include/spi.h

   1 /*
   2  * Common SPI Interface: Controller-specific definitions
   3  *
   4  * (C) Copyright 2001
   5  * Gerald Van Baren, Custom IDEAS, vanbaren@cideas.com.
   6  *
   7  * SPDX-License-Identifier:     GPL-2.0+
   8  */
   9
  10 #ifndef _SPI_H_
  11 #define _SPI_H_
  12
  13 /* SPI mode flags */
  14 #define SPI_CPHA        0x01                    /* clock phase */
  15 #define SPI_CPOL        0x02                    /* clock polarity */
  16 #define SPI_MODE_0      (0|0)                   /* (original MicroWire) */
  17 #define SPI_MODE_1      (0|SPI_CPHA)
  18 #define SPI_MODE_2      (SPI_CPOL|0)
  19 #define SPI_MODE_3      (SPI_CPOL|SPI_CPHA)
  20 #define SPI_CS_HIGH     0x04                    /* CS active high */
  21 #define SPI_LSB_FIRST   0x08                    /* per-word bits-on-wire */
  22 #define SPI_3WIRE       0x10                    /* SI/SO signals shared */
  23 #define SPI_LOOP        0x20                    /* loopback mode */
  24 #define SPI_SLAVE       0x40                    /* slave mode */
  25 #define SPI_PREAMBLE    0x80                    /* Skip preamble bytes */
  26
  27 /* SPI transfer flags */
  28 #define SPI_XFER_BEGIN          0x01    /* Assert CS before transfer */
  29 #define SPI_XFER_END            0x02    /* Deassert CS after transfer */
  30 #define SPI_XFER_MMAP           0x08    /* Memory Mapped start */
  31 #define SPI_XFER_MMAP_END       0x10    /* Memory Mapped End */
  32
  33 /* Header byte that marks the start of the message */
  34 #define SPI_PREAMBLE_END_BYTE   0xec
  35
  36 /**
  37  * struct spi_slave - Representation of a SPI slave
  38  *
  39  * Drivers are expected to extend this with controller-specific data.
  40  *
  41  * @bus:                ID of the bus that the slave is attached to.
  42  * @cs:                 ID of the chip select connected to the slave.
  43  * @max_write_size:     If non-zero, the maximum number of bytes which can
  44  *                      be written at once, excluding command bytes.
  45  * @memory_map:         Address of read-only SPI flash access.
  46  */
  47 struct spi_slave {
  48         unsigned int bus;
  49         unsigned int cs;
  50         unsigned int max_write_size;
  51         void *memory_map;
  52 };
  53
  54 /**
  55  * Initialization, must be called once on start up.
  56  *
  57  * TODO: I don't think we really need this.
  58  */
  59 void spi_init(void);
  60
  61 /**
  62  * spi_do_alloc_slave - Allocate a new SPI slave (internal)
  63  *
  64  * Allocate and zero all fields in the spi slave, and set the bus/chip
  65  * select. Use the helper macro spi_alloc_slave() to call this.
  66  *
  67  * @offset:     Offset of struct spi_slave within slave structure.
  68  * @size:       Size of slave structure.
  69  * @bus:        Bus ID of the slave chip.
  70  * @cs:         Chip select ID of the slave chip on the specified bus.
  71  */
  72 void *spi_do_alloc_slave(int offset, int size, unsigned int bus,
  73                          unsigned int cs);
  74
  75 /**
  76  * spi_alloc_slave - Allocate a new SPI slave
  77  *
  78  * Allocate and zero all fields in the spi slave, and set the bus/chip
  79  * select.
  80  *
  81  * @_struct:    Name of structure to allocate (e.g. struct tegra_spi).
  82  *              This structure must contain a member 'struct spi_slave *slave'.
  83  * @bus:        Bus ID of the slave chip.
  84  * @cs:         Chip select ID of the slave chip on the specified bus.
  85  */
  86 #define spi_alloc_slave(_struct, bus, cs) \
  87         spi_do_alloc_slave(offsetof(_struct, slave), \
  88                             sizeof(_struct), bus, cs)
  89
  90 /**
  91  * spi_alloc_slave_base - Allocate a new SPI slave with no private data
  92  *
  93  * Allocate and zero all fields in the spi slave, and set the bus/chip
  94  * select.
  95  *
  96  * @bus:        Bus ID of the slave chip.
  97  * @cs:         Chip select ID of the slave chip on the specified bus.
  98  */
  99 #define spi_alloc_slave_base(bus, cs) \
 100         spi_do_alloc_slave(0, sizeof(struct spi_slave), bus, cs)
 101
 102 /**
 103  * Set up communications parameters for a SPI slave.
 104  *
 105  * This must be called once for each slave. Note that this function
 106  * usually doesn't touch any actual hardware, it only initializes the
 107  * contents of spi_slave so that the hardware can be easily
 108  * initialized later.
 109  *
 110  * @bus:        Bus ID of the slave chip.
 111  * @cs:         Chip select ID of the slave chip on the specified bus.
 112  * @max_hz:     Maximum SCK rate in Hz.
 113  * @mode:       Clock polarity, clock phase and other parameters.
 114  *
 115  * Returns: A spi_slave reference that can be used in subsequent SPI
 116  * calls, or NULL if one or more of the parameters are not supported.
 117  */
 118 struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
 119                 unsigned int max_hz, unsigned int mode);
 120
 121 /**
 122  * Free any memory associated with a SPI slave.
 123  *
 124  * @slave:      The SPI slave
 125  */
 126 void spi_free_slave(struct spi_slave *slave);
 127
 128 /**
 129  * Claim the bus and prepare it for communication with a given slave.
 130  *
 131  * This must be called before doing any transfers with a SPI slave. It
 132  * will enable and initialize any SPI hardware as necessary, and make
 133  * sure that the SCK line is in the correct idle state. It is not
 134  * allowed to claim the same bus for several slaves without releasing
 135  * the bus in between.
 136  *
 137  * @slave:      The SPI slave
 138  *
 139  * Returns: 0 if the bus was claimed successfully, or a negative value
 140  * if it wasn't.
 141  */
 142 int spi_claim_bus(struct spi_slave *slave);
 143
 144 /**
 145  * Release the SPI bus
 146  *
 147  * This must be called once for every call to spi_claim_bus() after
 148  * all transfers have finished. It may disable any SPI hardware as
 149  * appropriate.
 150  *
 151  * @slave:      The SPI slave
 152  */
 153 void spi_release_bus(struct spi_slave *slave);
 154
 155 /**
 156  * SPI transfer
 157  *
 158  * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
 159  * "bitlen" bits in the SPI MISO port.  That's just the way SPI works.
 160  *
 161  * The source of the outgoing bits is the "dout" parameter and the
 162  * destination of the input bits is the "din" parameter.  Note that "dout"
 163  * and "din" can point to the same memory location, in which case the
 164  * input data overwrites the output data (since both are buffered by
 165  * temporary variables, this is OK).
 166  *
 167  * spi_xfer() interface:
 168  * @slave:      The SPI slave which will be sending/receiving the data.
 169  * @bitlen:     How many bits to write and read.
 170  * @dout:       Pointer to a string of bits to send out.  The bits are
 171  *              held in a byte array and are sent MSB first.
 172  * @din:        Pointer to a string of bits that will be filled in.
 173  * @flags:      A bitwise combination of SPI_XFER_* flags.
 174  *
 175  * Returns: 0 on success, not 0 on failure
 176  */
 177 int  spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
 178                 void *din, unsigned long flags);
 179
 180 /**
 181  * Determine if a SPI chipselect is valid.
 182  * This function is provided by the board if the low-level SPI driver
 183  * needs it to determine if a given chipselect is actually valid.
 184  *
 185  * Returns: 1 if bus:cs identifies a valid chip on this board, 0
 186  * otherwise.
 187  */
 188 int  spi_cs_is_valid(unsigned int bus, unsigned int cs);
 189
 190 /**
 191  * Activate a SPI chipselect.
 192  * This function is provided by the board code when using a driver
 193  * that can't control its chipselects automatically (e.g.
 194  * common/soft_spi.c). When called, it should activate the chip select
 195  * to the device identified by "slave".
 196  */
 197 void spi_cs_activate(struct spi_slave *slave);
 198
 199 /**
 200  * Deactivate a SPI chipselect.
 201  * This function is provided by the board code when using a driver
 202  * that can't control its chipselects automatically (e.g.
 203  * common/soft_spi.c). When called, it should deactivate the chip
 204  * select to the device identified by "slave".
 205  */
 206 void spi_cs_deactivate(struct spi_slave *slave);
 207
 208 /**
 209  * Set transfer speed.
 210  * This sets a new speed to be applied for next spi_xfer().
 211  * @slave:      The SPI slave
 212  * @hz:         The transfer speed
 213  */
 214 void spi_set_speed(struct spi_slave *slave, uint hz);
 215
 216 /**
 217  * Write 8 bits, then read 8 bits.
 218  * @slave:      The SPI slave we're communicating with
 219  * @byte:       Byte to be written
 220  *
 221  * Returns: The value that was read, or a negative value on error.
 222  *
 223  * TODO: This function probably shouldn't be inlined.
 224  */
 225 static inline int spi_w8r8(struct spi_slave *slave, unsigned char byte)
 226 {
 227         unsigned char dout[2];
 228         unsigned char din[2];
 229         int ret;
 230
 231         dout[0] = byte;
 232         dout[1] = 0;
 233
 234         ret = spi_xfer(slave, 16, dout, din, SPI_XFER_BEGIN | SPI_XFER_END);
 235         return ret < 0 ? ret : din[1];
 236 }
 237
 238 /**
 239  * Set up a SPI slave for a particular device tree node
 240  *
 241  * This calls spi_setup_slave() with the correct bus number. Call
 242  * spi_free_slave() to free it later.
 243  *
 244  * @param blob:         Device tree blob
 245  * @param node:         SPI peripheral node to use
 246  * @param cs:           Chip select to use
 247  * @param max_hz:       Maximum SCK rate in Hz (0 for default)
 248  * @param mode:         Clock polarity, clock phase and other parameters
 249  * @return pointer to new spi_slave structure
 250  */
 251 struct spi_slave *spi_setup_slave_fdt(const void *blob, int node,
 252                 unsigned int cs, unsigned int max_hz, unsigned int mode);
 253
 254 #endif  /* _SPI_H_ */