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 /* SPI mode flags */
  28 #define SPI_CPHA        0x01                    /* clock phase */
  29 #define SPI_CPOL        0x02                    /* clock polarity */
  30 #define SPI_MODE_0      (0|0)                   /* (original MicroWire) */
  31 #define SPI_MODE_1      (0|SPI_CPHA)
  32 #define SPI_MODE_2      (SPI_CPOL|0)
  33 #define SPI_MODE_3      (SPI_CPOL|SPI_CPHA)
  34 #define SPI_CS_HIGH     0x04                    /* CS active high */
  35 #define SPI_LSB_FIRST   0x08                    /* per-word bits-on-wire */
  36 #define SPI_3WIRE       0x10                    /* SI/SO signals shared */
  37 #define SPI_LOOP        0x20                    /* loopback mode */
  38
  39 /* SPI transfer flags */
  40 #define SPI_XFER_BEGIN  0x01                    /* Assert CS before transfer */
  41 #define SPI_XFER_END    0x02                    /* Deassert CS after transfer */
  42
  43 /*-----------------------------------------------------------------------
  44  * Representation of a SPI slave, i.e. what we're communicating with.
  45  *
  46  * Drivers are expected to extend this with controller-specific data.
  47  *
  48  *   bus:       ID of the bus that the slave is attached to.
  49  *   cs:        ID of the chip select connected to the slave.
  50  */
  51 struct spi_slave {
  52         unsigned int    bus;
  53         unsigned int    cs;
  54 };
  55
  56 /*-----------------------------------------------------------------------
  57  * Initialization, must be called once on start up.
  58  *
  59  * TODO: I don't think we really need this.
  60  */
  61 void spi_init(void);
  62
  63 /*-----------------------------------------------------------------------
  64  * Set up communications parameters for a SPI slave.
  65  *
  66  * This must be called once for each slave. Note that this function
  67  * usually doesn't touch any actual hardware, it only initializes the
  68  * contents of spi_slave so that the hardware can be easily
  69  * initialized later.
  70  *
  71  *   bus:     Bus ID of the slave chip.
  72  *   cs:      Chip select ID of the slave chip on the specified bus.
  73  *   max_hz:  Maximum SCK rate in Hz.
  74  *   mode:    Clock polarity, clock phase and other parameters.
  75  *
  76  * Returns: A spi_slave reference that can be used in subsequent SPI
  77  * calls, or NULL if one or more of the parameters are not supported.
  78  */
  79 struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
  80                 unsigned int max_hz, unsigned int mode);
  81
  82 /*-----------------------------------------------------------------------
  83  * Free any memory associated with a SPI slave.
  84  *
  85  *   slave:     The SPI slave
  86  */
  87 void spi_free_slave(struct spi_slave *slave);
  88
  89 /*-----------------------------------------------------------------------
  90  * Claim the bus and prepare it for communication with a given slave.
  91  *
  92  * This must be called before doing any transfers with a SPI slave. It
  93  * will enable and initialize any SPI hardware as necessary, and make
  94  * sure that the SCK line is in the correct idle state. It is not
  95  * allowed to claim the same bus for several slaves without releasing
  96  * the bus in between.
  97  *
  98  *   slave:     The SPI slave
  99  *
 100  * Returns: 0 if the bus was claimed successfully, or a negative value
 101  * if it wasn't.
 102  */
 103 int spi_claim_bus(struct spi_slave *slave);
 104
 105 /*-----------------------------------------------------------------------
 106  * Release the SPI bus
 107  *
 108  * This must be called once for every call to spi_claim_bus() after
 109  * all transfers have finished. It may disable any SPI hardware as
 110  * appropriate.
 111  *
 112  *   slave:     The SPI slave
 113  */
 114 void spi_release_bus(struct spi_slave *slave);
 115
 116 /*-----------------------------------------------------------------------
 117  * SPI transfer
 118  *
 119  * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
 120  * "bitlen" bits in the SPI MISO port.  That's just the way SPI works.
 121  *
 122  * The source of the outgoing bits is the "dout" parameter and the
 123  * destination of the input bits is the "din" parameter.  Note that "dout"
 124  * and "din" can point to the same memory location, in which case the
 125  * input data overwrites the output data (since both are buffered by
 126  * temporary variables, this is OK).
 127  *
 128  * spi_xfer() interface:
 129  *   slave:     The SPI slave which will be sending/receiving the data.
 130  *   bitlen:    How many bits to write and read.
 131  *   dout:      Pointer to a string of bits to send out.  The bits are
 132  *              held in a byte array and are sent MSB first.
 133  *   din:       Pointer to a string of bits that will be filled in.
 134  *   flags:     A bitwise combination of SPI_XFER_* flags.
 135  *
 136  *   Returns: 0 on success, not 0 on failure
 137  */
 138 int  spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
 139                 void *din, unsigned long flags);
 140
 141 /*-----------------------------------------------------------------------
 142  * Determine if a SPI chipselect is valid.
 143  * This function is provided by the board if the low-level SPI driver
 144  * needs it to determine if a given chipselect is actually valid.
 145  *
 146  * Returns: 1 if bus:cs identifies a valid chip on this board, 0
 147  * otherwise.
 148  */
 149 int  spi_cs_is_valid(unsigned int bus, unsigned int cs);
 150
 151 /*-----------------------------------------------------------------------
 152  * Activate a SPI chipselect.
 153  * This function is provided by the board code when using a driver
 154  * that can't control its chipselects automatically (e.g.
 155  * common/soft_spi.c). When called, it should activate the chip select
 156  * to the device identified by "slave".
 157  */
 158 void spi_cs_activate(struct spi_slave *slave);
 159
 160 /*-----------------------------------------------------------------------
 161  * Deactivate a SPI chipselect.
 162  * This function is provided by the board code when using a driver
 163  * that can't control its chipselects automatically (e.g.
 164  * common/soft_spi.c). When called, it should deactivate the chip
 165  * select to the device identified by "slave".
 166  */
 167 void spi_cs_deactivate(struct spi_slave *slave);
 168
 169 /*-----------------------------------------------------------------------
 170  * Write 8 bits, then read 8 bits.
 171  *   slave:     The SPI slave we're communicating with
 172  *   byte:      Byte to be written
 173  *
 174  * Returns: The value that was read, or a negative value on error.
 175  *
 176  * TODO: This function probably shouldn't be inlined.
 177  */
 178 static inline int spi_w8r8(struct spi_slave *slave, unsigned char byte)
 179 {
 180         unsigned char dout[2];
 181         unsigned char din[2];
 182         int ret;
 183
 184         dout[0] = byte;
 185         dout[1] = 0;
 186
 187         ret = spi_xfer(slave, 16, dout, din, SPI_XFER_BEGIN | SPI_XFER_END);
 188         return ret < 0 ? ret : din[1];
 189 }
 190
 191 #endif  /* _SPI_H_ */