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/*

 * spi_lm70llp.c - driver for lm70llp eval board for the LM70 sensor

 *

 * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>

 *

 * 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.

 *

 * The LM70 is a temperature sensor chip from National Semiconductor; its

 * datasheet is available at http://www.national.com/pf/LM/LM70.html

 *

 * 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.

 */

#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);

        parport_write_data(pp->port, data | nCS);

}

static inline void assertCS(struct spi_lm70llp *pp)

{

        u8 data = parport_read_data(pp->port);

        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 );

}

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

#define EXPAND_BITBANG_TXRX 1

#include <linux/spi/spi_bitbang.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)

{

        static u32 sio=0;

        static int first_time=1;

        /* First time: perform SPI bitbang and return the LSB of

         * the result of the SPI call.

         */

        if (first_time) {

                sio = bitbang_txrx_be_cpha0(spi, nsecs, 0, word, bits);

                first_time=0;

                return (sio & 0x00ff);

        }

        /* Return the MSB of the result of the SPI call */

        else {

                first_time=1;

                return (sio >> 8);

        }

}

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);

        master->bus_num = -1;   /* dynamic alloc of a bus number */

        master->num_chipselect = 1;

        /*

         * 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",

                                pp->spidev_lm70->dev.bus_id);

        else {

                printk(KERN_WARNING "%s: spi_new_device failed\n", DRVNAME);

                status = -ENODEV;

                goto out_bitbang_stop;

        }

        pp->spidev_lm70->bits_per_word = 16;

        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);

        msleep(10);

        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 <kaiwan@designergraphix.com>");

MODULE_DESCRIPTION(

        "Parport adapter for the National Semiconductor LM70 LLP eval board");

MODULE_LICENSE("GPL");