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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.
*/
FILE_LICENCE ( GPL2_OR_LATER );
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <byteswap.h>
#include <errno.h>
#include <assert.h>
#include <unistd.h>
#include <gpxe/bitbash.h>
#include <gpxe/spi_bit.h>
/** @file
*
* SPI bit-bashing interface
*
*/
/** Delay between SCLK changes and around SS changes */
static void spi_bit_delay ( void ) {
udelay ( SPI_BIT_UDELAY );
}
/** Chip select line will be asserted */
#define SELECT_SLAVE 0
/** Chip select line will be deasserted */
#define DESELECT_SLAVE SPI_MODE_SSPOL
/**
* Select/deselect slave
*
* @v spibit SPI bit-bashing interface
* @v slave Slave number
* @v state Slave select state
*
* @c state must be @c SELECT_SLAVE or @c DESELECT_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->bus.mode & SPI_MODE_SSPOL );
DBGC2 ( spibit, "SPIBIT %p setting slave %d select %s\n",
spibit, slave, ( state ? "high" : "low" ) );
spi_bit_delay();
write_bit ( basher, SPI_BIT_SS ( slave ), state );
spi_bit_delay();
}
/**
* Transfer bits over SPI bit-bashing bus
*
* @v bus SPI bus
* @v data_out TX data buffer (or NULL)
* @v data_in RX data buffer (or NULL)
* @v len Length of transfer (in @b bits)
* @v endianness Endianness of this data transfer
*
* 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_bit_basher *spibit,
const void *data_out, void *data_in,
unsigned int len, int endianness ) {
struct spi_bus *bus = &spibit->bus;
struct bit_basher *basher = &spibit->basher;
unsigned int sclk = ( ( bus->mode & SPI_MODE_CPOL ) ? 1 : 0 );
unsigned int cpha = ( ( bus->mode & SPI_MODE_CPHA ) ? 1 : 0 );
unsigned int bit_offset;
unsigned int byte_offset;
unsigned int byte_mask;
unsigned int bit;
unsigned int step;
DBGC2 ( spibit, "SPIBIT %p transferring %d bits in mode %#x\n",
spibit, len, bus->mode );
for ( step = 0 ; step < ( len * 2 ) ; step++ ) {
/* Calculate byte offset and byte mask */
bit_offset = ( ( endianness == SPI_BIT_BIG_ENDIAN ) ?
( len - ( step / 2 ) - 1 ) : ( step / 2 ) );
byte_offset = ( bit_offset / 8 );
byte_mask = ( 1 << ( bit_offset % 8 ) );
/* Shift data in or out */
if ( sclk == cpha ) {
const uint8_t *byte;
/* Shift data out */
if ( data_out ) {
byte = ( data_out + byte_offset );
bit = ( *byte & byte_mask );
DBGCP ( spibit, "SPIBIT %p wrote bit %d\n",
spibit, ( bit ? 1 : 0 ) );
} 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 ) {
DBGCP ( spibit, "SPIBIT %p read bit %d\n",
spibit, ( bit ? 1 : 0 ) );
byte = ( data_in + byte_offset );
*byte &= ~byte_mask;
*byte |= ( bit & byte_mask );
}
}
/* Toggle clock line */
spi_bit_delay();
sclk ^= 1;
write_bit ( basher, SPI_BIT_SCLK, sclk );
}
}
/**
* Read/write data via SPI bit-bashing bus
*
* @v bus SPI bus
* @v device SPI device
* @v command Command
* @v address Address to read/write (<0 for no address)
* @v data_out TX data buffer (or NULL)
* @v data_in RX data buffer (or NULL)
* @v len Length of transfer
* @ret rc Return status code
*/
static int spi_bit_rw ( struct spi_bus *bus, struct spi_device *device,
unsigned int command, int address,
const void *data_out, void *data_in, size_t len ) {
struct spi_bit_basher *spibit
= container_of ( bus, struct spi_bit_basher, bus );
uint32_t tmp_command;
uint32_t tmp_address;
uint32_t tmp_address_detect;
/* Set clock line to idle state */
write_bit ( &spibit->basher, SPI_BIT_SCLK,
( bus->mode & SPI_MODE_CPOL ) );
/* Assert chip select on specified slave */
spi_bit_set_slave_select ( spibit, device->slave, SELECT_SLAVE );
/* Transmit command */
assert ( device->command_len <= ( 8 * sizeof ( tmp_command ) ) );
tmp_command = cpu_to_le32 ( command );
spi_bit_transfer ( spibit, &tmp_command, NULL, device->command_len,
SPI_BIT_BIG_ENDIAN );
/* Transmit address, if present */
if ( address >= 0 ) {
assert ( device->address_len <= ( 8 * sizeof ( tmp_address )));
tmp_address = cpu_to_le32 ( address );
if ( device->address_len == SPI_AUTODETECT_ADDRESS_LEN ) {
/* Autodetect address length. This relies on
* the device responding with a dummy zero
* data bit before the first real data bit.
*/
DBGC ( spibit, "SPIBIT %p autodetecting device "
"address length\n", spibit );
assert ( address == 0 );
device->address_len = 0;
do {
spi_bit_transfer ( spibit, &tmp_address,
&tmp_address_detect, 1,
SPI_BIT_BIG_ENDIAN );
device->address_len++;
} while ( le32_to_cpu ( tmp_address_detect ) & 1 );
DBGC ( spibit, "SPIBIT %p autodetected device address "
"length %d\n", spibit, device->address_len );
} else {
spi_bit_transfer ( spibit, &tmp_address, NULL,
device->address_len,
SPI_BIT_BIG_ENDIAN );
}
}
/* Transmit/receive data */
spi_bit_transfer ( spibit, data_out, data_in, ( len * 8 ),
spibit->endianness );
/* Deassert chip select on specified slave */
spi_bit_set_slave_select ( spibit, device->slave, DESELECT_SLAVE );
return 0;
}
/**
* Initialise SPI bit-bashing interface
*
* @v spibit SPI bit-bashing interface
*/
void init_spi_bit_basher ( struct spi_bit_basher *spibit ) {
assert ( &spibit->basher.op->read != NULL );
assert ( &spibit->basher.op->write != NULL );
spibit->bus.rw = spi_bit_rw;
}
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