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A SPI slave may take time to react to a request. For SPI flash devices this time is defined as one bit time, or a whole byte for 'fast read' mode. If the SPI slave is another CPU, then the time it takes to react may vary. It is convenient to allow the slave device to tag the start of the actual reply so that the host can determine when this 'preamble' finishes and the actual message starts. Add a preamble flag to the available SPI flags. If supported by the driver then it will ignore any received bytes before the preamble on each transaction. This ensures that reliable communication with the slave is possible. Signed-off-by: Simon Glass <sjg@chromium.org> Signed-off-by: Rajeshwari Shinde <rajeshwari.s@samsung.com> Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>
251 lines
8.8 KiB
C
251 lines
8.8 KiB
C
/*
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* (C) Copyright 2001
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* Gerald Van Baren, Custom IDEAS, vanbaren@cideas.com.
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*
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* See file CREDITS for list of people who contributed to this
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* project.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of
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* the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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* MA 02111-1307 USA
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*/
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#ifndef _SPI_H_
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#define _SPI_H_
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/* Controller-specific definitions: */
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/* SPI mode flags */
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#define SPI_CPHA 0x01 /* clock phase */
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#define SPI_CPOL 0x02 /* clock polarity */
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#define SPI_MODE_0 (0|0) /* (original MicroWire) */
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#define SPI_MODE_1 (0|SPI_CPHA)
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#define SPI_MODE_2 (SPI_CPOL|0)
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#define SPI_MODE_3 (SPI_CPOL|SPI_CPHA)
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#define SPI_CS_HIGH 0x04 /* CS active high */
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#define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */
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#define SPI_3WIRE 0x10 /* SI/SO signals shared */
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#define SPI_LOOP 0x20 /* loopback mode */
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#define SPI_SLAVE 0x40 /* slave mode */
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#define SPI_PREAMBLE 0x80 /* Skip preamble bytes */
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/* SPI transfer flags */
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#define SPI_XFER_BEGIN 0x01 /* Assert CS before transfer */
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#define SPI_XFER_END 0x02 /* Deassert CS after transfer */
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/* Header byte that marks the start of the message */
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#define SPI_PREAMBLE_END_BYTE 0xec
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/*-----------------------------------------------------------------------
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* Representation of a SPI slave, i.e. what we're communicating with.
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*
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* Drivers are expected to extend this with controller-specific data.
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*
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* bus: ID of the bus that the slave is attached to.
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* cs: ID of the chip select connected to the slave.
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* max_write_size: If non-zero, the maximum number of bytes which can
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* be written at once, excluding command bytes.
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*/
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struct spi_slave {
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unsigned int bus;
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unsigned int cs;
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unsigned int max_write_size;
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};
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/*-----------------------------------------------------------------------
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* Initialization, must be called once on start up.
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*
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* TODO: I don't think we really need this.
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*/
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void spi_init(void);
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/**
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* spi_do_alloc_slave - Allocate a new SPI slave (internal)
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*
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* Allocate and zero all fields in the spi slave, and set the bus/chip
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* select. Use the helper macro spi_alloc_slave() to call this.
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*
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* @offset: Offset of struct spi_slave within slave structure
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* @size: Size of slave structure
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* @bus: Bus ID of the slave chip.
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* @cs: Chip select ID of the slave chip on the specified bus.
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*/
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void *spi_do_alloc_slave(int offset, int size, unsigned int bus,
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unsigned int cs);
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/**
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* spi_alloc_slave - Allocate a new SPI slave
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*
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* Allocate and zero all fields in the spi slave, and set the bus/chip
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* select.
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*
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* @_struct: Name of structure to allocate (e.g. struct tegra_spi). This
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* structure must contain a member 'struct spi_slave *slave'.
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* @bus: Bus ID of the slave chip.
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* @cs: Chip select ID of the slave chip on the specified bus.
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*/
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#define spi_alloc_slave(_struct, bus, cs) \
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spi_do_alloc_slave(offsetof(_struct, slave), \
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sizeof(_struct), bus, cs)
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/**
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* spi_alloc_slave_base - Allocate a new SPI slave with no private data
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*
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* Allocate and zero all fields in the spi slave, and set the bus/chip
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* select.
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*
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* @bus: Bus ID of the slave chip.
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* @cs: Chip select ID of the slave chip on the specified bus.
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*/
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#define spi_alloc_slave_base(bus, cs) \
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spi_do_alloc_slave(0, sizeof(struct spi_slave), bus, cs)
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/*-----------------------------------------------------------------------
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* Set up communications parameters for a SPI slave.
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*
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* This must be called once for each slave. Note that this function
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* usually doesn't touch any actual hardware, it only initializes the
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* contents of spi_slave so that the hardware can be easily
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* initialized later.
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*
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* bus: Bus ID of the slave chip.
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* cs: Chip select ID of the slave chip on the specified bus.
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* max_hz: Maximum SCK rate in Hz.
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* mode: Clock polarity, clock phase and other parameters.
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*
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* Returns: A spi_slave reference that can be used in subsequent SPI
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* calls, or NULL if one or more of the parameters are not supported.
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*/
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struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
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unsigned int max_hz, unsigned int mode);
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/*-----------------------------------------------------------------------
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* Free any memory associated with a SPI slave.
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*
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* slave: The SPI slave
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*/
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void spi_free_slave(struct spi_slave *slave);
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/*-----------------------------------------------------------------------
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* Claim the bus and prepare it for communication with a given slave.
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*
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* This must be called before doing any transfers with a SPI slave. It
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* will enable and initialize any SPI hardware as necessary, and make
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* sure that the SCK line is in the correct idle state. It is not
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* allowed to claim the same bus for several slaves without releasing
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* the bus in between.
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*
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* slave: The SPI slave
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*
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* Returns: 0 if the bus was claimed successfully, or a negative value
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* if it wasn't.
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*/
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int spi_claim_bus(struct spi_slave *slave);
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/*-----------------------------------------------------------------------
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* Release the SPI bus
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*
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* This must be called once for every call to spi_claim_bus() after
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* all transfers have finished. It may disable any SPI hardware as
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* appropriate.
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*
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* slave: The SPI slave
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*/
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void spi_release_bus(struct spi_slave *slave);
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/*-----------------------------------------------------------------------
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* SPI transfer
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*
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* This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
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* "bitlen" bits in the SPI MISO port. That's just the way SPI works.
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*
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* The source of the outgoing bits is the "dout" parameter and the
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* destination of the input bits is the "din" parameter. Note that "dout"
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* and "din" can point to the same memory location, in which case the
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* input data overwrites the output data (since both are buffered by
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* temporary variables, this is OK).
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*
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* spi_xfer() interface:
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* slave: The SPI slave which will be sending/receiving the data.
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* bitlen: How many bits to write and read.
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* dout: Pointer to a string of bits to send out. The bits are
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* held in a byte array and are sent MSB first.
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* din: Pointer to a string of bits that will be filled in.
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* flags: A bitwise combination of SPI_XFER_* flags.
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*
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* Returns: 0 on success, not 0 on failure
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*/
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int spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
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void *din, unsigned long flags);
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/*-----------------------------------------------------------------------
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* Determine if a SPI chipselect is valid.
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* This function is provided by the board if the low-level SPI driver
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* needs it to determine if a given chipselect is actually valid.
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*
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* Returns: 1 if bus:cs identifies a valid chip on this board, 0
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* otherwise.
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*/
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int spi_cs_is_valid(unsigned int bus, unsigned int cs);
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/*-----------------------------------------------------------------------
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* Activate a SPI chipselect.
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* This function is provided by the board code when using a driver
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* that can't control its chipselects automatically (e.g.
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* common/soft_spi.c). When called, it should activate the chip select
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* to the device identified by "slave".
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*/
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void spi_cs_activate(struct spi_slave *slave);
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/*-----------------------------------------------------------------------
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* Deactivate a SPI chipselect.
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* This function is provided by the board code when using a driver
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* that can't control its chipselects automatically (e.g.
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* common/soft_spi.c). When called, it should deactivate the chip
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* select to the device identified by "slave".
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*/
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void spi_cs_deactivate(struct spi_slave *slave);
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/*-----------------------------------------------------------------------
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* Set transfer speed.
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* This sets a new speed to be applied for next spi_xfer().
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* slave: The SPI slave
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* hz: The transfer speed
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*/
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void spi_set_speed(struct spi_slave *slave, uint hz);
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/*-----------------------------------------------------------------------
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* Write 8 bits, then read 8 bits.
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* slave: The SPI slave we're communicating with
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* byte: Byte to be written
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*
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* Returns: The value that was read, or a negative value on error.
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*
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* TODO: This function probably shouldn't be inlined.
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*/
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static inline int spi_w8r8(struct spi_slave *slave, unsigned char byte)
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{
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unsigned char dout[2];
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unsigned char din[2];
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int ret;
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dout[0] = byte;
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dout[1] = 0;
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ret = spi_xfer(slave, 16, dout, din, SPI_XFER_BEGIN | SPI_XFER_END);
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return ret < 0 ? ret : din[1];
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}
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#endif /* _SPI_H_ */
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