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
  42 enum {
  43         TOKEN_END = 0,
  44         TOKEN_START,
  45         TOKEN_SLAVE_ADDR_WRITE,
  46         TOKEN_SLAVE_ADDR_READ,
  47         TOKEN_DATA,
  48         TOKEN_DATA_LAST,
  49         TOKEN_STOP,
  50 };
  51
  52 enum {
  53         STATE_IDLE,
  54         STATE_READ,
  55         STATE_WRITE,
  56         STATE_STOP,
  57 };
  58
  59 /**
  60  * struct meson_i2c - Meson I2C device private data
  61  *
  62  * @adap:       I2C adapter instance
  63  * @dev:        Pointer to device structure
  64  * @regs:       Base address of the device memory mapped registers
  65  * @clk:        Pointer to clock structure
  66  * @irq:        IRQ number
  67  * @msg:        Pointer to the current I2C message
  68  * @state:      Current state in the driver state machine
  69  * @last:       Flag set for the last message in the transfer
  70  * @count:      Number of bytes to be sent/received in current transfer
  71  * @pos:        Current position in the send/receive buffer
  72  * @error:      Flag set when an error is received
  73  * @lock:       To avoid race conditions between irq handler and xfer code
  74  * @done:       Completion used to wait for transfer termination
  75  * @tokens:     Sequence of tokens to be written to the device
  76  * @num_tokens: Number of tokens
  77  */
  78 struct meson_i2c {
  79         struct i2c_adapter      adap;
  80         struct device           *dev;
  81         void __iomem            *regs;
  82         struct clk              *clk;
  83
  84         struct i2c_msg          *msg;
  85         int                     state;
  86         bool                    last;
  87         int                     count;
  88         int                     pos;
  89         int                     error;
  90
  91         spinlock_t              lock;
  92         struct completion       done;
  93         u32                     tokens[2];
  94         int                     num_tokens;
  95 };
  96
  97 static void meson_i2c_set_mask(struct meson_i2c *i2c, int reg, u32 mask,
  98                                u32 val)
  99 {
 100         u32 data;
 101
 102         data = readl(i2c->regs + reg);
 103         data &= ~mask;
 104         data |= val & mask;
 105         writel(data, i2c->regs + reg);
 106 }
 107
 108 static void meson_i2c_reset_tokens(struct meson_i2c *i2c)
 109 {
 110         i2c->tokens[0] = 0;
 111         i2c->tokens[1] = 0;
 112         i2c->num_tokens = 0;
 113 }
 114
 115 static void meson_i2c_add_token(struct meson_i2c *i2c, int token)
 116 {
 117         if (i2c->num_tokens < 8)
 118                 i2c->tokens[0] |= (token & 0xf) << (i2c->num_tokens * 4);
 119         else
 120                 i2c->tokens[1] |= (token & 0xf) << ((i2c->num_tokens % 8) * 4);
 121
 122         i2c->num_tokens++;
 123 }
 124
 125 static void meson_i2c_write_tokens(struct meson_i2c *i2c)
 126 {
 127         writel(i2c->tokens[0], i2c->regs + REG_TOK_LIST0);
 128         writel(i2c->tokens[1], i2c->regs + REG_TOK_LIST1);
 129 }
 130
 131 static void meson_i2c_set_clk_div(struct meson_i2c *i2c, unsigned int freq)
 132 {
 133         unsigned long clk_rate = clk_get_rate(i2c->clk);
 134         unsigned int div;
 135
 136         div = DIV_ROUND_UP(clk_rate, freq * 4);
 137         meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_CLKDIV_MASK,
 138                            div << REG_CTRL_CLKDIV_SHIFT);
 139
 140         dev_dbg(i2c->dev, "%s: clk %lu, freq %u, div %u\n", __func__,
 141                 clk_rate, freq, div);
 142 }
 143
 144 static void meson_i2c_get_data(struct meson_i2c *i2c, char *buf, int len)
 145 {
 146         u32 rdata0, rdata1;
 147         int i;
 148
 149         rdata0 = readl(i2c->regs + REG_TOK_RDATA0);
 150         rdata1 = readl(i2c->regs + REG_TOK_RDATA1);
 151
 152         dev_dbg(i2c->dev, "%s: data %08x %08x len %d\n", __func__,
 153                 rdata0, rdata1, len);
 154
 155         for (i = 0; i < min(4, len); i++)
 156                 *buf++ = (rdata0 >> i * 8) & 0xff;
 157
 158         for (i = 4; i < min(8, len); i++)
 159                 *buf++ = (rdata1 >> (i - 4) * 8) & 0xff;
 160 }
 161
 162 static void meson_i2c_put_data(struct meson_i2c *i2c, char *buf, int len)
 163 {
 164         u32 wdata0 = 0, wdata1 = 0;
 165         int i;
 166
 167         for (i = 0; i < min(4, len); i++)
 168                 wdata0 |= *buf++ << (i * 8);
 169
 170         for (i = 4; i < min(8, len); i++)
 171                 wdata1 |= *buf++ << ((i - 4) * 8);
 172
 173         writel(wdata0, i2c->regs + REG_TOK_WDATA0);
 174         writel(wdata1, i2c->regs + REG_TOK_WDATA1);
 175
 176         dev_dbg(i2c->dev, "%s: data %08x %08x len %d\n", __func__,
 177                 wdata0, wdata1, len);
 178 }
 179
 180 static void meson_i2c_prepare_xfer(struct meson_i2c *i2c)
 181 {
 182         bool write = !(i2c->msg->flags & I2C_M_RD);
 183         int i;
 184
 185         i2c->count = min(i2c->msg->len - i2c->pos, 8);
 186
 187         for (i = 0; i < i2c->count - 1; i++)
 188                 meson_i2c_add_token(i2c, TOKEN_DATA);
 189
 190         if (i2c->count) {
 191                 if (write || i2c->pos + i2c->count < i2c->msg->len)
 192                         meson_i2c_add_token(i2c, TOKEN_DATA);
 193                 else
 194                         meson_i2c_add_token(i2c, TOKEN_DATA_LAST);
 195         }
 196
 197         if (write)
 198                 meson_i2c_put_data(i2c, i2c->msg->buf + i2c->pos, i2c->count);
 199 }
 200
 201 static void meson_i2c_stop(struct meson_i2c *i2c)
 202 {
 203         dev_dbg(i2c->dev, "%s: last %d\n", __func__, i2c->last);
 204
 205         if (i2c->last) {
 206                 i2c->state = STATE_STOP;
 207                 meson_i2c_add_token(i2c, TOKEN_STOP);
 208         } else {
 209                 i2c->state = STATE_IDLE;
 210                 complete(&i2c->done);
 211         }
 212 }
 213
 214 static irqreturn_t meson_i2c_irq(int irqno, void *dev_id)
 215 {
 216         struct meson_i2c *i2c = dev_id;
 217         unsigned int ctrl;
 218
 219         spin_lock(&i2c->lock);
 220
 221         meson_i2c_reset_tokens(i2c);
 222         ctrl = readl(i2c->regs + REG_CTRL);
 223
 224         dev_dbg(i2c->dev, "irq: state %d, pos %d, count %d, ctrl %08x\n",
 225                 i2c->state, i2c->pos, i2c->count, ctrl);
 226
 227         if (ctrl & REG_CTRL_ERROR && i2c->state != STATE_IDLE) {
 228                 /*
 229                  * The bit is set when the IGNORE_NAK bit is cleared
 230                  * and the device didn't respond. In this case, the
 231                  * I2C controller automatically generates a STOP
 232                  * condition.
 233                  */
 234                 dev_dbg(i2c->dev, "error bit set\n");
 235                 i2c->error = -ENXIO;
 236                 i2c->state = STATE_IDLE;
 237                 complete(&i2c->done);
 238                 goto out;
 239         }
 240
 241         switch (i2c->state) {
 242         case STATE_READ:
 243                 if (i2c->count > 0) {
 244                         meson_i2c_get_data(i2c, i2c->msg->buf + i2c->pos,
 245                                            i2c->count);
 246                         i2c->pos += i2c->count;
 247                 }
 248
 249                 if (i2c->pos >= i2c->msg->len) {
 250                         meson_i2c_stop(i2c);
 251                         break;
 252                 }
 253
 254                 meson_i2c_prepare_xfer(i2c);
 255                 break;
 256         case STATE_WRITE:
 257                 i2c->pos += i2c->count;
 258
 259                 if (i2c->pos >= i2c->msg->len) {
 260                         meson_i2c_stop(i2c);
 261                         break;
 262                 }
 263
 264                 meson_i2c_prepare_xfer(i2c);
 265                 break;
 266         case STATE_STOP:
 267                 i2c->state = STATE_IDLE;
 268                 complete(&i2c->done);
 269                 break;
 270         case STATE_IDLE:
 271                 break;
 272         }
 273
 274 out:
 275         if (i2c->state != STATE_IDLE) {
 276                 /* Restart the processing */
 277                 meson_i2c_write_tokens(i2c);
 278                 meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, 0);
 279                 meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START,
 280                                    REG_CTRL_START);
 281         }
 282
 283         spin_unlock(&i2c->lock);
 284
 285         return IRQ_HANDLED;
 286 }
 287
 288 static void meson_i2c_do_start(struct meson_i2c *i2c, struct i2c_msg *msg)
 289 {
 290         int token;
 291
 292         token = (msg->flags & I2C_M_RD) ? TOKEN_SLAVE_ADDR_READ :
 293                 TOKEN_SLAVE_ADDR_WRITE;
 294
 295         writel(msg->addr << 1, i2c->regs + REG_SLAVE_ADDR);
 296         meson_i2c_add_token(i2c, TOKEN_START);
 297         meson_i2c_add_token(i2c, token);
 298 }
 299
 300 static int meson_i2c_xfer_msg(struct meson_i2c *i2c, struct i2c_msg *msg,
 301                               int last)
 302 {
 303         unsigned long time_left, flags;
 304         int ret = 0;
 305
 306         i2c->msg = msg;
 307         i2c->last = last;
 308         i2c->pos = 0;
 309         i2c->count = 0;
 310         i2c->error = 0;
 311
 312         meson_i2c_reset_tokens(i2c);
 313
 314         flags = (msg->flags & I2C_M_IGNORE_NAK) ? REG_CTRL_ACK_IGNORE : 0;
 315         meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_ACK_IGNORE, flags);
 316
 317         if (!(msg->flags & I2C_M_NOSTART))
 318                 meson_i2c_do_start(i2c, msg);
 319
 320         i2c->state = (msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;
 321         meson_i2c_prepare_xfer(i2c);
 322         meson_i2c_write_tokens(i2c);
 323         reinit_completion(&i2c->done);
 324
 325         /* Start the transfer */
 326         meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, REG_CTRL_START);
 327
 328         time_left = msecs_to_jiffies(I2C_TIMEOUT_MS);
 329         time_left = wait_for_completion_timeout(&i2c->done, time_left);
 330
 331         /*
 332          * Protect access to i2c struct and registers from interrupt
 333          * handlers triggered by a transfer terminated after the
 334          * timeout period
 335          */
 336         spin_lock_irqsave(&i2c->lock, flags);
 337
 338         /* Abort any active operation */
 339         meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, 0);
 340
 341         if (!time_left) {
 342                 i2c->state = STATE_IDLE;
 343                 ret = -ETIMEDOUT;
 344         }
 345
 346         if (i2c->error)
 347                 ret = i2c->error;
 348
 349         spin_unlock_irqrestore(&i2c->lock, flags);
 350
 351         return ret;
 352 }
 353
 354 static int meson_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 355                           int num)
 356 {
 357         struct meson_i2c *i2c = adap->algo_data;
 358         int i, ret = 0, count = 0;
 359
 360         clk_enable(i2c->clk);
 361
 362         for (i = 0; i < num; i++) {
 363                 ret = meson_i2c_xfer_msg(i2c, msgs + i, i == num - 1);
 364                 if (ret)
 365                         break;
 366                 count++;
 367         }
 368
 369         clk_disable(i2c->clk);
 370
 371         return ret ? ret : count;
 372 }
 373
 374 static u32 meson_i2c_func(struct i2c_adapter *adap)
 375 {
 376         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 377 }
 378
 379 static const struct i2c_algorithm meson_i2c_algorithm = {
 380         .master_xfer    = meson_i2c_xfer,
 381         .functionality  = meson_i2c_func,
 382 };
 383
 384 static int meson_i2c_probe(struct platform_device *pdev)
 385 {
 386         struct device_node *np = pdev->dev.of_node;
 387         struct meson_i2c *i2c;
 388         struct resource *mem;
 389         struct i2c_timings timings;
 390         int irq, ret = 0;
 391
 392         i2c = devm_kzalloc(&pdev->dev, sizeof(struct meson_i2c), GFP_KERNEL);
 393         if (!i2c)
 394                 return -ENOMEM;
 395
 396         i2c_parse_fw_timings(&pdev->dev, &timings, true);
 397
 398         i2c->dev = &pdev->dev;
 399         platform_set_drvdata(pdev, i2c);
 400
 401         spin_lock_init(&i2c->lock);
 402         init_completion(&i2c->done);
 403
 404         i2c->clk = devm_clk_get(&pdev->dev, NULL);
 405         if (IS_ERR(i2c->clk)) {
 406                 dev_err(&pdev->dev, "can't get device clock\n");
 407                 return PTR_ERR(i2c->clk);
 408         }
 409
 410         mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 411         i2c->regs = devm_ioremap_resource(&pdev->dev, mem);
 412         if (IS_ERR(i2c->regs))
 413                 return PTR_ERR(i2c->regs);
 414
 415         irq = platform_get_irq(pdev, 0);
 416         if (irq < 0) {
 417                 dev_err(&pdev->dev, "can't find IRQ\n");
 418                 return irq;
 419         }
 420
 421         ret = devm_request_irq(&pdev->dev, irq, meson_i2c_irq, 0, NULL, i2c);
 422         if (ret < 0) {
 423                 dev_err(&pdev->dev, "can't request IRQ\n");
 424                 return ret;
 425         }
 426
 427         ret = clk_prepare(i2c->clk);
 428         if (ret < 0) {
 429                 dev_err(&pdev->dev, "can't prepare clock\n");
 430                 return ret;
 431         }
 432
 433         strlcpy(i2c->adap.name, "Meson I2C adapter",
 434                 sizeof(i2c->adap.name));
 435         i2c->adap.owner = THIS_MODULE;
 436         i2c->adap.algo = &meson_i2c_algorithm;
 437         i2c->adap.dev.parent = &pdev->dev;
 438         i2c->adap.dev.of_node = np;
 439         i2c->adap.algo_data = i2c;
 440
 441         /*
 442          * A transfer is triggered when START bit changes from 0 to 1.
 443          * Ensure that the bit is set to 0 after probe
 444          */
 445         meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, 0);
 446
 447         ret = i2c_add_adapter(&i2c->adap);
 448         if (ret < 0) {
 449                 clk_unprepare(i2c->clk);
 450                 return ret;
 451         }
 452
 453         meson_i2c_set_clk_div(i2c, timings.bus_freq_hz);
 454
 455         return 0;
 456 }
 457
 458 static int meson_i2c_remove(struct platform_device *pdev)
 459 {
 460         struct meson_i2c *i2c = platform_get_drvdata(pdev);
 461
 462         i2c_del_adapter(&i2c->adap);
 463         clk_unprepare(i2c->clk);
 464
 465         return 0;
 466 }
 467
 468 static const struct of_device_id meson_i2c_match[] = {
 469         { .compatible = "amlogic,meson6-i2c" },
 470         { .compatible = "amlogic,meson-gxbb-i2c" },
 471         { },
 472 };
 473 MODULE_DEVICE_TABLE(of, meson_i2c_match);
 474
 475 static struct platform_driver meson_i2c_driver = {
 476         .probe   = meson_i2c_probe,
 477         .remove  = meson_i2c_remove,
 478         .driver  = {
 479                 .name  = "meson-i2c",
 480                 .of_match_table = meson_i2c_match,
 481         },
 482 };
 483
 484 module_platform_driver(meson_i2c_driver);
 485
 486 MODULE_DESCRIPTION("Amlogic Meson I2C Bus driver");
 487 MODULE_AUTHOR("Beniamino Galvani <b.galvani@gmail.com>");
 488 MODULE_LICENSE("GPL v2");