1 /* 2 * Driver for Broadcom BCM2835 SPI Controllers 3 * 4 * Copyright (C) 2012 Chris Boot 5 * Copyright (C) 2013 Stephen Warren 6 * 7 * This driver is inspired by: 8 * spi-ath79.c, Copyright (C) 2009-2011 Gabor Juhos <juhosg@openwrt.org> 9 * spi-atmel.c, Copyright (C) 2006 Atmel Corporation 10 * 11 * This program is free software; you can redistribute it and/or modify 12 * it under the terms of the GNU General Public License as published by 13 * the Free Software Foundation; either version 2 of the License, or 14 * (at your option) any later version. 15 * 16 * This program is distributed in the hope that it will be useful, 17 * but WITHOUT ANY WARRANTY; without even the implied warranty of 18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 19 * GNU General Public License for more details. 20 * 21 * You should have received a copy of the GNU General Public License 22 * along with this program; if not, write to the Free Software 23 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. 24 */ 25 26 #include <linux/clk.h> 27 #include <linux/completion.h> 28 #include <linux/delay.h> 29 #include <linux/err.h> 30 #include <linux/interrupt.h> 31 #include <linux/io.h> 32 #include <linux/kernel.h> 33 #include <linux/module.h> 34 #include <linux/of.h> 35 #include <linux/of_irq.h> 36 #include <linux/of_device.h> 37 #include <linux/spi/spi.h> 38 39 /* SPI register offsets */ 40 #define BCM2835_SPI_CS 0x00 41 #define BCM2835_SPI_FIFO 0x04 42 #define BCM2835_SPI_CLK 0x08 43 #define BCM2835_SPI_DLEN 0x0c 44 #define BCM2835_SPI_LTOH 0x10 45 #define BCM2835_SPI_DC 0x14 46 47 /* Bitfields in CS */ 48 #define BCM2835_SPI_CS_LEN_LONG 0x02000000 49 #define BCM2835_SPI_CS_DMA_LEN 0x01000000 50 #define BCM2835_SPI_CS_CSPOL2 0x00800000 51 #define BCM2835_SPI_CS_CSPOL1 0x00400000 52 #define BCM2835_SPI_CS_CSPOL0 0x00200000 53 #define BCM2835_SPI_CS_RXF 0x00100000 54 #define BCM2835_SPI_CS_RXR 0x00080000 55 #define BCM2835_SPI_CS_TXD 0x00040000 56 #define BCM2835_SPI_CS_RXD 0x00020000 57 #define BCM2835_SPI_CS_DONE 0x00010000 58 #define BCM2835_SPI_CS_LEN 0x00002000 59 #define BCM2835_SPI_CS_REN 0x00001000 60 #define BCM2835_SPI_CS_ADCS 0x00000800 61 #define BCM2835_SPI_CS_INTR 0x00000400 62 #define BCM2835_SPI_CS_INTD 0x00000200 63 #define BCM2835_SPI_CS_DMAEN 0x00000100 64 #define BCM2835_SPI_CS_TA 0x00000080 65 #define BCM2835_SPI_CS_CSPOL 0x00000040 66 #define BCM2835_SPI_CS_CLEAR_RX 0x00000020 67 #define BCM2835_SPI_CS_CLEAR_TX 0x00000010 68 #define BCM2835_SPI_CS_CPOL 0x00000008 69 #define BCM2835_SPI_CS_CPHA 0x00000004 70 #define BCM2835_SPI_CS_CS_10 0x00000002 71 #define BCM2835_SPI_CS_CS_01 0x00000001 72 73 #define BCM2835_SPI_TIMEOUT_MS 30000 74 #define BCM2835_SPI_MODE_BITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_NO_CS) 75 76 #define DRV_NAME "spi-bcm2835" 77 78 struct bcm2835_spi { 79 void __iomem *regs; 80 struct clk *clk; 81 int irq; 82 struct completion done; 83 const u8 *tx_buf; 84 u8 *rx_buf; 85 int len; 86 }; 87 88 static inline u32 bcm2835_rd(struct bcm2835_spi *bs, unsigned reg) 89 { 90 return readl(bs->regs + reg); 91 } 92 93 static inline void bcm2835_wr(struct bcm2835_spi *bs, unsigned reg, u32 val) 94 { 95 writel(val, bs->regs + reg); 96 } 97 98 static inline void bcm2835_rd_fifo(struct bcm2835_spi *bs, int len) 99 { 100 u8 byte; 101 102 while (len--) { 103 byte = bcm2835_rd(bs, BCM2835_SPI_FIFO); 104 if (bs->rx_buf) 105 *bs->rx_buf++ = byte; 106 } 107 } 108 109 static inline void bcm2835_wr_fifo(struct bcm2835_spi *bs, int len) 110 { 111 u8 byte; 112 113 if (len > bs->len) 114 len = bs->len; 115 116 while (len--) { 117 byte = bs->tx_buf ? *bs->tx_buf++ : 0; 118 bcm2835_wr(bs, BCM2835_SPI_FIFO, byte); 119 bs->len--; 120 } 121 } 122 123 static irqreturn_t bcm2835_spi_interrupt(int irq, void *dev_id) 124 { 125 struct spi_master *master = dev_id; 126 struct bcm2835_spi *bs = spi_master_get_devdata(master); 127 u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); 128 129 /* 130 * RXR - RX needs Reading. This means 12 (or more) bytes have been 131 * transmitted and hence 12 (or more) bytes have been received. 132 * 133 * The FIFO is 16-bytes deep. We check for this interrupt to keep the 134 * FIFO full; we have a 4-byte-time buffer for IRQ latency. We check 135 * this before DONE (TX empty) just in case we delayed processing this 136 * interrupt for some reason. 137 * 138 * We only check for this case if we have more bytes to TX; at the end 139 * of the transfer, we ignore this pipelining optimization, and let 140 * bcm2835_spi_finish_transfer() drain the RX FIFO. 141 */ 142 if (bs->len && (cs & BCM2835_SPI_CS_RXR)) { 143 /* Read 12 bytes of data */ 144 bcm2835_rd_fifo(bs, 12); 145 146 /* Write up to 12 bytes */ 147 bcm2835_wr_fifo(bs, 12); 148 149 /* 150 * We must have written something to the TX FIFO due to the 151 * bs->len check above, so cannot be DONE. Hence, return 152 * early. Note that DONE could also be set if we serviced an 153 * RXR interrupt really late. 154 */ 155 return IRQ_HANDLED; 156 } 157 158 /* 159 * DONE - TX empty. This occurs when we first enable the transfer 160 * since we do not pre-fill the TX FIFO. At any other time, given that 161 * we refill the TX FIFO above based on RXR, and hence ignore DONE if 162 * RXR is set, DONE really does mean end-of-transfer. 163 */ 164 if (cs & BCM2835_SPI_CS_DONE) { 165 if (bs->len) { /* First interrupt in a transfer */ 166 bcm2835_wr_fifo(bs, 16); 167 } else { /* Transfer complete */ 168 /* Disable SPI interrupts */ 169 cs &= ~(BCM2835_SPI_CS_INTR | BCM2835_SPI_CS_INTD); 170 bcm2835_wr(bs, BCM2835_SPI_CS, cs); 171 172 /* 173 * Wake up bcm2835_spi_transfer_one(), which will call 174 * bcm2835_spi_finish_transfer(), to drain the RX FIFO. 175 */ 176 complete(&bs->done); 177 } 178 179 return IRQ_HANDLED; 180 } 181 182 return IRQ_NONE; 183 } 184 185 static int bcm2835_spi_start_transfer(struct spi_device *spi, 186 struct spi_transfer *tfr) 187 { 188 struct bcm2835_spi *bs = spi_master_get_devdata(spi->master); 189 unsigned long spi_hz, clk_hz, cdiv; 190 u32 cs = BCM2835_SPI_CS_INTR | BCM2835_SPI_CS_INTD | BCM2835_SPI_CS_TA; 191 192 spi_hz = tfr->speed_hz; 193 clk_hz = clk_get_rate(bs->clk); 194 195 if (spi_hz >= clk_hz / 2) { 196 cdiv = 2; /* clk_hz/2 is the fastest we can go */ 197 } else if (spi_hz) { 198 /* CDIV must be a power of two */ 199 cdiv = roundup_pow_of_two(DIV_ROUND_UP(clk_hz, spi_hz)); 200 201 if (cdiv >= 65536) 202 cdiv = 0; /* 0 is the slowest we can go */ 203 } else 204 cdiv = 0; /* 0 is the slowest we can go */ 205 206 if (spi->mode & SPI_CPOL) 207 cs |= BCM2835_SPI_CS_CPOL; 208 if (spi->mode & SPI_CPHA) 209 cs |= BCM2835_SPI_CS_CPHA; 210 211 if (!(spi->mode & SPI_NO_CS)) { 212 if (spi->mode & SPI_CS_HIGH) { 213 cs |= BCM2835_SPI_CS_CSPOL; 214 cs |= BCM2835_SPI_CS_CSPOL0 << spi->chip_select; 215 } 216 217 cs |= spi->chip_select; 218 } 219 220 reinit_completion(&bs->done); 221 bs->tx_buf = tfr->tx_buf; 222 bs->rx_buf = tfr->rx_buf; 223 bs->len = tfr->len; 224 225 bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv); 226 /* 227 * Enable the HW block. This will immediately trigger a DONE (TX 228 * empty) interrupt, upon which we will fill the TX FIFO with the 229 * first TX bytes. Pre-filling the TX FIFO here to avoid the 230 * interrupt doesn't work:-( 231 */ 232 bcm2835_wr(bs, BCM2835_SPI_CS, cs); 233 234 return 0; 235 } 236 237 static int bcm2835_spi_finish_transfer(struct spi_device *spi, 238 struct spi_transfer *tfr, bool cs_change) 239 { 240 struct bcm2835_spi *bs = spi_master_get_devdata(spi->master); 241 u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); 242 243 /* Drain RX FIFO */ 244 while (cs & BCM2835_SPI_CS_RXD) { 245 bcm2835_rd_fifo(bs, 1); 246 cs = bcm2835_rd(bs, BCM2835_SPI_CS); 247 } 248 249 if (tfr->delay_usecs) 250 udelay(tfr->delay_usecs); 251 252 if (cs_change) 253 /* Clear TA flag */ 254 bcm2835_wr(bs, BCM2835_SPI_CS, cs & ~BCM2835_SPI_CS_TA); 255 256 return 0; 257 } 258 259 static int bcm2835_spi_transfer_one(struct spi_master *master, 260 struct spi_message *mesg) 261 { 262 struct bcm2835_spi *bs = spi_master_get_devdata(master); 263 struct spi_transfer *tfr; 264 struct spi_device *spi = mesg->spi; 265 int err = 0; 266 unsigned int timeout; 267 bool cs_change; 268 269 list_for_each_entry(tfr, &mesg->transfers, transfer_list) { 270 err = bcm2835_spi_start_transfer(spi, tfr); 271 if (err) 272 goto out; 273 274 timeout = wait_for_completion_timeout(&bs->done, 275 msecs_to_jiffies(BCM2835_SPI_TIMEOUT_MS)); 276 if (!timeout) { 277 err = -ETIMEDOUT; 278 goto out; 279 } 280 281 cs_change = tfr->cs_change || 282 list_is_last(&tfr->transfer_list, &mesg->transfers); 283 284 err = bcm2835_spi_finish_transfer(spi, tfr, cs_change); 285 if (err) 286 goto out; 287 288 mesg->actual_length += (tfr->len - bs->len); 289 } 290 291 out: 292 /* Clear FIFOs, and disable the HW block */ 293 bcm2835_wr(bs, BCM2835_SPI_CS, 294 BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX); 295 mesg->status = err; 296 spi_finalize_current_message(master); 297 298 return 0; 299 } 300 301 static int bcm2835_spi_probe(struct platform_device *pdev) 302 { 303 struct spi_master *master; 304 struct bcm2835_spi *bs; 305 struct resource *res; 306 int err; 307 308 master = spi_alloc_master(&pdev->dev, sizeof(*bs)); 309 if (!master) { 310 dev_err(&pdev->dev, "spi_alloc_master() failed\n"); 311 return -ENOMEM; 312 } 313 314 platform_set_drvdata(pdev, master); 315 316 master->mode_bits = BCM2835_SPI_MODE_BITS; 317 master->bits_per_word_mask = SPI_BPW_MASK(8); 318 master->num_chipselect = 3; 319 master->transfer_one_message = bcm2835_spi_transfer_one; 320 master->dev.of_node = pdev->dev.of_node; 321 322 bs = spi_master_get_devdata(master); 323 324 init_completion(&bs->done); 325 326 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 327 bs->regs = devm_ioremap_resource(&pdev->dev, res); 328 if (IS_ERR(bs->regs)) { 329 err = PTR_ERR(bs->regs); 330 goto out_master_put; 331 } 332 333 bs->clk = devm_clk_get(&pdev->dev, NULL); 334 if (IS_ERR(bs->clk)) { 335 err = PTR_ERR(bs->clk); 336 dev_err(&pdev->dev, "could not get clk: %d\n", err); 337 goto out_master_put; 338 } 339 340 bs->irq = irq_of_parse_and_map(pdev->dev.of_node, 0); 341 if (bs->irq <= 0) { 342 dev_err(&pdev->dev, "could not get IRQ: %d\n", bs->irq); 343 err = bs->irq ? bs->irq : -ENODEV; 344 goto out_master_put; 345 } 346 347 clk_prepare_enable(bs->clk); 348 349 err = devm_request_irq(&pdev->dev, bs->irq, bcm2835_spi_interrupt, 0, 350 dev_name(&pdev->dev), master); 351 if (err) { 352 dev_err(&pdev->dev, "could not request IRQ: %d\n", err); 353 goto out_clk_disable; 354 } 355 356 /* initialise the hardware */ 357 bcm2835_wr(bs, BCM2835_SPI_CS, 358 BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX); 359 360 err = devm_spi_register_master(&pdev->dev, master); 361 if (err) { 362 dev_err(&pdev->dev, "could not register SPI master: %d\n", err); 363 goto out_clk_disable; 364 } 365 366 return 0; 367 368 out_clk_disable: 369 clk_disable_unprepare(bs->clk); 370 out_master_put: 371 spi_master_put(master); 372 return err; 373 } 374 375 static int bcm2835_spi_remove(struct platform_device *pdev) 376 { 377 struct spi_master *master = platform_get_drvdata(pdev); 378 struct bcm2835_spi *bs = spi_master_get_devdata(master); 379 380 /* Clear FIFOs, and disable the HW block */ 381 bcm2835_wr(bs, BCM2835_SPI_CS, 382 BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX); 383 384 clk_disable_unprepare(bs->clk); 385 386 return 0; 387 } 388 389 static const struct of_device_id bcm2835_spi_match[] = { 390 { .compatible = "brcm,bcm2835-spi", }, 391 {} 392 }; 393 MODULE_DEVICE_TABLE(of, bcm2835_spi_match); 394 395 static struct platform_driver bcm2835_spi_driver = { 396 .driver = { 397 .name = DRV_NAME, 398 .of_match_table = bcm2835_spi_match, 399 }, 400 .probe = bcm2835_spi_probe, 401 .remove = bcm2835_spi_remove, 402 }; 403 module_platform_driver(bcm2835_spi_driver); 404 405 MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835"); 406 MODULE_AUTHOR("Chris Boot <bootc@bootc.net>"); 407 MODULE_LICENSE("GPL v2"); 408