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133 lines
3.1 KiB
C
133 lines
3.1 KiB
C
#ifndef _GPXE_SPI_H
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#define _GPXE_SPI_H
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/** @file
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*
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* SPI interface
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*
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*/
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#include <gpxe/bitbash.h>
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/** An SPI interface */
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struct spi_interface {
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/** SPI interface mode
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*
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* This is the bitwise OR of zero or more of @c SPI_MODE_CPHA
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* and @c SPI_MODE_CPOL. It is also the number conventionally
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* used to describe the SPI interface mode. For example, SPI
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* mode 1 is the mode in which CPOL=0 and CPHA=1, which
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* therefore corresponds to a mode value of (0|SPI_MODE_CPHA)
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* which, happily, equals 1.
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*/
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unsigned int mode;
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/**
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* Select slave
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*
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* @v spi SPI interface
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* @v slave Slave number
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*/
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void ( * select_slave ) ( struct spi_interface *spi,
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unsigned int slave );
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/**
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* Deselect slave
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*
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* @v spi SPI interface
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*/
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void ( * deselect_slave ) ( struct spi_interface *spi );
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/**
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* Transfer bits over SPI bit-bashing interface
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*
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* @v spi SPI interface
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* @v data_out TX data buffer (or NULL)
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* @v data_in RX data buffer (or NULL)
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* @v len Length of transfer (in @b bits)
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*/
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void ( * transfer ) ( struct spi_interface *spi, const void *data_out,
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void *data_in, unsigned int len );
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};
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/** Clock phase (CPHA) mode bit
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*
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* Phase 0 is sample on rising edge, shift data on falling edge.
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*
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* Phase 1 is shift data on rising edge, sample data on falling edge.
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*/
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#define SPI_MODE_CPHA 0x01
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/** Clock polarity (CPOL) mode bit
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*
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* This bit reflects the idle state of the clock line (SCLK).
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*/
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#define SPI_MODE_CPOL 0x02
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/** Slave select polarity mode bit
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*
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* This bit reflects that active state of the slave select lines. It
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* is not part of the normal SPI mode number (which covers only @c
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* SPI_MODE_CPOL and @c SPI_MODE_CPHA), but is included here for
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* convenience.
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*/
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#define SPI_MODE_SSPOL 0x10
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/** Microwire-compatible mode
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*
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* This is SPI mode 1 (i.e. CPOL=0, CPHA=1), and is compatible with
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* the original Microwire protocol.
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*/
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#define SPI_MODE_MICROWIRE 1
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/** Microwire/Plus-compatible mode
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*
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* This is SPI mode 0 (i.e. CPOL=0, CPHA=0), and is compatible with
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* the Microwire/Plus protocol
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*/
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#define SPI_MODE_MICROWIRE_PLUS 0
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/** Threewire-compatible mode
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*
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* This mode is compatible with Atmel's series of "three-wire"
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* interfaces.
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*/
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#define SPI_MODE_THREEWIRE ( SPI_MODE_MICROWIRE_PLUS | SPI_MODE_SSPOL )
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/** A bit-bashing SPI interface */
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struct spi_bit_basher {
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/** SPI interface */
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struct spi_interface spi;
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/** Bit-bashing interface */
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struct bit_basher basher;
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/** Currently selected slave
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*
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* Valid only when a slave is actually selected.
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*/
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unsigned int slave;
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};
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/** Bit indices used for SPI bit-bashing interface */
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enum {
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/** Serial clock */
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SPI_BIT_SCLK = 0,
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/** Master Out Slave In */
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SPI_BIT_MOSI,
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/** Master In Slave Out */
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SPI_BIT_MISO,
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/** Slave 0 select */
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SPI_BIT_SS0,
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};
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/**
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* Determine bit index for a particular slave
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*
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* @v slave Slave number
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* @ret index Bit index (i.e. SPI_BIT_SSN, where N=slave)
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*/
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#define SPI_BIT_SS( slave ) ( SPI_BIT_SS0 + (slave) )
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/** Delay between SCLK transitions */
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#define SPI_UDELAY 1
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extern void init_spi_bit_basher ( struct spi_bit_basher *spibit );
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#endif /* _GPXE_SPI_H */
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