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_ */ 192