spi-lm70llp.c

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/*
 * Driver for LM70EVAL-LLP board for the LM70 sensor
 *
 * Copyright (C) 2006 Kaiwan N Billimoria <[email protected]>
 *
 * 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/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/parport.h>
#include <linux/sysfs.h>
#include <linux/workqueue.h>


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


/*
 * The LM70 communicates with a host processor using a 3-wire variant of
 * the SPI/Microwire bus interface. This driver specifically supports an
 * NS LM70 LLP Evaluation Board, interfacing to a PC using its parallel
 * port to bitbang an SPI-parport bridge.  Accordingly, this is an SPI
 * master controller driver.  The hwmon/lm70 driver is a "SPI protocol
 * driver", layered on top of this one and usable without the lm70llp.
 *
 * Datasheet and Schematic:
 * The LM70 is a temperature sensor chip from National Semiconductor; its
 * datasheet is available at http://www.national.com/pf/LM/LM70.html
 * The schematic for this particular board (the LM70EVAL-LLP) is
 * available (on page 4) here:
 *  http://www.national.com/appinfo/tempsensors/files/LM70LLPEVALmanual.pdf
 *
 * Also see Documentation/spi/spi-lm70llp.  The SPI<->parport code here is
 * (heavily) based on spi-butterfly by David Brownell.
 *
 * The LM70 LLP connects to the PC parallel port in the following manner:
 *
 *   Parallel                 LM70 LLP
 *     Port      Direction   JP2 Header
 *  -----------  ---------  ------------
 *      D0    2      -         -
 *      D1    3     -->      V+   5
 *      D2    4     -->      V+   5
 *      D3    5     -->      V+   5
 *      D4    6     -->      V+   5
 *      D5    7     -->      nCS  8
 *      D6    8     -->      SCLK 3
 *      D7    9     -->      SI/O 5
 *     GND   25      -       GND  7
 *    Select 13     <--      SI/O 1
 *
 * Note that parport pin 13 actually gets inverted by the transistor
 * arrangement which lets either the parport or the LM70 drive the
 * SI/SO signal (see the schematic for details).
 */

#define DRVNAME     "spi-lm70llp"

#define lm70_INIT   0xBE
#define SIO     0x10
#define nCS     0x20
#define SCLK        0x40

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

struct spi_lm70llp {
    struct spi_bitbang  bitbang;
    struct parport      *port;
    struct pardevice    *pd;
    struct spi_device   *spidev_lm70;
    struct spi_board_info   info;
    //struct device     *dev;
};

/* REVISIT : ugly global ; provides "exclusive open" facility */
static struct spi_lm70llp *lm70llp;


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

static inline struct spi_lm70llp *spidev_to_pp(struct spi_device *spi)
{
    return spi->controller_data;
}

/*---------------------- LM70 LLP eval board-specific inlines follow */

/* NOTE:  we don't actually need to reread the output values, since they'll
 * still be what we wrote before.  Plus, going through parport builds in
 * a ~1ms/operation delay; these SPI transfers could easily be faster.
 */

static inline void deassertCS(struct spi_lm70llp *pp)
{
    u8 data = parport_read_data(pp->port);

    data &= ~0x80;      /* pull D7/SI-out low while de-asserted */
    parport_write_data(pp->port, data | nCS);
}

static inline void assertCS(struct spi_lm70llp *pp)
{
    u8 data = parport_read_data(pp->port);

    data |= 0x80;       /* pull D7/SI-out high so lm70 drives SO-in */
    parport_write_data(pp->port, data & ~nCS);
}

static inline void clkHigh(struct spi_lm70llp *pp)
{
    u8 data = parport_read_data(pp->port);
    parport_write_data(pp->port, data | SCLK);
}

static inline void clkLow(struct spi_lm70llp *pp)
{
    u8 data = parport_read_data(pp->port);
    parport_write_data(pp->port, data & ~SCLK);
}

/*------------------------- SPI-LM70-specific inlines ----------------------*/

static inline void spidelay(unsigned d)
{
    udelay(d);
}

static inline void setsck(struct spi_device *s, int is_on)
{
    struct spi_lm70llp *pp = spidev_to_pp(s);

    if (is_on)
        clkHigh(pp);
    else
        clkLow(pp);
}

static inline void setmosi(struct spi_device *s, int is_on)
{
    /* FIXME update D7 ... this way we can put the chip
     * into shutdown mode and read the manufacturer ID,
     * but we can't put it back into operational mode.
     */
}

/*
 * getmiso:
 * Why do we return 0 when the SIO line is high and vice-versa?
 * The fact is, the lm70 eval board from NS (which this driver drives),
 * is wired in just such a way : when the lm70's SIO goes high, a transistor
 * switches it to low reflecting this on the parport (pin 13), and vice-versa.
 */
static inline int getmiso(struct spi_device *s)
{
    struct spi_lm70llp *pp = spidev_to_pp(s);
    return ((SIO == (parport_read_status(pp->port) & SIO)) ? 0 : 1 );
}
/*--------------------------------------------------------------------*/

#include "spi-bitbang-txrx.h"

static void lm70_chipselect(struct spi_device *spi, int value)
{
    struct spi_lm70llp *pp = spidev_to_pp(spi);

    if (value)
        assertCS(pp);
    else
        deassertCS(pp);
}

/*
 * Our actual bitbanger routine.
 */
static u32 lm70_txrx(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits)
{
    return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits);
}

static void spi_lm70llp_attach(struct parport *p)
{
    struct pardevice    *pd;
    struct spi_lm70llp  *pp;
    struct spi_master   *master;
    int         status;

    if (lm70llp) {
        printk(KERN_WARNING
            "%s: spi_lm70llp instance already loaded. Aborting.\n",
            DRVNAME);
        return;
    }

    /* TODO:  this just _assumes_ a lm70 is there ... no probe;
     * the lm70 driver could verify it, reading the manf ID.
     */

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

    /*
     * SPI and bitbang hookup.
     */
    pp->bitbang.master = spi_master_get(master);
    pp->bitbang.chipselect = lm70_chipselect;
    pp->bitbang.txrx_word[SPI_MODE_0] = lm70_txrx;
    pp->bitbang.flags = SPI_3WIRE;

    /*
     * Parport hookup
     */
    pp->port = p;
    pd = parport_register_device(p, DRVNAME,
            NULL, NULL, NULL,
            PARPORT_FLAG_EXCL, pp);
    if (!pd) {
        status = -ENOMEM;
        goto out_free_master;
    }
    pp->pd = pd;

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

    /*
     * Start SPI ...
     */
    status = spi_bitbang_start(&pp->bitbang);
    if (status < 0) {
        printk(KERN_WARNING
            "%s: spi_bitbang_start failed with status %d\n",
            DRVNAME, status);
        goto out_off_and_release;
    }

    /*
     * The modalias name MUST match the device_driver name
     * for the bus glue code to match and subsequently bind them.
     * We are binding to the generic drivers/hwmon/lm70.c device
     * driver.
     */
    strcpy(pp->info.modalias, "lm70");
    pp->info.max_speed_hz = 6 * 1000 * 1000;
    pp->info.chip_select = 0;
    pp->info.mode = SPI_3WIRE | SPI_MODE_0;

    /* power up the chip, and let the LM70 control SI/SO */
    parport_write_data(pp->port, lm70_INIT);

    /* Enable access to our primary data structure via
     * the board info's (void *)controller_data.
     */
    pp->info.controller_data = pp;
    pp->spidev_lm70 = spi_new_device(pp->bitbang.master, &pp->info);
    if (pp->spidev_lm70)
        dev_dbg(&pp->spidev_lm70->dev, "spidev_lm70 at %s\n",
                dev_name(&pp->spidev_lm70->dev));
    else {
        printk(KERN_WARNING "%s: spi_new_device failed\n", DRVNAME);
        status = -ENODEV;
        goto out_bitbang_stop;
    }
    pp->spidev_lm70->bits_per_word = 8;

    lm70llp = pp;
    return;

out_bitbang_stop:
    spi_bitbang_stop(&pp->bitbang);
out_off_and_release:
    /* power down */
    parport_write_data(pp->port, 0);
    mdelay(10);
    parport_release(pp->pd);
out_parport_unreg:
    parport_unregister_device(pd);
out_free_master:
    (void) spi_master_put(master);
out_fail:
    pr_info("%s: spi_lm70llp probe fail, status %d\n", DRVNAME, status);
}

static void spi_lm70llp_detach(struct parport *p)
{
    struct spi_lm70llp      *pp;

    if (!lm70llp || lm70llp->port != p)
        return;

    pp = lm70llp;
    spi_bitbang_stop(&pp->bitbang);

    /* power down */
    parport_write_data(pp->port, 0);

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

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

    lm70llp = NULL;
}


static struct parport_driver spi_lm70llp_drv = {
    .name =     DRVNAME,
    .attach =   spi_lm70llp_attach,
    .detach =   spi_lm70llp_detach,
};

static int __init init_spi_lm70llp(void)
{
    return parport_register_driver(&spi_lm70llp_drv);
}
module_init(init_spi_lm70llp);

static void __exit cleanup_spi_lm70llp(void)
{
    parport_unregister_driver(&spi_lm70llp_drv);
}
module_exit(cleanup_spi_lm70llp);

MODULE_AUTHOR("Kaiwan N Billimoria <[email protected]>");
MODULE_DESCRIPTION(
    "Parport adapter for the National Semiconductor LM70 LLP eval board");
MODULE_LICENSE("GPL");