc2k_dev_pm_ops)
 483 #else
 484 #define I2C_LPC2K_DEV_PM_OPS NULL
 485 #endif
 486
 487 static const struct of_device_id lpc2k_i2c_match[] = {
 488         { .compatible = "nxp,lpc1788-i2c" },
 489         {},
 490 };
 491 MODULE_DEVICE_TABLE(of, lpc2k_i2c_match);
 492
 493 static struct platform_driver i2c_lpc2k_driver = {
 494         .probe  = i2c_lpc2k_probe,
 495         .remove = i2c_lpc2k_remove,
 496         .driver = {
 497                 .name           = "lpc2k-i2c",
 498                 .pm             = I2C_LPC2K_DEV_PM_OPS,
 499                 .of_match_table = lpc2k_i2c_match,
 500         },
 501 };
 502 module_platform_driver(i2c_lpc2k_driver);
 503
 504 MODULE_AUTHOR("Kevin Wells <[email protected]>");
 505 MODULE_DESCRIPTION("I2C driver for LPC2xxx devices");
 506 MODULE_LICENSE("GPL");
 507 MODULE_ALIAS("platform:lpc2k-i2c");