1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Driver for Broadcom BCM2835 auxiliary SPI Controllers 4 * 5 * the driver does not rely on the native chipselects at all 6 * but only uses the gpio type chipselects 7 * 8 * Based on: spi-bcm2835.c 9 * 10 * Copyright (C) 2015 Martin Sperl 11 */ 12 13 #include <linux/clk.h> 14 #include <linux/completion.h> 15 #include <linux/debugfs.h> 16 #include <linux/delay.h> 17 #include <linux/err.h> 18 #include <linux/interrupt.h> 19 #include <linux/io.h> 20 #include <linux/kernel.h> 21 #include <linux/module.h> 22 #include <linux/of.h> 23 #include <linux/platform_device.h> 24 #include <linux/regmap.h> 25 #include <linux/spi/spi.h> 26 #include <linux/spinlock.h> 27 28 /* define polling limits */ 29 static unsigned int polling_limit_us = 30; 30 module_param(polling_limit_us, uint, 0664); 31 MODULE_PARM_DESC(polling_limit_us, 32 "time in us to run a transfer in polling mode - if zero no polling is used\n"); 33 34 /* 35 * spi register defines 36 * 37 * note there is garbage in the "official" documentation, 38 * so some data is taken from the file: 39 * brcm_usrlib/dag/vmcsx/vcinclude/bcm2708_chip/aux_io.h 40 * inside of: 41 * http://www.broadcom.com/docs/support/videocore/Brcm_Android_ICS_Graphics_Stack.tar.gz 42 */ 43 44 /* SPI register offsets */ 45 #define BCM2835_AUX_SPI_CNTL0 0x00 46 #define BCM2835_AUX_SPI_CNTL1 0x04 47 #define BCM2835_AUX_SPI_STAT 0x08 48 #define BCM2835_AUX_SPI_PEEK 0x0C 49 #define BCM2835_AUX_SPI_IO 0x20 50 #define BCM2835_AUX_SPI_TXHOLD 0x30 51 52 /* Bitfields in CNTL0 */ 53 #define BCM2835_AUX_SPI_CNTL0_SPEED 0xFFF00000 54 #define BCM2835_AUX_SPI_CNTL0_SPEED_MAX 0xFFF 55 #define BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT 20 56 #define BCM2835_AUX_SPI_CNTL0_CS 0x000E0000 57 #define BCM2835_AUX_SPI_CNTL0_POSTINPUT 0x00010000 58 #define BCM2835_AUX_SPI_CNTL0_VAR_CS 0x00008000 59 #define BCM2835_AUX_SPI_CNTL0_VAR_WIDTH 0x00004000 60 #define BCM2835_AUX_SPI_CNTL0_DOUTHOLD 0x00003000 61 #define BCM2835_AUX_SPI_CNTL0_ENABLE 0x00000800 62 #define BCM2835_AUX_SPI_CNTL0_IN_RISING 0x00000400 63 #define BCM2835_AUX_SPI_CNTL0_CLEARFIFO 0x00000200 64 #define BCM2835_AUX_SPI_CNTL0_OUT_RISING 0x00000100 65 #define BCM2835_AUX_SPI_CNTL0_CPOL 0x00000080 66 #define BCM2835_AUX_SPI_CNTL0_MSBF_OUT 0x00000040 67 #define BCM2835_AUX_SPI_CNTL0_SHIFTLEN 0x0000003F 68 69 /* Bitfields in CNTL1 */ 70 #define BCM2835_AUX_SPI_CNTL1_CSHIGH 0x00000700 71 #define BCM2835_AUX_SPI_CNTL1_TXEMPTY 0x00000080 72 #define BCM2835_AUX_SPI_CNTL1_IDLE 0x00000040 73 #define BCM2835_AUX_SPI_CNTL1_MSBF_IN 0x00000002 74 #define BCM2835_AUX_SPI_CNTL1_KEEP_IN 0x00000001 75 76 /* Bitfields in STAT */ 77 #define BCM2835_AUX_SPI_STAT_TX_LVL 0xFF000000 78 #define BCM2835_AUX_SPI_STAT_RX_LVL 0x00FF0000 79 #define BCM2835_AUX_SPI_STAT_TX_FULL 0x00000400 80 #define BCM2835_AUX_SPI_STAT_TX_EMPTY 0x00000200 81 #define BCM2835_AUX_SPI_STAT_RX_FULL 0x00000100 82 #define BCM2835_AUX_SPI_STAT_RX_EMPTY 0x00000080 83 #define BCM2835_AUX_SPI_STAT_BUSY 0x00000040 84 #define BCM2835_AUX_SPI_STAT_BITCOUNT 0x0000003F 85 86 struct bcm2835aux_spi { 87 void __iomem *regs; 88 struct clk *clk; 89 int irq; 90 u32 cntl[2]; 91 const u8 *tx_buf; 92 u8 *rx_buf; 93 int tx_len; 94 int rx_len; 95 int pending; 96 97 u64 count_transfer_polling; 98 u64 count_transfer_irq; 99 u64 count_transfer_irq_after_poll; 100 101 struct dentry *debugfs_dir; 102 }; 103 104 #if defined(CONFIG_DEBUG_FS) 105 static void bcm2835aux_debugfs_create(struct bcm2835aux_spi *bs, 106 const char *dname) 107 { 108 char name[64]; 109 struct dentry *dir; 110 111 /* get full name */ 112 snprintf(name, sizeof(name), "spi-bcm2835aux-%s", dname); 113 114 /* the base directory */ 115 dir = debugfs_create_dir(name, NULL); 116 bs->debugfs_dir = dir; 117 118 /* the counters */ 119 debugfs_create_u64("count_transfer_polling", 0444, dir, 120 &bs->count_transfer_polling); 121 debugfs_create_u64("count_transfer_irq", 0444, dir, 122 &bs->count_transfer_irq); 123 debugfs_create_u64("count_transfer_irq_after_poll", 0444, dir, 124 &bs->count_transfer_irq_after_poll); 125 } 126 127 static void bcm2835aux_debugfs_remove(struct bcm2835aux_spi *bs) 128 { 129 debugfs_remove_recursive(bs->debugfs_dir); 130 bs->debugfs_dir = NULL; 131 } 132 #else 133 static void bcm2835aux_debugfs_create(struct bcm2835aux_spi *bs, 134 const char *dname) 135 { 136 } 137 138 static void bcm2835aux_debugfs_remove(struct bcm2835aux_spi *bs) 139 { 140 } 141 #endif /* CONFIG_DEBUG_FS */ 142 143 static inline u32 bcm2835aux_rd(struct bcm2835aux_spi *bs, unsigned int reg) 144 { 145 return readl(bs->regs + reg); 146 } 147 148 static inline void bcm2835aux_wr(struct bcm2835aux_spi *bs, unsigned int reg, 149 u32 val) 150 { 151 writel(val, bs->regs + reg); 152 } 153 154 static inline void bcm2835aux_rd_fifo(struct bcm2835aux_spi *bs) 155 { 156 u32 data; 157 int count = min(bs->rx_len, 3); 158 159 data = bcm2835aux_rd(bs, BCM2835_AUX_SPI_IO); 160 if (bs->rx_buf) { 161 switch (count) { 162 case 3: 163 *bs->rx_buf++ = (data >> 16) & 0xff; 164 fallthrough; 165 case 2: 166 *bs->rx_buf++ = (data >> 8) & 0xff; 167 fallthrough; 168 case 1: 169 *bs->rx_buf++ = (data >> 0) & 0xff; 170 /* fallthrough - no default */ 171 } 172 } 173 bs->rx_len -= count; 174 bs->pending -= count; 175 } 176 177 static inline void bcm2835aux_wr_fifo(struct bcm2835aux_spi *bs) 178 { 179 u32 data; 180 u8 byte; 181 int count; 182 int i; 183 184 /* gather up to 3 bytes to write to the FIFO */ 185 count = min(bs->tx_len, 3); 186 data = 0; 187 for (i = 0; i < count; i++) { 188 byte = bs->tx_buf ? *bs->tx_buf++ : 0; 189 data |= byte << (8 * (2 - i)); 190 } 191 192 /* and set the variable bit-length */ 193 data |= (count * 8) << 24; 194 195 /* and decrement length */ 196 bs->tx_len -= count; 197 bs->pending += count; 198 199 /* write to the correct TX-register */ 200 if (bs->tx_len) 201 bcm2835aux_wr(bs, BCM2835_AUX_SPI_TXHOLD, data); 202 else 203 bcm2835aux_wr(bs, BCM2835_AUX_SPI_IO, data); 204 } 205 206 static void bcm2835aux_spi_reset_hw(struct bcm2835aux_spi *bs) 207 { 208 /* disable spi clearing fifo and interrupts */ 209 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, 0); 210 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, 211 BCM2835_AUX_SPI_CNTL0_CLEARFIFO); 212 } 213 214 static void bcm2835aux_spi_transfer_helper(struct bcm2835aux_spi *bs) 215 { 216 u32 stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT); 217 218 /* check if we have data to read */ 219 for (; bs->rx_len && (stat & BCM2835_AUX_SPI_STAT_RX_LVL); 220 stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT)) 221 bcm2835aux_rd_fifo(bs); 222 223 /* check if we have data to write */ 224 while (bs->tx_len && 225 (bs->pending < 12) && 226 (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) & 227 BCM2835_AUX_SPI_STAT_TX_FULL))) { 228 bcm2835aux_wr_fifo(bs); 229 } 230 } 231 232 static irqreturn_t bcm2835aux_spi_interrupt(int irq, void *dev_id) 233 { 234 struct spi_controller *host = dev_id; 235 struct bcm2835aux_spi *bs = spi_controller_get_devdata(host); 236 237 /* IRQ may be shared, so return if our interrupts are disabled */ 238 if (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_CNTL1) & 239 (BCM2835_AUX_SPI_CNTL1_TXEMPTY | BCM2835_AUX_SPI_CNTL1_IDLE))) 240 return IRQ_NONE; 241 242 /* do common fifo handling */ 243 bcm2835aux_spi_transfer_helper(bs); 244 245 if (!bs->tx_len) { 246 /* disable tx fifo empty interrupt */ 247 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1] | 248 BCM2835_AUX_SPI_CNTL1_IDLE); 249 } 250 251 /* and if rx_len is 0 then disable interrupts and wake up completion */ 252 if (!bs->rx_len) { 253 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]); 254 spi_finalize_current_transfer(host); 255 } 256 257 return IRQ_HANDLED; 258 } 259 260 static int __bcm2835aux_spi_transfer_one_irq(struct spi_controller *host, 261 struct spi_device *spi, 262 struct spi_transfer *tfr) 263 { 264 struct bcm2835aux_spi *bs = spi_controller_get_devdata(host); 265 266 /* enable interrupts */ 267 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1] | 268 BCM2835_AUX_SPI_CNTL1_TXEMPTY | 269 BCM2835_AUX_SPI_CNTL1_IDLE); 270 271 /* and wait for finish... */ 272 return 1; 273 } 274 275 static int bcm2835aux_spi_transfer_one_irq(struct spi_controller *host, 276 struct spi_device *spi, 277 struct spi_transfer *tfr) 278 { 279 struct bcm2835aux_spi *bs = spi_controller_get_devdata(host); 280 281 /* update statistics */ 282 bs->count_transfer_irq++; 283 284 /* fill in registers and fifos before enabling interrupts */ 285 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]); 286 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]); 287 288 /* fill in tx fifo with data before enabling interrupts */ 289 while ((bs->tx_len) && 290 (bs->pending < 12) && 291 (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) & 292 BCM2835_AUX_SPI_STAT_TX_FULL))) { 293 bcm2835aux_wr_fifo(bs); 294 } 295 296 /* now run the interrupt mode */ 297 return __bcm2835aux_spi_transfer_one_irq(host, spi, tfr); 298 } 299 300 static int bcm2835aux_spi_transfer_one_poll(struct spi_controller *host, 301 struct spi_device *spi, 302 struct spi_transfer *tfr) 303 { 304 struct bcm2835aux_spi *bs = spi_controller_get_devdata(host); 305 unsigned long timeout; 306 307 /* update statistics */ 308 bs->count_transfer_polling++; 309 310 /* configure spi */ 311 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]); 312 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]); 313 314 /* set the timeout to at least 2 jiffies */ 315 timeout = jiffies + 2 + HZ * polling_limit_us / 1000000; 316 317 /* loop until finished the transfer */ 318 while (bs->rx_len) { 319 320 /* do common fifo handling */ 321 bcm2835aux_spi_transfer_helper(bs); 322 323 /* there is still data pending to read check the timeout */ 324 if (bs->rx_len && time_after(jiffies, timeout)) { 325 dev_dbg_ratelimited(&spi->dev, 326 "timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n", 327 jiffies - timeout, 328 bs->tx_len, bs->rx_len); 329 /* forward to interrupt handler */ 330 bs->count_transfer_irq_after_poll++; 331 return __bcm2835aux_spi_transfer_one_irq(host, 332 spi, tfr); 333 } 334 } 335 336 /* and return without waiting for completion */ 337 return 0; 338 } 339 340 static int bcm2835aux_spi_transfer_one(struct spi_controller *host, 341 struct spi_device *spi, 342 struct spi_transfer *tfr) 343 { 344 struct bcm2835aux_spi *bs = spi_controller_get_devdata(host); 345 unsigned long spi_hz, clk_hz, speed; 346 unsigned long hz_per_byte, byte_limit; 347 348 /* calculate the registers to handle 349 * 350 * note that we use the variable data mode, which 351 * is not optimal for longer transfers as we waste registers 352 * resulting (potentially) in more interrupts when transferring 353 * more than 12 bytes 354 */ 355 356 /* set clock */ 357 spi_hz = tfr->speed_hz; 358 clk_hz = clk_get_rate(bs->clk); 359 360 if (spi_hz >= clk_hz / 2) { 361 speed = 0; 362 } else if (spi_hz) { 363 speed = DIV_ROUND_UP(clk_hz, 2 * spi_hz) - 1; 364 if (speed > BCM2835_AUX_SPI_CNTL0_SPEED_MAX) 365 speed = BCM2835_AUX_SPI_CNTL0_SPEED_MAX; 366 } else { /* the slowest we can go */ 367 speed = BCM2835_AUX_SPI_CNTL0_SPEED_MAX; 368 } 369 /* mask out old speed from previous spi_transfer */ 370 bs->cntl[0] &= ~(BCM2835_AUX_SPI_CNTL0_SPEED); 371 /* set the new speed */ 372 bs->cntl[0] |= speed << BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT; 373 374 tfr->effective_speed_hz = clk_hz / (2 * (speed + 1)); 375 376 /* set transmit buffers and length */ 377 bs->tx_buf = tfr->tx_buf; 378 bs->rx_buf = tfr->rx_buf; 379 bs->tx_len = tfr->len; 380 bs->rx_len = tfr->len; 381 bs->pending = 0; 382 383 /* Calculate the estimated time in us the transfer runs. Note that 384 * there are 2 idle clocks cycles after each chunk getting 385 * transferred - in our case the chunk size is 3 bytes, so we 386 * approximate this by 9 cycles/byte. This is used to find the number 387 * of Hz per byte per polling limit. E.g., we can transfer 1 byte in 388 * 30 µs per 300,000 Hz of bus clock. 389 */ 390 hz_per_byte = polling_limit_us ? (9 * 1000000) / polling_limit_us : 0; 391 byte_limit = hz_per_byte ? tfr->effective_speed_hz / hz_per_byte : 1; 392 393 /* run in polling mode for short transfers */ 394 if (tfr->len < byte_limit) 395 return bcm2835aux_spi_transfer_one_poll(host, spi, tfr); 396 397 /* run in interrupt mode for all others */ 398 return bcm2835aux_spi_transfer_one_irq(host, spi, tfr); 399 } 400 401 static int bcm2835aux_spi_prepare_message(struct spi_controller *host, 402 struct spi_message *msg) 403 { 404 struct spi_device *spi = msg->spi; 405 struct bcm2835aux_spi *bs = spi_controller_get_devdata(host); 406 407 bs->cntl[0] = BCM2835_AUX_SPI_CNTL0_ENABLE | 408 BCM2835_AUX_SPI_CNTL0_VAR_WIDTH | 409 BCM2835_AUX_SPI_CNTL0_MSBF_OUT; 410 bs->cntl[1] = BCM2835_AUX_SPI_CNTL1_MSBF_IN; 411 412 /* handle all the modes */ 413 if (spi->mode & SPI_CPOL) { 414 bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_CPOL; 415 bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_OUT_RISING; 416 } else { 417 bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_IN_RISING; 418 } 419 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]); 420 bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]); 421 422 return 0; 423 } 424 425 static int bcm2835aux_spi_unprepare_message(struct spi_controller *host, 426 struct spi_message *msg) 427 { 428 struct bcm2835aux_spi *bs = spi_controller_get_devdata(host); 429 430 bcm2835aux_spi_reset_hw(bs); 431 432 return 0; 433 } 434 435 static void bcm2835aux_spi_handle_err(struct spi_controller *host, 436 struct spi_message *msg) 437 { 438 struct bcm2835aux_spi *bs = spi_controller_get_devdata(host); 439 440 bcm2835aux_spi_reset_hw(bs); 441 } 442 443 static int bcm2835aux_spi_setup(struct spi_device *spi) 444 { 445 /* sanity check for native cs */ 446 if (spi->mode & SPI_NO_CS) 447 return 0; 448 449 if (spi_get_csgpiod(spi, 0)) 450 return 0; 451 452 /* for dt-backwards compatibility: only support native on CS0 453 * known things not supported with broken native CS: 454 * * multiple chip-selects: cs0-cs2 are all 455 * simultaniously asserted whenever there is a transfer 456 * this even includes SPI_NO_CS 457 * * SPI_CS_HIGH: cs are always asserted low 458 * * cs_change: cs is deasserted after each spi_transfer 459 * * cs_delay_usec: cs is always deasserted one SCK cycle 460 * after the last transfer 461 * probably more... 462 */ 463 dev_warn(&spi->dev, 464 "Native CS is not supported - please configure cs-gpio in device-tree\n"); 465 466 if (spi_get_chipselect(spi, 0) == 0) 467 return 0; 468 469 dev_warn(&spi->dev, "Native CS is not working for cs > 0\n"); 470 471 return -EINVAL; 472 } 473 474 static int bcm2835aux_spi_probe(struct platform_device *pdev) 475 { 476 struct spi_controller *host; 477 struct bcm2835aux_spi *bs; 478 unsigned long clk_hz; 479 int err; 480 481 host = devm_spi_alloc_host(&pdev->dev, sizeof(*bs)); 482 if (!host) 483 return -ENOMEM; 484 485 platform_set_drvdata(pdev, host); 486 host->mode_bits = (SPI_CPOL | SPI_CS_HIGH | SPI_NO_CS); 487 host->bits_per_word_mask = SPI_BPW_MASK(8); 488 /* even though the driver never officially supported native CS 489 * allow a single native CS for legacy DT support purposes when 490 * no cs-gpio is configured. 491 * Known limitations for native cs are: 492 * * multiple chip-selects: cs0-cs2 are all simultaniously asserted 493 * whenever there is a transfer - this even includes SPI_NO_CS 494 * * SPI_CS_HIGH: is ignores - cs are always asserted low 495 * * cs_change: cs is deasserted after each spi_transfer 496 * * cs_delay_usec: cs is always deasserted one SCK cycle after 497 * a spi_transfer 498 */ 499 host->num_chipselect = 1; 500 host->setup = bcm2835aux_spi_setup; 501 host->transfer_one = bcm2835aux_spi_transfer_one; 502 host->handle_err = bcm2835aux_spi_handle_err; 503 host->prepare_message = bcm2835aux_spi_prepare_message; 504 host->unprepare_message = bcm2835aux_spi_unprepare_message; 505 host->dev.of_node = pdev->dev.of_node; 506 host->use_gpio_descriptors = true; 507 508 bs = spi_controller_get_devdata(host); 509 510 /* the main area */ 511 bs->regs = devm_platform_ioremap_resource(pdev, 0); 512 if (IS_ERR(bs->regs)) 513 return PTR_ERR(bs->regs); 514 515 bs->clk = devm_clk_get_enabled(&pdev->dev, NULL); 516 if (IS_ERR(bs->clk)) { 517 err = PTR_ERR(bs->clk); 518 dev_err(&pdev->dev, "could not get clk: %d\n", err); 519 return err; 520 } 521 522 bs->irq = platform_get_irq(pdev, 0); 523 if (bs->irq < 0) 524 return bs->irq; 525 526 /* just checking if the clock returns a sane value */ 527 clk_hz = clk_get_rate(bs->clk); 528 if (!clk_hz) { 529 dev_err(&pdev->dev, "clock returns 0 Hz\n"); 530 return -ENODEV; 531 } 532 533 /* reset SPI-HW block */ 534 bcm2835aux_spi_reset_hw(bs); 535 536 err = devm_request_irq(&pdev->dev, bs->irq, 537 bcm2835aux_spi_interrupt, 538 IRQF_SHARED, 539 dev_name(&pdev->dev), host); 540 if (err) { 541 dev_err(&pdev->dev, "could not request IRQ: %d\n", err); 542 return err; 543 } 544 545 err = spi_register_controller(host); 546 if (err) { 547 dev_err(&pdev->dev, "could not register SPI host: %d\n", err); 548 return err; 549 } 550 551 bcm2835aux_debugfs_create(bs, dev_name(&pdev->dev)); 552 553 return 0; 554 } 555 556 static void bcm2835aux_spi_remove(struct platform_device *pdev) 557 { 558 struct spi_controller *host = platform_get_drvdata(pdev); 559 struct bcm2835aux_spi *bs = spi_controller_get_devdata(host); 560 561 bcm2835aux_debugfs_remove(bs); 562 563 spi_unregister_controller(host); 564 565 bcm2835aux_spi_reset_hw(bs); 566 } 567 568 static const struct of_device_id bcm2835aux_spi_match[] = { 569 { .compatible = "brcm,bcm2835-aux-spi", }, 570 {} 571 }; 572 MODULE_DEVICE_TABLE(of, bcm2835aux_spi_match); 573 574 static struct platform_driver bcm2835aux_spi_driver = { 575 .driver = { 576 .name = "spi-bcm2835aux", 577 .of_match_table = bcm2835aux_spi_match, 578 }, 579 .probe = bcm2835aux_spi_probe, 580 .remove_new = bcm2835aux_spi_remove, 581 }; 582 module_platform_driver(bcm2835aux_spi_driver); 583 584 MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835 aux"); 585 MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>"); 586 MODULE_LICENSE("GPL"); 587