drivers/spi/spi-sifive.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 //
   3 // Copyright 2018 SiFive, Inc.
   4 //
   5 // SiFive SPI controller driver (master mode only)
   6 //
   7 // Author: SiFive, Inc.
   8 // sifive@sifive.com
   9
  10 #include <linux/clk.h>
  11 #include <linux/module.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/of.h>
  14 #include <linux/platform_device.h>
  15 #include <linux/spi/spi.h>
  16 #include <linux/io.h>
  17 #include <linux/log2.h>
  18
  19 #define SIFIVE_SPI_DRIVER_NAME           "sifive_spi"
  20
  21 #define SIFIVE_SPI_MAX_CS                32
  22 #define SIFIVE_SPI_DEFAULT_DEPTH         8
  23 #define SIFIVE_SPI_DEFAULT_MAX_BITS      8
  24
  25 /* register offsets */
  26 #define SIFIVE_SPI_REG_SCKDIV            0x00 /* Serial clock divisor */
  27 #define SIFIVE_SPI_REG_SCKMODE           0x04 /* Serial clock mode */
  28 #define SIFIVE_SPI_REG_CSID              0x10 /* Chip select ID */
  29 #define SIFIVE_SPI_REG_CSDEF             0x14 /* Chip select default */
  30 #define SIFIVE_SPI_REG_CSMODE            0x18 /* Chip select mode */
  31 #define SIFIVE_SPI_REG_DELAY0            0x28 /* Delay control 0 */
  32 #define SIFIVE_SPI_REG_DELAY1            0x2c /* Delay control 1 */
  33 #define SIFIVE_SPI_REG_FMT               0x40 /* Frame format */
  34 #define SIFIVE_SPI_REG_TXDATA            0x48 /* Tx FIFO data */
  35 #define SIFIVE_SPI_REG_RXDATA            0x4c /* Rx FIFO data */
  36 #define SIFIVE_SPI_REG_TXMARK            0x50 /* Tx FIFO watermark */
  37 #define SIFIVE_SPI_REG_RXMARK            0x54 /* Rx FIFO watermark */
  38 #define SIFIVE_SPI_REG_FCTRL             0x60 /* SPI flash interface control */
  39 #define SIFIVE_SPI_REG_FFMT              0x64 /* SPI flash instruction format */
  40 #define SIFIVE_SPI_REG_IE                0x70 /* Interrupt Enable Register */
  41 #define SIFIVE_SPI_REG_IP                0x74 /* Interrupt Pendings Register */
  42
  43 /* sckdiv bits */
  44 #define SIFIVE_SPI_SCKDIV_DIV_MASK       0xfffU
  45
  46 /* sckmode bits */
  47 #define SIFIVE_SPI_SCKMODE_PHA           BIT(0)
  48 #define SIFIVE_SPI_SCKMODE_POL           BIT(1)
  49 #define SIFIVE_SPI_SCKMODE_MODE_MASK     (SIFIVE_SPI_SCKMODE_PHA | \
  50                                           SIFIVE_SPI_SCKMODE_POL)
  51
  52 /* csmode bits */
  53 #define SIFIVE_SPI_CSMODE_MODE_AUTO      0U
  54 #define SIFIVE_SPI_CSMODE_MODE_HOLD      2U
  55 #define SIFIVE_SPI_CSMODE_MODE_OFF       3U
  56
  57 /* delay0 bits */
  58 #define SIFIVE_SPI_DELAY0_CSSCK(x)       ((u32)(x))
  59 #define SIFIVE_SPI_DELAY0_CSSCK_MASK     0xffU
  60 #define SIFIVE_SPI_DELAY0_SCKCS(x)       ((u32)(x) << 16)
  61 #define SIFIVE_SPI_DELAY0_SCKCS_MASK     (0xffU << 16)
  62
  63 /* delay1 bits */
  64 #define SIFIVE_SPI_DELAY1_INTERCS(x)     ((u32)(x))
  65 #define SIFIVE_SPI_DELAY1_INTERCS_MASK   0xffU
  66 #define SIFIVE_SPI_DELAY1_INTERXFR(x)    ((u32)(x) << 16)
  67 #define SIFIVE_SPI_DELAY1_INTERXFR_MASK  (0xffU << 16)
  68
  69 /* fmt bits */
  70 #define SIFIVE_SPI_FMT_PROTO_SINGLE      0U
  71 #define SIFIVE_SPI_FMT_PROTO_DUAL        1U
  72 #define SIFIVE_SPI_FMT_PROTO_QUAD        2U
  73 #define SIFIVE_SPI_FMT_PROTO_MASK        3U
  74 #define SIFIVE_SPI_FMT_ENDIAN            BIT(2)
  75 #define SIFIVE_SPI_FMT_DIR               BIT(3)
  76 #define SIFIVE_SPI_FMT_LEN(x)            ((u32)(x) << 16)
  77 #define SIFIVE_SPI_FMT_LEN_MASK          (0xfU << 16)
  78
  79 /* txdata bits */
  80 #define SIFIVE_SPI_TXDATA_DATA_MASK      0xffU
  81 #define SIFIVE_SPI_TXDATA_FULL           BIT(31)
  82
  83 /* rxdata bits */
  84 #define SIFIVE_SPI_RXDATA_DATA_MASK      0xffU
  85 #define SIFIVE_SPI_RXDATA_EMPTY          BIT(31)
  86
  87 /* ie and ip bits */
  88 #define SIFIVE_SPI_IP_TXWM               BIT(0)
  89 #define SIFIVE_SPI_IP_RXWM               BIT(1)
  90
  91 struct sifive_spi {
  92         void __iomem      *regs;        /* virt. address of control registers */
  93         struct clk        *clk;         /* bus clock */
  94         unsigned int      fifo_depth;   /* fifo depth in words */
  95         u32               cs_inactive;  /* level of the CS pins when inactive */
  96         struct completion done;         /* wake-up from interrupt */
  97 };
  98
  99 static void sifive_spi_write(struct sifive_spi *spi, int offset, u32 value)
 100 {
 101         iowrite32(value, spi->regs + offset);
 102 }
 103
 104 static u32 sifive_spi_read(struct sifive_spi *spi, int offset)
 105 {
 106         return ioread32(spi->regs + offset);
 107 }
 108
 109 static void sifive_spi_init(struct sifive_spi *spi)
 110 {
 111         /* Watermark interrupts are disabled by default */
 112         sifive_spi_write(spi, SIFIVE_SPI_REG_IE, 0);
 113
 114         /* Default watermark FIFO threshold values */
 115         sifive_spi_write(spi, SIFIVE_SPI_REG_TXMARK, 1);
 116         sifive_spi_write(spi, SIFIVE_SPI_REG_RXMARK, 0);
 117
 118         /* Set CS/SCK Delays and Inactive Time to defaults */
 119         sifive_spi_write(spi, SIFIVE_SPI_REG_DELAY0,
 120                          SIFIVE_SPI_DELAY0_CSSCK(1) |
 121                          SIFIVE_SPI_DELAY0_SCKCS(1));
 122         sifive_spi_write(spi, SIFIVE_SPI_REG_DELAY1,
 123                          SIFIVE_SPI_DELAY1_INTERCS(1) |
 124                          SIFIVE_SPI_DELAY1_INTERXFR(0));
 125
 126         /* Exit specialized memory-mapped SPI flash mode */
 127         sifive_spi_write(spi, SIFIVE_SPI_REG_FCTRL, 0);
 128 }
 129
 130 static int
 131 sifive_spi_prepare_message(struct spi_master *master, struct spi_message *msg)
 132 {
 133         struct sifive_spi *spi = spi_master_get_devdata(master);
 134         struct spi_device *device = msg->spi;
 135
 136         /* Update the chip select polarity */
 137         if (device->mode & SPI_CS_HIGH)
 138                 spi->cs_inactive &= ~BIT(device->chip_select);
 139         else
 140                 spi->cs_inactive |= BIT(device->chip_select);
 141         sifive_spi_write(spi, SIFIVE_SPI_REG_CSDEF, spi->cs_inactive);
 142
 143         /* Select the correct device */
 144         sifive_spi_write(spi, SIFIVE_SPI_REG_CSID, device->chip_select);
 145
 146         /* Set clock mode */
 147         sifive_spi_write(spi, SIFIVE_SPI_REG_SCKMODE,
 148                          device->mode & SIFIVE_SPI_SCKMODE_MODE_MASK);
 149
 150         return 0;
 151 }
 152
 153 static void sifive_spi_set_cs(struct spi_device *device, bool is_high)
 154 {
 155         struct sifive_spi *spi = spi_master_get_devdata(device->master);
 156
 157         /* Reverse polarity is handled by SCMR/CPOL. Not inverted CS. */
 158         if (device->mode & SPI_CS_HIGH)
 159                 is_high = !is_high;
 160
 161         sifive_spi_write(spi, SIFIVE_SPI_REG_CSMODE, is_high ?
 162                          SIFIVE_SPI_CSMODE_MODE_AUTO :
 163                          SIFIVE_SPI_CSMODE_MODE_HOLD);
 164 }
 165
 166 static int
 167 sifive_spi_prep_transfer(struct sifive_spi *spi, struct spi_device *device,
 168                          struct spi_transfer *t)
 169 {
 170         u32 cr;
 171         unsigned int mode;
 172
 173         /* Calculate and program the clock rate */
 174         cr = DIV_ROUND_UP(clk_get_rate(spi->clk) >> 1, t->speed_hz) - 1;
 175         cr &= SIFIVE_SPI_SCKDIV_DIV_MASK;
 176         sifive_spi_write(spi, SIFIVE_SPI_REG_SCKDIV, cr);
 177
 178         mode = max_t(unsigned int, t->rx_nbits, t->tx_nbits);
 179
 180         /* Set frame format */
 181         cr = SIFIVE_SPI_FMT_LEN(t->bits_per_word);
 182         switch (mode) {
 183         case SPI_NBITS_QUAD:
 184                 cr |= SIFIVE_SPI_FMT_PROTO_QUAD;
 185                 break;
 186         case SPI_NBITS_DUAL:
 187                 cr |= SIFIVE_SPI_FMT_PROTO_DUAL;
 188                 break;
 189         default:
 190                 cr |= SIFIVE_SPI_FMT_PROTO_SINGLE;
 191                 break;
 192         }
 193         if (device->mode & SPI_LSB_FIRST)
 194                 cr |= SIFIVE_SPI_FMT_ENDIAN;
 195         if (!t->rx_buf)
 196                 cr |= SIFIVE_SPI_FMT_DIR;
 197         sifive_spi_write(spi, SIFIVE_SPI_REG_FMT, cr);
 198
 199         /* We will want to poll if the time we need to wait is
 200          * less than the context switching time.
 201          * Let's call that threshold 5us. The operation will take:
 202          *    (8/mode) * fifo_depth / hz <= 5 * 10^-6
 203          *    1600000 * fifo_depth <= hz * mode
 204          */
 205         return 1600000 * spi->fifo_depth <= t->speed_hz * mode;
 206 }
 207
 208 static irqreturn_t sifive_spi_irq(int irq, void *dev_id)
 209 {
 210         struct sifive_spi *spi = dev_id;
 211         u32 ip = sifive_spi_read(spi, SIFIVE_SPI_REG_IP);
 212
 213         if (ip & (SIFIVE_SPI_IP_TXWM | SIFIVE_SPI_IP_RXWM)) {
 214                 /* Disable interrupts until next transfer */
 215                 sifive_spi_write(spi, SIFIVE_SPI_REG_IE, 0);
 216                 complete(&spi->done);
 217                 return IRQ_HANDLED;
 218         }
 219
 220         return IRQ_NONE;
 221 }
 222
 223 static void sifive_spi_wait(struct sifive_spi *spi, u32 bit, int poll)
 224 {
 225         if (poll) {
 226                 u32 cr;
 227
 228                 do {
 229                         cr = sifive_spi_read(spi, SIFIVE_SPI_REG_IP);
 230                 } while (!(cr & bit));
 231         } else {
 232                 reinit_completion(&spi->done);
 233                 sifive_spi_write(spi, SIFIVE_SPI_REG_IE, bit);
 234                 wait_for_completion(&spi->done);
 235         }
 236 }
 237
 238 static void sifive_spi_tx(struct sifive_spi *spi, const u8 *tx_ptr)
 239 {
 240         WARN_ON_ONCE((sifive_spi_read(spi, SIFIVE_SPI_REG_TXDATA)
 241                                 & SIFIVE_SPI_TXDATA_FULL) != 0);
 242         sifive_spi_write(spi, SIFIVE_SPI_REG_TXDATA,
 243                          *tx_ptr & SIFIVE_SPI_TXDATA_DATA_MASK);
 244 }
 245
 246 static void sifive_spi_rx(struct sifive_spi *spi, u8 *rx_ptr)
 247 {
 248         u32 data = sifive_spi_read(spi, SIFIVE_SPI_REG_RXDATA);
 249
 250         WARN_ON_ONCE((data & SIFIVE_SPI_RXDATA_EMPTY) != 0);
 251         *rx_ptr = data & SIFIVE_SPI_RXDATA_DATA_MASK;
 252 }
 253
 254 static int
 255 sifive_spi_transfer_one(struct spi_master *master, struct spi_device *device,
 256                         struct spi_transfer *t)
 257 {
 258         struct sifive_spi *spi = spi_master_get_devdata(master);
 259         int poll = sifive_spi_prep_transfer(spi, device, t);
 260         const u8 *tx_ptr = t->tx_buf;
 261         u8 *rx_ptr = t->rx_buf;
 262         unsigned int remaining_words = t->len;
 263
 264         while (remaining_words) {
 265                 unsigned int n_words = min(remaining_words, spi->fifo_depth);
 266                 unsigned int i;
 267
 268                 /* Enqueue n_words for transmission */
 269                 for (i = 0; i < n_words; i++)
 270                         sifive_spi_tx(spi, tx_ptr++);
 271
 272                 if (rx_ptr) {
 273                         /* Wait for transmission + reception to complete */
 274                         sifive_spi_write(spi, SIFIVE_SPI_REG_RXMARK,
 275                                          n_words - 1);
 276                         sifive_spi_wait(spi, SIFIVE_SPI_IP_RXWM, poll);
 277
 278                         /* Read out all the data from the RX FIFO */
 279                         for (i = 0; i < n_words; i++)
 280                                 sifive_spi_rx(spi, rx_ptr++);
 281                 } else {
 282                         /* Wait for transmission to complete */
 283                         sifive_spi_wait(spi, SIFIVE_SPI_IP_TXWM, poll);
 284                 }
 285
 286                 remaining_words -= n_words;
 287         }
 288
 289         return 0;
 290 }
 291
 292 static int sifive_spi_probe(struct platform_device *pdev)
 293 {
 294         struct sifive_spi *spi;
 295         int ret, irq, num_cs;
 296         u32 cs_bits, max_bits_per_word;
 297         struct spi_master *master;
 298
 299         master = spi_alloc_master(&pdev->dev, sizeof(struct sifive_spi));
 300         if (!master) {
 301                 dev_err(&pdev->dev, "out of memory\n");
 302                 return -ENOMEM;
 303         }
 304
 305         spi = spi_master_get_devdata(master);
 306         init_completion(&spi->done);
 307         platform_set_drvdata(pdev, master);
 308
 309         spi->regs = devm_platform_ioremap_resource(pdev, 0);
 310         if (IS_ERR(spi->regs)) {
 311                 ret = PTR_ERR(spi->regs);
 312                 goto put_master;
 313         }
 314
 315         spi->clk = devm_clk_get(&pdev->dev, NULL);
 316         if (IS_ERR(spi->clk)) {
 317                 dev_err(&pdev->dev, "Unable to find bus clock\n");
 318                 ret = PTR_ERR(spi->clk);
 319                 goto put_master;
 320         }
 321
 322         irq = platform_get_irq(pdev, 0);
 323         if (irq < 0) {
 324                 ret = irq;
 325                 goto put_master;
 326         }
 327
 328         /* Optional parameters */
 329         ret =
 330           of_property_read_u32(pdev->dev.of_node, "sifive,fifo-depth",
 331                                &spi->fifo_depth);
 332         if (ret < 0)
 333                 spi->fifo_depth = SIFIVE_SPI_DEFAULT_DEPTH;
 334
 335         ret =
 336           of_property_read_u32(pdev->dev.of_node, "sifive,max-bits-per-word",
 337                                &max_bits_per_word);
 338
 339         if (!ret && max_bits_per_word < 8) {
 340                 dev_err(&pdev->dev, "Only 8bit SPI words supported by the driver\n");
 341                 ret = -EINVAL;
 342                 goto put_master;
 343         }
 344
 345         /* Spin up the bus clock before hitting registers */
 346         ret = clk_prepare_enable(spi->clk);
 347         if (ret) {
 348                 dev_err(&pdev->dev, "Unable to enable bus clock\n");
 349                 goto put_master;
 350         }
 351
 352         /* probe the number of CS lines */
 353         spi->cs_inactive = sifive_spi_read(spi, SIFIVE_SPI_REG_CSDEF);
 354         sifive_spi_write(spi, SIFIVE_SPI_REG_CSDEF, 0xffffffffU);
 355         cs_bits = sifive_spi_read(spi, SIFIVE_SPI_REG_CSDEF);
 356         sifive_spi_write(spi, SIFIVE_SPI_REG_CSDEF, spi->cs_inactive);
 357         if (!cs_bits) {
 358                 dev_err(&pdev->dev, "Could not auto probe CS lines\n");
 359                 ret = -EINVAL;
 360                 goto disable_clk;
 361         }
 362
 363         num_cs = ilog2(cs_bits) + 1;
 364         if (num_cs > SIFIVE_SPI_MAX_CS) {
 365                 dev_err(&pdev->dev, "Invalid number of spi slaves\n");
 366                 ret = -EINVAL;
 367                 goto disable_clk;
 368         }
 369
 370         /* Define our master */
 371         master->dev.of_node = pdev->dev.of_node;
 372         master->bus_num = pdev->id;
 373         master->num_chipselect = num_cs;
 374         master->mode_bits = SPI_CPHA | SPI_CPOL
 375                           | SPI_CS_HIGH | SPI_LSB_FIRST
 376                           | SPI_TX_DUAL | SPI_TX_QUAD
 377                           | SPI_RX_DUAL | SPI_RX_QUAD;
 378         /* TODO: add driver support for bits_per_word < 8
 379          * we need to "left-align" the bits (unless SPI_LSB_FIRST)
 380          */
 381         master->bits_per_word_mask = SPI_BPW_MASK(8);
 382         master->flags = SPI_CONTROLLER_MUST_TX | SPI_MASTER_GPIO_SS;
 383         master->prepare_message = sifive_spi_prepare_message;
 384         master->set_cs = sifive_spi_set_cs;
 385         master->transfer_one = sifive_spi_transfer_one;
 386
 387         pdev->dev.dma_mask = NULL;
 388         /* Configure the SPI master hardware */
 389         sifive_spi_init(spi);
 390
 391         /* Register for SPI Interrupt */
 392         ret = devm_request_irq(&pdev->dev, irq, sifive_spi_irq, 0,
 393                                dev_name(&pdev->dev), spi);
 394         if (ret) {
 395                 dev_err(&pdev->dev, "Unable to bind to interrupt\n");
 396                 goto disable_clk;
 397         }
 398
 399         dev_info(&pdev->dev, "mapped; irq=%d, cs=%d\n",
 400                  irq, master->num_chipselect);
 401
 402         ret = devm_spi_register_master(&pdev->dev, master);
 403         if (ret < 0) {
 404                 dev_err(&pdev->dev, "spi_register_master failed\n");
 405                 goto disable_clk;
 406         }
 407
 408         return 0;
 409
 410 disable_clk:
 411         clk_disable_unprepare(spi->clk);
 412 put_master:
 413         spi_master_put(master);
 414
 415         return ret;
 416 }
 417
 418 static int sifive_spi_remove(struct platform_device *pdev)
 419 {
 420         struct spi_master *master = platform_get_drvdata(pdev);
 421         struct sifive_spi *spi = spi_master_get_devdata(master);
 422
 423         /* Disable all the interrupts just in case */
 424         sifive_spi_write(spi, SIFIVE_SPI_REG_IE, 0);
 425         clk_disable_unprepare(spi->clk);
 426
 427         return 0;
 428 }
 429
 430 static const struct of_device_id sifive_spi_of_match[] = {
 431         { .compatible = "sifive,spi0", },
 432         {}
 433 };
 434 MODULE_DEVICE_TABLE(of, sifive_spi_of_match);
 435
 436 static struct platform_driver sifive_spi_driver = {
 437         .probe = sifive_spi_probe,
 438         .remove = sifive_spi_remove,
 439         .driver = {
 440                 .name = SIFIVE_SPI_DRIVER_NAME,
 441                 .of_match_table = sifive_spi_of_match,
 442         },
 443 };
 444 module_platform_driver(sifive_spi_driver);
 445
 446 MODULE_AUTHOR("SiFive, Inc. <sifive@sifive.com>");
 447 MODULE_DESCRIPTION("SiFive SPI driver");
 448 MODULE_LICENSE("GPL");