LXR linux/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
  54struct 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        struct clk *bus_clk;
  62        int num_msgs;
  63        u32 msg_err;
  64        u8 *msg_buf;
  65        size_t msg_buf_remaining;
  66};
  67
  68static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev,
  69                                      u32 reg, u32 val)
  70{
  71        writel(val, i2c_dev->regs + reg);
  72}
  73
  74static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
  75{
  76        return readl(i2c_dev->regs + reg);
  77}
  78
  79#define to_clk_bcm2835_i2c(_hw) container_of(_hw, struct clk_bcm2835_i2c, hw)
  80struct clk_bcm2835_i2c {
  81        struct clk_hw hw;
  82        struct bcm2835_i2c_dev *i2c_dev;
  83};
  84
  85static int clk_bcm2835_i2c_calc_divider(unsigned long rate,
  86                                unsigned long parent_rate)
  87{
  88        u32 divider = DIV_ROUND_UP(parent_rate, rate);
  89
  90        /*
  91         * Per the datasheet, the register is always interpreted as an even
  92         * number, by rounding down. In other words, the LSB is ignored. So,
  93         * if the LSB is set, increment the divider to avoid any issue.
  94         */
  95        if (divider & 1)
  96                divider++;
  97        if ((divider < BCM2835_I2C_CDIV_MIN) ||
  98            (divider > BCM2835_I2C_CDIV_MAX))
  99                return -EINVAL;
 100
 101        return divider;
 102}
 103
 104static int clk_bcm2835_i2c_set_rate(struct clk_hw *hw, unsigned long rate,
 105                                unsigned long parent_rate)
 106{
 107        struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw);
 108        u32 redl, fedl;
 109        u32 divider = clk_bcm2835_i2c_calc_divider(rate, parent_rate);
 110
 111        if (divider == -EINVAL)
 112                return -EINVAL;
 113
 114        bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DIV, divider);
 115
 116        /*
 117         * Number of core clocks to wait after falling edge before
 118         * outputting the next data bit.  Note that both FEDL and REDL
 119         * can't be greater than CDIV/2.
 120         */
 121        fedl = max(divider / 16, 1u);
 122
 123        /*
 124         * Number of core clocks to wait after rising edge before
 125         * sampling the next incoming data bit.
 126         */
 127        redl = max(divider / 4, 1u);
 128
 129        bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DEL,
 130                           (fedl << BCM2835_I2C_FEDL_SHIFT) |
 131                           (redl << BCM2835_I2C_REDL_SHIFT));
 132        return 0;
 133}
 134
 135static long clk_bcm2835_i2c_round_rate(struct clk_hw *hw, unsigned long rate,
 136                                unsigned long *parent_rate)
 137{
 138        u32 divider = clk_bcm2835_i2c_calc_divider(rate, *parent_rate);
 139
 140        return DIV_ROUND_UP(*parent_rate, divider);
 141}
 142
 143static unsigned long clk_bcm2835_i2c_recalc_rate(struct clk_hw *hw,
 144                                                unsigned long parent_rate)
 145{
 146        struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw);
 147        u32 divider = bcm2835_i2c_readl(div->i2c_dev, BCM2835_I2C_DIV);
 148
 149        return DIV_ROUND_UP(parent_rate, divider);
 150}
 151
 152static const struct clk_ops clk_bcm2835_i2c_ops = {
 153        .set_rate = clk_bcm2835_i2c_set_rate,
 154        .round_rate = clk_bcm2835_i2c_round_rate,
 155        .recalc_rate = clk_bcm2835_i2c_recalc_rate,
 156};
 157
 158static struct clk *bcm2835_i2c_register_div(struct device *dev,
 159                                        struct clk *mclk,
 160                                        struct bcm2835_i2c_dev *i2c_dev)
 161{
 162        struct clk_init_data init;
 163        struct clk_bcm2835_i2c *priv;
 164        char name[32];
 165        const char *mclk_name;
 166
 167        snprintf(name, sizeof(name), "%s_div", dev_name(dev));
 168
 169        mclk_name = __clk_get_name(mclk);
 170
 171        init.ops = &clk_bcm2835_i2c_ops;
 172        init.name = name;
 173        init.parent_names = (const char* []) { mclk_name };
 174        init.num_parents = 1;
 175        init.flags = 0;
 176
 177        priv = devm_kzalloc(dev, sizeof(struct clk_bcm2835_i2c), GFP_KERNEL);
 178        if (priv == NULL)
 179                return ERR_PTR(-ENOMEM);
 180
 181        priv->hw.init = &init;
 182        priv->i2c_dev = i2c_dev;
 183
 184        clk_hw_register_clkdev(&priv->hw, "div", dev_name(dev));
 185        return devm_clk_register(dev, &priv->hw);
 186}
 187
 188static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
 189{
 190        u32 val;
 191
 192        while (i2c_dev->msg_buf_remaining) {
 193                val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 194                if (!(val & BCM2835_I2C_S_TXD))
 195                        break;
 196                bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO,
 197                                   *i2c_dev->msg_buf);
 198                i2c_dev->msg_buf++;
 199                i2c_dev->msg_buf_remaining--;
 200        }
 201}
 202
 203static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev)
 204{
 205        u32 val;
 206
 207        while (i2c_dev->msg_buf_remaining) {
 208                val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 209                if (!(val & BCM2835_I2C_S_RXD))
 210                        break;
 211                *i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev,
 212                                                      BCM2835_I2C_FIFO);
 213                i2c_dev->msg_buf++;
 214                i2c_dev->msg_buf_remaining--;
 215        }
 216}
 217
 218/*
 219 * Repeated Start Condition (Sr)
 220 * The BCM2835 ARM Peripherals datasheet mentions a way to trigger a Sr when it
 221 * talks about reading from a slave with 10 bit address. This is achieved by
 222 * issuing a write, poll the I2CS.TA flag and wait for it to be set, and then
 223 * issue a read.
 224 * A comment in https://github.com/raspberrypi/linux/issues/254 shows how the
 225 * firmware actually does it using polling and says that it's a workaround for
 226 * a problem in the state machine.
 227 * It turns out that it is possible to use the TXW interrupt to know when the
 228 * transfer is active, provided the FIFO has not been prefilled.
 229 */
 230
 231static void bcm2835_i2c_start_transfer(struct bcm2835_i2c_dev *i2c_dev)
 232{
 233        u32 c = BCM2835_I2C_C_ST | BCM2835_I2C_C_I2CEN;
 234        struct i2c_msg *msg = i2c_dev->curr_msg;
 235        bool last_msg = (i2c_dev->num_msgs == 1);
 236
 237        if (!i2c_dev->num_msgs)
 238                return;
 239
 240        i2c_dev->num_msgs--;
 241        i2c_dev->msg_buf = msg->buf;
 242        i2c_dev->msg_buf_remaining = msg->len;
 243
 244        if (msg->flags & I2C_M_RD)
 245                c |= BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR;
 246        else
 247                c |= BCM2835_I2C_C_INTT;
 248
 249        if (last_msg)
 250                c |= BCM2835_I2C_C_INTD;
 251
 252        bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr);
 253        bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len);
 254        bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c);
 255}
 256
 257static void bcm2835_i2c_finish_transfer(struct bcm2835_i2c_dev *i2c_dev)
 258{
 259        i2c_dev->curr_msg = NULL;
 260        i2c_dev->num_msgs = 0;
 261
 262        i2c_dev->msg_buf = NULL;
 263        i2c_dev->msg_buf_remaining = 0;
 264}
 265
 266/*
 267 * Note about I2C_C_CLEAR on error:
 268 * The I2C_C_CLEAR on errors will take some time to resolve -- if you were in
 269 * non-idle state and I2C_C_READ, it sets an abort_rx flag and runs through
 270 * the state machine to send a NACK and a STOP. Since we're setting CLEAR
 271 * without I2CEN, that NACK will be hanging around queued up for next time
 272 * we start the engine.
 273 */
 274
 275static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
 276{
 277        struct bcm2835_i2c_dev *i2c_dev = data;
 278        u32 val, err;
 279
 280        val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 281
 282        err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);
 283        if (err) {
 284                i2c_dev->msg_err = err;
 285                goto complete;
 286        }
 287
 288        if (val & BCM2835_I2C_S_DONE) {
 289                if (!i2c_dev->curr_msg) {
 290                        dev_err(i2c_dev->dev, "Got unexpected interrupt (from firmware?)\n");
 291                } else if (i2c_dev->curr_msg->flags & I2C_M_RD) {
 292                        bcm2835_drain_rxfifo(i2c_dev);
 293                        val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 294                }
 295
 296                if ((val & BCM2835_I2C_S_RXD) || i2c_dev->msg_buf_remaining)
 297                        i2c_dev->msg_err = BCM2835_I2C_S_LEN;
 298                else
 299                        i2c_dev->msg_err = 0;
 300                goto complete;
 301        }
 302
 303        if (val & BCM2835_I2C_S_TXW) {
 304                if (!i2c_dev->msg_buf_remaining) {
 305                        i2c_dev->msg_err = val | BCM2835_I2C_S_LEN;
 306                        goto complete;
 307                }
 308
 309                bcm2835_fill_txfifo(i2c_dev);
 310
 311                if (i2c_dev->num_msgs && !i2c_dev->msg_buf_remaining) {
 312                        i2c_dev->curr_msg++;
 313                        bcm2835_i2c_start_transfer(i2c_dev);
 314                }
 315
 316                return IRQ_HANDLED;
 317        }
 318
 319        if (val & BCM2835_I2C_S_RXR) {
 320                if (!i2c_dev->msg_buf_remaining) {
 321                        i2c_dev->msg_err = val | BCM2835_I2C_S_LEN;
 322                        goto complete;
 323                }
 324
 325                bcm2835_drain_rxfifo(i2c_dev);
 326                return IRQ_HANDLED;
 327        }
 328
 329        return IRQ_NONE;
 330
 331complete:
 332        bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
 333        bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, BCM2835_I2C_S_CLKT |
 334                           BCM2835_I2C_S_ERR | BCM2835_I2C_S_DONE);
 335        complete(&i2c_dev->completion);
 336
 337        return IRQ_HANDLED;
 338}
 339
 340static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 341                            int num)
 342{
 343        struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
 344        unsigned long time_left;
 345        int i;
 346
 347        for (i = 0; i < (num - 1); i++)
 348                if (msgs[i].flags & I2C_M_RD) {
 349                        dev_warn_once(i2c_dev->dev,
 350                                      "only one read message supported, has to be last\n");
 351                        return -EOPNOTSUPP;
 352                }
 353
 354        i2c_dev->curr_msg = msgs;
 355        i2c_dev->num_msgs = num;
 356        reinit_completion(&i2c_dev->completion);
 357
 358        bcm2835_i2c_start_transfer(i2c_dev);
 359
 360        time_left = wait_for_completion_timeout(&i2c_dev->completion,
 361                                                adap->timeout);
 362
 363        bcm2835_i2c_finish_transfer(i2c_dev);
 364
 365        if (!time_left) {
 366                bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C,
 367                                   BCM2835_I2C_C_CLEAR);
 368                dev_err(i2c_dev->dev, "i2c transfer timed out\n");
 369                return -ETIMEDOUT;
 370        }
 371
 372        if (!i2c_dev->msg_err)
 373                return num;
 374
 375        dev_dbg(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);
 376
 377        if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)
 378                return -EREMOTEIO;
 379
 380        return -EIO;
 381}
 382
 383static u32 bcm2835_i2c_func(struct i2c_adapter *adap)
 384{
 385        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 386}
 387
 388static const struct i2c_algorithm bcm2835_i2c_algo = {
 389        .master_xfer    = bcm2835_i2c_xfer,
 390        .functionality  = bcm2835_i2c_func,
 391};
 392
 393/*
 394 * The BCM2835 was reported to have problems with clock stretching:
 395 * https://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html
 396 * https://www.raspberrypi.org/forums/viewtopic.php?p=146272
 397 */
 398static const struct i2c_adapter_quirks bcm2835_i2c_quirks = {
 399        .flags = I2C_AQ_NO_CLK_STRETCH,
 400};
 401
 402static int bcm2835_i2c_probe(struct platform_device *pdev)
 403{
 404        struct bcm2835_i2c_dev *i2c_dev;
 405        struct resource *mem, *irq;
 406        int ret;
 407        struct i2c_adapter *adap;
 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                return dev_err_probe(&pdev->dev, PTR_ERR(mclk),
 426                                     "Could not get clock\n");
 427
 428        i2c_dev->bus_clk = bcm2835_i2c_register_div(&pdev->dev, mclk, i2c_dev);
 429
 430        if (IS_ERR(i2c_dev->bus_clk)) {
 431                dev_err(&pdev->dev, "Could not register clock\n");
 432                return PTR_ERR(i2c_dev->bus_clk);
 433        }
 434
 435        ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
 436                                   &bus_clk_rate);
 437        if (ret < 0) {
 438                dev_warn(&pdev->dev,
 439                         "Could not read clock-frequency property\n");
 440                bus_clk_rate = I2C_MAX_STANDARD_MODE_FREQ;
 441        }
 442
 443        ret = clk_set_rate_exclusive(i2c_dev->bus_clk, bus_clk_rate);
 444        if (ret < 0) {
 445                dev_err(&pdev->dev, "Could not set clock frequency\n");
 446                return ret;
 447        }
 448
 449        ret = clk_prepare_enable(i2c_dev->bus_clk);
 450        if (ret) {
 451                dev_err(&pdev->dev, "Couldn't prepare clock");
 452                return ret;
 453        }
 454
 455        irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 456        if (!irq) {
 457                dev_err(&pdev->dev, "No IRQ resource\n");
 458                return -ENODEV;
 459        }
 460        i2c_dev->irq = irq->start;
 461
 462        ret = request_irq(i2c_dev->irq, bcm2835_i2c_isr, IRQF_SHARED,
 463                          dev_name(&pdev->dev), i2c_dev);
 464        if (ret) {
 465                dev_err(&pdev->dev, "Could not request IRQ\n");
 466                return -ENODEV;
 467        }
 468
 469        adap = &i2c_dev->adapter;
 470        i2c_set_adapdata(adap, i2c_dev);
 471        adap->owner = THIS_MODULE;
 472        adap->class = I2C_CLASS_DEPRECATED;
 473        snprintf(adap->name, sizeof(adap->name), "bcm2835 (%s)",
 474                 of_node_full_name(pdev->dev.of_node));
 475        adap->algo = &bcm2835_i2c_algo;
 476        adap->dev.parent = &pdev->dev;
 477        adap->dev.of_node = pdev->dev.of_node;
 478        adap->quirks = of_device_get_match_data(&pdev->dev);
 479
 480        bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);
 481
 482        ret = i2c_add_adapter(adap);
 483        if (ret)
 484                free_irq(i2c_dev->irq, i2c_dev);
 485
 486        return ret;
 487}
 488
 489static int bcm2835_i2c_remove(struct platform_device *pdev)
 490{
 491        struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
 492
 493        clk_rate_exclusive_put(i2c_dev->bus_clk);
 494        clk_disable_unprepare(i2c_dev->bus_clk);
 495
 496        free_irq(i2c_dev->irq, i2c_dev);
 497        i2c_del_adapter(&i2c_dev->adapter);
 498
 499        return 0;
 500}
 501
 502static const struct of_device_id bcm2835_i2c_of_match[] = {
 503        { .compatible = "brcm,bcm2711-i2c" },
 504        { .compatible = "brcm,bcm2835-i2c", .data = &bcm2835_i2c_quirks },
 505        {},
 506};
 507MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match);
 508
 509static struct platform_driver bcm2835_i2c_driver = {
 510        .probe          = bcm2835_i2c_probe,
 511        .remove         = bcm2835_i2c_remove,
 512        .driver         = {
 513                .name   = "i2c-bcm2835",
 514                .of_match_table = bcm2835_i2c_of_match,
 515        },
 516};
 517module_platform_driver(bcm2835_i2c_driver);
 518
 519MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
 520MODULE_DESCRIPTION("BCM2835 I2C bus adapter");
 521MODULE_LICENSE("GPL v2");
 522MODULE_ALIAS("platform:i2c-bcm2835");
 523