drivers/i2c/busses/i2c-bcm2835.c

   1 /*
   2  * BCM2835 master mode driver
   3  *
   4  * This software is licensed under the terms of the GNU General Public
   5  * License version 2, as published by the Free Software Foundation, and
   6  * may be copied, distributed, and modified under those terms.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #include <linux/clk.h>
  15 #include <linux/completion.h>
  16 #include <linux/err.h>
  17 #include <linux/i2c.h>
  18 #include <linux/interrupt.h>
  19 #include <linux/io.h>
  20 #include <linux/module.h>
  21 #include <linux/platform_device.h>
  22 #include <linux/slab.h>
  23
  24 #define BCM2835_I2C_C           0x0
  25 #define BCM2835_I2C_S           0x4
  26 #define BCM2835_I2C_DLEN        0x8
  27 #define BCM2835_I2C_A           0xc
  28 #define BCM2835_I2C_FIFO        0x10
  29 #define BCM2835_I2C_DIV         0x14
  30 #define BCM2835_I2C_DEL         0x18
  31 #define BCM2835_I2C_CLKT        0x1c
  32
  33 #define BCM2835_I2C_C_READ      BIT(0)
  34 #define BCM2835_I2C_C_CLEAR     BIT(4) /* bits 4 and 5 both clear */
  35 #define BCM2835_I2C_C_ST        BIT(7)
  36 #define BCM2835_I2C_C_INTD      BIT(8)
  37 #define BCM2835_I2C_C_INTT      BIT(9)
  38 #define BCM2835_I2C_C_INTR      BIT(10)
  39 #define BCM2835_I2C_C_I2CEN     BIT(15)
  40
  41 #define BCM2835_I2C_S_TA        BIT(0)
  42 #define BCM2835_I2C_S_DONE      BIT(1)
  43 #define BCM2835_I2C_S_TXW       BIT(2)
  44 #define BCM2835_I2C_S_RXR       BIT(3)
  45 #define BCM2835_I2C_S_TXD       BIT(4)
  46 #define BCM2835_I2C_S_RXD       BIT(5)
  47 #define BCM2835_I2C_S_TXE       BIT(6)
  48 #define BCM2835_I2C_S_RXF       BIT(7)
  49 #define BCM2835_I2C_S_ERR       BIT(8)
  50 #define BCM2835_I2C_S_CLKT      BIT(9)
  51 #define BCM2835_I2C_S_LEN       BIT(10) /* Fake bit for SW error reporting */
  52
  53 #define BCM2835_I2C_FEDL_SHIFT  16
  54 #define BCM2835_I2C_REDL_SHIFT  0
  55
  56 #define BCM2835_I2C_CDIV_MIN    0x0002
  57 #define BCM2835_I2C_CDIV_MAX    0xFFFE
  58
  59 struct bcm2835_i2c_dev {
  60         struct device *dev;
  61         void __iomem *regs;
  62         struct clk *clk;
  63         int irq;
  64         u32 bus_clk_rate;
  65         struct i2c_adapter adapter;
  66         struct completion completion;
  67         struct i2c_msg *curr_msg;
  68         int num_msgs;
  69         u32 msg_err;
  70         u8 *msg_buf;
  71         size_t msg_buf_remaining;
  72 };
  73
  74 static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev,
  75                                       u32 reg, u32 val)
  76 {
  77         writel(val, i2c_dev->regs + reg);
  78 }
  79
  80 static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
  81 {
  82         return readl(i2c_dev->regs + reg);
  83 }
  84
  85 static int bcm2835_i2c_set_divider(struct bcm2835_i2c_dev *i2c_dev)
  86 {
  87         u32 divider, redl, fedl;
  88
  89         divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk),
  90                                i2c_dev->bus_clk_rate);
  91         /*
  92          * Per the datasheet, the register is always interpreted as an even
  93          * number, by rounding down. In other words, the LSB is ignored. So,
  94          * if the LSB is set, increment the divider to avoid any issue.
  95          */
  96         if (divider & 1)
  97                 divider++;
  98         if ((divider < BCM2835_I2C_CDIV_MIN) ||
  99             (divider > BCM2835_I2C_CDIV_MAX)) {
 100                 dev_err_ratelimited(i2c_dev->dev, "Invalid clock-frequency\n");
 101                 return -EINVAL;
 102         }
 103
 104         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
 105
 106         /*
 107          * Number of core clocks to wait after falling edge before
 108          * outputting the next data bit.  Note that both FEDL and REDL
 109          * can't be greater than CDIV/2.
 110          */
 111         fedl = max(divider / 16, 1u);
 112
 113         /*
 114          * Number of core clocks to wait after rising edge before
 115          * sampling the next incoming data bit.
 116          */
 117         redl = max(divider / 4, 1u);
 118
 119         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DEL,
 120                            (fedl << BCM2835_I2C_FEDL_SHIFT) |
 121                            (redl << BCM2835_I2C_REDL_SHIFT));
 122         return 0;
 123 }
 124
 125 static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
 126 {
 127         u32 val;
 128
 129         while (i2c_dev->msg_buf_remaining) {
 130                 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 131                 if (!(val & BCM2835_I2C_S_TXD))
 132                         break;
 133                 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO,
 134                                    *i2c_dev->msg_buf);
 135                 i2c_dev->msg_buf++;
 136                 i2c_dev->msg_buf_remaining--;
 137         }
 138 }
 139
 140 static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev)
 141 {
 142         u32 val;
 143
 144         while (i2c_dev->msg_buf_remaining) {
 145                 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 146                 if (!(val & BCM2835_I2C_S_RXD))
 147                         break;
 148                 *i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev,
 149                                                       BCM2835_I2C_FIFO);
 150                 i2c_dev->msg_buf++;
 151                 i2c_dev->msg_buf_remaining--;
 152         }
 153 }
 154
 155 /*
 156  * Repeated Start Condition (Sr)
 157  * The BCM2835 ARM Peripherals datasheet mentions a way to trigger a Sr when it
 158  * talks about reading from a slave with 10 bit address. This is achieved by
 159  * issuing a write, poll the I2CS.TA flag and wait for it to be set, and then
 160  * issue a read.
 161  * A comment in https://github.com/raspberrypi/linux/issues/254 shows how the
 162  * firmware actually does it using polling and says that it's a workaround for
 163  * a problem in the state machine.
 164  * It turns out that it is possible to use the TXW interrupt to know when the
 165  * transfer is active, provided the FIFO has not been prefilled.
 166  */
 167
 168 static void bcm2835_i2c_start_transfer(struct bcm2835_i2c_dev *i2c_dev)
 169 {
 170         u32 c = BCM2835_I2C_C_ST | BCM2835_I2C_C_I2CEN;
 171         struct i2c_msg *msg = i2c_dev->curr_msg;
 172         bool last_msg = (i2c_dev->num_msgs == 1);
 173
 174         if (!i2c_dev->num_msgs)
 175                 return;
 176
 177         i2c_dev->num_msgs--;
 178         i2c_dev->msg_buf = msg->buf;
 179         i2c_dev->msg_buf_remaining = msg->len;
 180
 181         if (msg->flags & I2C_M_RD)
 182                 c |= BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR;
 183         else
 184                 c |= BCM2835_I2C_C_INTT;
 185
 186         if (last_msg)
 187                 c |= BCM2835_I2C_C_INTD;
 188
 189         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr);
 190         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len);
 191         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c);
 192 }
 193
 194 static void bcm2835_i2c_finish_transfer(struct bcm2835_i2c_dev *i2c_dev)
 195 {
 196         i2c_dev->curr_msg = NULL;
 197         i2c_dev->num_msgs = 0;
 198
 199         i2c_dev->msg_buf = NULL;
 200         i2c_dev->msg_buf_remaining = 0;
 201 }
 202
 203 /*
 204  * Note about I2C_C_CLEAR on error:
 205  * The I2C_C_CLEAR on errors will take some time to resolve -- if you were in
 206  * non-idle state and I2C_C_READ, it sets an abort_rx flag and runs through
 207  * the state machine to send a NACK and a STOP. Since we're setting CLEAR
 208  * without I2CEN, that NACK will be hanging around queued up for next time
 209  * we start the engine.
 210  */
 211
 212 static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
 213 {
 214         struct bcm2835_i2c_dev *i2c_dev = data;
 215         u32 val, err;
 216
 217         val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 218
 219         err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);
 220         if (err) {
 221                 i2c_dev->msg_err = err;
 222                 goto complete;
 223         }
 224
 225         if (val & BCM2835_I2C_S_DONE) {
 226                 if (!i2c_dev->curr_msg) {
 227                         dev_err(i2c_dev->dev, "Got unexpected interrupt (from firmware?)\n");
 228                 } else if (i2c_dev->curr_msg->flags & I2C_M_RD) {
 229                         bcm2835_drain_rxfifo(i2c_dev);
 230                         val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 231                 }
 232
 233                 if ((val & BCM2835_I2C_S_RXD) || i2c_dev->msg_buf_remaining)
 234                         i2c_dev->msg_err = BCM2835_I2C_S_LEN;
 235                 else
 236                         i2c_dev->msg_err = 0;
 237                 goto complete;
 238         }
 239
 240         if (val & BCM2835_I2C_S_TXW) {
 241                 if (!i2c_dev->msg_buf_remaining) {
 242                         i2c_dev->msg_err = val | BCM2835_I2C_S_LEN;
 243                         goto complete;
 244                 }
 245
 246                 bcm2835_fill_txfifo(i2c_dev);
 247
 248                 if (i2c_dev->num_msgs && !i2c_dev->msg_buf_remaining) {
 249                         i2c_dev->curr_msg++;
 250                         bcm2835_i2c_start_transfer(i2c_dev);
 251                 }
 252
 253                 return IRQ_HANDLED;
 254         }
 255
 256         if (val & BCM2835_I2C_S_RXR) {
 257                 if (!i2c_dev->msg_buf_remaining) {
 258                         i2c_dev->msg_err = val | BCM2835_I2C_S_LEN;
 259                         goto complete;
 260                 }
 261
 262                 bcm2835_drain_rxfifo(i2c_dev);
 263                 return IRQ_HANDLED;
 264         }
 265
 266         return IRQ_NONE;
 267
 268 complete:
 269         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
 270         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, BCM2835_I2C_S_CLKT |
 271                            BCM2835_I2C_S_ERR | BCM2835_I2C_S_DONE);
 272         complete(&i2c_dev->completion);
 273
 274         return IRQ_HANDLED;
 275 }
 276
 277 static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 278                             int num)
 279 {
 280         struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
 281         unsigned long time_left;
 282         int i, ret;
 283
 284         for (i = 0; i < (num - 1); i++)
 285                 if (msgs[i].flags & I2C_M_RD) {
 286                         dev_warn_once(i2c_dev->dev,
 287                                       "only one read message supported, has to be last\n");
 288                         return -EOPNOTSUPP;
 289                 }
 290
 291         ret = bcm2835_i2c_set_divider(i2c_dev);
 292         if (ret)
 293                 return ret;
 294
 295         i2c_dev->curr_msg = msgs;
 296         i2c_dev->num_msgs = num;
 297         reinit_completion(&i2c_dev->completion);
 298
 299         bcm2835_i2c_start_transfer(i2c_dev);
 300
 301         time_left = wait_for_completion_timeout(&i2c_dev->completion,
 302                                                 adap->timeout);
 303
 304         bcm2835_i2c_finish_transfer(i2c_dev);
 305
 306         if (!time_left) {
 307                 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C,
 308                                    BCM2835_I2C_C_CLEAR);
 309                 dev_err(i2c_dev->dev, "i2c transfer timed out\n");
 310                 return -ETIMEDOUT;
 311         }
 312
 313         if (!i2c_dev->msg_err)
 314                 return num;
 315
 316         dev_dbg(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);
 317
 318         if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)
 319                 return -EREMOTEIO;
 320
 321         return -EIO;
 322 }
 323
 324 static u32 bcm2835_i2c_func(struct i2c_adapter *adap)
 325 {
 326         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 327 }
 328
 329 static const struct i2c_algorithm bcm2835_i2c_algo = {
 330         .master_xfer    = bcm2835_i2c_xfer,
 331         .functionality  = bcm2835_i2c_func,
 332 };
 333
 334 /*
 335  * This HW was reported to have problems with clock stretching:
 336  * http://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html
 337  * https://www.raspberrypi.org/forums/viewtopic.php?p=146272
 338  */
 339 static const struct i2c_adapter_quirks bcm2835_i2c_quirks = {
 340         .flags = I2C_AQ_NO_CLK_STRETCH,
 341 };
 342
 343 static int bcm2835_i2c_probe(struct platform_device *pdev)
 344 {
 345         struct bcm2835_i2c_dev *i2c_dev;
 346         struct resource *mem, *irq;
 347         int ret;
 348         struct i2c_adapter *adap;
 349
 350         i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
 351         if (!i2c_dev)
 352                 return -ENOMEM;
 353         platform_set_drvdata(pdev, i2c_dev);
 354         i2c_dev->dev = &pdev->dev;
 355         init_completion(&i2c_dev->completion);
 356
 357         mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 358         i2c_dev->regs = devm_ioremap_resource(&pdev->dev, mem);
 359         if (IS_ERR(i2c_dev->regs))
 360                 return PTR_ERR(i2c_dev->regs);
 361
 362         i2c_dev->clk = devm_clk_get(&pdev->dev, NULL);
 363         if (IS_ERR(i2c_dev->clk)) {
 364                 if (PTR_ERR(i2c_dev->clk) != -EPROBE_DEFER)
 365                         dev_err(&pdev->dev, "Could not get clock\n");
 366                 return PTR_ERR(i2c_dev->clk);
 367         }
 368
 369         ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
 370                                    &i2c_dev->bus_clk_rate);
 371         if (ret < 0) {
 372                 dev_warn(&pdev->dev,
 373                          "Could not read clock-frequency property\n");
 374                 i2c_dev->bus_clk_rate = 100000;
 375         }
 376
 377         irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 378         if (!irq) {
 379                 dev_err(&pdev->dev, "No IRQ resource\n");
 380                 return -ENODEV;
 381         }
 382         i2c_dev->irq = irq->start;
 383
 384         ret = request_irq(i2c_dev->irq, bcm2835_i2c_isr, IRQF_SHARED,
 385                           dev_name(&pdev->dev), i2c_dev);
 386         if (ret) {
 387                 dev_err(&pdev->dev, "Could not request IRQ\n");
 388                 return -ENODEV;
 389         }
 390
 391         adap = &i2c_dev->adapter;
 392         i2c_set_adapdata(adap, i2c_dev);
 393         adap->owner = THIS_MODULE;
 394         adap->class = I2C_CLASS_DEPRECATED;
 395         strlcpy(adap->name, "bcm2835 I2C adapter", sizeof(adap->name));
 396         adap->algo = &bcm2835_i2c_algo;
 397         adap->dev.parent = &pdev->dev;
 398         adap->dev.of_node = pdev->dev.of_node;
 399         adap->quirks = &bcm2835_i2c_quirks;
 400
 401         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);
 402
 403         ret = i2c_add_adapter(adap);
 404         if (ret)
 405                 free_irq(i2c_dev->irq, i2c_dev);
 406
 407         return ret;
 408 }
 409
 410 static int bcm2835_i2c_remove(struct platform_device *pdev)
 411 {
 412         struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
 413
 414         free_irq(i2c_dev->irq, i2c_dev);
 415         i2c_del_adapter(&i2c_dev->adapter);
 416
 417         return 0;
 418 }
 419
 420 static const struct of_device_id bcm2835_i2c_of_match[] = {
 421         { .compatible = "brcm,bcm2835-i2c" },
 422         {},
 423 };
 424 MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match);
 425
 426 static struct platform_driver bcm2835_i2c_driver = {
 427         .probe          = bcm2835_i2c_probe,
 428         .remove         = bcm2835_i2c_remove,
 429         .driver         = {
 430                 .name   = "i2c-bcm2835",
 431                 .of_match_table = bcm2835_i2c_of_match,
 432         },
 433 };
 434 module_platform_driver(bcm2835_i2c_driver);
 435
 436 MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
 437 MODULE_DESCRIPTION("BCM2835 I2C bus adapter");
 438 MODULE_LICENSE("GPL v2");
 439 MODULE_ALIAS("platform:i2c-bcm2835");