drivers/i2c/busses/i2c-meson.c

   1 /*
   2  * I2C bus driver for Amlogic Meson SoCs
   3  *
   4  * Copyright (C) 2014 Beniamino Galvani <b.galvani@gmail.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10
  11 #include <linux/clk.h>
  12 #include <linux/completion.h>
  13 #include <linux/i2c.h>
  14 #include <linux/interrupt.h>
  15 #include <linux/io.h>
  16 #include <linux/kernel.h>
  17 #include <linux/module.h>
  18 #include <linux/of.h>
  19 #include <linux/platform_device.h>
  20 #include <linux/types.h>
  21
  22 /* Meson I2C register map */
  23 #define REG_CTRL                0x00
  24 #define REG_SLAVE_ADDR          0x04
  25 #define REG_TOK_LIST0           0x08
  26 #define REG_TOK_LIST1           0x0c
  27 #define REG_TOK_WDATA0          0x10
  28 #define REG_TOK_WDATA1          0x14
  29 #define REG_TOK_RDATA0          0x18
  30 #define REG_TOK_RDATA1          0x1c
  31
  32 /* Control register fields */
  33 #define REG_CTRL_START          BIT(0)
  34 #define REG_CTRL_ACK_IGNORE     BIT(1)
  35 #define REG_CTRL_STATUS         BIT(2)
  36 #define REG_CTRL_ERROR          BIT(3)
  37 #define REG_CTRL_CLKDIV_SHIFT   12
  38 #define REG_CTRL_CLKDIV_MASK    ((BIT(10) - 1) << REG_CTRL_CLKDIV_SHIFT)
  39
  40 #define I2C_TIMEOUT_MS          500
  41 #define DEFAULT_FREQ            100000
  42
  43 enum {
  44         TOKEN_END = 0,
  45         TOKEN_START,
  46         TOKEN_SLAVE_ADDR_WRITE,
  47         TOKEN_SLAVE_ADDR_READ,
  48         TOKEN_DATA,
  49         TOKEN_DATA_LAST,
  50         TOKEN_STOP,
  51 };
  52
  53 enum {
  54         STATE_IDLE,
  55         STATE_READ,
  56         STATE_WRITE,
  57         STATE_STOP,
  58 };
  59
  60 /**
  61  * struct meson_i2c - Meson I2C device private data
  62  *
  63  * @adap:       I2C adapter instance
  64  * @dev:        Pointer to device structure
  65  * @regs:       Base address of the device memory mapped registers
  66  * @clk:        Pointer to clock structure
  67  * @irq:        IRQ number
  68  * @msg:        Pointer to the current I2C message
  69  * @state:      Current state in the driver state machine
  70  * @last:       Flag set for the last message in the transfer
  71  * @count:      Number of bytes to be sent/received in current transfer
  72  * @pos:        Current position in the send/receive buffer
  73  * @error:      Flag set when an error is received
  74  * @lock:       To avoid race conditions between irq handler and xfer code
  75  * @done:       Completion used to wait for transfer termination
  76  * @frequency:  Operating frequency of I2C bus clock
  77  * @tokens:     Sequence of tokens to be written to the device
  78  * @num_tokens: Number of tokens
  79  */
  80 struct meson_i2c {
  81         struct i2c_adapter      adap;
  82         struct device           *dev;
  83         void __iomem            *regs;
  84         struct clk              *clk;
  85         int                     irq;
  86
  87         struct i2c_msg          *msg;
  88         int                     state;
  89         bool                    last;
  90         int                     count;
  91         int                     pos;
  92         int                     error;
  93
  94         spinlock_t              lock;
  95         struct completion       done;
  96         unsigned int            frequency;
  97         u32                     tokens[2];
  98         int                     num_tokens;
  99 };
 100
 101 static void meson_i2c_set_mask(struct meson_i2c *i2c, int reg, u32 mask,
 102                                u32 val)
 103 {
 104         u32 data;
 105
 106         data = readl(i2c->regs + reg);
 107         data &= ~mask;
 108         data |= val & mask;
 109         writel(data, i2c->regs + reg);
 110 }
 111
 112 static void meson_i2c_reset_tokens(struct meson_i2c *i2c)
 113 {
 114         i2c->tokens[0] = 0;
 115         i2c->tokens[1] = 0;
 116         i2c->num_tokens = 0;
 117 }
 118
 119 static void meson_i2c_add_token(struct meson_i2c *i2c, int token)
 120 {
 121         if (i2c->num_tokens < 8)
 122                 i2c->tokens[0] |= (token & 0xf) << (i2c->num_tokens * 4);
 123         else
 124                 i2c->tokens[1] |= (token & 0xf) << ((i2c->num_tokens % 8) * 4);
 125
 126         i2c->num_tokens++;
 127 }
 128
 129 static void meson_i2c_write_tokens(struct meson_i2c *i2c)
 130 {
 131         writel(i2c->tokens[0], i2c->regs + REG_TOK_LIST0);
 132         writel(i2c->tokens[1], i2c->regs + REG_TOK_LIST1);
 133 }
 134
 135 static void meson_i2c_set_clk_div(struct meson_i2c *i2c)
 136 {
 137         unsigned long clk_rate = clk_get_rate(i2c->clk);
 138         unsigned int div;
 139
 140         div = DIV_ROUND_UP(clk_rate, i2c->frequency * 4);
 141         meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_CLKDIV_MASK,
 142                            div << REG_CTRL_CLKDIV_SHIFT);
 143
 144         dev_dbg(i2c->dev, "%s: clk %lu, freq %u, div %u\n", __func__,
 145                 clk_rate, i2c->frequency, div);
 146 }
 147
 148 static void meson_i2c_get_data(struct meson_i2c *i2c, char *buf, int len)
 149 {
 150         u32 rdata0, rdata1;
 151         int i;
 152
 153         rdata0 = readl(i2c->regs + REG_TOK_RDATA0);
 154         rdata1 = readl(i2c->regs + REG_TOK_RDATA1);
 155
 156         dev_dbg(i2c->dev, "%s: data %08x %08x len %d\n", __func__,
 157                 rdata0, rdata1, len);
 158
 159         for (i = 0; i < min_t(int, 4, len); i++)
 160                 *buf++ = (rdata0 >> i * 8) & 0xff;
 161
 162         for (i = 4; i < min_t(int, 8, len); i++)
 163                 *buf++ = (rdata1 >> (i - 4) * 8) & 0xff;
 164 }
 165
 166 static void meson_i2c_put_data(struct meson_i2c *i2c, char *buf, int len)
 167 {
 168         u32 wdata0 = 0, wdata1 = 0;
 169         int i;
 170
 171         for (i = 0; i < min_t(int, 4, len); i++)
 172                 wdata0 |= *buf++ << (i * 8);
 173
 174         for (i = 4; i < min_t(int, 8, len); i++)
 175                 wdata1 |= *buf++ << ((i - 4) * 8);
 176
 177         writel(wdata0, i2c->regs + REG_TOK_WDATA0);
 178         writel(wdata0, i2c->regs + REG_TOK_WDATA1);
 179
 180         dev_dbg(i2c->dev, "%s: data %08x %08x len %d\n", __func__,
 181                 wdata0, wdata1, len);
 182 }
 183
 184 static void meson_i2c_prepare_xfer(struct meson_i2c *i2c)
 185 {
 186         bool write = !(i2c->msg->flags & I2C_M_RD);
 187         int i;
 188
 189         i2c->count = min_t(int, i2c->msg->len - i2c->pos, 8);
 190
 191         for (i = 0; i < i2c->count - 1; i++)
 192                 meson_i2c_add_token(i2c, TOKEN_DATA);
 193
 194         if (i2c->count) {
 195                 if (write || i2c->pos + i2c->count < i2c->msg->len)
 196                         meson_i2c_add_token(i2c, TOKEN_DATA);
 197                 else
 198                         meson_i2c_add_token(i2c, TOKEN_DATA_LAST);
 199         }
 200
 201         if (write)
 202                 meson_i2c_put_data(i2c, i2c->msg->buf + i2c->pos, i2c->count);
 203 }
 204
 205 static void meson_i2c_stop(struct meson_i2c *i2c)
 206 {
 207         dev_dbg(i2c->dev, "%s: last %d\n", __func__, i2c->last);
 208
 209         if (i2c->last) {
 210                 i2c->state = STATE_STOP;
 211                 meson_i2c_add_token(i2c, TOKEN_STOP);
 212         } else {
 213                 i2c->state = STATE_IDLE;
 214                 complete(&i2c->done);
 215         }
 216 }
 217
 218 static irqreturn_t meson_i2c_irq(int irqno, void *dev_id)
 219 {
 220         struct meson_i2c *i2c = dev_id;
 221         unsigned int ctrl;
 222
 223         spin_lock(&i2c->lock);
 224
 225         meson_i2c_reset_tokens(i2c);
 226         ctrl = readl(i2c->regs + REG_CTRL);
 227
 228         dev_dbg(i2c->dev, "irq: state %d, pos %d, count %d, ctrl %08x\n",
 229                 i2c->state, i2c->pos, i2c->count, ctrl);
 230
 231         if (ctrl & REG_CTRL_ERROR && i2c->state != STATE_IDLE) {
 232                 /*
 233                  * The bit is set when the IGNORE_NAK bit is cleared
 234                  * and the device didn't respond. In this case, the
 235                  * I2C controller automatically generates a STOP
 236                  * condition.
 237                  */
 238                 dev_dbg(i2c->dev, "error bit set\n");
 239                 i2c->error = -ENXIO;
 240                 i2c->state = STATE_IDLE;
 241                 complete(&i2c->done);
 242                 goto out;
 243         }
 244
 245         switch (i2c->state) {
 246         case STATE_READ:
 247                 if (i2c->count > 0) {
 248                         meson_i2c_get_data(i2c, i2c->msg->buf + i2c->pos,
 249                                            i2c->count);
 250                         i2c->pos += i2c->count;
 251                 }
 252
 253                 if (i2c->pos >= i2c->msg->len) {
 254                         meson_i2c_stop(i2c);
 255                         break;
 256                 }
 257
 258                 meson_i2c_prepare_xfer(i2c);
 259                 break;
 260         case STATE_WRITE:
 261                 i2c->pos += i2c->count;
 262
 263                 if (i2c->pos >= i2c->msg->len) {
 264                         meson_i2c_stop(i2c);
 265                         break;
 266                 }
 267
 268                 meson_i2c_prepare_xfer(i2c);
 269                 break;
 270         case STATE_STOP:
 271                 i2c->state = STATE_IDLE;
 272                 complete(&i2c->done);
 273                 break;
 274         case STATE_IDLE:
 275                 break;
 276         }
 277
 278 out:
 279         if (i2c->state != STATE_IDLE) {
 280                 /* Restart the processing */
 281                 meson_i2c_write_tokens(i2c);
 282                 meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, 0);
 283                 meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START,
 284                                    REG_CTRL_START);
 285         }
 286
 287         spin_unlock(&i2c->lock);
 288
 289         return IRQ_HANDLED;
 290 }
 291
 292 static void meson_i2c_do_start(struct meson_i2c *i2c, struct i2c_msg *msg)
 293 {
 294         int token;
 295
 296         token = (msg->flags & I2C_M_RD) ? TOKEN_SLAVE_ADDR_READ :
 297                 TOKEN_SLAVE_ADDR_WRITE;
 298
 299         writel(msg->addr << 1, i2c->regs + REG_SLAVE_ADDR);
 300         meson_i2c_add_token(i2c, TOKEN_START);
 301         meson_i2c_add_token(i2c, token);
 302 }
 303
 304 static int meson_i2c_xfer_msg(struct meson_i2c *i2c, struct i2c_msg *msg,
 305                               int last)
 306 {
 307         unsigned long time_left, flags;
 308         int ret = 0;
 309
 310         i2c->msg = msg;
 311         i2c->last = last;
 312         i2c->pos = 0;
 313         i2c->count = 0;
 314         i2c->error = 0;
 315
 316         meson_i2c_reset_tokens(i2c);
 317
 318         flags = (msg->flags & I2C_M_IGNORE_NAK) ? REG_CTRL_ACK_IGNORE : 0;
 319         meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_ACK_IGNORE, flags);
 320
 321         if (!(msg->flags & I2C_M_NOSTART))
 322                 meson_i2c_do_start(i2c, msg);
 323
 324         i2c->state = (msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;
 325         meson_i2c_prepare_xfer(i2c);
 326         meson_i2c_write_tokens(i2c);
 327         reinit_completion(&i2c->done);
 328
 329         /* Start the transfer */
 330         meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, REG_CTRL_START);
 331
 332         time_left = msecs_to_jiffies(I2C_TIMEOUT_MS);
 333         time_left = wait_for_completion_timeout(&i2c->done, time_left);
 334
 335         /*
 336          * Protect access to i2c struct and registers from interrupt
 337          * handlers triggered by a transfer terminated after the
 338          * timeout period
 339          */
 340         spin_lock_irqsave(&i2c->lock, flags);
 341
 342         /* Abort any active operation */
 343         meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, 0);
 344
 345         if (!time_left) {
 346                 i2c->state = STATE_IDLE;
 347                 ret = -ETIMEDOUT;
 348         }
 349
 350         if (i2c->error)
 351                 ret = i2c->error;
 352
 353         spin_unlock_irqrestore(&i2c->lock, flags);
 354
 355         return ret;
 356 }
 357
 358 static int meson_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 359                           int num)
 360 {
 361         struct meson_i2c *i2c = adap->algo_data;
 362         int i, ret = 0, count = 0;
 363
 364         clk_enable(i2c->clk);
 365         meson_i2c_set_clk_div(i2c);
 366
 367         for (i = 0; i < num; i++) {
 368                 ret = meson_i2c_xfer_msg(i2c, msgs + i, i == num - 1);
 369                 if (ret)
 370                         break;
 371                 count++;
 372         }
 373
 374         clk_disable(i2c->clk);
 375
 376         return ret ? ret : count;
 377 }
 378
 379 static u32 meson_i2c_func(struct i2c_adapter *adap)
 380 {
 381         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 382 }
 383
 384 static const struct i2c_algorithm meson_i2c_algorithm = {
 385         .master_xfer    = meson_i2c_xfer,
 386         .functionality  = meson_i2c_func,
 387 };
 388
 389 static int meson_i2c_probe(struct platform_device *pdev)
 390 {
 391         struct device_node *np = pdev->dev.of_node;
 392         struct meson_i2c *i2c;
 393         struct resource *mem;
 394         int ret = 0;
 395
 396         i2c = devm_kzalloc(&pdev->dev, sizeof(struct meson_i2c), GFP_KERNEL);
 397         if (!i2c)
 398                 return -ENOMEM;
 399
 400         if (of_property_read_u32(pdev->dev.of_node, "clock-frequency",
 401                                  &i2c->frequency))
 402                 i2c->frequency = DEFAULT_FREQ;
 403
 404         i2c->dev = &pdev->dev;
 405         platform_set_drvdata(pdev, i2c);
 406
 407         spin_lock_init(&i2c->lock);
 408         init_completion(&i2c->done);
 409
 410         i2c->clk = devm_clk_get(&pdev->dev, NULL);
 411         if (IS_ERR(i2c->clk)) {
 412                 dev_err(&pdev->dev, "can't get device clock\n");
 413                 return PTR_ERR(i2c->clk);
 414         }
 415
 416         mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 417         i2c->regs = devm_ioremap_resource(&pdev->dev, mem);
 418         if (IS_ERR(i2c->regs))
 419                 return PTR_ERR(i2c->regs);
 420
 421         i2c->irq = platform_get_irq(pdev, 0);
 422         if (i2c->irq < 0) {
 423                 dev_err(&pdev->dev, "can't find IRQ\n");
 424                 return i2c->irq;
 425         }
 426
 427         ret = devm_request_irq(&pdev->dev, i2c->irq, meson_i2c_irq,
 428                                0, dev_name(&pdev->dev), i2c);
 429         if (ret < 0) {
 430                 dev_err(&pdev->dev, "can't request IRQ\n");
 431                 return ret;
 432         }
 433
 434         ret = clk_prepare(i2c->clk);
 435         if (ret < 0) {
 436                 dev_err(&pdev->dev, "can't prepare clock\n");
 437                 return ret;
 438         }
 439
 440         strlcpy(i2c->adap.name, "Meson I2C adapter",
 441                 sizeof(i2c->adap.name));
 442         i2c->adap.owner = THIS_MODULE;
 443         i2c->adap.algo = &meson_i2c_algorithm;
 444         i2c->adap.dev.parent = &pdev->dev;
 445         i2c->adap.dev.of_node = np;
 446         i2c->adap.algo_data = i2c;
 447
 448         /*
 449          * A transfer is triggered when START bit changes from 0 to 1.
 450          * Ensure that the bit is set to 0 after probe
 451          */
 452         meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, 0);
 453
 454         ret = i2c_add_adapter(&i2c->adap);
 455         if (ret < 0) {
 456                 dev_err(&pdev->dev, "can't register adapter\n");
 457                 clk_unprepare(i2c->clk);
 458                 return ret;
 459         }
 460
 461         return 0;
 462 }
 463
 464 static int meson_i2c_remove(struct platform_device *pdev)
 465 {
 466         struct meson_i2c *i2c = platform_get_drvdata(pdev);
 467
 468         i2c_del_adapter(&i2c->adap);
 469         clk_unprepare(i2c->clk);
 470
 471         return 0;
 472 }
 473
 474 static const struct of_device_id meson_i2c_match[] = {
 475         { .compatible = "amlogic,meson6-i2c" },
 476         { },
 477 };
 478 MODULE_DEVICE_TABLE(of, meson_i2c_match);
 479
 480 static struct platform_driver meson_i2c_driver = {
 481         .probe   = meson_i2c_probe,
 482         .remove  = meson_i2c_remove,
 483         .driver  = {
 484                 .name  = "meson-i2c",
 485                 .of_match_table = meson_i2c_match,
 486         },
 487 };
 488
 489 module_platform_driver(meson_i2c_driver);
 490
 491 MODULE_DESCRIPTION("Amlogic Meson I2C Bus driver");
 492 MODULE_AUTHOR("Beniamino Galvani <b.galvani@gmail.com>");
 493 MODULE_LICENSE("GPL v2");