spi-butterfly.c

Go to the documentation of this file.

/*
 * parport-to-butterfly adapter
 *
 * Copyright (C) 2005 David Brownell
 *
 * 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
 * (at your option) 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 <linux/kernel.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/parport.h>

#include <linux/sched.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>
#include <linux/spi/flash.h>

#include <linux/mtd/partitions.h>


/*
 * This uses SPI to talk with an "AVR Butterfly", which is a $US20 card
 * with a battery powered AVR microcontroller and lots of goodies.  You
 * can use GCC to develop firmware for this.
 *
 * See Documentation/spi/butterfly for information about how to build
 * and use this custom parallel port cable.
 */


/* DATA output bits (pins 2..9 == D0..D7) */
#define butterfly_nreset (1 << 1)       /* pin 3 */

#define spi_sck_bit (1 << 0)        /* pin 2 */
#define spi_mosi_bit    (1 << 7)        /* pin 9 */

#define vcc_bits    ((1 << 6) | (1 << 5))   /* pins 7, 8 */

/* STATUS input bits */
#define spi_miso_bit    PARPORT_STATUS_BUSY /* pin 11 */

/* CONTROL output bits */
#define spi_cs_bit  PARPORT_CONTROL_SELECT  /* pin 17 */



static inline struct butterfly *spidev_to_pp(struct spi_device *spi)
{
    return spi->controller_data;
}


struct butterfly {
    /* REVISIT ... for now, this must be first */
    struct spi_bitbang  bitbang;

    struct parport      *port;
    struct pardevice    *pd;

    u8          lastbyte;

    struct spi_device   *dataflash;
    struct spi_device   *butterfly;
    struct spi_board_info   info[2];

};

/*----------------------------------------------------------------------*/

static inline void
setsck(struct spi_device *spi, int is_on)
{
    struct butterfly    *pp = spidev_to_pp(spi);
    u8          bit, byte = pp->lastbyte;

    bit = spi_sck_bit;

    if (is_on)
        byte |= bit;
    else
        byte &= ~bit;
    parport_write_data(pp->port, byte);
    pp->lastbyte = byte;
}

static inline void
setmosi(struct spi_device *spi, int is_on)
{
    struct butterfly    *pp = spidev_to_pp(spi);
    u8          bit, byte = pp->lastbyte;

    bit = spi_mosi_bit;

    if (is_on)
        byte |= bit;
    else
        byte &= ~bit;
    parport_write_data(pp->port, byte);
    pp->lastbyte = byte;
}

static inline int getmiso(struct spi_device *spi)
{
    struct butterfly    *pp = spidev_to_pp(spi);
    int         value;
    u8          bit;

    bit = spi_miso_bit;

    /* only STATUS_BUSY is NOT negated */
    value = !(parport_read_status(pp->port) & bit);
    return (bit == PARPORT_STATUS_BUSY) ? value : !value;
}

static void butterfly_chipselect(struct spi_device *spi, int value)
{
    struct butterfly    *pp = spidev_to_pp(spi);

    /* set default clock polarity */
    if (value != BITBANG_CS_INACTIVE)
        setsck(spi, spi->mode & SPI_CPOL);

    /* here, value == "activate or not";
     * most PARPORT_CONTROL_* bits are negated, so we must
     * morph it to value == "bit value to write in control register"
     */
    if (spi_cs_bit == PARPORT_CONTROL_INIT)
        value = !value;

    parport_frob_control(pp->port, spi_cs_bit, value ? spi_cs_bit : 0);
}


/* we only needed to implement one mode here, and choose SPI_MODE_0 */

#define spidelay(X) do{}while(0)
//#define   spidelay    ndelay

#include "spi-bitbang-txrx.h"

static u32
butterfly_txrx_word_mode0(struct spi_device *spi,
        unsigned nsecs,
        u32 word, u8 bits)
{
    return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits);
}

/*----------------------------------------------------------------------*/

/* override default partitioning with cmdlinepart */
static struct mtd_partition partitions[] = { {
    /* JFFS2 wants partitions of 4*N blocks for this device,
     * so sectors 0 and 1 can't be partitions by themselves.
     */

    /* sector 0 = 8 pages * 264 bytes/page (1 block)
     * sector 1 = 248 pages * 264 bytes/page
     */
    .name       = "bookkeeping",    // 66 KB
    .offset     = 0,
    .size       = (8 + 248) * 264,
//  .mask_flags = MTD_WRITEABLE,
}, {
    /* sector 2 = 256 pages * 264 bytes/page
     * sectors 3-5 = 512 pages * 264 bytes/page
     */
    .name       = "filesystem",     // 462 KB
    .offset     = MTDPART_OFS_APPEND,
    .size       = MTDPART_SIZ_FULL,
} };

static struct flash_platform_data flash = {
    .name       = "butterflash",
    .parts      = partitions,
    .nr_parts   = ARRAY_SIZE(partitions),
};


/* REVISIT remove this ugly global and its "only one" limitation */
static struct butterfly *butterfly;

static void butterfly_attach(struct parport *p)
{
    struct pardevice    *pd;
    int         status;
    struct butterfly    *pp;
    struct spi_master   *master;
    struct device       *dev = p->physport->dev;

    if (butterfly || !dev)
        return;

    /* REVISIT:  this just _assumes_ a butterfly is there ... no probe,
     * and no way to be selective about what it binds to.
     */

    master = spi_alloc_master(dev, sizeof *pp);
    if (!master) {
        status = -ENOMEM;
        goto done;
    }
    pp = spi_master_get_devdata(master);

    /*
     * SPI and bitbang hookup
     *
     * use default setup(), cleanup(), and transfer() methods; and
     * only bother implementing mode 0.  Start it later.
     */
    master->bus_num = 42;
    master->num_chipselect = 2;

    pp->bitbang.master = spi_master_get(master);
    pp->bitbang.chipselect = butterfly_chipselect;
    pp->bitbang.txrx_word[SPI_MODE_0] = butterfly_txrx_word_mode0;

    /*
     * parport hookup
     */
    pp->port = p;
    pd = parport_register_device(p, "spi_butterfly",
            NULL, NULL, NULL,
            0 /* FLAGS */, pp);
    if (!pd) {
        status = -ENOMEM;
        goto clean0;
    }
    pp->pd = pd;

    status = parport_claim(pd);
    if (status < 0)
        goto clean1;

    /*
     * Butterfly reset, powerup, run firmware
     */
    pr_debug("%s: powerup/reset Butterfly\n", p->name);

    /* nCS for dataflash (this bit is inverted on output) */
    parport_frob_control(pp->port, spi_cs_bit, 0);

    /* stabilize power with chip in reset (nRESET), and
     * spi_sck_bit clear (CPOL=0)
     */
    pp->lastbyte |= vcc_bits;
    parport_write_data(pp->port, pp->lastbyte);
    msleep(5);

    /* take it out of reset; assume long reset delay */
    pp->lastbyte |= butterfly_nreset;
    parport_write_data(pp->port, pp->lastbyte);
    msleep(100);


    /*
     * Start SPI ... for now, hide that we're two physical busses.
     */
    status = spi_bitbang_start(&pp->bitbang);
    if (status < 0)
        goto clean2;

    /* Bus 1 lets us talk to at45db041b (firmware disables AVR SPI), AVR
     * (firmware resets at45, acts as spi slave) or neither (we ignore
     * both, AVR uses AT45).  Here we expect firmware for the first option.
     */

    pp->info[0].max_speed_hz = 15 * 1000 * 1000;
    strcpy(pp->info[0].modalias, "mtd_dataflash");
    pp->info[0].platform_data = &flash;
    pp->info[0].chip_select = 1;
    pp->info[0].controller_data = pp;
    pp->dataflash = spi_new_device(pp->bitbang.master, &pp->info[0]);
    if (pp->dataflash)
        pr_debug("%s: dataflash at %s\n", p->name,
                dev_name(&pp->dataflash->dev));

    // dev_info(_what?_, ...)
    pr_info("%s: AVR Butterfly\n", p->name);
    butterfly = pp;
    return;

clean2:
    /* turn off VCC */
    parport_write_data(pp->port, 0);

    parport_release(pp->pd);
clean1:
    parport_unregister_device(pd);
clean0:
    (void) spi_master_put(pp->bitbang.master);
done:
    pr_debug("%s: butterfly probe, fail %d\n", p->name, status);
}

static void butterfly_detach(struct parport *p)
{
    struct butterfly    *pp;
    int         status;

    /* FIXME this global is ugly ... but, how to quickly get from
     * the parport to the "struct butterfly" associated with it?
     * "old school" driver-internal device lists?
     */
    if (!butterfly || butterfly->port != p)
        return;
    pp = butterfly;
    butterfly = NULL;

    /* stop() unregisters child devices too */
    status = spi_bitbang_stop(&pp->bitbang);

    /* turn off VCC */
    parport_write_data(pp->port, 0);
    msleep(10);

    parport_release(pp->pd);
    parport_unregister_device(pp->pd);

    (void) spi_master_put(pp->bitbang.master);
}

static struct parport_driver butterfly_driver = {
    .name =     "spi_butterfly",
    .attach =   butterfly_attach,
    .detach =   butterfly_detach,
};


static int __init butterfly_init(void)
{
    return parport_register_driver(&butterfly_driver);
}
device_initcall(butterfly_init);

static void __exit butterfly_exit(void)
{
    parport_unregister_driver(&butterfly_driver);
}
module_exit(butterfly_exit);

MODULE_DESCRIPTION("Parport Adapter driver for AVR Butterfly");
MODULE_LICENSE("GPL");