include/spi.h

   1 /*
   2  * (C) Copyright 2001
   3  * Gerald Van Baren, Custom IDEAS, vanbaren@cideas.com.
   4  *
   5  * See file CREDITS for list of people who contributed to this
   6  * project.
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of
  11  * the License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  21  * MA 02111-1307 USA
  22  */
  23
  24 #ifndef _SPI_H_
  25 #define _SPI_H_
  26
  27 /* Controller-specific definitions: */
  28
  29 /* SPI mode flags */
  30 #define SPI_CPHA        0x01                    /* clock phase */
  31 #define SPI_CPOL        0x02                    /* clock polarity */
  32 #define SPI_MODE_0      (0|0)                   /* (original MicroWire) */
  33 #define SPI_MODE_1      (0|SPI_CPHA)
  34 #define SPI_MODE_2      (SPI_CPOL|0)
  35 #define SPI_MODE_3      (SPI_CPOL|SPI_CPHA)
  36 #define SPI_CS_HIGH     0x04                    /* CS active high */
  37 #define SPI_LSB_FIRST   0x08                    /* per-word bits-on-wire */
  38 #define SPI_3WIRE       0x10                    /* SI/SO signals shared */
  39 #define SPI_LOOP        0x20                    /* loopback mode */
  40
  41 /* SPI transfer flags */
  42 #define SPI_XFER_BEGIN  0x01                    /* Assert CS before transfer */
  43 #define SPI_XFER_END    0x02                    /* Deassert CS after transfer */
  44
  45 /*-----------------------------------------------------------------------
  46  * Representation of a SPI slave, i.e. what we're communicating with.
  47  *
  48  * Drivers are expected to extend this with controller-specific data.
  49  *
  50  *   bus:       ID of the bus that the slave is attached to.
  51  *   cs:        ID of the chip select connected to the slave.
  52  *   max_write_size:    If non-zero, the maximum number of bytes which can
  53  *              be written at once, excluding command bytes.
  54  */
  55 struct spi_slave {
  56         unsigned int    bus;
  57         unsigned int    cs;
  58         unsigned int max_write_size;
  59 };
  60
  61 /*-----------------------------------------------------------------------
  62  * Initialization, must be called once on start up.
  63  *
  64  * TODO: I don't think we really need this.
  65  */
  66 void spi_init(void);
  67
  68 /**
  69  * spi_do_alloc_slave - Allocate a new SPI slave (internal)
  70  *
  71  * Allocate and zero all fields in the spi slave, and set the bus/chip
  72  * select. Use the helper macro spi_alloc_slave() to call this.
  73  *
  74  * @offset: Offset of struct spi_slave within slave structure
  75  * @size: Size of slave structure
  76  * @bus: Bus ID of the slave chip.
  77  * @cs: Chip select ID of the slave chip on the specified bus.
  78  */
  79 void *spi_do_alloc_slave(int offset, int size, unsigned int bus,
  80                          unsigned int cs);
  81
  82 /**
  83  * spi_alloc_slave - Allocate a new SPI slave
  84  *
  85  * Allocate and zero all fields in the spi slave, and set the bus/chip
  86  * select.
  87  *
  88  * @_struct: Name of structure to allocate (e.g. struct tegra_spi). This
  89  *      structure must contain a member 'struct spi_slave *slave'.
  90  * @bus: Bus ID of the slave chip.
  91  * @cs: Chip select ID of the slave chip on the specified bus.
  92  */
  93 #define spi_alloc_slave(_struct, bus, cs) \
  94         spi_do_alloc_slave(offsetof(_struct, slave), \
  95                             sizeof(_struct), bus, cs)
  96
  97 /**
  98  * spi_alloc_slave_base - Allocate a new SPI slave with no private data
  99  *
 100  * Allocate and zero all fields in the spi slave, and set the bus/chip
 101  * select.
 102  *
 103  * @bus: Bus ID of the slave chip.
 104  * @cs: Chip select ID of the slave chip on the specified bus.
 105  */
 106 #define spi_alloc_slave_base(bus, cs) \
 107         spi_do_alloc_slave(0, sizeof(struct spi_slave), bus, cs)
 108
 109 /*-----------------------------------------------------------------------
 110  * Set up communications parameters for a SPI slave.
 111  *
 112  * This must be called once for each slave. Note that this function
 113  * usually doesn't touch any actual hardware, it only initializes the
 114  * contents of spi_slave so that the hardware can be easily
 115  * initialized later.
 116  *
 117  *   bus:     Bus ID of the slave chip.
 118  *   cs:      Chip select ID of the slave chip on the specified bus.
 119  *   max_hz:  Maximum SCK rate in Hz.
 120  *   mode:    Clock polarity, clock phase and other parameters.
 121  *
 122  * Returns: A spi_slave reference that can be used in subsequent SPI
 123  * calls, or NULL if one or more of the parameters are not supported.
 124  */
 125 struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
 126                 unsigned int max_hz, unsigned int mode);
 127
 128 /*-----------------------------------------------------------------------
 129  * Free any memory associated with a SPI slave.
 130  *
 131  *   slave:     The SPI slave
 132  */
 133 void spi_free_slave(struct spi_slave *slave);
 134
 135 /*-----------------------------------------------------------------------
 136  * Claim the bus and prepare it for communication with a given slave.
 137  *
 138  * This must be called before doing any transfers with a SPI slave. It
 139  * will enable and initialize any SPI hardware as necessary, and make
 140  * sure that the SCK line is in the correct idle state. It is not
 141  * allowed to claim the same bus for several slaves without releasing
 142  * the bus in between.
 143  *
 144  *   slave:     The SPI slave
 145  *
 146  * Returns: 0 if the bus was claimed successfully, or a negative value
 147  * if it wasn't.
 148  */
 149 int spi_claim_bus(struct spi_slave *slave);
 150
 151 /*-----------------------------------------------------------------------
 152  * Release the SPI bus
 153  *
 154  * This must be called once for every call to spi_claim_bus() after
 155  * all transfers have finished. It may disable any SPI hardware as
 156  * appropriate.
 157  *
 158  *   slave:     The SPI slave
 159  */
 160 void spi_release_bus(struct spi_slave *slave);
 161
 162 /*-----------------------------------------------------------------------
 163  * SPI transfer
 164  *
 165  * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
 166  * "bitlen" bits in the SPI MISO port.  That's just the way SPI works.
 167  *
 168  * The source of the outgoing bits is the "dout" parameter and the
 169  * destination of the input bits is the "din" parameter.  Note that "dout"
 170  * and "din" can point to the same memory location, in which case the
 171  * input data overwrites the output data (since both are buffered by
 172  * temporary variables, this is OK).
 173  *
 174  * spi_xfer() interface:
 175  *   slave:     The SPI slave which will be sending/receiving the data.
 176  *   bitlen:    How many bits to write and read.
 177  *   dout:      Pointer to a string of bits to send out.  The bits are
 178  *              held in a byte array and are sent MSB first.
 179  *   din:       Pointer to a string of bits that will be filled in.
 180  *   flags:     A bitwise combination of SPI_XFER_* flags.
 181  *
 182  *   Returns: 0 on success, not 0 on failure
 183  */
 184 int  spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
 185                 void *din, unsigned long flags);
 186
 187 /*-----------------------------------------------------------------------
 188  * Determine if a SPI chipselect is valid.
 189  * This function is provided by the board if the low-level SPI driver
 190  * needs it to determine if a given chipselect is actually valid.
 191  *
 192  * Returns: 1 if bus:cs identifies a valid chip on this board, 0
 193  * otherwise.
 194  */
 195 int  spi_cs_is_valid(unsigned int bus, unsigned int cs);
 196
 197 /*-----------------------------------------------------------------------
 198  * Activate a SPI chipselect.
 199  * This function is provided by the board code when using a driver
 200  * that can't control its chipselects automatically (e.g.
 201  * common/soft_spi.c). When called, it should activate the chip select
 202  * to the device identified by "slave".
 203  */
 204 void spi_cs_activate(struct spi_slave *slave);
 205
 206 /*-----------------------------------------------------------------------
 207  * Deactivate a SPI chipselect.
 208  * This function is provided by the board code when using a driver
 209  * that can't control its chipselects automatically (e.g.
 210  * common/soft_spi.c). When called, it should deactivate the chip
 211  * select to the device identified by "slave".
 212  */
 213 void spi_cs_deactivate(struct spi_slave *slave);
 214
 215 /*-----------------------------------------------------------------------
 216  * Set transfer speed.
 217  * This sets a new speed to be applied for next spi_xfer().
 218  *   slave:     The SPI slave
 219  *   hz:        The transfer speed
 220  */
 221 void spi_set_speed(struct spi_slave *slave, uint hz);
 222
 223 /*-----------------------------------------------------------------------
 224  * Write 8 bits, then read 8 bits.
 225  *   slave:     The SPI slave we're communicating with
 226  *   byte:      Byte to be written
 227  *
 228  * Returns: The value that was read, or a negative value on error.
 229  *
 230  * TODO: This function probably shouldn't be inlined.
 231  */
 232 static inline int spi_w8r8(struct spi_slave *slave, unsigned char byte)
 233 {
 234         unsigned char dout[2];
 235         unsigned char din[2];
 236         int ret;
 237
 238         dout[0] = byte;
 239         dout[1] = 0;
 240
 241         ret = spi_xfer(slave, 16, dout, din, SPI_XFER_BEGIN | SPI_XFER_END);
 242         return ret < 0 ? ret : din[1];
 243 }
 244
 245 #endif  /* _SPI_H_ */