include/spi.h

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