spi.c

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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 <errno.h>
#include <unistd.h>
#include <gpxe/spi.h>

/** @file
 *
 * SPI devices
 *
 */

/**
 * Munge SPI device address into command
 *
 * @v command           SPI command
 * @v address           Address
 * @v munge_address     Device requires address munging
 * @ret command         Actual SPI command to use
 *
 * Some devices with 9-bit addresses (e.g. AT25040A EEPROM) use bit 3
 * of the command byte as address bit A8, rather than having a
 * two-byte address.  This function takes care of generating the
 * appropriate command.
 */
static inline unsigned int spi_command ( unsigned int command,
                                         unsigned int address,
                                         int munge_address ) {
        return ( command | ( ( ( address >> 8 ) & munge_address ) << 3 ) );
}

/**
 * Wait for SPI device to complete operation
 *
 * @v device            SPI device
 * @ret rc              Return status code
 */
static int spi_wait ( struct spi_device *device ) {
        struct spi_bus *bus = device->bus;
        uint8_t status;
        int i;
        int rc;

        for ( i = 0 ; i < 50 ; i++ ) {
                udelay ( 20 );
                if ( ( rc = bus->rw ( bus, device, SPI_RDSR, -1, NULL,
                                      &status, sizeof ( status ) ) ) != 0 )
                        return rc;
                if ( ! ( status & SPI_STATUS_NRDY ) )
                        return 0;
        }
        DBG ( "SPI %p timed out\n", device );
        return -ETIMEDOUT;
}

/**
 * Read data from SPI device
 *
 * @v nvs               NVS device
 * @v address           Address from which to read
 * @v data              Data buffer
 * @v len               Length of data buffer
 * @ret rc              Return status code
 */
int spi_read ( struct nvs_device *nvs, unsigned int address,
               void *data, size_t len ) {
        struct spi_device *device = nvs_to_spi ( nvs );
        struct spi_bus *bus = device->bus;
        unsigned int command = spi_command ( SPI_READ, address,
                                             device->munge_address );
        int rc;

        DBG ( "SPI %p reading %zd bytes from %#04x\n", device, len, address );
        if ( ( rc = bus->rw ( bus, device, command, address,
                              NULL, data, len ) ) != 0 ) {
                DBG ( "SPI %p failed to read data from device\n", device );
                return rc;
        }

        return 0;
}

/**
 * Write data to SPI device
 *
 * @v nvs               NVS device
 * @v address           Address from which to read
 * @v data              Data buffer
 * @v len               Length of data buffer
 * @ret rc              Return status code
 */
int spi_write ( struct nvs_device *nvs, unsigned int address,
                const void *data, size_t len ) {
        struct spi_device *device = nvs_to_spi ( nvs );
        struct spi_bus *bus = device->bus;
        unsigned int command = spi_command ( SPI_WRITE, address,
                                             device->munge_address );
        int rc;

        DBG ( "SPI %p writing %zd bytes to %#04x\n", device, len, address );

        if ( ( rc = bus->rw ( bus, device, SPI_WREN, -1,
                              NULL, NULL, 0 ) ) != 0 ) {
                DBG ( "SPI %p failed to write-enable device\n", device );
                return rc;
        }

        if ( ( rc = bus->rw ( bus, device, command, address,
                              data, NULL, len ) ) != 0 ) {
                DBG ( "SPI %p failed to write data to device\n", device );
                return rc;
        }
        
        if ( ( rc = spi_wait ( device ) ) != 0 ) {
                DBG ( "SPI %p failed to complete write operation\n", device );
                return rc;
        }

        return 0;
}