1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * BCM2835 I2C controller 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.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 /* 27 * 16-bit field for the number of SCL cycles to wait after rising SCL 28 * before deciding the target is not responding. 0 disables the 29 * timeout detection. 30 */ 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 int irq; 63 struct i2c_adapter adapter; 64 struct completion completion; 65 struct i2c_msg *curr_msg; 66 struct clk *bus_clk; 67 int num_msgs; 68 u32 msg_err; 69 u8 *msg_buf; 70 size_t msg_buf_remaining; 71 }; 72 73 static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev, 74 u32 reg, u32 val) 75 { 76 writel(val, i2c_dev->regs + reg); 77 } 78 79 static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg) 80 { 81 return readl(i2c_dev->regs + reg); 82 } 83 84 #define to_clk_bcm2835_i2c(_hw) container_of(_hw, struct clk_bcm2835_i2c, hw) 85 struct clk_bcm2835_i2c { 86 struct clk_hw hw; 87 struct bcm2835_i2c_dev *i2c_dev; 88 }; 89 90 static int clk_bcm2835_i2c_calc_divider(unsigned long rate, 91 unsigned long parent_rate) 92 { 93 u32 divider = DIV_ROUND_UP(parent_rate, rate); 94 95 /* 96 * Per the datasheet, the register is always interpreted as an even 97 * number, by rounding down. In other words, the LSB is ignored. So, 98 * if the LSB is set, increment the divider to avoid any issue. 99 */ 100 if (divider & 1) 101 divider++; 102 if ((divider < BCM2835_I2C_CDIV_MIN) || 103 (divider > BCM2835_I2C_CDIV_MAX)) 104 return -EINVAL; 105 106 return divider; 107 } 108 109 static int clk_bcm2835_i2c_set_rate(struct clk_hw *hw, unsigned long rate, 110 unsigned long parent_rate) 111 { 112 struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw); 113 u32 redl, fedl; 114 u32 divider = clk_bcm2835_i2c_calc_divider(rate, parent_rate); 115 116 if (divider == -EINVAL) 117 return -EINVAL; 118 119 bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DIV, divider); 120 121 /* 122 * Number of core clocks to wait after falling edge before 123 * outputting the next data bit. Note that both FEDL and REDL 124 * can't be greater than CDIV/2. 125 */ 126 fedl = max(divider / 16, 1u); 127 128 /* 129 * Number of core clocks to wait after rising edge before 130 * sampling the next incoming data bit. 131 */ 132 redl = max(divider / 4, 1u); 133 134 bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DEL, 135 (fedl << BCM2835_I2C_FEDL_SHIFT) | 136 (redl << BCM2835_I2C_REDL_SHIFT)); 137 return 0; 138 } 139 140 static long clk_bcm2835_i2c_round_rate(struct clk_hw *hw, unsigned long rate, 141 unsigned long *parent_rate) 142 { 143 u32 divider = clk_bcm2835_i2c_calc_divider(rate, *parent_rate); 144 145 return DIV_ROUND_UP(*parent_rate, divider); 146 } 147 148 static unsigned long clk_bcm2835_i2c_recalc_rate(struct clk_hw *hw, 149 unsigned long parent_rate) 150 { 151 struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw); 152 u32 divider = bcm2835_i2c_readl(div->i2c_dev, BCM2835_I2C_DIV); 153 154 return DIV_ROUND_UP(parent_rate, divider); 155 } 156 157 static const struct clk_ops clk_bcm2835_i2c_ops = { 158 .set_rate = clk_bcm2835_i2c_set_rate, 159 .round_rate = clk_bcm2835_i2c_round_rate, 160 .recalc_rate = clk_bcm2835_i2c_recalc_rate, 161 }; 162 163 static struct clk *bcm2835_i2c_register_div(struct device *dev, 164 struct clk *mclk, 165 struct bcm2835_i2c_dev *i2c_dev) 166 { 167 struct clk_init_data init; 168 struct clk_bcm2835_i2c *priv; 169 char name[32]; 170 const char *mclk_name; 171 172 snprintf(name, sizeof(name), "%s_div", dev_name(dev)); 173 174 mclk_name = __clk_get_name(mclk); 175 176 init.ops = &clk_bcm2835_i2c_ops; 177 init.name = name; 178 init.parent_names = (const char* []) { mclk_name }; 179 init.num_parents = 1; 180 init.flags = 0; 181 182 priv = devm_kzalloc(dev, sizeof(struct clk_bcm2835_i2c), GFP_KERNEL); 183 if (priv == NULL) 184 return ERR_PTR(-ENOMEM); 185 186 priv->hw.init = &init; 187 priv->i2c_dev = i2c_dev; 188 189 clk_hw_register_clkdev(&priv->hw, "div", dev_name(dev)); 190 return devm_clk_register(dev, &priv->hw); 191 } 192 193 static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev) 194 { 195 u32 val; 196 197 while (i2c_dev->msg_buf_remaining) { 198 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S); 199 if (!(val & BCM2835_I2C_S_TXD)) 200 break; 201 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO, 202 *i2c_dev->msg_buf); 203 i2c_dev->msg_buf++; 204 i2c_dev->msg_buf_remaining--; 205 } 206 } 207 208 static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev) 209 { 210 u32 val; 211 212 while (i2c_dev->msg_buf_remaining) { 213 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S); 214 if (!(val & BCM2835_I2C_S_RXD)) 215 break; 216 *i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev, 217 BCM2835_I2C_FIFO); 218 i2c_dev->msg_buf++; 219 i2c_dev->msg_buf_remaining--; 220 } 221 } 222 223 /* 224 * Repeated Start Condition (Sr) 225 * The BCM2835 ARM Peripherals datasheet mentions a way to trigger a Sr when it 226 * talks about reading from a target with 10 bit address. This is achieved by 227 * issuing a write, poll the I2CS.TA flag and wait for it to be set, and then 228 * issue a read. 229 * A comment in https://github.com/raspberrypi/linux/issues/254 shows how the 230 * firmware actually does it using polling and says that it's a workaround for 231 * a problem in the state machine. 232 * It turns out that it is possible to use the TXW interrupt to know when the 233 * transfer is active, provided the FIFO has not been prefilled. 234 */ 235 236 static void bcm2835_i2c_start_transfer(struct bcm2835_i2c_dev *i2c_dev) 237 { 238 u32 c = BCM2835_I2C_C_ST | BCM2835_I2C_C_I2CEN; 239 struct i2c_msg *msg = i2c_dev->curr_msg; 240 bool last_msg = (i2c_dev->num_msgs == 1); 241 242 if (!i2c_dev->num_msgs) 243 return; 244 245 i2c_dev->num_msgs--; 246 i2c_dev->msg_buf = msg->buf; 247 i2c_dev->msg_buf_remaining = msg->len; 248 249 if (msg->flags & I2C_M_RD) 250 c |= BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR; 251 else 252 c |= BCM2835_I2C_C_INTT; 253 254 if (last_msg) 255 c |= BCM2835_I2C_C_INTD; 256 257 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr); 258 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len); 259 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c); 260 } 261 262 static void bcm2835_i2c_finish_transfer(struct bcm2835_i2c_dev *i2c_dev) 263 { 264 i2c_dev->curr_msg = NULL; 265 i2c_dev->num_msgs = 0; 266 267 i2c_dev->msg_buf = NULL; 268 i2c_dev->msg_buf_remaining = 0; 269 } 270 271 /* 272 * Note about I2C_C_CLEAR on error: 273 * The I2C_C_CLEAR on errors will take some time to resolve -- if you were in 274 * non-idle state and I2C_C_READ, it sets an abort_rx flag and runs through 275 * the state machine to send a NACK and a STOP. Since we're setting CLEAR 276 * without I2CEN, that NACK will be hanging around queued up for next time 277 * we start the engine. 278 */ 279 280 static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data) 281 { 282 struct bcm2835_i2c_dev *i2c_dev = data; 283 u32 val, err; 284 285 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S); 286 287 err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR); 288 if (err) { 289 i2c_dev->msg_err = err; 290 goto complete; 291 } 292 293 if (val & BCM2835_I2C_S_DONE) { 294 if (!i2c_dev->curr_msg) { 295 dev_err(i2c_dev->dev, "Got unexpected interrupt (from firmware?)\n"); 296 } else if (i2c_dev->curr_msg->flags & I2C_M_RD) { 297 bcm2835_drain_rxfifo(i2c_dev); 298 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S); 299 } 300 301 if ((val & BCM2835_I2C_S_RXD) || i2c_dev->msg_buf_remaining) 302 i2c_dev->msg_err = BCM2835_I2C_S_LEN; 303 else 304 i2c_dev->msg_err = 0; 305 goto complete; 306 } 307 308 if (val & BCM2835_I2C_S_TXW) { 309 if (!i2c_dev->msg_buf_remaining) { 310 i2c_dev->msg_err = val | BCM2835_I2C_S_LEN; 311 goto complete; 312 } 313 314 bcm2835_fill_txfifo(i2c_dev); 315 316 if (i2c_dev->num_msgs && !i2c_dev->msg_buf_remaining) { 317 i2c_dev->curr_msg++; 318 bcm2835_i2c_start_transfer(i2c_dev); 319 } 320 321 return IRQ_HANDLED; 322 } 323 324 if (val & BCM2835_I2C_S_RXR) { 325 if (!i2c_dev->msg_buf_remaining) { 326 i2c_dev->msg_err = val | BCM2835_I2C_S_LEN; 327 goto complete; 328 } 329 330 bcm2835_drain_rxfifo(i2c_dev); 331 return IRQ_HANDLED; 332 } 333 334 return IRQ_NONE; 335 336 complete: 337 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR); 338 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, BCM2835_I2C_S_CLKT | 339 BCM2835_I2C_S_ERR | BCM2835_I2C_S_DONE); 340 complete(&i2c_dev->completion); 341 342 return IRQ_HANDLED; 343 } 344 345 static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], 346 int num) 347 { 348 struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap); 349 unsigned long time_left; 350 int i; 351 352 for (i = 0; i < (num - 1); i++) 353 if (msgs[i].flags & I2C_M_RD) { 354 dev_warn_once(i2c_dev->dev, 355 "only one read message supported, has to be last\n"); 356 return -EOPNOTSUPP; 357 } 358 359 i2c_dev->curr_msg = msgs; 360 i2c_dev->num_msgs = num; 361 reinit_completion(&i2c_dev->completion); 362 363 bcm2835_i2c_start_transfer(i2c_dev); 364 365 time_left = wait_for_completion_timeout(&i2c_dev->completion, 366 adap->timeout); 367 368 bcm2835_i2c_finish_transfer(i2c_dev); 369 370 if (!time_left) { 371 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 372 BCM2835_I2C_C_CLEAR); 373 return -ETIMEDOUT; 374 } 375 376 if (!i2c_dev->msg_err) 377 return num; 378 379 dev_dbg(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err); 380 381 if (i2c_dev->msg_err & BCM2835_I2C_S_ERR) 382 return -EREMOTEIO; 383 384 return -EIO; 385 } 386 387 static u32 bcm2835_i2c_func(struct i2c_adapter *adap) 388 { 389 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL; 390 } 391 392 static const struct i2c_algorithm bcm2835_i2c_algo = { 393 .xfer = bcm2835_i2c_xfer, 394 .functionality = bcm2835_i2c_func, 395 }; 396 397 /* 398 * The BCM2835 was reported to have problems with clock stretching: 399 * https://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html 400 * https://www.raspberrypi.org/forums/viewtopic.php?p=146272 401 */ 402 static const struct i2c_adapter_quirks bcm2835_i2c_quirks = { 403 .flags = I2C_AQ_NO_CLK_STRETCH, 404 }; 405 406 static int bcm2835_i2c_probe(struct platform_device *pdev) 407 { 408 struct bcm2835_i2c_dev *i2c_dev; 409 int ret; 410 struct i2c_adapter *adap; 411 struct clk *mclk; 412 u32 bus_clk_rate; 413 414 i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL); 415 if (!i2c_dev) 416 return -ENOMEM; 417 platform_set_drvdata(pdev, i2c_dev); 418 i2c_dev->dev = &pdev->dev; 419 init_completion(&i2c_dev->completion); 420 421 i2c_dev->regs = devm_platform_get_and_ioremap_resource(pdev, 0, NULL); 422 if (IS_ERR(i2c_dev->regs)) 423 return PTR_ERR(i2c_dev->regs); 424 425 mclk = devm_clk_get(&pdev->dev, NULL); 426 if (IS_ERR(mclk)) 427 return dev_err_probe(&pdev->dev, PTR_ERR(mclk), 428 "Could not get clock\n"); 429 430 i2c_dev->bus_clk = bcm2835_i2c_register_div(&pdev->dev, mclk, i2c_dev); 431 432 if (IS_ERR(i2c_dev->bus_clk)) 433 return dev_err_probe(&pdev->dev, PTR_ERR(i2c_dev->bus_clk), 434 "Could not register clock\n"); 435 436 ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency", 437 &bus_clk_rate); 438 if (ret < 0) { 439 dev_warn(&pdev->dev, 440 "Could not read clock-frequency property\n"); 441 bus_clk_rate = I2C_MAX_STANDARD_MODE_FREQ; 442 } 443 444 ret = clk_set_rate_exclusive(i2c_dev->bus_clk, bus_clk_rate); 445 if (ret < 0) 446 return dev_err_probe(&pdev->dev, ret, 447 "Could not set clock frequency\n"); 448 449 ret = clk_prepare_enable(i2c_dev->bus_clk); 450 if (ret) { 451 dev_err(&pdev->dev, "Couldn't prepare clock"); 452 goto err_put_exclusive_rate; 453 } 454 455 i2c_dev->irq = platform_get_irq(pdev, 0); 456 if (i2c_dev->irq < 0) { 457 ret = i2c_dev->irq; 458 goto err_disable_unprepare_clk; 459 } 460 461 ret = request_irq(i2c_dev->irq, bcm2835_i2c_isr, IRQF_SHARED, 462 dev_name(&pdev->dev), i2c_dev); 463 if (ret) { 464 dev_err(&pdev->dev, "Could not request IRQ\n"); 465 goto err_disable_unprepare_clk; 466 } 467 468 adap = &i2c_dev->adapter; 469 i2c_set_adapdata(adap, i2c_dev); 470 adap->owner = THIS_MODULE; 471 adap->class = I2C_CLASS_DEPRECATED; 472 snprintf(adap->name, sizeof(adap->name), "bcm2835 (%s)", 473 of_node_full_name(pdev->dev.of_node)); 474 adap->algo = &bcm2835_i2c_algo; 475 adap->dev.parent = &pdev->dev; 476 adap->dev.of_node = pdev->dev.of_node; 477 adap->quirks = of_device_get_match_data(&pdev->dev); 478 479 /* 480 * Disable the hardware clock stretching timeout. SMBUS 481 * specifies a limit for how long the device can stretch the 482 * clock, but core I2C doesn't. 483 */ 484 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_CLKT, 0); 485 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0); 486 487 ret = i2c_add_adapter(adap); 488 if (ret) 489 goto err_free_irq; 490 491 return 0; 492 493 err_free_irq: 494 free_irq(i2c_dev->irq, i2c_dev); 495 err_disable_unprepare_clk: 496 clk_disable_unprepare(i2c_dev->bus_clk); 497 err_put_exclusive_rate: 498 clk_rate_exclusive_put(i2c_dev->bus_clk); 499 500 return ret; 501 } 502 503 static void bcm2835_i2c_remove(struct platform_device *pdev) 504 { 505 struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev); 506 507 clk_rate_exclusive_put(i2c_dev->bus_clk); 508 clk_disable_unprepare(i2c_dev->bus_clk); 509 510 free_irq(i2c_dev->irq, i2c_dev); 511 i2c_del_adapter(&i2c_dev->adapter); 512 } 513 514 static const struct of_device_id bcm2835_i2c_of_match[] = { 515 { .compatible = "brcm,bcm2711-i2c" }, 516 { .compatible = "brcm,bcm2835-i2c", .data = &bcm2835_i2c_quirks }, 517 {}, 518 }; 519 MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match); 520 521 static struct platform_driver bcm2835_i2c_driver = { 522 .probe = bcm2835_i2c_probe, 523 .remove_new = bcm2835_i2c_remove, 524 .driver = { 525 .name = "i2c-bcm2835", 526 .of_match_table = bcm2835_i2c_of_match, 527 }, 528 }; 529 module_platform_driver(bcm2835_i2c_driver); 530 531 MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>"); 532 MODULE_DESCRIPTION("BCM2835 I2C bus adapter"); 533 MODULE_LICENSE("GPL v2"); 534 MODULE_ALIAS("platform:i2c-bcm2835"); 535