include/spi.h

   1 /* SPDX-License-Identifier: GPL-2.0+ */
   2 /*
   3  * Common SPI Interface: Controller-specific definitions
   4  *
   5  * (C) Copyright 2001
   6  * Gerald Van Baren, Custom IDEAS, vanbaren@cideas.com.
   7  */
   8
   9 #ifndef _SPI_H_
  10 #define _SPI_H_
  11
  12 #include <common.h>
  13
  14 /* SPI mode flags */
  15 #define SPI_CPHA        BIT(0)                  /* clock phase */
  16 #define SPI_CPOL        BIT(1)                  /* clock polarity */
  17 #define SPI_MODE_0      (0|0)                   /* (original MicroWire) */
  18 #define SPI_MODE_1      (0|SPI_CPHA)
  19 #define SPI_MODE_2      (SPI_CPOL|0)
  20 #define SPI_MODE_3      (SPI_CPOL|SPI_CPHA)
  21 #define SPI_CS_HIGH     BIT(2)                  /* CS active high */
  22 #define SPI_LSB_FIRST   BIT(3)                  /* per-word bits-on-wire */
  23 #define SPI_3WIRE       BIT(4)                  /* SI/SO signals shared */
  24 #define SPI_LOOP        BIT(5)                  /* loopback mode */
  25 #define SPI_SLAVE       BIT(6)                  /* slave mode */
  26 #define SPI_PREAMBLE    BIT(7)                  /* Skip preamble bytes */
  27 #define SPI_TX_BYTE     BIT(8)                  /* transmit with 1 wire byte */
  28 #define SPI_TX_DUAL     BIT(9)                  /* transmit with 2 wires */
  29 #define SPI_TX_QUAD     BIT(10)                 /* transmit with 4 wires */
  30 #define SPI_RX_SLOW     BIT(11)                 /* receive with 1 wire slow */
  31 #define SPI_RX_DUAL     BIT(12)                 /* receive with 2 wires */
  32 #define SPI_RX_QUAD     BIT(13)                 /* receive with 4 wires */
  33
  34 /* Header byte that marks the start of the message */
  35 #define SPI_PREAMBLE_END_BYTE   0xec
  36
  37 #define SPI_DEFAULT_WORDLEN     8
  38
  39 #ifdef CONFIG_DM_SPI
  40 /* TODO(sjg@chromium.org): Remove this and use max_hz from struct spi_slave */
  41 struct dm_spi_bus {
  42         uint max_hz;
  43 };
  44
  45 /**
  46  * struct dm_spi_platdata - platform data for all SPI slaves
  47  *
  48  * This describes a SPI slave, a child device of the SPI bus. To obtain this
  49  * struct from a spi_slave, use dev_get_parent_platdata(dev) or
  50  * dev_get_parent_platdata(slave->dev).
  51  *
  52  * This data is immuatable. Each time the device is probed, @max_hz and @mode
  53  * will be copied to struct spi_slave.
  54  *
  55  * @cs:         Chip select number (0..n-1)
  56  * @max_hz:     Maximum bus speed that this slave can tolerate
  57  * @mode:       SPI mode to use for this device (see SPI mode flags)
  58  */
  59 struct dm_spi_slave_platdata {
  60         unsigned int cs;
  61         uint max_hz;
  62         uint mode;
  63 };
  64
  65 #endif /* CONFIG_DM_SPI */
  66
  67 /**
  68  * struct spi_slave - Representation of a SPI slave
  69  *
  70  * For driver model this is the per-child data used by the SPI bus. It can
  71  * be accessed using dev_get_parent_priv() on the slave device. The SPI uclass
  72  * sets uip per_child_auto_alloc_size to sizeof(struct spi_slave), and the
  73  * driver should not override it. Two platform data fields (max_hz and mode)
  74  * are copied into this structure to provide an initial value. This allows
  75  * them to be changed, since we should never change platform data in drivers.
  76  *
  77  * If not using driver model, drivers are expected to extend this with
  78  * controller-specific data.
  79  *
  80  * @dev:                SPI slave device
  81  * @max_hz:             Maximum speed for this slave
  82  * @speed:              Current bus speed. This is 0 until the bus is first
  83  *                      claimed.
  84  * @bus:                ID of the bus that the slave is attached to. For
  85  *                      driver model this is the sequence number of the SPI
  86  *                      bus (bus->seq) so does not need to be stored
  87  * @cs:                 ID of the chip select connected to the slave.
  88  * @mode:               SPI mode to use for this slave (see SPI mode flags)
  89  * @wordlen:            Size of SPI word in number of bits
  90  * @max_read_size:      If non-zero, the maximum number of bytes which can
  91  *                      be read at once.
  92  * @max_write_size:     If non-zero, the maximum number of bytes which can
  93  *                      be written at once.
  94  * @memory_map:         Address of read-only SPI flash access.
  95  * @flags:              Indication of SPI flags.
  96  */
  97 struct spi_slave {
  98 #ifdef CONFIG_DM_SPI
  99         struct udevice *dev;    /* struct spi_slave is dev->parentdata */
 100         uint max_hz;
 101         uint speed;
 102 #else
 103         unsigned int bus;
 104         unsigned int cs;
 105 #endif
 106         uint mode;
 107         unsigned int wordlen;
 108         unsigned int max_read_size;
 109         unsigned int max_write_size;
 110         void *memory_map;
 111
 112         u8 flags;
 113 #define SPI_XFER_BEGIN          BIT(0)  /* Assert CS before transfer */
 114 #define SPI_XFER_END            BIT(1)  /* Deassert CS after transfer */
 115 #define SPI_XFER_ONCE           (SPI_XFER_BEGIN | SPI_XFER_END)
 116 #define SPI_XFER_MMAP           BIT(2)  /* Memory Mapped start */
 117 #define SPI_XFER_MMAP_END       BIT(3)  /* Memory Mapped End */
 118 };
 119
 120 /**
 121  * spi_do_alloc_slave - Allocate a new SPI slave (internal)
 122  *
 123  * Allocate and zero all fields in the spi slave, and set the bus/chip
 124  * select. Use the helper macro spi_alloc_slave() to call this.
 125  *
 126  * @offset:     Offset of struct spi_slave within slave structure.
 127  * @size:       Size of slave structure.
 128  * @bus:        Bus ID of the slave chip.
 129  * @cs:         Chip select ID of the slave chip on the specified bus.
 130  */
 131 void *spi_do_alloc_slave(int offset, int size, unsigned int bus,
 132                          unsigned int cs);
 133
 134 /**
 135  * spi_alloc_slave - Allocate a new SPI slave
 136  *
 137  * Allocate and zero all fields in the spi slave, and set the bus/chip
 138  * select.
 139  *
 140  * @_struct:    Name of structure to allocate (e.g. struct tegra_spi).
 141  *              This structure must contain a member 'struct spi_slave *slave'.
 142  * @bus:        Bus ID of the slave chip.
 143  * @cs:         Chip select ID of the slave chip on the specified bus.
 144  */
 145 #define spi_alloc_slave(_struct, bus, cs) \
 146         spi_do_alloc_slave(offsetof(_struct, slave), \
 147                             sizeof(_struct), bus, cs)
 148
 149 /**
 150  * spi_alloc_slave_base - Allocate a new SPI slave with no private data
 151  *
 152  * Allocate and zero all fields in the spi slave, and set the bus/chip
 153  * select.
 154  *
 155  * @bus:        Bus ID of the slave chip.
 156  * @cs:         Chip select ID of the slave chip on the specified bus.
 157  */
 158 #define spi_alloc_slave_base(bus, cs) \
 159         spi_do_alloc_slave(0, sizeof(struct spi_slave), bus, cs)
 160
 161 /**
 162  * Set up communications parameters for a SPI slave.
 163  *
 164  * This must be called once for each slave. Note that this function
 165  * usually doesn't touch any actual hardware, it only initializes the
 166  * contents of spi_slave so that the hardware can be easily
 167  * initialized later.
 168  *
 169  * @bus:        Bus ID of the slave chip.
 170  * @cs:         Chip select ID of the slave chip on the specified bus.
 171  * @max_hz:     Maximum SCK rate in Hz.
 172  * @mode:       Clock polarity, clock phase and other parameters.
 173  *
 174  * Returns: A spi_slave reference that can be used in subsequent SPI
 175  * calls, or NULL if one or more of the parameters are not supported.
 176  */
 177 struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
 178                 unsigned int max_hz, unsigned int mode);
 179
 180 /**
 181  * Free any memory associated with a SPI slave.
 182  *
 183  * @slave:      The SPI slave
 184  */
 185 void spi_free_slave(struct spi_slave *slave);
 186
 187 /**
 188  * Claim the bus and prepare it for communication with a given slave.
 189  *
 190  * This must be called before doing any transfers with a SPI slave. It
 191  * will enable and initialize any SPI hardware as necessary, and make
 192  * sure that the SCK line is in the correct idle state. It is not
 193  * allowed to claim the same bus for several slaves without releasing
 194  * the bus in between.
 195  *
 196  * @slave:      The SPI slave
 197  *
 198  * Returns: 0 if the bus was claimed successfully, or a negative value
 199  * if it wasn't.
 200  */
 201 int spi_claim_bus(struct spi_slave *slave);
 202
 203 /**
 204  * Release the SPI bus
 205  *
 206  * This must be called once for every call to spi_claim_bus() after
 207  * all transfers have finished. It may disable any SPI hardware as
 208  * appropriate.
 209  *
 210  * @slave:      The SPI slave
 211  */
 212 void spi_release_bus(struct spi_slave *slave);
 213
 214 /**
 215  * Set the word length for SPI transactions
 216  *
 217  * Set the word length (number of bits per word) for SPI transactions.
 218  *
 219  * @slave:      The SPI slave
 220  * @wordlen:    The number of bits in a word
 221  *
 222  * Returns: 0 on success, -1 on failure.
 223  */
 224 int spi_set_wordlen(struct spi_slave *slave, unsigned int wordlen);
 225
 226 /**
 227  * SPI transfer
 228  *
 229  * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
 230  * "bitlen" bits in the SPI MISO port.  That's just the way SPI works.
 231  *
 232  * The source of the outgoing bits is the "dout" parameter and the
 233  * destination of the input bits is the "din" parameter.  Note that "dout"
 234  * and "din" can point to the same memory location, in which case the
 235  * input data overwrites the output data (since both are buffered by
 236  * temporary variables, this is OK).
 237  *
 238  * spi_xfer() interface:
 239  * @slave:      The SPI slave which will be sending/receiving the data.
 240  * @bitlen:     How many bits to write and read.
 241  * @dout:       Pointer to a string of bits to send out.  The bits are
 242  *              held in a byte array and are sent MSB first.
 243  * @din:        Pointer to a string of bits that will be filled in.
 244  * @flags:      A bitwise combination of SPI_XFER_* flags.
 245  *
 246  * Returns: 0 on success, not 0 on failure
 247  */
 248 int  spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
 249                 void *din, unsigned long flags);
 250
 251 /* Copy memory mapped data */
 252 void spi_flash_copy_mmap(void *data, void *offset, size_t len);
 253
 254 /**
 255  * Determine if a SPI chipselect is valid.
 256  * This function is provided by the board if the low-level SPI driver
 257  * needs it to determine if a given chipselect is actually valid.
 258  *
 259  * Returns: 1 if bus:cs identifies a valid chip on this board, 0
 260  * otherwise.
 261  */
 262 int spi_cs_is_valid(unsigned int bus, unsigned int cs);
 263
 264 #ifndef CONFIG_DM_SPI
 265 /**
 266  * Activate a SPI chipselect.
 267  * This function is provided by the board code when using a driver
 268  * that can't control its chipselects automatically (e.g.
 269  * common/soft_spi.c). When called, it should activate the chip select
 270  * to the device identified by "slave".
 271  */
 272 void spi_cs_activate(struct spi_slave *slave);
 273
 274 /**
 275  * Deactivate a SPI chipselect.
 276  * This function is provided by the board code when using a driver
 277  * that can't control its chipselects automatically (e.g.
 278  * common/soft_spi.c). When called, it should deactivate the chip
 279  * select to the device identified by "slave".
 280  */
 281 void spi_cs_deactivate(struct spi_slave *slave);
 282
 283 /**
 284  * Set transfer speed.
 285  * This sets a new speed to be applied for next spi_xfer().
 286  * @slave:      The SPI slave
 287  * @hz:         The transfer speed
 288  */
 289 void spi_set_speed(struct spi_slave *slave, uint hz);
 290 #endif
 291
 292 /**
 293  * Write 8 bits, then read 8 bits.
 294  * @slave:      The SPI slave we're communicating with
 295  * @byte:       Byte to be written
 296  *
 297  * Returns: The value that was read, or a negative value on error.
 298  *
 299  * TODO: This function probably shouldn't be inlined.
 300  */
 301 static inline int spi_w8r8(struct spi_slave *slave, unsigned char byte)
 302 {
 303         unsigned char dout[2];
 304         unsigned char din[2];
 305         int ret;
 306
 307         dout[0] = byte;
 308         dout[1] = 0;
 309
 310         ret = spi_xfer(slave, 16, dout, din, SPI_XFER_BEGIN | SPI_XFER_END);
 311         return ret < 0 ? ret : din[1];
 312 }
 313
 314 #ifdef CONFIG_DM_SPI
 315
 316 /**
 317  * struct spi_cs_info - Information about a bus chip select
 318  *
 319  * @dev:        Connected device, or NULL if none
 320  */
 321 struct spi_cs_info {
 322         struct udevice *dev;
 323 };
 324
 325 /**
 326  * struct struct dm_spi_ops - Driver model SPI operations
 327  *
 328  * The uclass interface is implemented by all SPI devices which use
 329  * driver model.
 330  */
 331 struct dm_spi_ops {
 332         /**
 333          * Claim the bus and prepare it for communication.
 334          *
 335          * The device provided is the slave device. It's parent controller
 336          * will be used to provide the communication.
 337          *
 338          * This must be called before doing any transfers with a SPI slave. It
 339          * will enable and initialize any SPI hardware as necessary, and make
 340          * sure that the SCK line is in the correct idle state. It is not
 341          * allowed to claim the same bus for several slaves without releasing
 342          * the bus in between.
 343          *
 344          * @dev:        The SPI slave
 345          *
 346          * Returns: 0 if the bus was claimed successfully, or a negative value
 347          * if it wasn't.
 348          */
 349         int (*claim_bus)(struct udevice *dev);
 350
 351         /**
 352          * Release the SPI bus
 353          *
 354          * This must be called once for every call to spi_claim_bus() after
 355          * all transfers have finished. It may disable any SPI hardware as
 356          * appropriate.
 357          *
 358          * @dev:        The SPI slave
 359          */
 360         int (*release_bus)(struct udevice *dev);
 361
 362         /**
 363          * Set the word length for SPI transactions
 364          *
 365          * Set the word length (number of bits per word) for SPI transactions.
 366          *
 367          * @bus:        The SPI slave
 368          * @wordlen:    The number of bits in a word
 369          *
 370          * Returns: 0 on success, -ve on failure.
 371          */
 372         int (*set_wordlen)(struct udevice *dev, unsigned int wordlen);
 373
 374         /**
 375          * SPI transfer
 376          *
 377          * This writes "bitlen" bits out the SPI MOSI port and simultaneously
 378          * clocks "bitlen" bits in the SPI MISO port.  That's just the way SPI
 379          * works.
 380          *
 381          * The source of the outgoing bits is the "dout" parameter and the
 382          * destination of the input bits is the "din" parameter.  Note that
 383          * "dout" and "din" can point to the same memory location, in which
 384          * case the input data overwrites the output data (since both are
 385          * buffered by temporary variables, this is OK).
 386          *
 387          * spi_xfer() interface:
 388          * @dev:        The slave device to communicate with
 389          * @bitlen:     How many bits to write and read.
 390          * @dout:       Pointer to a string of bits to send out.  The bits are
 391          *              held in a byte array and are sent MSB first.
 392          * @din:        Pointer to a string of bits that will be filled in.
 393          * @flags:      A bitwise combination of SPI_XFER_* flags.
 394          *
 395          * Returns: 0 on success, not -1 on failure
 396          */
 397         int (*xfer)(struct udevice *dev, unsigned int bitlen, const void *dout,
 398                     void *din, unsigned long flags);
 399
 400         /**
 401          * Optimized handlers for SPI memory-like operations.
 402          *
 403          * Optimized/dedicated operations for interactions with SPI memory. This
 404          * field is optional and should only be implemented if the controller
 405          * has native support for memory like operations.
 406          */
 407         const struct spi_controller_mem_ops *mem_ops;
 408
 409         /**
 410          * Set transfer speed.
 411          * This sets a new speed to be applied for next spi_xfer().
 412          * @bus:        The SPI bus
 413          * @hz:         The transfer speed
 414          * @return 0 if OK, -ve on error
 415          */
 416         int (*set_speed)(struct udevice *bus, uint hz);
 417
 418         /**
 419          * Set the SPI mode/flags
 420          *
 421          * It is unclear if we want to set speed and mode together instead
 422          * of separately.
 423          *
 424          * @bus:        The SPI bus
 425          * @mode:       Requested SPI mode (SPI_... flags)
 426          * @return 0 if OK, -ve on error
 427          */
 428         int (*set_mode)(struct udevice *bus, uint mode);
 429
 430         /**
 431          * Get information on a chip select
 432          *
 433          * This is only called when the SPI uclass does not know about a
 434          * chip select, i.e. it has no attached device. It gives the driver
 435          * a chance to allow activity on that chip select even so.
 436          *
 437          * @bus:        The SPI bus
 438          * @cs:         The chip select (0..n-1)
 439          * @info:       Returns information about the chip select, if valid.
 440          *              On entry info->dev is NULL
 441          * @return 0 if OK (and @info is set up), -ENODEV if the chip select
 442          *         is invalid, other -ve value on error
 443          */
 444         int (*cs_info)(struct udevice *bus, uint cs, struct spi_cs_info *info);
 445 };
 446
 447 struct dm_spi_emul_ops {
 448         /**
 449          * SPI transfer
 450          *
 451          * This writes "bitlen" bits out the SPI MOSI port and simultaneously
 452          * clocks "bitlen" bits in the SPI MISO port.  That's just the way SPI
 453          * works. Here the device is a slave.
 454          *
 455          * The source of the outgoing bits is the "dout" parameter and the
 456          * destination of the input bits is the "din" parameter.  Note that
 457          * "dout" and "din" can point to the same memory location, in which
 458          * case the input data overwrites the output data (since both are
 459          * buffered by temporary variables, this is OK).
 460          *
 461          * spi_xfer() interface:
 462          * @slave:      The SPI slave which will be sending/receiving the data.
 463          * @bitlen:     How many bits to write and read.
 464          * @dout:       Pointer to a string of bits sent to the device. The
 465          *              bits are held in a byte array and are sent MSB first.
 466          * @din:        Pointer to a string of bits that will be sent back to
 467          *              the master.
 468          * @flags:      A bitwise combination of SPI_XFER_* flags.
 469          *
 470          * Returns: 0 on success, not -1 on failure
 471          */
 472         int (*xfer)(struct udevice *slave, unsigned int bitlen,
 473                     const void *dout, void *din, unsigned long flags);
 474 };
 475
 476 /**
 477  * spi_find_bus_and_cs() - Find bus and slave devices by number
 478  *
 479  * Given a bus number and chip select, this finds the corresponding bus
 480  * device and slave device. Neither device is activated by this function,
 481  * although they may have been activated previously.
 482  *
 483  * @busnum:     SPI bus number
 484  * @cs:         Chip select to look for
 485  * @busp:       Returns bus device
 486  * @devp:       Return slave device
 487  * @return 0 if found, -ENODEV on error
 488  */
 489 int spi_find_bus_and_cs(int busnum, int cs, struct udevice **busp,
 490                         struct udevice **devp);
 491
 492 /**
 493  * spi_get_bus_and_cs() - Find and activate bus and slave devices by number
 494  *
 495  * Given a bus number and chip select, this finds the corresponding bus
 496  * device and slave device.
 497  *
 498  * If no such slave exists, and drv_name is not NULL, then a new slave device
 499  * is automatically bound on this chip select with requested speed and mode.
 500  *
 501  * Ths new slave device is probed ready for use with the speed and mode
 502  * from platdata when available or the requested values.
 503  *
 504  * @busnum:     SPI bus number
 505  * @cs:         Chip select to look for
 506  * @speed:      SPI speed to use for this slave when not available in platdata
 507  * @mode:       SPI mode to use for this slave when not available in platdata
 508  * @drv_name:   Name of driver to attach to this chip select
 509  * @dev_name:   Name of the new device thus created
 510  * @busp:       Returns bus device
 511  * @devp:       Return slave device
 512  * @return 0 if found, -ve on error
 513  */
 514 int spi_get_bus_and_cs(int busnum, int cs, int speed, int mode,
 515                         const char *drv_name, const char *dev_name,
 516                         struct udevice **busp, struct spi_slave **devp);
 517
 518 /**
 519  * spi_chip_select() - Get the chip select for a slave
 520  *
 521  * @return the chip select this slave is attached to
 522  */
 523 int spi_chip_select(struct udevice *slave);
 524
 525 /**
 526  * spi_find_chip_select() - Find the slave attached to chip select
 527  *
 528  * @bus:        SPI bus to search
 529  * @cs:         Chip select to look for
 530  * @devp:       Returns the slave device if found
 531  * @return 0 if found, -ENODEV on error
 532  */
 533 int spi_find_chip_select(struct udevice *bus, int cs, struct udevice **devp);
 534
 535 /**
 536  * spi_slave_ofdata_to_platdata() - decode standard SPI platform data
 537  *
 538  * This decodes the speed and mode for a slave from a device tree node
 539  *
 540  * @blob:       Device tree blob
 541  * @node:       Node offset to read from
 542  * @plat:       Place to put the decoded information
 543  */
 544 int spi_slave_ofdata_to_platdata(struct udevice *dev,
 545                                  struct dm_spi_slave_platdata *plat);
 546
 547 /**
 548  * spi_cs_info() - Check information on a chip select
 549  *
 550  * This checks a particular chip select on a bus to see if it has a device
 551  * attached, or is even valid.
 552  *
 553  * @bus:        The SPI bus
 554  * @cs:         The chip select (0..n-1)
 555  * @info:       Returns information about the chip select, if valid
 556  * @return 0 if OK (and @info is set up), -ENODEV if the chip select
 557  *         is invalid, other -ve value on error
 558  */
 559 int spi_cs_info(struct udevice *bus, uint cs, struct spi_cs_info *info);
 560
 561 struct sandbox_state;
 562
 563 /**
 564  * sandbox_spi_get_emul() - get an emulator for a SPI slave
 565  *
 566  * This provides a way to attach an emulated SPI device to a particular SPI
 567  * slave, so that xfer() operations on the slave will be handled by the
 568  * emulator. If a emulator already exists on that chip select it is returned.
 569  * Otherwise one is created.
 570  *
 571  * @state:      Sandbox state
 572  * @bus:        SPI bus requesting the emulator
 573  * @slave:      SPI slave device requesting the emulator
 574  * @emuip:      Returns pointer to emulator
 575  * @return 0 if OK, -ve on error
 576  */
 577 int sandbox_spi_get_emul(struct sandbox_state *state,
 578                          struct udevice *bus, struct udevice *slave,
 579                          struct udevice **emulp);
 580
 581 /**
 582  * Claim the bus and prepare it for communication with a given slave.
 583  *
 584  * This must be called before doing any transfers with a SPI slave. It
 585  * will enable and initialize any SPI hardware as necessary, and make
 586  * sure that the SCK line is in the correct idle state. It is not
 587  * allowed to claim the same bus for several slaves without releasing
 588  * the bus in between.
 589  *
 590  * @dev:        The SPI slave device
 591  *
 592  * Returns: 0 if the bus was claimed successfully, or a negative value
 593  * if it wasn't.
 594  */
 595 int dm_spi_claim_bus(struct udevice *dev);
 596
 597 /**
 598  * Release the SPI bus
 599  *
 600  * This must be called once for every call to dm_spi_claim_bus() after
 601  * all transfers have finished. It may disable any SPI hardware as
 602  * appropriate.
 603  *
 604  * @slave:      The SPI slave device
 605  */
 606 void dm_spi_release_bus(struct udevice *dev);
 607
 608 /**
 609  * SPI transfer
 610  *
 611  * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
 612  * "bitlen" bits in the SPI MISO port.  That's just the way SPI works.
 613  *
 614  * The source of the outgoing bits is the "dout" parameter and the
 615  * destination of the input bits is the "din" parameter.  Note that "dout"
 616  * and "din" can point to the same memory location, in which case the
 617  * input data overwrites the output data (since both are buffered by
 618  * temporary variables, this is OK).
 619  *
 620  * dm_spi_xfer() interface:
 621  * @dev:        The SPI slave device which will be sending/receiving the data.
 622  * @bitlen:     How many bits to write and read.
 623  * @dout:       Pointer to a string of bits to send out.  The bits are
 624  *              held in a byte array and are sent MSB first.
 625  * @din:        Pointer to a string of bits that will be filled in.
 626  * @flags:      A bitwise combination of SPI_XFER_* flags.
 627  *
 628  * Returns: 0 on success, not 0 on failure
 629  */
 630 int dm_spi_xfer(struct udevice *dev, unsigned int bitlen,
 631                 const void *dout, void *din, unsigned long flags);
 632
 633 /* Access the operations for a SPI device */
 634 #define spi_get_ops(dev)        ((struct dm_spi_ops *)(dev)->driver->ops)
 635 #define spi_emul_get_ops(dev)   ((struct dm_spi_emul_ops *)(dev)->driver->ops)
 636 #endif /* CONFIG_DM_SPI */
 637
 638 #endif  /* _SPI_H_ */