1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Driver for Broadcom BCM2835 SPI Controllers 4 * 5 * Copyright (C) 2012 Chris Boot 6 * Copyright (C) 2013 Stephen Warren 7 * Copyright (C) 2015 Martin Sperl 8 * 9 * This driver is inspired by: 10 * spi-ath79.c, Copyright (C) 2009-2011 Gabor Juhos <juhosg@openwrt.org> 11 * spi-atmel.c, Copyright (C) 2006 Atmel Corporation 12 */ 13 14 #include <linux/clk.h> 15 #include <linux/completion.h> 16 #include <linux/debugfs.h> 17 #include <linux/delay.h> 18 #include <linux/dma-mapping.h> 19 #include <linux/dmaengine.h> 20 #include <linux/err.h> 21 #include <linux/interrupt.h> 22 #include <linux/io.h> 23 #include <linux/kernel.h> 24 #include <linux/module.h> 25 #include <linux/of.h> 26 #include <linux/of_address.h> 27 #include <linux/platform_device.h> 28 #include <linux/gpio/consumer.h> 29 #include <linux/gpio/machine.h> /* FIXME: using chip internals */ 30 #include <linux/gpio/driver.h> /* FIXME: using chip internals */ 31 #include <linux/of_irq.h> 32 #include <linux/spi/spi.h> 33 34 /* SPI register offsets */ 35 #define BCM2835_SPI_CS 0x00 36 #define BCM2835_SPI_FIFO 0x04 37 #define BCM2835_SPI_CLK 0x08 38 #define BCM2835_SPI_DLEN 0x0c 39 #define BCM2835_SPI_LTOH 0x10 40 #define BCM2835_SPI_DC 0x14 41 42 /* Bitfields in CS */ 43 #define BCM2835_SPI_CS_LEN_LONG 0x02000000 44 #define BCM2835_SPI_CS_DMA_LEN 0x01000000 45 #define BCM2835_SPI_CS_CSPOL2 0x00800000 46 #define BCM2835_SPI_CS_CSPOL1 0x00400000 47 #define BCM2835_SPI_CS_CSPOL0 0x00200000 48 #define BCM2835_SPI_CS_RXF 0x00100000 49 #define BCM2835_SPI_CS_RXR 0x00080000 50 #define BCM2835_SPI_CS_TXD 0x00040000 51 #define BCM2835_SPI_CS_RXD 0x00020000 52 #define BCM2835_SPI_CS_DONE 0x00010000 53 #define BCM2835_SPI_CS_LEN 0x00002000 54 #define BCM2835_SPI_CS_REN 0x00001000 55 #define BCM2835_SPI_CS_ADCS 0x00000800 56 #define BCM2835_SPI_CS_INTR 0x00000400 57 #define BCM2835_SPI_CS_INTD 0x00000200 58 #define BCM2835_SPI_CS_DMAEN 0x00000100 59 #define BCM2835_SPI_CS_TA 0x00000080 60 #define BCM2835_SPI_CS_CSPOL 0x00000040 61 #define BCM2835_SPI_CS_CLEAR_RX 0x00000020 62 #define BCM2835_SPI_CS_CLEAR_TX 0x00000010 63 #define BCM2835_SPI_CS_CPOL 0x00000008 64 #define BCM2835_SPI_CS_CPHA 0x00000004 65 #define BCM2835_SPI_CS_CS_10 0x00000002 66 #define BCM2835_SPI_CS_CS_01 0x00000001 67 68 #define BCM2835_SPI_FIFO_SIZE 64 69 #define BCM2835_SPI_FIFO_SIZE_3_4 48 70 #define BCM2835_SPI_DMA_MIN_LENGTH 96 71 #define BCM2835_SPI_MODE_BITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH \ 72 | SPI_NO_CS | SPI_3WIRE) 73 74 #define DRV_NAME "spi-bcm2835" 75 76 /* define polling limits */ 77 static unsigned int polling_limit_us = 30; 78 module_param(polling_limit_us, uint, 0664); 79 MODULE_PARM_DESC(polling_limit_us, 80 "time in us to run a transfer in polling mode\n"); 81 82 /** 83 * struct bcm2835_spi - BCM2835 SPI controller 84 * @regs: base address of register map 85 * @clk: core clock, divided to calculate serial clock 86 * @clk_hz: core clock cached speed 87 * @irq: interrupt, signals TX FIFO empty or RX FIFO ¾ full 88 * @tfr: SPI transfer currently processed 89 * @ctlr: SPI controller reverse lookup 90 * @tx_buf: pointer whence next transmitted byte is read 91 * @rx_buf: pointer where next received byte is written 92 * @tx_len: remaining bytes to transmit 93 * @rx_len: remaining bytes to receive 94 * @tx_prologue: bytes transmitted without DMA if first TX sglist entry's 95 * length is not a multiple of 4 (to overcome hardware limitation) 96 * @rx_prologue: bytes received without DMA if first RX sglist entry's 97 * length is not a multiple of 4 (to overcome hardware limitation) 98 * @tx_spillover: whether @tx_prologue spills over to second TX sglist entry 99 * @debugfs_dir: the debugfs directory - neede to remove debugfs when 100 * unloading the module 101 * @count_transfer_polling: count of how often polling mode is used 102 * @count_transfer_irq: count of how often interrupt mode is used 103 * @count_transfer_irq_after_polling: count of how often we fall back to 104 * interrupt mode after starting in polling mode. 105 * These are counted as well in @count_transfer_polling and 106 * @count_transfer_irq 107 * @count_transfer_dma: count how often dma mode is used 108 * @target: SPI target currently selected 109 * (used by bcm2835_spi_dma_tx_done() to write @clear_rx_cs) 110 * @tx_dma_active: whether a TX DMA descriptor is in progress 111 * @rx_dma_active: whether a RX DMA descriptor is in progress 112 * (used by bcm2835_spi_dma_tx_done() to handle a race) 113 * @fill_tx_desc: preallocated TX DMA descriptor used for RX-only transfers 114 * (cyclically copies from zero page to TX FIFO) 115 * @fill_tx_addr: bus address of zero page 116 */ 117 struct bcm2835_spi { 118 void __iomem *regs; 119 struct clk *clk; 120 unsigned long clk_hz; 121 int irq; 122 struct spi_transfer *tfr; 123 struct spi_controller *ctlr; 124 const u8 *tx_buf; 125 u8 *rx_buf; 126 int tx_len; 127 int rx_len; 128 int tx_prologue; 129 int rx_prologue; 130 unsigned int tx_spillover; 131 132 struct dentry *debugfs_dir; 133 u64 count_transfer_polling; 134 u64 count_transfer_irq; 135 u64 count_transfer_irq_after_polling; 136 u64 count_transfer_dma; 137 138 struct bcm2835_spidev *target; 139 unsigned int tx_dma_active; 140 unsigned int rx_dma_active; 141 struct dma_async_tx_descriptor *fill_tx_desc; 142 dma_addr_t fill_tx_addr; 143 }; 144 145 /** 146 * struct bcm2835_spidev - BCM2835 SPI target 147 * @prepare_cs: precalculated CS register value for ->prepare_message() 148 * (uses target-specific clock polarity and phase settings) 149 * @clear_rx_desc: preallocated RX DMA descriptor used for TX-only transfers 150 * (cyclically clears RX FIFO by writing @clear_rx_cs to CS register) 151 * @clear_rx_addr: bus address of @clear_rx_cs 152 * @clear_rx_cs: precalculated CS register value to clear RX FIFO 153 * (uses target-specific clock polarity and phase settings) 154 */ 155 struct bcm2835_spidev { 156 u32 prepare_cs; 157 struct dma_async_tx_descriptor *clear_rx_desc; 158 dma_addr_t clear_rx_addr; 159 u32 clear_rx_cs ____cacheline_aligned; 160 }; 161 162 #if defined(CONFIG_DEBUG_FS) 163 static void bcm2835_debugfs_create(struct bcm2835_spi *bs, 164 const char *dname) 165 { 166 char name[64]; 167 struct dentry *dir; 168 169 /* get full name */ 170 snprintf(name, sizeof(name), "spi-bcm2835-%s", dname); 171 172 /* the base directory */ 173 dir = debugfs_create_dir(name, NULL); 174 bs->debugfs_dir = dir; 175 176 /* the counters */ 177 debugfs_create_u64("count_transfer_polling", 0444, dir, 178 &bs->count_transfer_polling); 179 debugfs_create_u64("count_transfer_irq", 0444, dir, 180 &bs->count_transfer_irq); 181 debugfs_create_u64("count_transfer_irq_after_polling", 0444, dir, 182 &bs->count_transfer_irq_after_polling); 183 debugfs_create_u64("count_transfer_dma", 0444, dir, 184 &bs->count_transfer_dma); 185 } 186 187 static void bcm2835_debugfs_remove(struct bcm2835_spi *bs) 188 { 189 debugfs_remove_recursive(bs->debugfs_dir); 190 bs->debugfs_dir = NULL; 191 } 192 #else 193 static void bcm2835_debugfs_create(struct bcm2835_spi *bs, 194 const char *dname) 195 { 196 } 197 198 static void bcm2835_debugfs_remove(struct bcm2835_spi *bs) 199 { 200 } 201 #endif /* CONFIG_DEBUG_FS */ 202 203 static inline u32 bcm2835_rd(struct bcm2835_spi *bs, unsigned int reg) 204 { 205 return readl(bs->regs + reg); 206 } 207 208 static inline void bcm2835_wr(struct bcm2835_spi *bs, unsigned int reg, u32 val) 209 { 210 writel(val, bs->regs + reg); 211 } 212 213 static inline void bcm2835_rd_fifo(struct bcm2835_spi *bs) 214 { 215 u8 byte; 216 217 while ((bs->rx_len) && 218 (bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_RXD)) { 219 byte = bcm2835_rd(bs, BCM2835_SPI_FIFO); 220 if (bs->rx_buf) 221 *bs->rx_buf++ = byte; 222 bs->rx_len--; 223 } 224 } 225 226 static inline void bcm2835_wr_fifo(struct bcm2835_spi *bs) 227 { 228 u8 byte; 229 230 while ((bs->tx_len) && 231 (bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_TXD)) { 232 byte = bs->tx_buf ? *bs->tx_buf++ : 0; 233 bcm2835_wr(bs, BCM2835_SPI_FIFO, byte); 234 bs->tx_len--; 235 } 236 } 237 238 /** 239 * bcm2835_rd_fifo_count() - blindly read exactly @count bytes from RX FIFO 240 * @bs: BCM2835 SPI controller 241 * @count: bytes to read from RX FIFO 242 * 243 * The caller must ensure that @bs->rx_len is greater than or equal to @count, 244 * that the RX FIFO contains at least @count bytes and that the DMA Enable flag 245 * in the CS register is set (such that a read from the FIFO register receives 246 * 32-bit instead of just 8-bit). Moreover @bs->rx_buf must not be %NULL. 247 */ 248 static inline void bcm2835_rd_fifo_count(struct bcm2835_spi *bs, int count) 249 { 250 u32 val; 251 int len; 252 253 bs->rx_len -= count; 254 255 do { 256 val = bcm2835_rd(bs, BCM2835_SPI_FIFO); 257 len = min(count, 4); 258 memcpy(bs->rx_buf, &val, len); 259 bs->rx_buf += len; 260 count -= 4; 261 } while (count > 0); 262 } 263 264 /** 265 * bcm2835_wr_fifo_count() - blindly write exactly @count bytes to TX FIFO 266 * @bs: BCM2835 SPI controller 267 * @count: bytes to write to TX FIFO 268 * 269 * The caller must ensure that @bs->tx_len is greater than or equal to @count, 270 * that the TX FIFO can accommodate @count bytes and that the DMA Enable flag 271 * in the CS register is set (such that a write to the FIFO register transmits 272 * 32-bit instead of just 8-bit). 273 */ 274 static inline void bcm2835_wr_fifo_count(struct bcm2835_spi *bs, int count) 275 { 276 u32 val; 277 int len; 278 279 bs->tx_len -= count; 280 281 do { 282 if (bs->tx_buf) { 283 len = min(count, 4); 284 memcpy(&val, bs->tx_buf, len); 285 bs->tx_buf += len; 286 } else { 287 val = 0; 288 } 289 bcm2835_wr(bs, BCM2835_SPI_FIFO, val); 290 count -= 4; 291 } while (count > 0); 292 } 293 294 /** 295 * bcm2835_wait_tx_fifo_empty() - busy-wait for TX FIFO to empty 296 * @bs: BCM2835 SPI controller 297 * 298 * The caller must ensure that the RX FIFO can accommodate as many bytes 299 * as have been written to the TX FIFO: Transmission is halted once the 300 * RX FIFO is full, causing this function to spin forever. 301 */ 302 static inline void bcm2835_wait_tx_fifo_empty(struct bcm2835_spi *bs) 303 { 304 while (!(bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_DONE)) 305 cpu_relax(); 306 } 307 308 /** 309 * bcm2835_rd_fifo_blind() - blindly read up to @count bytes from RX FIFO 310 * @bs: BCM2835 SPI controller 311 * @count: bytes available for reading in RX FIFO 312 */ 313 static inline void bcm2835_rd_fifo_blind(struct bcm2835_spi *bs, int count) 314 { 315 u8 val; 316 317 count = min(count, bs->rx_len); 318 bs->rx_len -= count; 319 320 do { 321 val = bcm2835_rd(bs, BCM2835_SPI_FIFO); 322 if (bs->rx_buf) 323 *bs->rx_buf++ = val; 324 } while (--count); 325 } 326 327 /** 328 * bcm2835_wr_fifo_blind() - blindly write up to @count bytes to TX FIFO 329 * @bs: BCM2835 SPI controller 330 * @count: bytes available for writing in TX FIFO 331 */ 332 static inline void bcm2835_wr_fifo_blind(struct bcm2835_spi *bs, int count) 333 { 334 u8 val; 335 336 count = min(count, bs->tx_len); 337 bs->tx_len -= count; 338 339 do { 340 val = bs->tx_buf ? *bs->tx_buf++ : 0; 341 bcm2835_wr(bs, BCM2835_SPI_FIFO, val); 342 } while (--count); 343 } 344 345 static void bcm2835_spi_reset_hw(struct bcm2835_spi *bs) 346 { 347 u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); 348 349 /* Disable SPI interrupts and transfer */ 350 cs &= ~(BCM2835_SPI_CS_INTR | 351 BCM2835_SPI_CS_INTD | 352 BCM2835_SPI_CS_DMAEN | 353 BCM2835_SPI_CS_TA); 354 /* 355 * Transmission sometimes breaks unless the DONE bit is written at the 356 * end of every transfer. The spec says it's a RO bit. Either the 357 * spec is wrong and the bit is actually of type RW1C, or it's a 358 * hardware erratum. 359 */ 360 cs |= BCM2835_SPI_CS_DONE; 361 /* and reset RX/TX FIFOS */ 362 cs |= BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX; 363 364 /* and reset the SPI_HW */ 365 bcm2835_wr(bs, BCM2835_SPI_CS, cs); 366 /* as well as DLEN */ 367 bcm2835_wr(bs, BCM2835_SPI_DLEN, 0); 368 } 369 370 static irqreturn_t bcm2835_spi_interrupt(int irq, void *dev_id) 371 { 372 struct bcm2835_spi *bs = dev_id; 373 u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); 374 375 /* Bail out early if interrupts are not enabled */ 376 if (!(cs & BCM2835_SPI_CS_INTR)) 377 return IRQ_NONE; 378 379 /* 380 * An interrupt is signaled either if DONE is set (TX FIFO empty) 381 * or if RXR is set (RX FIFO >= ¾ full). 382 */ 383 if (cs & BCM2835_SPI_CS_RXF) 384 bcm2835_rd_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE); 385 else if (cs & BCM2835_SPI_CS_RXR) 386 bcm2835_rd_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE_3_4); 387 388 if (bs->tx_len && cs & BCM2835_SPI_CS_DONE) 389 bcm2835_wr_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE); 390 391 /* Read as many bytes as possible from FIFO */ 392 bcm2835_rd_fifo(bs); 393 /* Write as many bytes as possible to FIFO */ 394 bcm2835_wr_fifo(bs); 395 396 if (!bs->rx_len) { 397 /* Transfer complete - reset SPI HW */ 398 bcm2835_spi_reset_hw(bs); 399 /* wake up the framework */ 400 spi_finalize_current_transfer(bs->ctlr); 401 } 402 403 return IRQ_HANDLED; 404 } 405 406 static int bcm2835_spi_transfer_one_irq(struct spi_controller *ctlr, 407 struct spi_device *spi, 408 struct spi_transfer *tfr, 409 u32 cs, bool fifo_empty) 410 { 411 struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr); 412 413 /* update usage statistics */ 414 bs->count_transfer_irq++; 415 416 /* 417 * Enable HW block, but with interrupts still disabled. 418 * Otherwise the empty TX FIFO would immediately trigger an interrupt. 419 */ 420 bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA); 421 422 /* fill TX FIFO as much as possible */ 423 if (fifo_empty) 424 bcm2835_wr_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE); 425 bcm2835_wr_fifo(bs); 426 427 /* enable interrupts */ 428 cs |= BCM2835_SPI_CS_INTR | BCM2835_SPI_CS_INTD | BCM2835_SPI_CS_TA; 429 bcm2835_wr(bs, BCM2835_SPI_CS, cs); 430 431 /* signal that we need to wait for completion */ 432 return 1; 433 } 434 435 /** 436 * bcm2835_spi_transfer_prologue() - transfer first few bytes without DMA 437 * @ctlr: SPI host controller 438 * @tfr: SPI transfer 439 * @bs: BCM2835 SPI controller 440 * @cs: CS register 441 * 442 * A limitation in DMA mode is that the FIFO must be accessed in 4 byte chunks. 443 * Only the final write access is permitted to transmit less than 4 bytes, the 444 * SPI controller deduces its intended size from the DLEN register. 445 * 446 * If a TX or RX sglist contains multiple entries, one per page, and the first 447 * entry starts in the middle of a page, that first entry's length may not be 448 * a multiple of 4. Subsequent entries are fine because they span an entire 449 * page, hence do have a length that's a multiple of 4. 450 * 451 * This cannot happen with kmalloc'ed buffers (which is what most clients use) 452 * because they are contiguous in physical memory and therefore not split on 453 * page boundaries by spi_map_buf(). But it *can* happen with vmalloc'ed 454 * buffers. 455 * 456 * The DMA engine is incapable of combining sglist entries into a continuous 457 * stream of 4 byte chunks, it treats every entry separately: A TX entry is 458 * rounded up a to a multiple of 4 bytes by transmitting surplus bytes, an RX 459 * entry is rounded up by throwing away received bytes. 460 * 461 * Overcome this limitation by transferring the first few bytes without DMA: 462 * E.g. if the first TX sglist entry's length is 23 and the first RX's is 42, 463 * write 3 bytes to the TX FIFO but read only 2 bytes from the RX FIFO. 464 * The residue of 1 byte in the RX FIFO is picked up by DMA. Together with 465 * the rest of the first RX sglist entry it makes up a multiple of 4 bytes. 466 * 467 * Should the RX prologue be larger, say, 3 vis-à-vis a TX prologue of 1, 468 * write 1 + 4 = 5 bytes to the TX FIFO and read 3 bytes from the RX FIFO. 469 * Caution, the additional 4 bytes spill over to the second TX sglist entry 470 * if the length of the first is *exactly* 1. 471 * 472 * At most 6 bytes are written and at most 3 bytes read. Do we know the 473 * transfer has this many bytes? Yes, see BCM2835_SPI_DMA_MIN_LENGTH. 474 * 475 * The FIFO is normally accessed with 8-bit width by the CPU and 32-bit width 476 * by the DMA engine. Toggling the DMA Enable flag in the CS register switches 477 * the width but also garbles the FIFO's contents. The prologue must therefore 478 * be transmitted in 32-bit width to ensure that the following DMA transfer can 479 * pick up the residue in the RX FIFO in ungarbled form. 480 */ 481 static void bcm2835_spi_transfer_prologue(struct spi_controller *ctlr, 482 struct spi_transfer *tfr, 483 struct bcm2835_spi *bs, 484 u32 cs) 485 { 486 int tx_remaining; 487 488 bs->tfr = tfr; 489 bs->tx_prologue = 0; 490 bs->rx_prologue = 0; 491 bs->tx_spillover = false; 492 493 if (bs->tx_buf && !sg_is_last(&tfr->tx_sg.sgl[0])) 494 bs->tx_prologue = sg_dma_len(&tfr->tx_sg.sgl[0]) & 3; 495 496 if (bs->rx_buf && !sg_is_last(&tfr->rx_sg.sgl[0])) { 497 bs->rx_prologue = sg_dma_len(&tfr->rx_sg.sgl[0]) & 3; 498 499 if (bs->rx_prologue > bs->tx_prologue) { 500 if (!bs->tx_buf || sg_is_last(&tfr->tx_sg.sgl[0])) { 501 bs->tx_prologue = bs->rx_prologue; 502 } else { 503 bs->tx_prologue += 4; 504 bs->tx_spillover = 505 !(sg_dma_len(&tfr->tx_sg.sgl[0]) & ~3); 506 } 507 } 508 } 509 510 /* rx_prologue > 0 implies tx_prologue > 0, so check only the latter */ 511 if (!bs->tx_prologue) 512 return; 513 514 /* Write and read RX prologue. Adjust first entry in RX sglist. */ 515 if (bs->rx_prologue) { 516 bcm2835_wr(bs, BCM2835_SPI_DLEN, bs->rx_prologue); 517 bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA 518 | BCM2835_SPI_CS_DMAEN); 519 bcm2835_wr_fifo_count(bs, bs->rx_prologue); 520 bcm2835_wait_tx_fifo_empty(bs); 521 bcm2835_rd_fifo_count(bs, bs->rx_prologue); 522 bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_CLEAR_RX 523 | BCM2835_SPI_CS_CLEAR_TX 524 | BCM2835_SPI_CS_DONE); 525 526 dma_sync_single_for_device(ctlr->dma_rx->device->dev, 527 sg_dma_address(&tfr->rx_sg.sgl[0]), 528 bs->rx_prologue, DMA_FROM_DEVICE); 529 530 sg_dma_address(&tfr->rx_sg.sgl[0]) += bs->rx_prologue; 531 sg_dma_len(&tfr->rx_sg.sgl[0]) -= bs->rx_prologue; 532 } 533 534 if (!bs->tx_buf) 535 return; 536 537 /* 538 * Write remaining TX prologue. Adjust first entry in TX sglist. 539 * Also adjust second entry if prologue spills over to it. 540 */ 541 tx_remaining = bs->tx_prologue - bs->rx_prologue; 542 if (tx_remaining) { 543 bcm2835_wr(bs, BCM2835_SPI_DLEN, tx_remaining); 544 bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA 545 | BCM2835_SPI_CS_DMAEN); 546 bcm2835_wr_fifo_count(bs, tx_remaining); 547 bcm2835_wait_tx_fifo_empty(bs); 548 bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_CLEAR_TX 549 | BCM2835_SPI_CS_DONE); 550 } 551 552 if (likely(!bs->tx_spillover)) { 553 sg_dma_address(&tfr->tx_sg.sgl[0]) += bs->tx_prologue; 554 sg_dma_len(&tfr->tx_sg.sgl[0]) -= bs->tx_prologue; 555 } else { 556 sg_dma_len(&tfr->tx_sg.sgl[0]) = 0; 557 sg_dma_address(&tfr->tx_sg.sgl[1]) += 4; 558 sg_dma_len(&tfr->tx_sg.sgl[1]) -= 4; 559 } 560 } 561 562 /** 563 * bcm2835_spi_undo_prologue() - reconstruct original sglist state 564 * @bs: BCM2835 SPI controller 565 * 566 * Undo changes which were made to an SPI transfer's sglist when transmitting 567 * the prologue. This is necessary to ensure the same memory ranges are 568 * unmapped that were originally mapped. 569 */ 570 static void bcm2835_spi_undo_prologue(struct bcm2835_spi *bs) 571 { 572 struct spi_transfer *tfr = bs->tfr; 573 574 if (!bs->tx_prologue) 575 return; 576 577 if (bs->rx_prologue) { 578 sg_dma_address(&tfr->rx_sg.sgl[0]) -= bs->rx_prologue; 579 sg_dma_len(&tfr->rx_sg.sgl[0]) += bs->rx_prologue; 580 } 581 582 if (!bs->tx_buf) 583 goto out; 584 585 if (likely(!bs->tx_spillover)) { 586 sg_dma_address(&tfr->tx_sg.sgl[0]) -= bs->tx_prologue; 587 sg_dma_len(&tfr->tx_sg.sgl[0]) += bs->tx_prologue; 588 } else { 589 sg_dma_len(&tfr->tx_sg.sgl[0]) = bs->tx_prologue - 4; 590 sg_dma_address(&tfr->tx_sg.sgl[1]) -= 4; 591 sg_dma_len(&tfr->tx_sg.sgl[1]) += 4; 592 } 593 out: 594 bs->tx_prologue = 0; 595 } 596 597 /** 598 * bcm2835_spi_dma_rx_done() - callback for DMA RX channel 599 * @data: SPI host controller 600 * 601 * Used for bidirectional and RX-only transfers. 602 */ 603 static void bcm2835_spi_dma_rx_done(void *data) 604 { 605 struct spi_controller *ctlr = data; 606 struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr); 607 608 /* terminate tx-dma as we do not have an irq for it 609 * because when the rx dma will terminate and this callback 610 * is called the tx-dma must have finished - can't get to this 611 * situation otherwise... 612 */ 613 dmaengine_terminate_async(ctlr->dma_tx); 614 bs->tx_dma_active = false; 615 bs->rx_dma_active = false; 616 bcm2835_spi_undo_prologue(bs); 617 618 /* reset fifo and HW */ 619 bcm2835_spi_reset_hw(bs); 620 621 /* and mark as completed */; 622 spi_finalize_current_transfer(ctlr); 623 } 624 625 /** 626 * bcm2835_spi_dma_tx_done() - callback for DMA TX channel 627 * @data: SPI host controller 628 * 629 * Used for TX-only transfers. 630 */ 631 static void bcm2835_spi_dma_tx_done(void *data) 632 { 633 struct spi_controller *ctlr = data; 634 struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr); 635 636 /* busy-wait for TX FIFO to empty */ 637 while (!(bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_DONE)) 638 bcm2835_wr(bs, BCM2835_SPI_CS, bs->target->clear_rx_cs); 639 640 bs->tx_dma_active = false; 641 smp_wmb(); 642 643 /* 644 * In case of a very short transfer, RX DMA may not have been 645 * issued yet. The onus is then on bcm2835_spi_transfer_one_dma() 646 * to terminate it immediately after issuing. 647 */ 648 if (cmpxchg(&bs->rx_dma_active, true, false)) 649 dmaengine_terminate_async(ctlr->dma_rx); 650 651 bcm2835_spi_undo_prologue(bs); 652 bcm2835_spi_reset_hw(bs); 653 spi_finalize_current_transfer(ctlr); 654 } 655 656 /** 657 * bcm2835_spi_prepare_sg() - prepare and submit DMA descriptor for sglist 658 * @ctlr: SPI host controller 659 * @tfr: SPI transfer 660 * @bs: BCM2835 SPI controller 661 * @target: BCM2835 SPI target 662 * @is_tx: whether to submit DMA descriptor for TX or RX sglist 663 * 664 * Prepare and submit a DMA descriptor for the TX or RX sglist of @tfr. 665 * Return 0 on success or a negative error number. 666 */ 667 static int bcm2835_spi_prepare_sg(struct spi_controller *ctlr, 668 struct spi_transfer *tfr, 669 struct bcm2835_spi *bs, 670 struct bcm2835_spidev *target, 671 bool is_tx) 672 { 673 struct dma_chan *chan; 674 struct scatterlist *sgl; 675 unsigned int nents; 676 enum dma_transfer_direction dir; 677 unsigned long flags; 678 679 struct dma_async_tx_descriptor *desc; 680 dma_cookie_t cookie; 681 682 if (is_tx) { 683 dir = DMA_MEM_TO_DEV; 684 chan = ctlr->dma_tx; 685 nents = tfr->tx_sg.nents; 686 sgl = tfr->tx_sg.sgl; 687 flags = tfr->rx_buf ? 0 : DMA_PREP_INTERRUPT; 688 } else { 689 dir = DMA_DEV_TO_MEM; 690 chan = ctlr->dma_rx; 691 nents = tfr->rx_sg.nents; 692 sgl = tfr->rx_sg.sgl; 693 flags = DMA_PREP_INTERRUPT; 694 } 695 /* prepare the channel */ 696 desc = dmaengine_prep_slave_sg(chan, sgl, nents, dir, flags); 697 if (!desc) 698 return -EINVAL; 699 700 /* 701 * Completion is signaled by the RX channel for bidirectional and 702 * RX-only transfers; else by the TX channel for TX-only transfers. 703 */ 704 if (!is_tx) { 705 desc->callback = bcm2835_spi_dma_rx_done; 706 desc->callback_param = ctlr; 707 } else if (!tfr->rx_buf) { 708 desc->callback = bcm2835_spi_dma_tx_done; 709 desc->callback_param = ctlr; 710 bs->target = target; 711 } 712 713 /* submit it to DMA-engine */ 714 cookie = dmaengine_submit(desc); 715 716 return dma_submit_error(cookie); 717 } 718 719 /** 720 * bcm2835_spi_transfer_one_dma() - perform SPI transfer using DMA engine 721 * @ctlr: SPI host controller 722 * @tfr: SPI transfer 723 * @target: BCM2835 SPI target 724 * @cs: CS register 725 * 726 * For *bidirectional* transfers (both tx_buf and rx_buf are non-%NULL), set up 727 * the TX and RX DMA channel to copy between memory and FIFO register. 728 * 729 * For *TX-only* transfers (rx_buf is %NULL), copying the RX FIFO's contents to 730 * memory is pointless. However not reading the RX FIFO isn't an option either 731 * because transmission is halted once it's full. As a workaround, cyclically 732 * clear the RX FIFO by setting the CLEAR_RX bit in the CS register. 733 * 734 * The CS register value is precalculated in bcm2835_spi_setup(). Normally 735 * this is called only once, on target registration. A DMA descriptor to write 736 * this value is preallocated in bcm2835_dma_init(). All that's left to do 737 * when performing a TX-only transfer is to submit this descriptor to the RX 738 * DMA channel. Latency is thereby minimized. The descriptor does not 739 * generate any interrupts while running. It must be terminated once the 740 * TX DMA channel is done. 741 * 742 * Clearing the RX FIFO is paced by the DREQ signal. The signal is asserted 743 * when the RX FIFO becomes half full, i.e. 32 bytes. (Tuneable with the DC 744 * register.) Reading 32 bytes from the RX FIFO would normally require 8 bus 745 * accesses, whereas clearing it requires only 1 bus access. So an 8-fold 746 * reduction in bus traffic and thus energy consumption is achieved. 747 * 748 * For *RX-only* transfers (tx_buf is %NULL), fill the TX FIFO by cyclically 749 * copying from the zero page. The DMA descriptor to do this is preallocated 750 * in bcm2835_dma_init(). It must be terminated once the RX DMA channel is 751 * done and can then be reused. 752 * 753 * The BCM2835 DMA driver autodetects when a transaction copies from the zero 754 * page and utilizes the DMA controller's ability to synthesize zeroes instead 755 * of copying them from memory. This reduces traffic on the memory bus. The 756 * feature is not available on so-called "lite" channels, but normally TX DMA 757 * is backed by a full-featured channel. 758 * 759 * Zero-filling the TX FIFO is paced by the DREQ signal. Unfortunately the 760 * BCM2835 SPI controller continues to assert DREQ even after the DLEN register 761 * has been counted down to zero (hardware erratum). Thus, when the transfer 762 * has finished, the DMA engine zero-fills the TX FIFO until it is half full. 763 * (Tuneable with the DC register.) So up to 9 gratuitous bus accesses are 764 * performed at the end of an RX-only transfer. 765 */ 766 static int bcm2835_spi_transfer_one_dma(struct spi_controller *ctlr, 767 struct spi_transfer *tfr, 768 struct bcm2835_spidev *target, 769 u32 cs) 770 { 771 struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr); 772 dma_cookie_t cookie; 773 int ret; 774 775 /* update usage statistics */ 776 bs->count_transfer_dma++; 777 778 /* 779 * Transfer first few bytes without DMA if length of first TX or RX 780 * sglist entry is not a multiple of 4 bytes (hardware limitation). 781 */ 782 bcm2835_spi_transfer_prologue(ctlr, tfr, bs, cs); 783 784 /* setup tx-DMA */ 785 if (bs->tx_buf) { 786 ret = bcm2835_spi_prepare_sg(ctlr, tfr, bs, target, true); 787 } else { 788 cookie = dmaengine_submit(bs->fill_tx_desc); 789 ret = dma_submit_error(cookie); 790 } 791 if (ret) 792 goto err_reset_hw; 793 794 /* set the DMA length */ 795 bcm2835_wr(bs, BCM2835_SPI_DLEN, bs->tx_len); 796 797 /* start the HW */ 798 bcm2835_wr(bs, BCM2835_SPI_CS, 799 cs | BCM2835_SPI_CS_TA | BCM2835_SPI_CS_DMAEN); 800 801 bs->tx_dma_active = true; 802 smp_wmb(); 803 804 /* start TX early */ 805 dma_async_issue_pending(ctlr->dma_tx); 806 807 /* setup rx-DMA late - to run transfers while 808 * mapping of the rx buffers still takes place 809 * this saves 10us or more. 810 */ 811 if (bs->rx_buf) { 812 ret = bcm2835_spi_prepare_sg(ctlr, tfr, bs, target, false); 813 } else { 814 cookie = dmaengine_submit(target->clear_rx_desc); 815 ret = dma_submit_error(cookie); 816 } 817 if (ret) { 818 /* need to reset on errors */ 819 dmaengine_terminate_sync(ctlr->dma_tx); 820 bs->tx_dma_active = false; 821 goto err_reset_hw; 822 } 823 824 /* start rx dma late */ 825 dma_async_issue_pending(ctlr->dma_rx); 826 bs->rx_dma_active = true; 827 smp_mb(); 828 829 /* 830 * In case of a very short TX-only transfer, bcm2835_spi_dma_tx_done() 831 * may run before RX DMA is issued. Terminate RX DMA if so. 832 */ 833 if (!bs->rx_buf && !bs->tx_dma_active && 834 cmpxchg(&bs->rx_dma_active, true, false)) { 835 dmaengine_terminate_async(ctlr->dma_rx); 836 bcm2835_spi_reset_hw(bs); 837 } 838 839 /* wait for wakeup in framework */ 840 return 1; 841 842 err_reset_hw: 843 bcm2835_spi_reset_hw(bs); 844 bcm2835_spi_undo_prologue(bs); 845 return ret; 846 } 847 848 static bool bcm2835_spi_can_dma(struct spi_controller *ctlr, 849 struct spi_device *spi, 850 struct spi_transfer *tfr) 851 { 852 /* we start DMA efforts only on bigger transfers */ 853 if (tfr->len < BCM2835_SPI_DMA_MIN_LENGTH) 854 return false; 855 856 /* return OK */ 857 return true; 858 } 859 860 static void bcm2835_dma_release(struct spi_controller *ctlr, 861 struct bcm2835_spi *bs) 862 { 863 if (ctlr->dma_tx) { 864 dmaengine_terminate_sync(ctlr->dma_tx); 865 866 if (bs->fill_tx_desc) 867 dmaengine_desc_free(bs->fill_tx_desc); 868 869 if (bs->fill_tx_addr) 870 dma_unmap_page_attrs(ctlr->dma_tx->device->dev, 871 bs->fill_tx_addr, sizeof(u32), 872 DMA_TO_DEVICE, 873 DMA_ATTR_SKIP_CPU_SYNC); 874 875 dma_release_channel(ctlr->dma_tx); 876 ctlr->dma_tx = NULL; 877 } 878 879 if (ctlr->dma_rx) { 880 dmaengine_terminate_sync(ctlr->dma_rx); 881 dma_release_channel(ctlr->dma_rx); 882 ctlr->dma_rx = NULL; 883 } 884 } 885 886 static int bcm2835_dma_init(struct spi_controller *ctlr, struct device *dev, 887 struct bcm2835_spi *bs) 888 { 889 struct dma_slave_config slave_config; 890 const __be32 *addr; 891 dma_addr_t dma_reg_base; 892 int ret; 893 894 /* base address in dma-space */ 895 addr = of_get_address(ctlr->dev.of_node, 0, NULL, NULL); 896 if (!addr) { 897 dev_err(dev, "could not get DMA-register address - not using dma mode\n"); 898 /* Fall back to interrupt mode */ 899 return 0; 900 } 901 dma_reg_base = be32_to_cpup(addr); 902 903 /* get tx/rx dma */ 904 ctlr->dma_tx = dma_request_chan(dev, "tx"); 905 if (IS_ERR(ctlr->dma_tx)) { 906 ret = dev_err_probe(dev, PTR_ERR(ctlr->dma_tx), 907 "no tx-dma configuration found - not using dma mode\n"); 908 ctlr->dma_tx = NULL; 909 goto err; 910 } 911 ctlr->dma_rx = dma_request_chan(dev, "rx"); 912 if (IS_ERR(ctlr->dma_rx)) { 913 ret = dev_err_probe(dev, PTR_ERR(ctlr->dma_rx), 914 "no rx-dma configuration found - not using dma mode\n"); 915 ctlr->dma_rx = NULL; 916 goto err_release; 917 } 918 919 /* 920 * The TX DMA channel either copies a transfer's TX buffer to the FIFO 921 * or, in case of an RX-only transfer, cyclically copies from the zero 922 * page to the FIFO using a preallocated, reusable descriptor. 923 */ 924 slave_config.dst_addr = (u32)(dma_reg_base + BCM2835_SPI_FIFO); 925 slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES; 926 927 ret = dmaengine_slave_config(ctlr->dma_tx, &slave_config); 928 if (ret) 929 goto err_config; 930 931 bs->fill_tx_addr = dma_map_page_attrs(ctlr->dma_tx->device->dev, 932 ZERO_PAGE(0), 0, sizeof(u32), 933 DMA_TO_DEVICE, 934 DMA_ATTR_SKIP_CPU_SYNC); 935 if (dma_mapping_error(ctlr->dma_tx->device->dev, bs->fill_tx_addr)) { 936 dev_err(dev, "cannot map zero page - not using DMA mode\n"); 937 bs->fill_tx_addr = 0; 938 ret = -ENOMEM; 939 goto err_release; 940 } 941 942 bs->fill_tx_desc = dmaengine_prep_dma_cyclic(ctlr->dma_tx, 943 bs->fill_tx_addr, 944 sizeof(u32), 0, 945 DMA_MEM_TO_DEV, 0); 946 if (!bs->fill_tx_desc) { 947 dev_err(dev, "cannot prepare fill_tx_desc - not using DMA mode\n"); 948 ret = -ENOMEM; 949 goto err_release; 950 } 951 952 ret = dmaengine_desc_set_reuse(bs->fill_tx_desc); 953 if (ret) { 954 dev_err(dev, "cannot reuse fill_tx_desc - not using DMA mode\n"); 955 goto err_release; 956 } 957 958 /* 959 * The RX DMA channel is used bidirectionally: It either reads the 960 * RX FIFO or, in case of a TX-only transfer, cyclically writes a 961 * precalculated value to the CS register to clear the RX FIFO. 962 */ 963 slave_config.src_addr = (u32)(dma_reg_base + BCM2835_SPI_FIFO); 964 slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES; 965 slave_config.dst_addr = (u32)(dma_reg_base + BCM2835_SPI_CS); 966 slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES; 967 968 ret = dmaengine_slave_config(ctlr->dma_rx, &slave_config); 969 if (ret) 970 goto err_config; 971 972 /* all went well, so set can_dma */ 973 ctlr->can_dma = bcm2835_spi_can_dma; 974 975 return 0; 976 977 err_config: 978 dev_err(dev, "issue configuring dma: %d - not using DMA mode\n", 979 ret); 980 err_release: 981 bcm2835_dma_release(ctlr, bs); 982 err: 983 /* 984 * Only report error for deferred probing, otherwise fall back to 985 * interrupt mode 986 */ 987 if (ret != -EPROBE_DEFER) 988 ret = 0; 989 990 return ret; 991 } 992 993 static int bcm2835_spi_transfer_one_poll(struct spi_controller *ctlr, 994 struct spi_device *spi, 995 struct spi_transfer *tfr, 996 u32 cs) 997 { 998 struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr); 999 unsigned long timeout; 1000 1001 /* update usage statistics */ 1002 bs->count_transfer_polling++; 1003 1004 /* enable HW block without interrupts */ 1005 bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA); 1006 1007 /* fill in the fifo before timeout calculations 1008 * if we are interrupted here, then the data is 1009 * getting transferred by the HW while we are interrupted 1010 */ 1011 bcm2835_wr_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE); 1012 1013 /* set the timeout to at least 2 jiffies */ 1014 timeout = jiffies + 2 + HZ * polling_limit_us / 1000000; 1015 1016 /* loop until finished the transfer */ 1017 while (bs->rx_len) { 1018 /* fill in tx fifo with remaining data */ 1019 bcm2835_wr_fifo(bs); 1020 1021 /* read from fifo as much as possible */ 1022 bcm2835_rd_fifo(bs); 1023 1024 /* if there is still data pending to read 1025 * then check the timeout 1026 */ 1027 if (bs->rx_len && time_after(jiffies, timeout)) { 1028 dev_dbg_ratelimited(&spi->dev, 1029 "timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n", 1030 jiffies - timeout, 1031 bs->tx_len, bs->rx_len); 1032 /* fall back to interrupt mode */ 1033 1034 /* update usage statistics */ 1035 bs->count_transfer_irq_after_polling++; 1036 1037 return bcm2835_spi_transfer_one_irq(ctlr, spi, 1038 tfr, cs, false); 1039 } 1040 } 1041 1042 /* Transfer complete - reset SPI HW */ 1043 bcm2835_spi_reset_hw(bs); 1044 /* and return without waiting for completion */ 1045 return 0; 1046 } 1047 1048 static int bcm2835_spi_transfer_one(struct spi_controller *ctlr, 1049 struct spi_device *spi, 1050 struct spi_transfer *tfr) 1051 { 1052 struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr); 1053 struct bcm2835_spidev *target = spi_get_ctldata(spi); 1054 unsigned long spi_hz, cdiv; 1055 unsigned long hz_per_byte, byte_limit; 1056 u32 cs = target->prepare_cs; 1057 1058 /* set clock */ 1059 spi_hz = tfr->speed_hz; 1060 1061 if (spi_hz >= bs->clk_hz / 2) { 1062 cdiv = 2; /* clk_hz/2 is the fastest we can go */ 1063 } else if (spi_hz) { 1064 /* CDIV must be a multiple of two */ 1065 cdiv = DIV_ROUND_UP(bs->clk_hz, spi_hz); 1066 cdiv += (cdiv % 2); 1067 1068 if (cdiv >= 65536) 1069 cdiv = 0; /* 0 is the slowest we can go */ 1070 } else { 1071 cdiv = 0; /* 0 is the slowest we can go */ 1072 } 1073 tfr->effective_speed_hz = cdiv ? (bs->clk_hz / cdiv) : (bs->clk_hz / 65536); 1074 bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv); 1075 1076 /* handle all the 3-wire mode */ 1077 if (spi->mode & SPI_3WIRE && tfr->rx_buf) 1078 cs |= BCM2835_SPI_CS_REN; 1079 1080 /* set transmit buffers and length */ 1081 bs->tx_buf = tfr->tx_buf; 1082 bs->rx_buf = tfr->rx_buf; 1083 bs->tx_len = tfr->len; 1084 bs->rx_len = tfr->len; 1085 1086 /* Calculate the estimated time in us the transfer runs. Note that 1087 * there is 1 idle clocks cycles after each byte getting transferred 1088 * so we have 9 cycles/byte. This is used to find the number of Hz 1089 * per byte per polling limit. E.g., we can transfer 1 byte in 30 us 1090 * per 300,000 Hz of bus clock. 1091 */ 1092 hz_per_byte = polling_limit_us ? (9 * 1000000) / polling_limit_us : 0; 1093 byte_limit = hz_per_byte ? tfr->effective_speed_hz / hz_per_byte : 1; 1094 1095 /* run in polling mode for short transfers */ 1096 if (tfr->len < byte_limit) 1097 return bcm2835_spi_transfer_one_poll(ctlr, spi, tfr, cs); 1098 1099 /* run in dma mode if conditions are right 1100 * Note that unlike poll or interrupt mode DMA mode does not have 1101 * this 1 idle clock cycle pattern but runs the spi clock without gaps 1102 */ 1103 if (ctlr->can_dma && bcm2835_spi_can_dma(ctlr, spi, tfr)) 1104 return bcm2835_spi_transfer_one_dma(ctlr, tfr, target, cs); 1105 1106 /* run in interrupt-mode */ 1107 return bcm2835_spi_transfer_one_irq(ctlr, spi, tfr, cs, true); 1108 } 1109 1110 static int bcm2835_spi_prepare_message(struct spi_controller *ctlr, 1111 struct spi_message *msg) 1112 { 1113 struct spi_device *spi = msg->spi; 1114 struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr); 1115 struct bcm2835_spidev *target = spi_get_ctldata(spi); 1116 int ret; 1117 1118 if (ctlr->can_dma) { 1119 /* 1120 * DMA transfers are limited to 16 bit (0 to 65535 bytes) by 1121 * the SPI HW due to DLEN. Split up transfers (32-bit FIFO 1122 * aligned) if the limit is exceeded. 1123 */ 1124 ret = spi_split_transfers_maxsize(ctlr, msg, 65532, 1125 GFP_KERNEL | GFP_DMA); 1126 if (ret) 1127 return ret; 1128 } 1129 1130 /* 1131 * Set up clock polarity before spi_transfer_one_message() asserts 1132 * chip select to avoid a gratuitous clock signal edge. 1133 */ 1134 bcm2835_wr(bs, BCM2835_SPI_CS, target->prepare_cs); 1135 1136 return 0; 1137 } 1138 1139 static void bcm2835_spi_handle_err(struct spi_controller *ctlr, 1140 struct spi_message *msg) 1141 { 1142 struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr); 1143 1144 /* if an error occurred and we have an active dma, then terminate */ 1145 if (ctlr->dma_tx) { 1146 dmaengine_terminate_sync(ctlr->dma_tx); 1147 bs->tx_dma_active = false; 1148 } 1149 if (ctlr->dma_rx) { 1150 dmaengine_terminate_sync(ctlr->dma_rx); 1151 bs->rx_dma_active = false; 1152 } 1153 bcm2835_spi_undo_prologue(bs); 1154 1155 /* and reset */ 1156 bcm2835_spi_reset_hw(bs); 1157 } 1158 1159 static int chip_match_name(struct gpio_chip *chip, void *data) 1160 { 1161 return !strcmp(chip->label, data); 1162 } 1163 1164 static void bcm2835_spi_cleanup(struct spi_device *spi) 1165 { 1166 struct bcm2835_spidev *target = spi_get_ctldata(spi); 1167 struct spi_controller *ctlr = spi->controller; 1168 1169 if (target->clear_rx_desc) 1170 dmaengine_desc_free(target->clear_rx_desc); 1171 1172 if (target->clear_rx_addr) 1173 dma_unmap_single(ctlr->dma_rx->device->dev, 1174 target->clear_rx_addr, 1175 sizeof(u32), 1176 DMA_TO_DEVICE); 1177 1178 kfree(target); 1179 } 1180 1181 static int bcm2835_spi_setup_dma(struct spi_controller *ctlr, 1182 struct spi_device *spi, 1183 struct bcm2835_spi *bs, 1184 struct bcm2835_spidev *target) 1185 { 1186 int ret; 1187 1188 if (!ctlr->dma_rx) 1189 return 0; 1190 1191 target->clear_rx_addr = dma_map_single(ctlr->dma_rx->device->dev, 1192 &target->clear_rx_cs, 1193 sizeof(u32), 1194 DMA_TO_DEVICE); 1195 if (dma_mapping_error(ctlr->dma_rx->device->dev, target->clear_rx_addr)) { 1196 dev_err(&spi->dev, "cannot map clear_rx_cs\n"); 1197 target->clear_rx_addr = 0; 1198 return -ENOMEM; 1199 } 1200 1201 target->clear_rx_desc = dmaengine_prep_dma_cyclic(ctlr->dma_rx, 1202 target->clear_rx_addr, 1203 sizeof(u32), 0, 1204 DMA_MEM_TO_DEV, 0); 1205 if (!target->clear_rx_desc) { 1206 dev_err(&spi->dev, "cannot prepare clear_rx_desc\n"); 1207 return -ENOMEM; 1208 } 1209 1210 ret = dmaengine_desc_set_reuse(target->clear_rx_desc); 1211 if (ret) { 1212 dev_err(&spi->dev, "cannot reuse clear_rx_desc\n"); 1213 return ret; 1214 } 1215 1216 return 0; 1217 } 1218 1219 static int bcm2835_spi_setup(struct spi_device *spi) 1220 { 1221 struct spi_controller *ctlr = spi->controller; 1222 struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr); 1223 struct bcm2835_spidev *target = spi_get_ctldata(spi); 1224 struct gpio_chip *chip; 1225 int ret; 1226 u32 cs; 1227 1228 if (!target) { 1229 target = kzalloc(ALIGN(sizeof(*target), dma_get_cache_alignment()), 1230 GFP_KERNEL); 1231 if (!target) 1232 return -ENOMEM; 1233 1234 spi_set_ctldata(spi, target); 1235 1236 ret = bcm2835_spi_setup_dma(ctlr, spi, bs, target); 1237 if (ret) 1238 goto err_cleanup; 1239 } 1240 1241 /* 1242 * Precalculate SPI target's CS register value for ->prepare_message(): 1243 * The driver always uses software-controlled GPIO chip select, hence 1244 * set the hardware-controlled native chip select to an invalid value 1245 * to prevent it from interfering. 1246 */ 1247 cs = BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01; 1248 if (spi->mode & SPI_CPOL) 1249 cs |= BCM2835_SPI_CS_CPOL; 1250 if (spi->mode & SPI_CPHA) 1251 cs |= BCM2835_SPI_CS_CPHA; 1252 target->prepare_cs = cs; 1253 1254 /* 1255 * Precalculate SPI target's CS register value to clear RX FIFO 1256 * in case of a TX-only DMA transfer. 1257 */ 1258 if (ctlr->dma_rx) { 1259 target->clear_rx_cs = cs | BCM2835_SPI_CS_TA | 1260 BCM2835_SPI_CS_DMAEN | 1261 BCM2835_SPI_CS_CLEAR_RX; 1262 dma_sync_single_for_device(ctlr->dma_rx->device->dev, 1263 target->clear_rx_addr, 1264 sizeof(u32), 1265 DMA_TO_DEVICE); 1266 } 1267 1268 /* 1269 * sanity checking the native-chipselects 1270 */ 1271 if (spi->mode & SPI_NO_CS) 1272 return 0; 1273 /* 1274 * The SPI core has successfully requested the CS GPIO line from the 1275 * device tree, so we are done. 1276 */ 1277 if (spi_get_csgpiod(spi, 0)) 1278 return 0; 1279 if (spi_get_chipselect(spi, 0) > 1) { 1280 /* error in the case of native CS requested with CS > 1 1281 * officially there is a CS2, but it is not documented 1282 * which GPIO is connected with that... 1283 */ 1284 dev_err(&spi->dev, 1285 "setup: only two native chip-selects are supported\n"); 1286 ret = -EINVAL; 1287 goto err_cleanup; 1288 } 1289 1290 /* 1291 * Translate native CS to GPIO 1292 * 1293 * FIXME: poking around in the gpiolib internals like this is 1294 * not very good practice. Find a way to locate the real problem 1295 * and fix it. Why is the GPIO descriptor in spi->cs_gpiod 1296 * sometimes not assigned correctly? Erroneous device trees? 1297 */ 1298 1299 /* get the gpio chip for the base */ 1300 chip = gpiochip_find("pinctrl-bcm2835", chip_match_name); 1301 if (!chip) 1302 return 0; 1303 1304 spi_set_csgpiod(spi, 0, gpiochip_request_own_desc(chip, 1305 8 - (spi_get_chipselect(spi, 0)), 1306 DRV_NAME, 1307 GPIO_LOOKUP_FLAGS_DEFAULT, 1308 GPIOD_OUT_LOW)); 1309 if (IS_ERR(spi_get_csgpiod(spi, 0))) { 1310 ret = PTR_ERR(spi_get_csgpiod(spi, 0)); 1311 goto err_cleanup; 1312 } 1313 1314 /* and set up the "mode" and level */ 1315 dev_info(&spi->dev, "setting up native-CS%i to use GPIO\n", 1316 spi_get_chipselect(spi, 0)); 1317 1318 return 0; 1319 1320 err_cleanup: 1321 bcm2835_spi_cleanup(spi); 1322 return ret; 1323 } 1324 1325 static int bcm2835_spi_probe(struct platform_device *pdev) 1326 { 1327 struct spi_controller *ctlr; 1328 struct bcm2835_spi *bs; 1329 int err; 1330 1331 ctlr = devm_spi_alloc_host(&pdev->dev, sizeof(*bs)); 1332 if (!ctlr) 1333 return -ENOMEM; 1334 1335 platform_set_drvdata(pdev, ctlr); 1336 1337 ctlr->use_gpio_descriptors = true; 1338 ctlr->mode_bits = BCM2835_SPI_MODE_BITS; 1339 ctlr->bits_per_word_mask = SPI_BPW_MASK(8); 1340 ctlr->num_chipselect = 3; 1341 ctlr->setup = bcm2835_spi_setup; 1342 ctlr->cleanup = bcm2835_spi_cleanup; 1343 ctlr->transfer_one = bcm2835_spi_transfer_one; 1344 ctlr->handle_err = bcm2835_spi_handle_err; 1345 ctlr->prepare_message = bcm2835_spi_prepare_message; 1346 ctlr->dev.of_node = pdev->dev.of_node; 1347 1348 bs = spi_controller_get_devdata(ctlr); 1349 bs->ctlr = ctlr; 1350 1351 bs->regs = devm_platform_ioremap_resource(pdev, 0); 1352 if (IS_ERR(bs->regs)) 1353 return PTR_ERR(bs->regs); 1354 1355 bs->clk = devm_clk_get(&pdev->dev, NULL); 1356 if (IS_ERR(bs->clk)) 1357 return dev_err_probe(&pdev->dev, PTR_ERR(bs->clk), 1358 "could not get clk\n"); 1359 1360 ctlr->max_speed_hz = clk_get_rate(bs->clk) / 2; 1361 1362 bs->irq = platform_get_irq(pdev, 0); 1363 if (bs->irq < 0) 1364 return bs->irq; 1365 1366 err = clk_prepare_enable(bs->clk); 1367 if (err) 1368 return err; 1369 bs->clk_hz = clk_get_rate(bs->clk); 1370 1371 err = bcm2835_dma_init(ctlr, &pdev->dev, bs); 1372 if (err) 1373 goto out_clk_disable; 1374 1375 /* initialise the hardware with the default polarities */ 1376 bcm2835_wr(bs, BCM2835_SPI_CS, 1377 BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX); 1378 1379 err = devm_request_irq(&pdev->dev, bs->irq, bcm2835_spi_interrupt, 1380 IRQF_SHARED, dev_name(&pdev->dev), bs); 1381 if (err) { 1382 dev_err(&pdev->dev, "could not request IRQ: %d\n", err); 1383 goto out_dma_release; 1384 } 1385 1386 err = spi_register_controller(ctlr); 1387 if (err) { 1388 dev_err(&pdev->dev, "could not register SPI controller: %d\n", 1389 err); 1390 goto out_dma_release; 1391 } 1392 1393 bcm2835_debugfs_create(bs, dev_name(&pdev->dev)); 1394 1395 return 0; 1396 1397 out_dma_release: 1398 bcm2835_dma_release(ctlr, bs); 1399 out_clk_disable: 1400 clk_disable_unprepare(bs->clk); 1401 return err; 1402 } 1403 1404 static void bcm2835_spi_remove(struct platform_device *pdev) 1405 { 1406 struct spi_controller *ctlr = platform_get_drvdata(pdev); 1407 struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr); 1408 1409 bcm2835_debugfs_remove(bs); 1410 1411 spi_unregister_controller(ctlr); 1412 1413 bcm2835_dma_release(ctlr, bs); 1414 1415 /* Clear FIFOs, and disable the HW block */ 1416 bcm2835_wr(bs, BCM2835_SPI_CS, 1417 BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX); 1418 1419 clk_disable_unprepare(bs->clk); 1420 } 1421 1422 static const struct of_device_id bcm2835_spi_match[] = { 1423 { .compatible = "brcm,bcm2835-spi", }, 1424 {} 1425 }; 1426 MODULE_DEVICE_TABLE(of, bcm2835_spi_match); 1427 1428 static struct platform_driver bcm2835_spi_driver = { 1429 .driver = { 1430 .name = DRV_NAME, 1431 .of_match_table = bcm2835_spi_match, 1432 }, 1433 .probe = bcm2835_spi_probe, 1434 .remove_new = bcm2835_spi_remove, 1435 .shutdown = bcm2835_spi_remove, 1436 }; 1437 module_platform_driver(bcm2835_spi_driver); 1438 1439 MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835"); 1440 MODULE_AUTHOR("Chris Boot <bootc@bootc.net>"); 1441 MODULE_LICENSE("GPL"); 1442