drivers/spi/spi-pic32.c

   1 /*
   2  * Microchip PIC32 SPI controller driver.
   3  *
   4  * Purna Chandra Mandal <purna.mandal@microchip.com>
   5  * Copyright (c) 2016, Microchip Technology Inc.
   6  *
   7  * This program is free software; you can distribute it and/or modify it
   8  * under the terms of the GNU General Public License (Version 2) as
   9  * published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * for more details.
  15  */
  16
  17 #include <linux/clk.h>
  18 #include <linux/clkdev.h>
  19 #include <linux/delay.h>
  20 #include <linux/dmaengine.h>
  21 #include <linux/dma-mapping.h>
  22 #include <linux/highmem.h>
  23 #include <linux/module.h>
  24 #include <linux/io.h>
  25 #include <linux/interrupt.h>
  26 #include <linux/of.h>
  27 #include <linux/of_irq.h>
  28 #include <linux/of_gpio.h>
  29 #include <linux/of_address.h>
  30 #include <linux/platform_device.h>
  31 #include <linux/spi/spi.h>
  32
  33 /* SPI controller registers */
  34 struct pic32_spi_regs {
  35         u32 ctrl;
  36         u32 ctrl_clr;
  37         u32 ctrl_set;
  38         u32 ctrl_inv;
  39         u32 status;
  40         u32 status_clr;
  41         u32 status_set;
  42         u32 status_inv;
  43         u32 buf;
  44         u32 dontuse[3];
  45         u32 baud;
  46         u32 dontuse2[3];
  47         u32 ctrl2;
  48         u32 ctrl2_clr;
  49         u32 ctrl2_set;
  50         u32 ctrl2_inv;
  51 };
  52
  53 /* Bit fields of SPI Control Register */
  54 #define CTRL_RX_INT_SHIFT       0  /* Rx interrupt generation */
  55 #define  RX_FIFO_EMTPY          0
  56 #define  RX_FIFO_NOT_EMPTY      1 /* not empty */
  57 #define  RX_FIFO_HALF_FULL      2 /* full by half or more */
  58 #define  RX_FIFO_FULL           3 /* completely full */
  59
  60 #define CTRL_TX_INT_SHIFT       2  /* TX interrupt generation */
  61 #define  TX_FIFO_ALL_EMPTY      0 /* completely empty */
  62 #define  TX_FIFO_EMTPY          1 /* empty */
  63 #define  TX_FIFO_HALF_EMPTY     2 /* empty by half or more */
  64 #define  TX_FIFO_NOT_FULL       3 /* atleast one empty */
  65
  66 #define CTRL_MSTEN      BIT(5) /* enable master mode */
  67 #define CTRL_CKP        BIT(6) /* active low */
  68 #define CTRL_CKE        BIT(8) /* Tx on falling edge */
  69 #define CTRL_SMP        BIT(9) /* Rx at middle or end of tx */
  70 #define CTRL_BPW_MASK   0x03   /* bits per word/sample */
  71 #define CTRL_BPW_SHIFT  10
  72 #define  PIC32_BPW_8    0
  73 #define  PIC32_BPW_16   1
  74 #define  PIC32_BPW_32   2
  75 #define CTRL_SIDL       BIT(13) /* sleep when idle */
  76 #define CTRL_ON         BIT(15) /* enable macro */
  77 #define CTRL_ENHBUF     BIT(16) /* enable enhanced buffering */
  78 #define CTRL_MCLKSEL    BIT(23) /* select clock source */
  79 #define CTRL_MSSEN      BIT(28) /* macro driven /SS */
  80 #define CTRL_FRMEN      BIT(31) /* enable framing mode */
  81
  82 /* Bit fields of SPI Status Register */
  83 #define STAT_RF_EMPTY   BIT(5) /* RX Fifo empty */
  84 #define STAT_RX_OV      BIT(6) /* err, s/w needs to clear */
  85 #define STAT_TX_UR      BIT(8) /* UR in Framed SPI modes */
  86 #define STAT_FRM_ERR    BIT(12) /* Multiple Frame Sync pulse */
  87 #define STAT_TF_LVL_MASK        0x1F
  88 #define STAT_TF_LVL_SHIFT       16
  89 #define STAT_RF_LVL_MASK        0x1F
  90 #define STAT_RF_LVL_SHIFT       24
  91
  92 /* Bit fields of SPI Baud Register */
  93 #define BAUD_MASK               0x1ff
  94
  95 /* Bit fields of SPI Control2 Register */
  96 #define CTRL2_TX_UR_EN          BIT(10) /* Enable int on Tx under-run */
  97 #define CTRL2_RX_OV_EN          BIT(11) /* Enable int on Rx over-run */
  98 #define CTRL2_FRM_ERR_EN        BIT(12) /* Enable frame err int */
  99
 100 /* Minimum DMA transfer size */
 101 #define PIC32_DMA_LEN_MIN       64
 102
 103 struct pic32_spi {
 104         dma_addr_t              dma_base;
 105         struct pic32_spi_regs __iomem *regs;
 106         int                     fault_irq;
 107         int                     rx_irq;
 108         int                     tx_irq;
 109         u32                     fifo_n_byte; /* FIFO depth in bytes */
 110         struct clk              *clk;
 111         struct spi_master       *master;
 112         /* Current controller setting */
 113         u32                     speed_hz; /* spi-clk rate */
 114         u32                     mode;
 115         u32                     bits_per_word;
 116         u32                     fifo_n_elm; /* FIFO depth in words */
 117 #define PIC32F_DMA_PREP         0 /* DMA chnls configured */
 118         unsigned long           flags;
 119         /* Current transfer state */
 120         struct completion       xfer_done;
 121         /* PIO transfer specific */
 122         const void              *tx;
 123         const void              *tx_end;
 124         const void              *rx;
 125         const void              *rx_end;
 126         int                     len;
 127         void (*rx_fifo)(struct pic32_spi *);
 128         void (*tx_fifo)(struct pic32_spi *);
 129 };
 130
 131 static inline void pic32_spi_enable(struct pic32_spi *pic32s)
 132 {
 133         writel(CTRL_ON | CTRL_SIDL, &pic32s->regs->ctrl_set);
 134 }
 135
 136 static inline void pic32_spi_disable(struct pic32_spi *pic32s)
 137 {
 138         writel(CTRL_ON | CTRL_SIDL, &pic32s->regs->ctrl_clr);
 139
 140         /* avoid SPI registers read/write at immediate next CPU clock */
 141         ndelay(20);
 142 }
 143
 144 static void pic32_spi_set_clk_rate(struct pic32_spi *pic32s, u32 spi_ck)
 145 {
 146         u32 div;
 147
 148         /* div = (clk_in / 2 * spi_ck) - 1 */
 149         div = DIV_ROUND_CLOSEST(clk_get_rate(pic32s->clk), 2 * spi_ck) - 1;
 150
 151         writel(div & BAUD_MASK, &pic32s->regs->baud);
 152 }
 153
 154 static inline u32 pic32_rx_fifo_level(struct pic32_spi *pic32s)
 155 {
 156         u32 sr = readl(&pic32s->regs->status);
 157
 158         return (sr >> STAT_RF_LVL_SHIFT) & STAT_RF_LVL_MASK;
 159 }
 160
 161 static inline u32 pic32_tx_fifo_level(struct pic32_spi *pic32s)
 162 {
 163         u32 sr = readl(&pic32s->regs->status);
 164
 165         return (sr >> STAT_TF_LVL_SHIFT) & STAT_TF_LVL_MASK;
 166 }
 167
 168 /* Return the max entries we can fill into tx fifo */
 169 static u32 pic32_tx_max(struct pic32_spi *pic32s, int n_bytes)
 170 {
 171         u32 tx_left, tx_room, rxtx_gap;
 172
 173         tx_left = (pic32s->tx_end - pic32s->tx) / n_bytes;
 174         tx_room = pic32s->fifo_n_elm - pic32_tx_fifo_level(pic32s);
 175
 176         /*
 177          * Another concern is about the tx/rx mismatch, we
 178          * though to use (pic32s->fifo_n_byte - rxfl - txfl) as
 179          * one maximum value for tx, but it doesn't cover the
 180          * data which is out of tx/rx fifo and inside the
 181          * shift registers. So a ctrl from sw point of
 182          * view is taken.
 183          */
 184         rxtx_gap = ((pic32s->rx_end - pic32s->rx) -
 185                     (pic32s->tx_end - pic32s->tx)) / n_bytes;
 186         return min3(tx_left, tx_room, (u32)(pic32s->fifo_n_elm - rxtx_gap));
 187 }
 188
 189 /* Return the max entries we should read out of rx fifo */
 190 static u32 pic32_rx_max(struct pic32_spi *pic32s, int n_bytes)
 191 {
 192         u32 rx_left = (pic32s->rx_end - pic32s->rx) / n_bytes;
 193
 194         return min_t(u32, rx_left, pic32_rx_fifo_level(pic32s));
 195 }
 196
 197 #define BUILD_SPI_FIFO_RW(__name, __type, __bwl)                \
 198 static void pic32_spi_rx_##__name(struct pic32_spi *pic32s)     \
 199 {                                                               \
 200         __type v;                                               \
 201         u32 mx = pic32_rx_max(pic32s, sizeof(__type));          \
 202         for (; mx; mx--) {                                      \
 203                 v = read##__bwl(&pic32s->regs->buf);            \
 204                 if (pic32s->rx_end - pic32s->len)               \
 205                         *(__type *)(pic32s->rx) = v;            \
 206                 pic32s->rx += sizeof(__type);                   \
 207         }                                                       \
 208 }                                                               \
 209                                                                 \
 210 static void pic32_spi_tx_##__name(struct pic32_spi *pic32s)     \
 211 {                                                               \
 212         __type v;                                               \
 213         u32 mx = pic32_tx_max(pic32s, sizeof(__type));          \
 214         for (; mx ; mx--) {                                     \
 215                 v = (__type)~0U;                                \
 216                 if (pic32s->tx_end - pic32s->len)               \
 217                         v = *(__type *)(pic32s->tx);            \
 218                 write##__bwl(v, &pic32s->regs->buf);            \
 219                 pic32s->tx += sizeof(__type);                   \
 220         }                                                       \
 221 }
 222
 223 BUILD_SPI_FIFO_RW(byte, u8, b);
 224 BUILD_SPI_FIFO_RW(word, u16, w);
 225 BUILD_SPI_FIFO_RW(dword, u32, l);
 226
 227 static void pic32_err_stop(struct pic32_spi *pic32s, const char *msg)
 228 {
 229         /* disable all interrupts */
 230         disable_irq_nosync(pic32s->fault_irq);
 231         disable_irq_nosync(pic32s->rx_irq);
 232         disable_irq_nosync(pic32s->tx_irq);
 233
 234         /* Show err message and abort xfer with err */
 235         dev_err(&pic32s->master->dev, "%s\n", msg);
 236         if (pic32s->master->cur_msg)
 237                 pic32s->master->cur_msg->status = -EIO;
 238         complete(&pic32s->xfer_done);
 239 }
 240
 241 static irqreturn_t pic32_spi_fault_irq(int irq, void *dev_id)
 242 {
 243         struct pic32_spi *pic32s = dev_id;
 244         u32 status;
 245
 246         status = readl(&pic32s->regs->status);
 247
 248         /* Error handling */
 249         if (status & (STAT_RX_OV | STAT_TX_UR)) {
 250                 writel(STAT_RX_OV, &pic32s->regs->status_clr);
 251                 writel(STAT_TX_UR, &pic32s->regs->status_clr);
 252                 pic32_err_stop(pic32s, "err_irq: fifo ov/ur-run\n");
 253                 return IRQ_HANDLED;
 254         }
 255
 256         if (status & STAT_FRM_ERR) {
 257                 pic32_err_stop(pic32s, "err_irq: frame error");
 258                 return IRQ_HANDLED;
 259         }
 260
 261         if (!pic32s->master->cur_msg) {
 262                 pic32_err_stop(pic32s, "err_irq: no mesg");
 263                 return IRQ_NONE;
 264         }
 265
 266         return IRQ_NONE;
 267 }
 268
 269 static irqreturn_t pic32_spi_rx_irq(int irq, void *dev_id)
 270 {
 271         struct pic32_spi *pic32s = dev_id;
 272
 273         pic32s->rx_fifo(pic32s);
 274
 275         /* rx complete ? */
 276         if (pic32s->rx_end == pic32s->rx) {
 277                 /* disable all interrupts */
 278                 disable_irq_nosync(pic32s->fault_irq);
 279                 disable_irq_nosync(pic32s->rx_irq);
 280
 281                 /* complete current xfer */
 282                 complete(&pic32s->xfer_done);
 283         }
 284
 285         return IRQ_HANDLED;
 286 }
 287
 288 static irqreturn_t pic32_spi_tx_irq(int irq, void *dev_id)
 289 {
 290         struct pic32_spi *pic32s = dev_id;
 291
 292         pic32s->tx_fifo(pic32s);
 293
 294         /* tx complete? disable tx interrupt */
 295         if (pic32s->tx_end == pic32s->tx)
 296                 disable_irq_nosync(pic32s->tx_irq);
 297
 298         return IRQ_HANDLED;
 299 }
 300
 301 static void pic32_spi_dma_rx_notify(void *data)
 302 {
 303         struct pic32_spi *pic32s = data;
 304
 305         complete(&pic32s->xfer_done);
 306 }
 307
 308 static int pic32_spi_dma_transfer(struct pic32_spi *pic32s,
 309                                   struct spi_transfer *xfer)
 310 {
 311         struct spi_master *master = pic32s->master;
 312         struct dma_async_tx_descriptor *desc_rx;
 313         struct dma_async_tx_descriptor *desc_tx;
 314         dma_cookie_t cookie;
 315         int ret;
 316
 317         if (!master->dma_rx || !master->dma_tx)
 318                 return -ENODEV;
 319
 320         desc_rx = dmaengine_prep_slave_sg(master->dma_rx,
 321                                           xfer->rx_sg.sgl,
 322                                           xfer->rx_sg.nents,
 323                                           DMA_FROM_DEVICE,
 324                                           DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
 325         if (!desc_rx) {
 326                 ret = -EINVAL;
 327                 goto err_dma;
 328         }
 329
 330         desc_tx = dmaengine_prep_slave_sg(master->dma_tx,
 331                                           xfer->tx_sg.sgl,
 332                                           xfer->tx_sg.nents,
 333                                           DMA_TO_DEVICE,
 334                                           DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
 335         if (!desc_tx) {
 336                 ret = -EINVAL;
 337                 goto err_dma;
 338         }
 339
 340         /* Put callback on the RX transfer, that should finish last */
 341         desc_rx->callback = pic32_spi_dma_rx_notify;
 342         desc_rx->callback_param = pic32s;
 343
 344         cookie = dmaengine_submit(desc_rx);
 345         ret = dma_submit_error(cookie);
 346         if (ret)
 347                 goto err_dma;
 348
 349         cookie = dmaengine_submit(desc_tx);
 350         ret = dma_submit_error(cookie);
 351         if (ret)
 352                 goto err_dma_tx;
 353
 354         dma_async_issue_pending(master->dma_rx);
 355         dma_async_issue_pending(master->dma_tx);
 356
 357         return 0;
 358
 359 err_dma_tx:
 360         dmaengine_terminate_all(master->dma_rx);
 361 err_dma:
 362         return ret;
 363 }
 364
 365 static int pic32_spi_dma_config(struct pic32_spi *pic32s, u32 dma_width)
 366 {
 367         int buf_offset = offsetof(struct pic32_spi_regs, buf);
 368         struct spi_master *master = pic32s->master;
 369         struct dma_slave_config cfg;
 370         int ret;
 371
 372         cfg.device_fc = true;
 373         cfg.src_addr = pic32s->dma_base + buf_offset;
 374         cfg.dst_addr = pic32s->dma_base + buf_offset;
 375         cfg.src_maxburst = pic32s->fifo_n_elm / 2; /* fill one-half */
 376         cfg.dst_maxburst = pic32s->fifo_n_elm / 2; /* drain one-half */
 377         cfg.src_addr_width = dma_width;
 378         cfg.dst_addr_width = dma_width;
 379         /* tx channel */
 380         cfg.slave_id = pic32s->tx_irq;
 381         cfg.direction = DMA_MEM_TO_DEV;
 382         ret = dmaengine_slave_config(master->dma_tx, &cfg);
 383         if (ret) {
 384                 dev_err(&master->dev, "tx channel setup failed\n");
 385                 return ret;
 386         }
 387         /* rx channel */
 388         cfg.slave_id = pic32s->rx_irq;
 389         cfg.direction = DMA_DEV_TO_MEM;
 390         ret = dmaengine_slave_config(master->dma_rx, &cfg);
 391         if (ret)
 392                 dev_err(&master->dev, "rx channel setup failed\n");
 393
 394         return ret;
 395 }
 396
 397 static int pic32_spi_set_word_size(struct pic32_spi *pic32s, u8 bits_per_word)
 398 {
 399         enum dma_slave_buswidth dmawidth;
 400         u32 buswidth, v;
 401
 402         switch (bits_per_word) {
 403         case 8:
 404                 pic32s->rx_fifo = pic32_spi_rx_byte;
 405                 pic32s->tx_fifo = pic32_spi_tx_byte;
 406                 buswidth = PIC32_BPW_8;
 407                 dmawidth = DMA_SLAVE_BUSWIDTH_1_BYTE;
 408                 break;
 409         case 16:
 410                 pic32s->rx_fifo = pic32_spi_rx_word;
 411                 pic32s->tx_fifo = pic32_spi_tx_word;
 412                 buswidth = PIC32_BPW_16;
 413                 dmawidth = DMA_SLAVE_BUSWIDTH_2_BYTES;
 414                 break;
 415         case 32:
 416                 pic32s->rx_fifo = pic32_spi_rx_dword;
 417                 pic32s->tx_fifo = pic32_spi_tx_dword;
 418                 buswidth = PIC32_BPW_32;
 419                 dmawidth = DMA_SLAVE_BUSWIDTH_4_BYTES;
 420                 break;
 421         default:
 422                 /* not supported */
 423                 return -EINVAL;
 424         }
 425
 426         /* calculate maximum number of words fifos can hold */
 427         pic32s->fifo_n_elm = DIV_ROUND_UP(pic32s->fifo_n_byte,
 428                                           bits_per_word / 8);
 429         /* set word size */
 430         v = readl(&pic32s->regs->ctrl);
 431         v &= ~(CTRL_BPW_MASK << CTRL_BPW_SHIFT);
 432         v |= buswidth << CTRL_BPW_SHIFT;
 433         writel(v, &pic32s->regs->ctrl);
 434
 435         /* re-configure dma width, if required */
 436         if (test_bit(PIC32F_DMA_PREP, &pic32s->flags))
 437                 pic32_spi_dma_config(pic32s, dmawidth);
 438
 439         return 0;
 440 }
 441
 442 static int pic32_spi_prepare_hardware(struct spi_master *master)
 443 {
 444         struct pic32_spi *pic32s = spi_master_get_devdata(master);
 445
 446         pic32_spi_enable(pic32s);
 447
 448         return 0;
 449 }
 450
 451 static int pic32_spi_prepare_message(struct spi_master *master,
 452                                      struct spi_message *msg)
 453 {
 454         struct pic32_spi *pic32s = spi_master_get_devdata(master);
 455         struct spi_device *spi = msg->spi;
 456         u32 val;
 457
 458         /* set device specific bits_per_word */
 459         if (pic32s->bits_per_word != spi->bits_per_word) {
 460                 pic32_spi_set_word_size(pic32s, spi->bits_per_word);
 461                 pic32s->bits_per_word = spi->bits_per_word;
 462         }
 463
 464         /* device specific speed change */
 465         if (pic32s->speed_hz != spi->max_speed_hz) {
 466                 pic32_spi_set_clk_rate(pic32s, spi->max_speed_hz);
 467                 pic32s->speed_hz = spi->max_speed_hz;
 468         }
 469
 470         /* device specific mode change */
 471         if (pic32s->mode != spi->mode) {
 472                 val = readl(&pic32s->regs->ctrl);
 473                 /* active low */
 474                 if (spi->mode & SPI_CPOL)
 475                         val |= CTRL_CKP;
 476                 else
 477                         val &= ~CTRL_CKP;
 478                 /* tx on rising edge */
 479                 if (spi->mode & SPI_CPHA)
 480                         val &= ~CTRL_CKE;
 481                 else
 482                         val |= CTRL_CKE;
 483
 484                 /* rx at end of tx */
 485                 val |= CTRL_SMP;
 486                 writel(val, &pic32s->regs->ctrl);
 487                 pic32s->mode = spi->mode;
 488         }
 489
 490         return 0;
 491 }
 492
 493 static bool pic32_spi_can_dma(struct spi_master *master,
 494                               struct spi_device *spi,
 495                               struct spi_transfer *xfer)
 496 {
 497         struct pic32_spi *pic32s = spi_master_get_devdata(master);
 498
 499         /* skip using DMA on small size transfer to avoid overhead.*/
 500         return (xfer->len >= PIC32_DMA_LEN_MIN) &&
 501                test_bit(PIC32F_DMA_PREP, &pic32s->flags);
 502 }
 503
 504 static int pic32_spi_one_transfer(struct spi_master *master,
 505                                   struct spi_device *spi,
 506                                   struct spi_transfer *transfer)
 507 {
 508         struct pic32_spi *pic32s;
 509         bool dma_issued = false;
 510         unsigned long timeout;
 511         int ret;
 512
 513         pic32s = spi_master_get_devdata(master);
 514
 515         /* handle transfer specific word size change */
 516         if (transfer->bits_per_word &&
 517             (transfer->bits_per_word != pic32s->bits_per_word)) {
 518                 ret = pic32_spi_set_word_size(pic32s, transfer->bits_per_word);
 519                 if (ret)
 520                         return ret;
 521                 pic32s->bits_per_word = transfer->bits_per_word;
 522         }
 523
 524         /* handle transfer specific speed change */
 525         if (transfer->speed_hz && (transfer->speed_hz != pic32s->speed_hz)) {
 526                 pic32_spi_set_clk_rate(pic32s, transfer->speed_hz);
 527                 pic32s->speed_hz = transfer->speed_hz;
 528         }
 529
 530         reinit_completion(&pic32s->xfer_done);
 531
 532         /* transact by DMA mode */
 533         if (transfer->rx_sg.nents && transfer->tx_sg.nents) {
 534                 ret = pic32_spi_dma_transfer(pic32s, transfer);
 535                 if (ret) {
 536                         dev_err(&spi->dev, "dma submit error\n");
 537                         return ret;
 538                 }
 539
 540                 /* DMA issued */
 541                 dma_issued = true;
 542         } else {
 543                 /* set current transfer information */
 544                 pic32s->tx = (const void *)transfer->tx_buf;
 545                 pic32s->rx = (const void *)transfer->rx_buf;
 546                 pic32s->tx_end = pic32s->tx + transfer->len;
 547                 pic32s->rx_end = pic32s->rx + transfer->len;
 548                 pic32s->len = transfer->len;
 549
 550                 /* transact by interrupt driven PIO */
 551                 enable_irq(pic32s->fault_irq);
 552                 enable_irq(pic32s->rx_irq);
 553                 enable_irq(pic32s->tx_irq);
 554         }
 555
 556         /* wait for completion */
 557         timeout = wait_for_completion_timeout(&pic32s->xfer_done, 2 * HZ);
 558         if (timeout == 0) {
 559                 dev_err(&spi->dev, "wait error/timedout\n");
 560                 if (dma_issued) {
 561                         dmaengine_terminate_all(master->dma_rx);
 562                         dmaengine_terminate_all(master->dma_rx);
 563                 }
 564                 ret = -ETIMEDOUT;
 565         } else {
 566                 ret = 0;
 567         }
 568
 569         return ret;
 570 }
 571
 572 static int pic32_spi_unprepare_message(struct spi_master *master,
 573                                        struct spi_message *msg)
 574 {
 575         /* nothing to do */
 576         return 0;
 577 }
 578
 579 static int pic32_spi_unprepare_hardware(struct spi_master *master)
 580 {
 581         struct pic32_spi *pic32s = spi_master_get_devdata(master);
 582
 583         pic32_spi_disable(pic32s);
 584
 585         return 0;
 586 }
 587
 588 /* This may be called multiple times by same spi dev */
 589 static int pic32_spi_setup(struct spi_device *spi)
 590 {
 591         if (!spi->max_speed_hz) {
 592                 dev_err(&spi->dev, "No max speed HZ parameter\n");
 593                 return -EINVAL;
 594         }
 595
 596         /* PIC32 spi controller can drive /CS during transfer depending
 597          * on tx fifo fill-level. /CS will stay asserted as long as TX
 598          * fifo is non-empty, else will be deasserted indicating
 599          * completion of the ongoing transfer. This might result into
 600          * unreliable/erroneous SPI transactions.
 601          * To avoid that we will always handle /CS by toggling GPIO.
 602          */
 603         if (!gpio_is_valid(spi->cs_gpio))
 604                 return -EINVAL;
 605
 606         gpio_direction_output(spi->cs_gpio, !(spi->mode & SPI_CS_HIGH));
 607
 608         return 0;
 609 }
 610
 611 static void pic32_spi_cleanup(struct spi_device *spi)
 612 {
 613         /* de-activate cs-gpio */
 614         gpio_direction_output(spi->cs_gpio, !(spi->mode & SPI_CS_HIGH));
 615 }
 616
 617 static void pic32_spi_dma_prep(struct pic32_spi *pic32s, struct device *dev)
 618 {
 619         struct spi_master *master = pic32s->master;
 620         dma_cap_mask_t mask;
 621
 622         dma_cap_zero(mask);
 623         dma_cap_set(DMA_SLAVE, mask);
 624
 625         master->dma_rx = dma_request_slave_channel_compat(mask, NULL, NULL,
 626                                                           dev, "spi-rx");
 627         if (!master->dma_rx) {
 628                 dev_warn(dev, "RX channel not found.\n");
 629                 goto out_err;
 630         }
 631
 632         master->dma_tx = dma_request_slave_channel_compat(mask, NULL, NULL,
 633                                                           dev, "spi-tx");
 634         if (!master->dma_tx) {
 635                 dev_warn(dev, "TX channel not found.\n");
 636                 goto out_err;
 637         }
 638
 639         if (pic32_spi_dma_config(pic32s, DMA_SLAVE_BUSWIDTH_1_BYTE))
 640                 goto out_err;
 641
 642         /* DMA chnls allocated and prepared */
 643         set_bit(PIC32F_DMA_PREP, &pic32s->flags);
 644
 645         return;
 646
 647 out_err:
 648         if (master->dma_rx)
 649                 dma_release_channel(master->dma_rx);
 650
 651         if (master->dma_tx)
 652                 dma_release_channel(master->dma_tx);
 653 }
 654
 655 static void pic32_spi_dma_unprep(struct pic32_spi *pic32s)
 656 {
 657         if (!test_bit(PIC32F_DMA_PREP, &pic32s->flags))
 658                 return;
 659
 660         clear_bit(PIC32F_DMA_PREP, &pic32s->flags);
 661         if (pic32s->master->dma_rx)
 662                 dma_release_channel(pic32s->master->dma_rx);
 663
 664         if (pic32s->master->dma_tx)
 665                 dma_release_channel(pic32s->master->dma_tx);
 666 }
 667
 668 static void pic32_spi_hw_init(struct pic32_spi *pic32s)
 669 {
 670         u32 ctrl;
 671
 672         /* disable hardware */
 673         pic32_spi_disable(pic32s);
 674
 675         ctrl = readl(&pic32s->regs->ctrl);
 676         /* enable enhanced fifo of 128bit deep */
 677         ctrl |= CTRL_ENHBUF;
 678         pic32s->fifo_n_byte = 16;
 679
 680         /* disable framing mode */
 681         ctrl &= ~CTRL_FRMEN;
 682
 683         /* enable master mode while disabled */
 684         ctrl |= CTRL_MSTEN;
 685
 686         /* set tx fifo threshold interrupt */
 687         ctrl &= ~(0x3 << CTRL_TX_INT_SHIFT);
 688         ctrl |= (TX_FIFO_HALF_EMPTY << CTRL_TX_INT_SHIFT);
 689
 690         /* set rx fifo threshold interrupt */
 691         ctrl &= ~(0x3 << CTRL_RX_INT_SHIFT);
 692         ctrl |= (RX_FIFO_NOT_EMPTY << CTRL_RX_INT_SHIFT);
 693
 694         /* select clk source */
 695         ctrl &= ~CTRL_MCLKSEL;
 696
 697         /* set manual /CS mode */
 698         ctrl &= ~CTRL_MSSEN;
 699
 700         writel(ctrl, &pic32s->regs->ctrl);
 701
 702         /* enable error reporting */
 703         ctrl = CTRL2_TX_UR_EN | CTRL2_RX_OV_EN | CTRL2_FRM_ERR_EN;
 704         writel(ctrl, &pic32s->regs->ctrl2_set);
 705 }
 706
 707 static int pic32_spi_hw_probe(struct platform_device *pdev,
 708                               struct pic32_spi *pic32s)
 709 {
 710         struct resource *mem;
 711         int ret;
 712
 713         mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 714         pic32s->regs = devm_ioremap_resource(&pdev->dev, mem);
 715         if (IS_ERR(pic32s->regs))
 716                 return PTR_ERR(pic32s->regs);
 717
 718         pic32s->dma_base = mem->start;
 719
 720         /* get irq resources: err-irq, rx-irq, tx-irq */
 721         pic32s->fault_irq = platform_get_irq_byname(pdev, "fault");
 722         if (pic32s->fault_irq < 0) {
 723                 dev_err(&pdev->dev, "fault-irq not found\n");
 724                 return pic32s->fault_irq;
 725         }
 726
 727         pic32s->rx_irq = platform_get_irq_byname(pdev, "rx");
 728         if (pic32s->rx_irq < 0) {
 729                 dev_err(&pdev->dev, "rx-irq not found\n");
 730                 return pic32s->rx_irq;
 731         }
 732
 733         pic32s->tx_irq = platform_get_irq_byname(pdev, "tx");
 734         if (pic32s->tx_irq < 0) {
 735                 dev_err(&pdev->dev, "tx-irq not found\n");
 736                 return pic32s->tx_irq;
 737         }
 738
 739         /* get clock */
 740         pic32s->clk = devm_clk_get(&pdev->dev, "mck0");
 741         if (IS_ERR(pic32s->clk)) {
 742                 dev_err(&pdev->dev, "clk not found\n");
 743                 ret = PTR_ERR(pic32s->clk);
 744                 goto err_unmap_mem;
 745         }
 746
 747         ret = clk_prepare_enable(pic32s->clk);
 748         if (ret)
 749                 goto err_unmap_mem;
 750
 751         pic32_spi_hw_init(pic32s);
 752
 753         return 0;
 754
 755 err_unmap_mem:
 756         dev_err(&pdev->dev, "%s failed, err %d\n", __func__, ret);
 757         return ret;
 758 }
 759
 760 static int pic32_spi_probe(struct platform_device *pdev)
 761 {
 762         struct spi_master *master;
 763         struct pic32_spi *pic32s;
 764         int ret;
 765
 766         master = spi_alloc_master(&pdev->dev, sizeof(*pic32s));
 767         if (!master)
 768                 return -ENOMEM;
 769
 770         pic32s = spi_master_get_devdata(master);
 771         pic32s->master = master;
 772
 773         ret = pic32_spi_hw_probe(pdev, pic32s);
 774         if (ret)
 775                 goto err_master;
 776
 777         master->dev.of_node     = of_node_get(pdev->dev.of_node);
 778         master->mode_bits       = SPI_MODE_3 | SPI_MODE_0 | SPI_CS_HIGH;
 779         master->num_chipselect  = 1; /* single chip-select */
 780         master->max_speed_hz    = clk_get_rate(pic32s->clk);
 781         master->setup           = pic32_spi_setup;
 782         master->cleanup         = pic32_spi_cleanup;
 783         master->flags           = SPI_MASTER_MUST_TX | SPI_MASTER_MUST_RX;
 784         master->bits_per_word_mask      = SPI_BPW_MASK(8) | SPI_BPW_MASK(16) |
 785                                           SPI_BPW_MASK(32);
 786         master->transfer_one            = pic32_spi_one_transfer;
 787         master->prepare_message         = pic32_spi_prepare_message;
 788         master->unprepare_message       = pic32_spi_unprepare_message;
 789         master->prepare_transfer_hardware       = pic32_spi_prepare_hardware;
 790         master->unprepare_transfer_hardware     = pic32_spi_unprepare_hardware;
 791
 792         /* optional DMA support */
 793         pic32_spi_dma_prep(pic32s, &pdev->dev);
 794         if (test_bit(PIC32F_DMA_PREP, &pic32s->flags))
 795                 master->can_dma = pic32_spi_can_dma;
 796
 797         init_completion(&pic32s->xfer_done);
 798         pic32s->mode = -1;
 799
 800         /* install irq handlers (with irq-disabled) */
 801         irq_set_status_flags(pic32s->fault_irq, IRQ_NOAUTOEN);
 802         ret = devm_request_irq(&pdev->dev, pic32s->fault_irq,
 803                                pic32_spi_fault_irq, IRQF_NO_THREAD,
 804                                dev_name(&pdev->dev), pic32s);
 805         if (ret < 0) {
 806                 dev_err(&pdev->dev, "request fault-irq %d\n", pic32s->rx_irq);
 807                 goto err_bailout;
 808         }
 809
 810         /* receive interrupt handler */
 811         irq_set_status_flags(pic32s->rx_irq, IRQ_NOAUTOEN);
 812         ret = devm_request_irq(&pdev->dev, pic32s->rx_irq,
 813                                pic32_spi_rx_irq, IRQF_NO_THREAD,
 814                                dev_name(&pdev->dev), pic32s);
 815         if (ret < 0) {
 816                 dev_err(&pdev->dev, "request rx-irq %d\n", pic32s->rx_irq);
 817                 goto err_bailout;
 818         }
 819
 820         /* transmit interrupt handler */
 821         irq_set_status_flags(pic32s->tx_irq, IRQ_NOAUTOEN);
 822         ret = devm_request_irq(&pdev->dev, pic32s->tx_irq,
 823                                pic32_spi_tx_irq, IRQF_NO_THREAD,
 824                                dev_name(&pdev->dev), pic32s);
 825         if (ret < 0) {
 826                 dev_err(&pdev->dev, "request tx-irq %d\n", pic32s->tx_irq);
 827                 goto err_bailout;
 828         }
 829
 830         /* register master */
 831         ret = devm_spi_register_master(&pdev->dev, master);
 832         if (ret) {
 833                 dev_err(&master->dev, "failed registering spi master\n");
 834                 goto err_bailout;
 835         }
 836
 837         platform_set_drvdata(pdev, pic32s);
 838
 839         return 0;
 840
 841 err_bailout:
 842         clk_disable_unprepare(pic32s->clk);
 843 err_master:
 844         spi_master_put(master);
 845         return ret;
 846 }
 847
 848 static int pic32_spi_remove(struct platform_device *pdev)
 849 {
 850         struct pic32_spi *pic32s;
 851
 852         pic32s = platform_get_drvdata(pdev);
 853         pic32_spi_disable(pic32s);
 854         clk_disable_unprepare(pic32s->clk);
 855         pic32_spi_dma_unprep(pic32s);
 856
 857         return 0;
 858 }
 859
 860 static const struct of_device_id pic32_spi_of_match[] = {
 861         {.compatible = "microchip,pic32mzda-spi",},
 862         {},
 863 };
 864 MODULE_DEVICE_TABLE(of, pic32_spi_of_match);
 865
 866 static struct platform_driver pic32_spi_driver = {
 867         .driver = {
 868                 .name = "spi-pic32",
 869                 .of_match_table = of_match_ptr(pic32_spi_of_match),
 870         },
 871         .probe = pic32_spi_probe,
 872         .remove = pic32_spi_remove,
 873 };
 874
 875 module_platform_driver(pic32_spi_driver);
 876
 877 MODULE_AUTHOR("Purna Chandra Mandal <purna.mandal@microchip.com>");
 878 MODULE_DESCRIPTION("Microchip SPI driver for PIC32 SPI controller.");
 879 MODULE_LICENSE("GPL v2");