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/*
* Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
*
* 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 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
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <stdio.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <timer.h>
#include <gpxe/bitbash.h>
#include <gpxe/spi.h>
/** @file
*
* SPI bit-bashing interface
*
*/
/** Delay between SCLK changes and around SS changes */
static void spi_delay ( void ) {
udelay ( SPI_UDELAY );
}
/**
* Select/deselect slave
*
* @v spi SPI bit-bashing interface
* @v slave Slave number
* @v state Slave select state
*
* @c state must be set to zero to select the specified slave, or to
* @c SPI_MODE_SSPOL to deselect the slave.
*/
static void spi_bit_set_slave_select ( struct spi_bit_basher *spibit,
unsigned int slave,
unsigned int state ) {
struct bit_basher *basher = &spibit->basher;
state ^= ( spibit->spi.mode & SPI_MODE_SSPOL );
DBG ( "Setting slave %d select %s\n", slave,
( state ? "high" : "low" ) );
spi_delay();
write_bit ( basher, SPI_BIT_SS ( slave ), state );
spi_delay();
}
/**
* Select slave
*
* @v spi SPI interface
* @v slave Slave number
*/
static void spi_bit_select_slave ( struct spi_interface *spi,
unsigned int slave ) {
struct spi_bit_basher *spibit
= container_of ( spi, struct spi_bit_basher, spi );
spibit->slave = slave;
spi_bit_set_slave_select ( spibit, slave, 0 );
}
/**
* Deselect slave
*
* @v spi SPI interface
*/
static void spi_bit_deselect_slave ( struct spi_interface *spi ) {
struct spi_bit_basher *spibit
= container_of ( spi, struct spi_bit_basher, spi );
spi_bit_set_slave_select ( spibit, spibit->slave, SPI_MODE_SSPOL );
}
/**
* Transfer bits over SPI bit-bashing interface
*
* @v spi SPI interface
* @v data_out TX data buffer (or NULL)
* @v data_in RX data buffer (or NULL)
* @v len Length of transfer (in @b bits)
*
* This issues @c len clock cycles on the SPI bus, shifting out data
* from the @c data_out buffer to the MOSI line and shifting in data
* from the MISO line to the @c data_in buffer. If @c data_out is
* NULL, then the data sent will be all zeroes. If @c data_in is
* NULL, then the incoming data will be discarded.
*/
static void spi_bit_transfer ( struct spi_interface *spi, const void *data_out,
void *data_in, unsigned int len ) {
struct spi_bit_basher *spibit
= container_of ( spi, struct spi_bit_basher, spi );
struct bit_basher *basher = &spibit->basher;
unsigned int sclk = ( ( spi->mode & SPI_MODE_CPOL ) ? 1 : 0 );
unsigned int cpha = ( ( spi->mode & SPI_MODE_CPHA ) ? 1 : 0 );
unsigned int offset;
unsigned int mask;
unsigned int bit;
int step;
DBG ( "Transferring %d bits in mode %x\n", len, spi->mode );
for ( step = ( ( len * 2 ) - 1 ) ; step >= 0 ; step-- ) {
/* Calculate byte offset within data and bit mask */
offset = ( step / 16 );
mask = ( 1 << ( ( step % 16 ) / 2 ) );
/* Shift data in or out */
if ( sclk == cpha ) {
const uint8_t *byte;
/* Shift data out */
if ( data_out ) {
byte = ( data_out + offset );
bit = ( *byte & mask );
} else {
bit = 0;
}
write_bit ( basher, SPI_BIT_MOSI, bit );
} else {
uint8_t *byte;
/* Shift data in */
bit = read_bit ( basher, SPI_BIT_MISO );
if ( data_in ) {
byte = ( data_in + offset );
*byte &= ~mask;
*byte |= ( bit & mask );
}
}
/* Toggle clock line */
spi_delay();
sclk = ~sclk;
write_bit ( basher, SPI_BIT_SCLK, sclk );
}
}
/**
* Initialise SPI bit-bashing interface
*
* @v spibit SPI bit-bashing interface
*/
void init_spi_bit_basher ( struct spi_bit_basher *spibit ) {
assert ( &spibit->basher.read != NULL );
assert ( &spibit->basher.write != NULL );
spibit->spi.select_slave = spi_bit_select_slave;
spibit->spi.deselect_slave = spi_bit_deselect_slave;
spibit->spi.transfer = spi_bit_transfer;
}
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