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  */
  53 struct spi_slave {
  54         unsigned int    bus;
  55         unsigned int    cs;
  56 };
  57
  58 /*-----------------------------------------------------------------------
  59  * Initialization, must be called once on start up.
  60  *
  61  * TODO: I don't think we really need this.
  62  */
  63 void spi_init(void);
  64
  65 /*-----------------------------------------------------------------------
  66  * Set up communications parameters for a SPI slave.
  67  *
  68  * This must be called once for each slave. Note that this function
  69  * usually doesn't touch any actual hardware, it only initializes the
  70  * contents of spi_slave so that the hardware can be easily
  71  * initialized later.
  72  *
  73  *   bus:     Bus ID of the slave chip.
  74  *   cs:      Chip select ID of the slave chip on the specified bus.
  75  *   max_hz:  Maximum SCK rate in Hz.
  76  *   mode:    Clock polarity, clock phase and other parameters.
  77  *
  78  * Returns: A spi_slave reference that can be used in subsequent SPI
  79  * calls, or NULL if one or more of the parameters are not supported.
  80  */
  81 struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
  82                 unsigned int max_hz, unsigned int mode);
  83
  84 /*-----------------------------------------------------------------------
  85  * Free any memory associated with a SPI slave.
  86  *
  87  *   slave:     The SPI slave
  88  */
  89 void spi_free_slave(struct spi_slave *slave);
  90
  91 /*-----------------------------------------------------------------------
  92  * Claim the bus and prepare it for communication with a given slave.
  93  *
  94  * This must be called before doing any transfers with a SPI slave. It
  95  * will enable and initialize any SPI hardware as necessary, and make
  96  * sure that the SCK line is in the correct idle state. It is not
  97  * allowed to claim the same bus for several slaves without releasing
  98  * the bus in between.
  99  *
 100  *   slave:     The SPI slave
 101  *
 102  * Returns: 0 if the bus was claimed successfully, or a negative value
 103  * if it wasn't.
 104  */
 105 int spi_claim_bus(struct spi_slave *slave);
 106
 107 /*-----------------------------------------------------------------------
 108  * Release the SPI bus
 109  *
 110  * This must be called once for every call to spi_claim_bus() after
 111  * all transfers have finished. It may disable any SPI hardware as
 112  * appropriate.
 113  *
 114  *   slave:     The SPI slave
 115  */
 116 void spi_release_bus(struct spi_slave *slave);
 117
 118 /*-----------------------------------------------------------------------
 119  * SPI transfer
 120  *
 121  * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
 122  * "bitlen" bits in the SPI MISO port.  That's just the way SPI works.
 123  *
 124  * The source of the outgoing bits is the "dout" parameter and the
 125  * destination of the input bits is the "din" parameter.  Note that "dout"
 126  * and "din" can point to the same memory location, in which case the
 127  * input data overwrites the output data (since both are buffered by
 128  * temporary variables, this is OK).
 129  *
 130  * spi_xfer() interface:
 131  *   slave:     The SPI slave which will be sending/receiving the data.
 132  *   bitlen:    How many bits to write and read.
 133  *   dout:      Pointer to a string of bits to send out.  The bits are
 134  *              held in a byte array and are sent MSB first.
 135  *   din:       Pointer to a string of bits that will be filled in.
 136  *   flags:     A bitwise combination of SPI_XFER_* flags.
 137  *
 138  *   Returns: 0 on success, not 0 on failure
 139  */
 140 int  spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
 141                 void *din, unsigned long flags);
 142
 143 /*-----------------------------------------------------------------------
 144  * Determine if a SPI chipselect is valid.
 145  * This function is provided by the board if the low-level SPI driver
 146  * needs it to determine if a given chipselect is actually valid.
 147  *
 148  * Returns: 1 if bus:cs identifies a valid chip on this board, 0
 149  * otherwise.
 150  */
 151 int  spi_cs_is_valid(unsigned int bus, unsigned int cs);
 152
 153 /*-----------------------------------------------------------------------
 154  * Activate a SPI chipselect.
 155  * This function is provided by the board code when using a driver
 156  * that can't control its chipselects automatically (e.g.
 157  * common/soft_spi.c). When called, it should activate the chip select
 158  * to the device identified by "slave".
 159  */
 160 void spi_cs_activate(struct spi_slave *slave);
 161
 162 /*-----------------------------------------------------------------------
 163  * Deactivate a SPI chipselect.
 164  * This function is provided by the board code when using a driver
 165  * that can't control its chipselects automatically (e.g.
 166  * common/soft_spi.c). When called, it should deactivate the chip
 167  * select to the device identified by "slave".
 168  */
 169 void spi_cs_deactivate(struct spi_slave *slave);
 170
 171 /*-----------------------------------------------------------------------
 172  * Set transfer speed.
 173  * This sets a new speed to be applied for next spi_xfer().
 174  *   slave:     The SPI slave
 175  *   hz:        The transfer speed
 176  */
 177 void spi_set_speed(struct spi_slave *slave, uint hz);
 178
 179 /*-----------------------------------------------------------------------
 180  * Write 8 bits, then read 8 bits.
 181  *   slave:     The SPI slave we're communicating with
 182  *   byte:      Byte to be written
 183  *
 184  * Returns: The value that was read, or a negative value on error.
 185  *
 186  * TODO: This function probably shouldn't be inlined.
 187  */
 188 static inline int spi_w8r8(struct spi_slave *slave, unsigned char byte)
 189 {
 190         unsigned char dout[2];
 191         unsigned char din[2];
 192         int ret;
 193
 194         dout[0] = byte;
 195         dout[1] = 0;
 196
 197         ret = spi_xfer(slave, 16, dout, din, SPI_XFER_BEGIN | SPI_XFER_END);
 198         return ret < 0 ? ret : din[1];
 199 }
 200
 201 #endif  /* _SPI_H_ */