drivers/i2c/busses/i2c-bcm2835.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * BCM2835 master mode driver
   4  */
   5
   6 #include <linux/clk.h>
   7 #include <linux/clkdev.h>
   8 #include <linux/clk-provider.h>
   9 #include <linux/completion.h>
  10 #include <linux/err.h>
  11 #include <linux/i2c.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/io.h>
  14 #include <linux/module.h>
  15 #include <linux/of_device.h>
  16 #include <linux/platform_device.h>
  17 #include <linux/slab.h>
  18
  19 #define BCM2835_I2C_C           0x0
  20 #define BCM2835_I2C_S           0x4
  21 #define BCM2835_I2C_DLEN        0x8
  22 #define BCM2835_I2C_A           0xc
  23 #define BCM2835_I2C_FIFO        0x10
  24 #define BCM2835_I2C_DIV         0x14
  25 #define BCM2835_I2C_DEL         0x18
  26 #define BCM2835_I2C_CLKT        0x1c
  27
  28 #define BCM2835_I2C_C_READ      BIT(0)
  29 #define BCM2835_I2C_C_CLEAR     BIT(4) /* bits 4 and 5 both clear */
  30 #define BCM2835_I2C_C_ST        BIT(7)
  31 #define BCM2835_I2C_C_INTD      BIT(8)
  32 #define BCM2835_I2C_C_INTT      BIT(9)
  33 #define BCM2835_I2C_C_INTR      BIT(10)
  34 #define BCM2835_I2C_C_I2CEN     BIT(15)
  35
  36 #define BCM2835_I2C_S_TA        BIT(0)
  37 #define BCM2835_I2C_S_DONE      BIT(1)
  38 #define BCM2835_I2C_S_TXW       BIT(2)
  39 #define BCM2835_I2C_S_RXR       BIT(3)
  40 #define BCM2835_I2C_S_TXD       BIT(4)
  41 #define BCM2835_I2C_S_RXD       BIT(5)
  42 #define BCM2835_I2C_S_TXE       BIT(6)
  43 #define BCM2835_I2C_S_RXF       BIT(7)
  44 #define BCM2835_I2C_S_ERR       BIT(8)
  45 #define BCM2835_I2C_S_CLKT      BIT(9)
  46 #define BCM2835_I2C_S_LEN       BIT(10) /* Fake bit for SW error reporting */
  47
  48 #define BCM2835_I2C_FEDL_SHIFT  16
  49 #define BCM2835_I2C_REDL_SHIFT  0
  50
  51 #define BCM2835_I2C_CDIV_MIN    0x0002
  52 #define BCM2835_I2C_CDIV_MAX    0xFFFE
  53
  54 struct bcm2835_i2c_dev {
  55         struct device *dev;
  56         void __iomem *regs;
  57         int irq;
  58         struct i2c_adapter adapter;
  59         struct completion completion;
  60         struct i2c_msg *curr_msg;
  61         int num_msgs;
  62         u32 msg_err;
  63         u8 *msg_buf;
  64         size_t msg_buf_remaining;
  65 };
  66
  67 static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev,
  68                                       u32 reg, u32 val)
  69 {
  70         writel(val, i2c_dev->regs + reg);
  71 }
  72
  73 static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
  74 {
  75         return readl(i2c_dev->regs + reg);
  76 }
  77
  78 #define to_clk_bcm2835_i2c(_hw) container_of(_hw, struct clk_bcm2835_i2c, hw)
  79 struct clk_bcm2835_i2c {
  80         struct clk_hw hw;
  81         struct bcm2835_i2c_dev *i2c_dev;
  82 };
  83
  84 static int clk_bcm2835_i2c_calc_divider(unsigned long rate,
  85                                 unsigned long parent_rate)
  86 {
  87         u32 divider = DIV_ROUND_UP(parent_rate, rate);
  88
  89         /*
  90          * Per the datasheet, the register is always interpreted as an even
  91          * number, by rounding down. In other words, the LSB is ignored. So,
  92          * if the LSB is set, increment the divider to avoid any issue.
  93          */
  94         if (divider & 1)
  95                 divider++;
  96         if ((divider < BCM2835_I2C_CDIV_MIN) ||
  97             (divider > BCM2835_I2C_CDIV_MAX))
  98                 return -EINVAL;
  99
 100         return divider;
 101 }
 102
 103 static int clk_bcm2835_i2c_set_rate(struct clk_hw *hw, unsigned long rate,
 104                                 unsigned long parent_rate)
 105 {
 106         struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw);
 107         u32 redl, fedl;
 108         u32 divider = clk_bcm2835_i2c_calc_divider(rate, parent_rate);
 109
 110         if (divider == -EINVAL)
 111                 return -EINVAL;
 112
 113         bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DIV, divider);
 114
 115         /*
 116          * Number of core clocks to wait after falling edge before
 117          * outputting the next data bit.  Note that both FEDL and REDL
 118          * can't be greater than CDIV/2.
 119          */
 120         fedl = max(divider / 16, 1u);
 121
 122         /*
 123          * Number of core clocks to wait after rising edge before
 124          * sampling the next incoming data bit.
 125          */
 126         redl = max(divider / 4, 1u);
 127
 128         bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DEL,
 129                            (fedl << BCM2835_I2C_FEDL_SHIFT) |
 130                            (redl << BCM2835_I2C_REDL_SHIFT));
 131         return 0;
 132 }
 133
 134 static long clk_bcm2835_i2c_round_rate(struct clk_hw *hw, unsigned long rate,
 135                                 unsigned long *parent_rate)
 136 {
 137         u32 divider = clk_bcm2835_i2c_calc_divider(rate, *parent_rate);
 138
 139         return DIV_ROUND_UP(*parent_rate, divider);
 140 }
 141
 142 static unsigned long clk_bcm2835_i2c_recalc_rate(struct clk_hw *hw,
 143                                                 unsigned long parent_rate)
 144 {
 145         struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw);
 146         u32 divider = bcm2835_i2c_readl(div->i2c_dev, BCM2835_I2C_DIV);
 147
 148         return DIV_ROUND_UP(parent_rate, divider);
 149 }
 150
 151 static const struct clk_ops clk_bcm2835_i2c_ops = {
 152         .set_rate = clk_bcm2835_i2c_set_rate,
 153         .round_rate = clk_bcm2835_i2c_round_rate,
 154         .recalc_rate = clk_bcm2835_i2c_recalc_rate,
 155 };
 156
 157 static struct clk *bcm2835_i2c_register_div(struct device *dev,
 158                                         struct clk *mclk,
 159                                         struct bcm2835_i2c_dev *i2c_dev)
 160 {
 161         struct clk_init_data init;
 162         struct clk_bcm2835_i2c *priv;
 163         char name[32];
 164         const char *mclk_name;
 165
 166         snprintf(name, sizeof(name), "%s_div", dev_name(dev));
 167
 168         mclk_name = __clk_get_name(mclk);
 169
 170         init.ops = &clk_bcm2835_i2c_ops;
 171         init.name = name;
 172         init.parent_names = (const char* []) { mclk_name };
 173         init.num_parents = 1;
 174         init.flags = 0;
 175
 176         priv = devm_kzalloc(dev, sizeof(struct clk_bcm2835_i2c), GFP_KERNEL);
 177         if (priv == NULL)
 178                 return ERR_PTR(-ENOMEM);
 179
 180         priv->hw.init = &init;
 181         priv->i2c_dev = i2c_dev;
 182
 183         clk_hw_register_clkdev(&priv->hw, "div", dev_name(dev));
 184         return devm_clk_register(dev, &priv->hw);
 185 }
 186
 187 static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
 188 {
 189         u32 val;
 190
 191         while (i2c_dev->msg_buf_remaining) {
 192                 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 193                 if (!(val & BCM2835_I2C_S_TXD))
 194                         break;
 195                 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO,
 196                                    *i2c_dev->msg_buf);
 197                 i2c_dev->msg_buf++;
 198                 i2c_dev->msg_buf_remaining--;
 199         }
 200 }
 201
 202 static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev)
 203 {
 204         u32 val;
 205
 206         while (i2c_dev->msg_buf_remaining) {
 207                 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 208                 if (!(val & BCM2835_I2C_S_RXD))
 209                         break;
 210                 *i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev,
 211                                                       BCM2835_I2C_FIFO);
 212                 i2c_dev->msg_buf++;
 213                 i2c_dev->msg_buf_remaining--;
 214         }
 215 }
 216
 217 /*
 218  * Repeated Start Condition (Sr)
 219  * The BCM2835 ARM Peripherals datasheet mentions a way to trigger a Sr when it
 220  * talks about reading from a slave with 10 bit address. This is achieved by
 221  * issuing a write, poll the I2CS.TA flag and wait for it to be set, and then
 222  * issue a read.
 223  * A comment in https://github.com/raspberrypi/linux/issues/254 shows how the
 224  * firmware actually does it using polling and says that it's a workaround for
 225  * a problem in the state machine.
 226  * It turns out that it is possible to use the TXW interrupt to know when the
 227  * transfer is active, provided the FIFO has not been prefilled.
 228  */
 229
 230 static void bcm2835_i2c_start_transfer(struct bcm2835_i2c_dev *i2c_dev)
 231 {
 232         u32 c = BCM2835_I2C_C_ST | BCM2835_I2C_C_I2CEN;
 233         struct i2c_msg *msg = i2c_dev->curr_msg;
 234         bool last_msg = (i2c_dev->num_msgs == 1);
 235
 236         if (!i2c_dev->num_msgs)
 237                 return;
 238
 239         i2c_dev->num_msgs--;
 240         i2c_dev->msg_buf = msg->buf;
 241         i2c_dev->msg_buf_remaining = msg->len;
 242
 243         if (msg->flags & I2C_M_RD)
 244                 c |= BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR;
 245         else
 246                 c |= BCM2835_I2C_C_INTT;
 247
 248         if (last_msg)
 249                 c |= BCM2835_I2C_C_INTD;
 250
 251         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr);
 252         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len);
 253         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c);
 254 }
 255
 256 static void bcm2835_i2c_finish_transfer(struct bcm2835_i2c_dev *i2c_dev)
 257 {
 258         i2c_dev->curr_msg = NULL;
 259         i2c_dev->num_msgs = 0;
 260
 261         i2c_dev->msg_buf = NULL;
 262         i2c_dev->msg_buf_remaining = 0;
 263 }
 264
 265 /*
 266  * Note about I2C_C_CLEAR on error:
 267  * The I2C_C_CLEAR on errors will take some time to resolve -- if you were in
 268  * non-idle state and I2C_C_READ, it sets an abort_rx flag and runs through
 269  * the state machine to send a NACK and a STOP. Since we're setting CLEAR
 270  * without I2CEN, that NACK will be hanging around queued up for next time
 271  * we start the engine.
 272  */
 273
 274 static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
 275 {
 276         struct bcm2835_i2c_dev *i2c_dev = data;
 277         u32 val, err;
 278
 279         val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 280
 281         err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);
 282         if (err) {
 283                 i2c_dev->msg_err = err;
 284                 goto complete;
 285         }
 286
 287         if (val & BCM2835_I2C_S_DONE) {
 288                 if (!i2c_dev->curr_msg) {
 289                         dev_err(i2c_dev->dev, "Got unexpected interrupt (from firmware?)\n");
 290                 } else if (i2c_dev->curr_msg->flags & I2C_M_RD) {
 291                         bcm2835_drain_rxfifo(i2c_dev);
 292                         val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 293                 }
 294
 295                 if ((val & BCM2835_I2C_S_RXD) || i2c_dev->msg_buf_remaining)
 296                         i2c_dev->msg_err = BCM2835_I2C_S_LEN;
 297                 else
 298                         i2c_dev->msg_err = 0;
 299                 goto complete;
 300         }
 301
 302         if (val & BCM2835_I2C_S_TXW) {
 303                 if (!i2c_dev->msg_buf_remaining) {
 304                         i2c_dev->msg_err = val | BCM2835_I2C_S_LEN;
 305                         goto complete;
 306                 }
 307
 308                 bcm2835_fill_txfifo(i2c_dev);
 309
 310                 if (i2c_dev->num_msgs && !i2c_dev->msg_buf_remaining) {
 311                         i2c_dev->curr_msg++;
 312                         bcm2835_i2c_start_transfer(i2c_dev);
 313                 }
 314
 315                 return IRQ_HANDLED;
 316         }
 317
 318         if (val & BCM2835_I2C_S_RXR) {
 319                 if (!i2c_dev->msg_buf_remaining) {
 320                         i2c_dev->msg_err = val | BCM2835_I2C_S_LEN;
 321                         goto complete;
 322                 }
 323
 324                 bcm2835_drain_rxfifo(i2c_dev);
 325                 return IRQ_HANDLED;
 326         }
 327
 328         return IRQ_NONE;
 329
 330 complete:
 331         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
 332         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, BCM2835_I2C_S_CLKT |
 333                            BCM2835_I2C_S_ERR | BCM2835_I2C_S_DONE);
 334         complete(&i2c_dev->completion);
 335
 336         return IRQ_HANDLED;
 337 }
 338
 339 static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 340                             int num)
 341 {
 342         struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
 343         unsigned long time_left;
 344         int i;
 345
 346         for (i = 0; i < (num - 1); i++)
 347                 if (msgs[i].flags & I2C_M_RD) {
 348                         dev_warn_once(i2c_dev->dev,
 349                                       "only one read message supported, has to be last\n");
 350                         return -EOPNOTSUPP;
 351                 }
 352
 353         i2c_dev->curr_msg = msgs;
 354         i2c_dev->num_msgs = num;
 355         reinit_completion(&i2c_dev->completion);
 356
 357         bcm2835_i2c_start_transfer(i2c_dev);
 358
 359         time_left = wait_for_completion_timeout(&i2c_dev->completion,
 360                                                 adap->timeout);
 361
 362         bcm2835_i2c_finish_transfer(i2c_dev);
 363
 364         if (!time_left) {
 365                 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C,
 366                                    BCM2835_I2C_C_CLEAR);
 367                 dev_err(i2c_dev->dev, "i2c transfer timed out\n");
 368                 return -ETIMEDOUT;
 369         }
 370
 371         if (!i2c_dev->msg_err)
 372                 return num;
 373
 374         dev_dbg(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);
 375
 376         if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)
 377                 return -EREMOTEIO;
 378
 379         return -EIO;
 380 }
 381
 382 static u32 bcm2835_i2c_func(struct i2c_adapter *adap)
 383 {
 384         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 385 }
 386
 387 static const struct i2c_algorithm bcm2835_i2c_algo = {
 388         .master_xfer    = bcm2835_i2c_xfer,
 389         .functionality  = bcm2835_i2c_func,
 390 };
 391
 392 /*
 393  * The BCM2835 was reported to have problems with clock stretching:
 394  * http://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html
 395  * https://www.raspberrypi.org/forums/viewtopic.php?p=146272
 396  */
 397 static const struct i2c_adapter_quirks bcm2835_i2c_quirks = {
 398         .flags = I2C_AQ_NO_CLK_STRETCH,
 399 };
 400
 401 static int bcm2835_i2c_probe(struct platform_device *pdev)
 402 {
 403         struct bcm2835_i2c_dev *i2c_dev;
 404         struct resource *mem, *irq;
 405         int ret;
 406         struct i2c_adapter *adap;
 407         struct clk *bus_clk;
 408         struct clk *mclk;
 409         u32 bus_clk_rate;
 410
 411         i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
 412         if (!i2c_dev)
 413                 return -ENOMEM;
 414         platform_set_drvdata(pdev, i2c_dev);
 415         i2c_dev->dev = &pdev->dev;
 416         init_completion(&i2c_dev->completion);
 417
 418         mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 419         i2c_dev->regs = devm_ioremap_resource(&pdev->dev, mem);
 420         if (IS_ERR(i2c_dev->regs))
 421                 return PTR_ERR(i2c_dev->regs);
 422
 423         mclk = devm_clk_get(&pdev->dev, NULL);
 424         if (IS_ERR(mclk)) {
 425                 if (PTR_ERR(mclk) != -EPROBE_DEFER)
 426                         dev_err(&pdev->dev, "Could not get clock\n");
 427                 return PTR_ERR(mclk);
 428         }
 429
 430         bus_clk = bcm2835_i2c_register_div(&pdev->dev, mclk, i2c_dev);
 431
 432         if (IS_ERR(bus_clk)) {
 433                 dev_err(&pdev->dev, "Could not register clock\n");
 434                 return PTR_ERR(bus_clk);
 435         }
 436
 437         ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
 438                                    &bus_clk_rate);
 439         if (ret < 0) {
 440                 dev_warn(&pdev->dev,
 441                          "Could not read clock-frequency property\n");
 442                 bus_clk_rate = 100000;
 443         }
 444
 445         ret = clk_set_rate_exclusive(bus_clk, bus_clk_rate);
 446         if (ret < 0) {
 447                 dev_err(&pdev->dev, "Could not set clock frequency\n");
 448                 return ret;
 449         }
 450
 451         ret = clk_prepare_enable(bus_clk);
 452         if (ret) {
 453                 dev_err(&pdev->dev, "Couldn't prepare clock");
 454                 return ret;
 455         }
 456
 457         irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 458         if (!irq) {
 459                 dev_err(&pdev->dev, "No IRQ resource\n");
 460                 return -ENODEV;
 461         }
 462         i2c_dev->irq = irq->start;
 463
 464         ret = request_irq(i2c_dev->irq, bcm2835_i2c_isr, IRQF_SHARED,
 465                           dev_name(&pdev->dev), i2c_dev);
 466         if (ret) {
 467                 dev_err(&pdev->dev, "Could not request IRQ\n");
 468                 return -ENODEV;
 469         }
 470
 471         adap = &i2c_dev->adapter;
 472         i2c_set_adapdata(adap, i2c_dev);
 473         adap->owner = THIS_MODULE;
 474         adap->class = I2C_CLASS_DEPRECATED;
 475         snprintf(adap->name, sizeof(adap->name), "bcm2835 (%s)",
 476                  of_node_full_name(pdev->dev.of_node));
 477         adap->algo = &bcm2835_i2c_algo;
 478         adap->dev.parent = &pdev->dev;
 479         adap->dev.of_node = pdev->dev.of_node;
 480         adap->quirks = of_device_get_match_data(&pdev->dev);
 481
 482         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);
 483
 484         ret = i2c_add_adapter(adap);
 485         if (ret)
 486                 free_irq(i2c_dev->irq, i2c_dev);
 487
 488         return ret;
 489 }
 490
 491 static int bcm2835_i2c_remove(struct platform_device *pdev)
 492 {
 493         struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
 494         struct clk *bus_clk = devm_clk_get(i2c_dev->dev, "div");
 495
 496         clk_rate_exclusive_put(bus_clk);
 497         clk_disable_unprepare(bus_clk);
 498
 499         free_irq(i2c_dev->irq, i2c_dev);
 500         i2c_del_adapter(&i2c_dev->adapter);
 501
 502         return 0;
 503 }
 504
 505 static const struct of_device_id bcm2835_i2c_of_match[] = {
 506         { .compatible = "brcm,bcm2711-i2c" },
 507         { .compatible = "brcm,bcm2835-i2c", .data = &bcm2835_i2c_quirks },
 508         {},
 509 };
 510 MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match);
 511
 512 static struct platform_driver bcm2835_i2c_driver = {
 513         .probe          = bcm2835_i2c_probe,
 514         .remove         = bcm2835_i2c_remove,
 515         .driver         = {
 516                 .name   = "i2c-bcm2835",
 517                 .of_match_table = bcm2835_i2c_of_match,
 518         },
 519 };
 520 module_platform_driver(bcm2835_i2c_driver);
 521
 522 MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
 523 MODULE_DESCRIPTION("BCM2835 I2C bus adapter");
 524 MODULE_LICENSE("GPL v2");
 525 MODULE_ALIAS("platform:i2c-bcm2835");