drivers/spi/spi-bcm2835.c

   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         INIT_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 = BIT(8 - 1);
 318         master->bus_num = -1;
 319         master->num_chipselect = 3;
 320         master->transfer_one_message = bcm2835_spi_transfer_one;
 321         master->dev.of_node = pdev->dev.of_node;
 322
 323         bs = spi_master_get_devdata(master);
 324
 325         init_completion(&bs->done);
 326
 327         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 328         if (!res) {
 329                 dev_err(&pdev->dev, "could not get memory resource\n");
 330                 err = -ENODEV;
 331                 goto out_master_put;
 332         }
 333
 334         bs->regs = devm_ioremap_resource(&pdev->dev, res);
 335         if (IS_ERR(bs->regs)) {
 336                 err = PTR_ERR(bs->regs);
 337                 goto out_master_put;
 338         }
 339
 340         bs->clk = devm_clk_get(&pdev->dev, NULL);
 341         if (IS_ERR(bs->clk)) {
 342                 err = PTR_ERR(bs->clk);
 343                 dev_err(&pdev->dev, "could not get clk: %d\n", err);
 344                 goto out_master_put;
 345         }
 346
 347         bs->irq = irq_of_parse_and_map(pdev->dev.of_node, 0);
 348         if (bs->irq <= 0) {
 349                 dev_err(&pdev->dev, "could not get IRQ: %d\n", bs->irq);
 350                 err = bs->irq ? bs->irq : -ENODEV;
 351                 goto out_master_put;
 352         }
 353
 354         clk_prepare_enable(bs->clk);
 355
 356         err = request_irq(bs->irq, bcm2835_spi_interrupt, 0,
 357                         dev_name(&pdev->dev), master);
 358         if (err) {
 359                 dev_err(&pdev->dev, "could not request IRQ: %d\n", err);
 360                 goto out_clk_disable;
 361         }
 362
 363         /* initialise the hardware */
 364         bcm2835_wr(bs, BCM2835_SPI_CS,
 365                    BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);
 366
 367         err = spi_register_master(master);
 368         if (err) {
 369                 dev_err(&pdev->dev, "could not register SPI master: %d\n", err);
 370                 goto out_free_irq;
 371         }
 372
 373         return 0;
 374
 375 out_free_irq:
 376         free_irq(bs->irq, master);
 377 out_clk_disable:
 378         clk_disable_unprepare(bs->clk);
 379 out_master_put:
 380         spi_master_put(master);
 381         return err;
 382 }
 383
 384 static int bcm2835_spi_remove(struct platform_device *pdev)
 385 {
 386         struct spi_master *master = platform_get_drvdata(pdev);
 387         struct bcm2835_spi *bs = spi_master_get_devdata(master);
 388
 389         free_irq(bs->irq, master);
 390         spi_unregister_master(master);
 391
 392         /* Clear FIFOs, and disable the HW block */
 393         bcm2835_wr(bs, BCM2835_SPI_CS,
 394                    BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);
 395
 396         clk_disable_unprepare(bs->clk);
 397         spi_master_put(master);
 398
 399         return 0;
 400 }
 401
 402 static const struct of_device_id bcm2835_spi_match[] = {
 403         { .compatible = "brcm,bcm2835-spi", },
 404         {}
 405 };
 406 MODULE_DEVICE_TABLE(of, bcm2835_spi_match);
 407
 408 static struct platform_driver bcm2835_spi_driver = {
 409         .driver         = {
 410                 .name           = DRV_NAME,
 411                 .owner          = THIS_MODULE,
 412                 .of_match_table = bcm2835_spi_match,
 413         },
 414         .probe          = bcm2835_spi_probe,
 415         .remove         = bcm2835_spi_remove,
 416 };
 417 module_platform_driver(bcm2835_spi_driver);
 418
 419 MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835");
 420 MODULE_AUTHOR("Chris Boot <bootc@bootc.net>");
 421 MODULE_LICENSE("GPL v2");