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* (C) Copyright 2001
* Gerald Van Baren, Custom IDEAS,
* See file CREDITS for list of people who contributed to this
* project.
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
* MA 02111-1307 USA
#ifndef _SPI_GENERIC_H_
#define _SPI_GENERIC_H_
#include <stdint.h>
/* Controller-specific definitions: */
/* SPI mode flags */
#define SPI_CPHA 0x01 /* clock phase */
#define SPI_CPOL 0x02 /* clock polarity */
#define SPI_MODE_0 (0|0) /* (original MicroWire) */
#define SPI_MODE_1 (0|SPI_CPHA)
#define SPI_MODE_2 (SPI_CPOL|0)
#define SPI_CS_HIGH 0x04 /* CS active high */
#define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */
#define SPI_3WIRE 0x10 /* SI/SO signals shared */
#define SPI_LOOP 0x20 /* loopback mode */
/* SPI transfer flags */
#define SPI_XFER_BEGIN 0x01 /* Assert CS before transfer */
#define SPI_XFER_END 0x02 /* Deassert CS after transfer */
/* SPI opcodes */
#define SPI_OPCODE_WREN 0x06
#define SPI_READ_FLAG 0x01
#define SPI_WRITE_FLAG 0x02
* Representation of a SPI slave, i.e. what we're communicating with.
* Drivers are expected to extend this with controller-specific data.
* bus: ID of the bus that the slave is attached to.
* cs: ID of the chip select connected to the slave.
* rw: Read or Write flag
struct spi_slave {
unsigned int bus;
unsigned int cs;
unsigned int rw;
* Initialization, must be called once on start up.
void spi_init(void);
* Set up communications parameters for a SPI slave.
* This must be called once for each slave. Note that this function
* usually doesn't touch any actual hardware, it only initializes the
* contents of spi_slave so that the hardware can be easily
* initialized later.
* bus: Bus ID of the slave chip.
* cs: Chip select ID of the slave chip on the specified bus.
* max_hz: Maximum SCK rate in Hz.
* mode: Clock polarity, clock phase and other parameters.
* Returns: A spi_slave reference that can be used in subsequent SPI
* calls, or NULL if one or more of the parameters are not supported.
struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
unsigned int max_hz, unsigned int mode);
* Claim the bus and prepare it for communication with a given slave.
* This must be called before doing any transfers with a SPI slave. It
* will enable and initialize any SPI hardware as necessary, and make
* sure that the SCK line is in the correct idle state. It is not
* allowed to claim the same bus for several slaves without releasing
* the bus in between.
* slave: The SPI slave
* Returns: 0 if the bus was claimed successfully, or a negative value
* if it wasn't.
int spi_claim_bus(struct spi_slave *slave);
* Release the SPI bus
* This must be called once for every call to spi_claim_bus() after
* all transfers have finished. It may disable any SPI hardware as
* appropriate.
* slave: The SPI slave
void spi_release_bus(struct spi_slave *slave);
* SPI transfer
* This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
* "bitlen" bits in the SPI MISO port. That's just the way SPI works.
* The source of the outgoing bits is the "dout" parameter and the
* destination of the input bits is the "din" parameter. Note that "dout"
* and "din" can point to the same memory location, in which case the
* input data overwrites the output data (since both are buffered by
* temporary variables, this is OK).
* spi_xfer() interface:
* slave: The SPI slave which will be sending/receiving the data.
* dout: Pointer to a string of bits to send out. The bits are
* held in a byte array and are sent MSB first.
* bitsout: How many bits to write.
* din: Pointer to a string of bits that will be filled in.
* bitsin: How many bits to read.
* Returns: 0 on success, not 0 on failure
int spi_xfer(struct spi_slave *slave, const void *dout, unsigned int bitsout,
void *din, unsigned int bitsin);
* Determine if a SPI chipselect is valid.
* This function is provided by the board if the low-level SPI driver
* needs it to determine if a given chipselect is actually valid.
* Returns: 1 if bus:cs identifies a valid chip on this board, 0
* otherwise.
int spi_cs_is_valid(unsigned int bus, unsigned int cs);
* Activate a SPI chipselect.
* This function is provided by the board code when using a driver
* that can't control its chipselects automatically (e.g.
* common/soft_spi.c). When called, it should activate the chip select
* to the device identified by "slave".
void spi_cs_activate(struct spi_slave *slave);
* Deactivate a SPI chipselect.
* This function is provided by the board code when using a driver
* that can't control its chipselects automatically (e.g.
* common/soft_spi.c). When called, it should deactivate the chip
* select to the device identified by "slave".
void spi_cs_deactivate(struct spi_slave *slave);
* Set transfer speed.
* This sets a new speed to be applied for next spi_xfer().
* slave: The SPI slave
* hz: The transfer speed
void spi_set_speed(struct spi_slave *slave, uint32_t hz);
* Write 8 bits, then read 8 bits.
* slave: The SPI slave we're communicating with
* byte: Byte to be written
* Returns: The value that was read, or a negative value on error.
* TODO: This function probably shouldn't be inlined.
static inline int spi_w8r8(struct spi_slave *slave, unsigned char byte)
unsigned char dout[2];
unsigned char din[2];
int ret;
dout[0] = byte;
dout[1] = 0;
ret = spi_xfer(slave, dout, 16, din, 16);
return ret < 0 ? ret : din[1];
#endif /* _SPI_GENERIC_H_ */