ads7846.c

Go to the documentation of this file.

/*
 * ADS7846 based touchscreen and sensor driver
 *
 * Copyright (c) 2005 David Brownell
 * Copyright (c) 2006 Nokia Corporation
 * Various changes: Imre Deak <[email protected]>
 *
 * Using code from:
 *  - corgi_ts.c
 *  Copyright (C) 2004-2005 Richard Purdie
 *  - omap_ts.[hc], ads7846.h, ts_osk.c
 *  Copyright (C) 2002 MontaVista Software
 *  Copyright (C) 2004 Texas Instruments
 *  Copyright (C) 2005 Dirk Behme
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 */
#include <linux/types.h>
#include <linux/hwmon.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/input.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/pm.h>
#include <linux/gpio.h>
#include <linux/spi/spi.h>
#include <linux/spi/ads7846.h>
#include <linux/regulator/consumer.h>
#include <linux/module.h>
#include <asm/irq.h>

/*
 * This code has been heavily tested on a Nokia 770, and lightly
 * tested on other ads7846 devices (OSK/Mistral, Lubbock, Spitz).
 * TSC2046 is just newer ads7846 silicon.
 * Support for ads7843 tested on Atmel at91sam926x-EK.
 * Support for ads7845 has only been stubbed in.
 * Support for Analog Devices AD7873 and AD7843 tested.
 *
 * IRQ handling needs a workaround because of a shortcoming in handling
 * edge triggered IRQs on some platforms like the OMAP1/2. These
 * platforms don't handle the ARM lazy IRQ disabling properly, thus we
 * have to maintain our own SW IRQ disabled status. This should be
 * removed as soon as the affected platform's IRQ handling is fixed.
 *
 * App note sbaa036 talks in more detail about accurate sampling...
 * that ought to help in situations like LCDs inducing noise (which
 * can also be helped by using synch signals) and more generally.
 * This driver tries to utilize the measures described in the app
 * note. The strength of filtering can be set in the board-* specific
 * files.
 */

#define TS_POLL_DELAY   1   /* ms delay before the first sample */
#define TS_POLL_PERIOD  5   /* ms delay between samples */

/* this driver doesn't aim at the peak continuous sample rate */
#define SAMPLE_BITS (8 /*cmd*/ + 16 /*sample*/ + 2 /* before, after */)

struct ts_event {
    /*
     * For portability, we can't read 12 bit values using SPI (which
     * would make the controller deliver them as native byte order u16
     * with msbs zeroed).  Instead, we read them as two 8-bit values,
     * *** WHICH NEED BYTESWAPPING *** and range adjustment.
     */
    u16 x;
    u16 y;
    u16 z1, z2;
    bool    ignore;
    u8  x_buf[3];
    u8  y_buf[3];
};

/*
 * We allocate this separately to avoid cache line sharing issues when
 * driver is used with DMA-based SPI controllers (like atmel_spi) on
 * systems where main memory is not DMA-coherent (most non-x86 boards).
 */
struct ads7846_packet {
    u8          read_x, read_y, read_z1, read_z2, pwrdown;
    u16         dummy;      /* for the pwrdown read */
    struct ts_event     tc;
    /* for ads7845 with mpc5121 psc spi we use 3-byte buffers */
    u8          read_x_cmd[3], read_y_cmd[3], pwrdown_cmd[3];
};

struct ads7846 {
    struct input_dev    *input;
    char            phys[32];
    char            name[32];

    struct spi_device   *spi;
    struct regulator    *reg;

#if defined(CONFIG_HWMON) || defined(CONFIG_HWMON_MODULE)
    struct attribute_group  *attr_group;
    struct device       *hwmon;
#endif

    u16         model;
    u16         vref_mv;
    u16         vref_delay_usecs;
    u16         x_plate_ohms;
    u16         pressure_max;

    bool            swap_xy;
    bool            use_internal;

    struct ads7846_packet   *packet;

    struct spi_transfer xfer[18];
    struct spi_message  msg[5];
    int         msg_count;
    wait_queue_head_t   wait;

    bool            pendown;

    int         read_cnt;
    int         read_rep;
    int         last_read;

    u16         debounce_max;
    u16         debounce_tol;
    u16         debounce_rep;

    u16         penirq_recheck_delay_usecs;

    struct mutex        lock;
    bool            stopped;    /* P: lock */
    bool            disabled;   /* P: lock */
    bool            suspended;  /* P: lock */

    int         (*filter)(void *data, int data_idx, int *val);
    void            *filter_data;
    void            (*filter_cleanup)(void *data);
    int         (*get_pendown_state)(void);
    int         gpio_pendown;

    void            (*wait_for_sync)(void);
};

/* leave chip selected when we're done, for quicker re-select? */
#if 0
#define CS_CHANGE(xfer) ((xfer).cs_change = 1)
#else
#define CS_CHANGE(xfer) ((xfer).cs_change = 0)
#endif

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

/* The ADS7846 has touchscreen and other sensors.
 * Earlier ads784x chips are somewhat compatible.
 */
#define ADS_START       (1 << 7)
#define ADS_A2A1A0_d_y      (1 << 4)    /* differential */
#define ADS_A2A1A0_d_z1     (3 << 4)    /* differential */
#define ADS_A2A1A0_d_z2     (4 << 4)    /* differential */
#define ADS_A2A1A0_d_x      (5 << 4)    /* differential */
#define ADS_A2A1A0_temp0    (0 << 4)    /* non-differential */
#define ADS_A2A1A0_vbatt    (2 << 4)    /* non-differential */
#define ADS_A2A1A0_vaux     (6 << 4)    /* non-differential */
#define ADS_A2A1A0_temp1    (7 << 4)    /* non-differential */
#define ADS_8_BIT       (1 << 3)
#define ADS_12_BIT      (0 << 3)
#define ADS_SER         (1 << 2)    /* non-differential */
#define ADS_DFR         (0 << 2)    /* differential */
#define ADS_PD10_PDOWN      (0 << 0)    /* low power mode + penirq */
#define ADS_PD10_ADC_ON     (1 << 0)    /* ADC on */
#define ADS_PD10_REF_ON     (2 << 0)    /* vREF on + penirq */
#define ADS_PD10_ALL_ON     (3 << 0)    /* ADC + vREF on */

#define MAX_12BIT   ((1<<12)-1)

/* leave ADC powered up (disables penirq) between differential samples */
#define READ_12BIT_DFR(x, adc, vref) (ADS_START | ADS_A2A1A0_d_ ## x \
    | ADS_12_BIT | ADS_DFR | \
    (adc ? ADS_PD10_ADC_ON : 0) | (vref ? ADS_PD10_REF_ON : 0))

#define READ_Y(vref)    (READ_12BIT_DFR(y,  1, vref))
#define READ_Z1(vref)   (READ_12BIT_DFR(z1, 1, vref))
#define READ_Z2(vref)   (READ_12BIT_DFR(z2, 1, vref))

#define READ_X(vref)    (READ_12BIT_DFR(x,  1, vref))
#define PWRDOWN     (READ_12BIT_DFR(y,  0, 0))  /* LAST */

/* single-ended samples need to first power up reference voltage;
 * we leave both ADC and VREF powered
 */
#define READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
    | ADS_12_BIT | ADS_SER)

#define REF_ON  (READ_12BIT_DFR(x, 1, 1))
#define REF_OFF (READ_12BIT_DFR(y, 0, 0))

/* Must be called with ts->lock held */
static void ads7846_stop(struct ads7846 *ts)
{
    if (!ts->disabled && !ts->suspended) {
        /* Signal IRQ thread to stop polling and disable the handler. */
        ts->stopped = true;
        mb();
        wake_up(&ts->wait);
        disable_irq(ts->spi->irq);
    }
}

/* Must be called with ts->lock held */
static void ads7846_restart(struct ads7846 *ts)
{
    if (!ts->disabled && !ts->suspended) {
        /* Tell IRQ thread that it may poll the device. */
        ts->stopped = false;
        mb();
        enable_irq(ts->spi->irq);
    }
}

/* Must be called with ts->lock held */
static void __ads7846_disable(struct ads7846 *ts)
{
    ads7846_stop(ts);
    regulator_disable(ts->reg);

    /*
     * We know the chip's in low power mode since we always
     * leave it that way after every request
     */
}

/* Must be called with ts->lock held */
static void __ads7846_enable(struct ads7846 *ts)
{
    regulator_enable(ts->reg);
    ads7846_restart(ts);
}

static void ads7846_disable(struct ads7846 *ts)
{
    mutex_lock(&ts->lock);

    if (!ts->disabled) {

        if  (!ts->suspended)
            __ads7846_disable(ts);

        ts->disabled = true;
    }

    mutex_unlock(&ts->lock);
}

static void ads7846_enable(struct ads7846 *ts)
{
    mutex_lock(&ts->lock);

    if (ts->disabled) {

        ts->disabled = false;

        if (!ts->suspended)
            __ads7846_enable(ts);
    }

    mutex_unlock(&ts->lock);
}

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

/*
 * Non-touchscreen sensors only use single-ended conversions.
 * The range is GND..vREF. The ads7843 and ads7835 must use external vREF;
 * ads7846 lets that pin be unconnected, to use internal vREF.
 */

struct ser_req {
    u8          ref_on;
    u8          command;
    u8          ref_off;
    u16         scratch;
    struct spi_message  msg;
    struct spi_transfer xfer[6];
    /*
     * DMA (thus cache coherency maintenance) requires the
     * transfer buffers to live in their own cache lines.
     */
    __be16 sample ____cacheline_aligned;
};

struct ads7845_ser_req {
    u8          command[3];
    struct spi_message  msg;
    struct spi_transfer xfer[2];
    /*
     * DMA (thus cache coherency maintenance) requires the
     * transfer buffers to live in their own cache lines.
     */
    u8 sample[3] ____cacheline_aligned;
};

static int ads7846_read12_ser(struct device *dev, unsigned command)
{
    struct spi_device *spi = to_spi_device(dev);
    struct ads7846 *ts = dev_get_drvdata(dev);
    struct ser_req *req;
    int status;

    req = kzalloc(sizeof *req, GFP_KERNEL);
    if (!req)
        return -ENOMEM;

    spi_message_init(&req->msg);

    /* maybe turn on internal vREF, and let it settle */
    if (ts->use_internal) {
        req->ref_on = REF_ON;
        req->xfer[0].tx_buf = &req->ref_on;
        req->xfer[0].len = 1;
        spi_message_add_tail(&req->xfer[0], &req->msg);

        req->xfer[1].rx_buf = &req->scratch;
        req->xfer[1].len = 2;

        /* for 1uF, settle for 800 usec; no cap, 100 usec.  */
        req->xfer[1].delay_usecs = ts->vref_delay_usecs;
        spi_message_add_tail(&req->xfer[1], &req->msg);

        /* Enable reference voltage */
        command |= ADS_PD10_REF_ON;
    }

    /* Enable ADC in every case */
    command |= ADS_PD10_ADC_ON;

    /* take sample */
    req->command = (u8) command;
    req->xfer[2].tx_buf = &req->command;
    req->xfer[2].len = 1;
    spi_message_add_tail(&req->xfer[2], &req->msg);

    req->xfer[3].rx_buf = &req->sample;
    req->xfer[3].len = 2;
    spi_message_add_tail(&req->xfer[3], &req->msg);

    /* REVISIT:  take a few more samples, and compare ... */

    /* converter in low power mode & enable PENIRQ */
    req->ref_off = PWRDOWN;
    req->xfer[4].tx_buf = &req->ref_off;
    req->xfer[4].len = 1;
    spi_message_add_tail(&req->xfer[4], &req->msg);

    req->xfer[5].rx_buf = &req->scratch;
    req->xfer[5].len = 2;
    CS_CHANGE(req->xfer[5]);
    spi_message_add_tail(&req->xfer[5], &req->msg);

    mutex_lock(&ts->lock);
    ads7846_stop(ts);
    status = spi_sync(spi, &req->msg);
    ads7846_restart(ts);
    mutex_unlock(&ts->lock);

    if (status == 0) {
        /* on-wire is a must-ignore bit, a BE12 value, then padding */
        status = be16_to_cpu(req->sample);
        status = status >> 3;
        status &= 0x0fff;
    }

    kfree(req);
    return status;
}

static int ads7845_read12_ser(struct device *dev, unsigned command)
{
    struct spi_device *spi = to_spi_device(dev);
    struct ads7846 *ts = dev_get_drvdata(dev);
    struct ads7845_ser_req *req;
    int status;

    req = kzalloc(sizeof *req, GFP_KERNEL);
    if (!req)
        return -ENOMEM;

    spi_message_init(&req->msg);

    req->command[0] = (u8) command;
    req->xfer[0].tx_buf = req->command;
    req->xfer[0].rx_buf = req->sample;
    req->xfer[0].len = 3;
    spi_message_add_tail(&req->xfer[0], &req->msg);

    mutex_lock(&ts->lock);
    ads7846_stop(ts);
    status = spi_sync(spi, &req->msg);
    ads7846_restart(ts);
    mutex_unlock(&ts->lock);

    if (status == 0) {
        /* BE12 value, then padding */
        status = be16_to_cpu(*((u16 *)&req->sample[1]));
        status = status >> 3;
        status &= 0x0fff;
    }

    kfree(req);
    return status;
}

#if defined(CONFIG_HWMON) || defined(CONFIG_HWMON_MODULE)

#define SHOW(name, var, adjust) static ssize_t \
name ## _show(struct device *dev, struct device_attribute *attr, char *buf) \
{ \
    struct ads7846 *ts = dev_get_drvdata(dev); \
    ssize_t v = ads7846_read12_ser(dev, \
            READ_12BIT_SER(var)); \
    if (v < 0) \
        return v; \
    return sprintf(buf, "%u\n", adjust(ts, v)); \
} \
static DEVICE_ATTR(name, S_IRUGO, name ## _show, NULL);


/* Sysfs conventions report temperatures in millidegrees Celsius.
 * ADS7846 could use the low-accuracy two-sample scheme, but can't do the high
 * accuracy scheme without calibration data.  For now we won't try either;
 * userspace sees raw sensor values, and must scale/calibrate appropriately.
 */
static inline unsigned null_adjust(struct ads7846 *ts, ssize_t v)
{
    return v;
}

SHOW(temp0, temp0, null_adjust)     /* temp1_input */
SHOW(temp1, temp1, null_adjust)     /* temp2_input */


/* sysfs conventions report voltages in millivolts.  We can convert voltages
 * if we know vREF.  userspace may need to scale vAUX to match the board's
 * external resistors; we assume that vBATT only uses the internal ones.
 */
static inline unsigned vaux_adjust(struct ads7846 *ts, ssize_t v)
{
    unsigned retval = v;

    /* external resistors may scale vAUX into 0..vREF */
    retval *= ts->vref_mv;
    retval = retval >> 12;

    return retval;
}

static inline unsigned vbatt_adjust(struct ads7846 *ts, ssize_t v)
{
    unsigned retval = vaux_adjust(ts, v);

    /* ads7846 has a resistor ladder to scale this signal down */
    if (ts->model == 7846)
        retval *= 4;

    return retval;
}

SHOW(in0_input, vaux, vaux_adjust)
SHOW(in1_input, vbatt, vbatt_adjust)

static struct attribute *ads7846_attributes[] = {
    &dev_attr_temp0.attr,
    &dev_attr_temp1.attr,
    &dev_attr_in0_input.attr,
    &dev_attr_in1_input.attr,
    NULL,
};

static struct attribute_group ads7846_attr_group = {
    .attrs = ads7846_attributes,
};

static struct attribute *ads7843_attributes[] = {
    &dev_attr_in0_input.attr,
    &dev_attr_in1_input.attr,
    NULL,
};

static struct attribute_group ads7843_attr_group = {
    .attrs = ads7843_attributes,
};

static struct attribute *ads7845_attributes[] = {
    &dev_attr_in0_input.attr,
    NULL,
};

static struct attribute_group ads7845_attr_group = {
    .attrs = ads7845_attributes,
};

static int ads784x_hwmon_register(struct spi_device *spi, struct ads7846 *ts)
{
    struct device *hwmon;
    int err;

    /* hwmon sensors need a reference voltage */
    switch (ts->model) {
    case 7846:
        if (!ts->vref_mv) {
            dev_dbg(&spi->dev, "assuming 2.5V internal vREF\n");
            ts->vref_mv = 2500;
            ts->use_internal = true;
        }
        break;
    case 7845:
    case 7843:
        if (!ts->vref_mv) {
            dev_warn(&spi->dev,
                "external vREF for ADS%d not specified\n",
                ts->model);
            return 0;
        }
        break;
    }

    /* different chips have different sensor groups */
    switch (ts->model) {
    case 7846:
        ts->attr_group = &ads7846_attr_group;
        break;
    case 7845:
        ts->attr_group = &ads7845_attr_group;
        break;
    case 7843:
        ts->attr_group = &ads7843_attr_group;
        break;
    default:
        dev_dbg(&spi->dev, "ADS%d not recognized\n", ts->model);
        return 0;
    }

    err = sysfs_create_group(&spi->dev.kobj, ts->attr_group);
    if (err)
        return err;

    hwmon = hwmon_device_register(&spi->dev);
    if (IS_ERR(hwmon)) {
        sysfs_remove_group(&spi->dev.kobj, ts->attr_group);
        return PTR_ERR(hwmon);
    }

    ts->hwmon = hwmon;
    return 0;
}

static void ads784x_hwmon_unregister(struct spi_device *spi,
                     struct ads7846 *ts)
{
    if (ts->hwmon) {
        sysfs_remove_group(&spi->dev.kobj, ts->attr_group);
        hwmon_device_unregister(ts->hwmon);
    }
}

#else
static inline int ads784x_hwmon_register(struct spi_device *spi,
                     struct ads7846 *ts)
{
    return 0;
}

static inline void ads784x_hwmon_unregister(struct spi_device *spi,
                        struct ads7846 *ts)
{
}
#endif

static ssize_t ads7846_pen_down_show(struct device *dev,
                     struct device_attribute *attr, char *buf)
{
    struct ads7846 *ts = dev_get_drvdata(dev);

    return sprintf(buf, "%u\n", ts->pendown);
}

static DEVICE_ATTR(pen_down, S_IRUGO, ads7846_pen_down_show, NULL);

static ssize_t ads7846_disable_show(struct device *dev,
                     struct device_attribute *attr, char *buf)
{
    struct ads7846 *ts = dev_get_drvdata(dev);

    return sprintf(buf, "%u\n", ts->disabled);
}

static ssize_t ads7846_disable_store(struct device *dev,
                     struct device_attribute *attr,
                     const char *buf, size_t count)
{
    struct ads7846 *ts = dev_get_drvdata(dev);
    unsigned int i;
    int err;

    err = kstrtouint(buf, 10, &i);
    if (err)
        return err;

    if (i)
        ads7846_disable(ts);
    else
        ads7846_enable(ts);

    return count;
}

static DEVICE_ATTR(disable, 0664, ads7846_disable_show, ads7846_disable_store);

static struct attribute *ads784x_attributes[] = {
    &dev_attr_pen_down.attr,
    &dev_attr_disable.attr,
    NULL,
};

static struct attribute_group ads784x_attr_group = {
    .attrs = ads784x_attributes,
};

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

static int get_pendown_state(struct ads7846 *ts)
{
    if (ts->get_pendown_state)
        return ts->get_pendown_state();

    return !gpio_get_value(ts->gpio_pendown);
}

static void null_wait_for_sync(void)
{
}

static int ads7846_debounce_filter(void *ads, int data_idx, int *val)
{
    struct ads7846 *ts = ads;

    if (!ts->read_cnt || (abs(ts->last_read - *val) > ts->debounce_tol)) {
        /* Start over collecting consistent readings. */
        ts->read_rep = 0;
        /*
         * Repeat it, if this was the first read or the read
         * wasn't consistent enough.
         */
        if (ts->read_cnt < ts->debounce_max) {
            ts->last_read = *val;
            ts->read_cnt++;
            return ADS7846_FILTER_REPEAT;
        } else {
            /*
             * Maximum number of debouncing reached and still
             * not enough number of consistent readings. Abort
             * the whole sample, repeat it in the next sampling
             * period.
             */
            ts->read_cnt = 0;
            return ADS7846_FILTER_IGNORE;
        }
    } else {
        if (++ts->read_rep > ts->debounce_rep) {
            /*
             * Got a good reading for this coordinate,
             * go for the next one.
             */
            ts->read_cnt = 0;
            ts->read_rep = 0;
            return ADS7846_FILTER_OK;
        } else {
            /* Read more values that are consistent. */
            ts->read_cnt++;
            return ADS7846_FILTER_REPEAT;
        }
    }
}

static int ads7846_no_filter(void *ads, int data_idx, int *val)
{
    return ADS7846_FILTER_OK;
}

static int ads7846_get_value(struct ads7846 *ts, struct spi_message *m)
{
    struct spi_transfer *t =
        list_entry(m->transfers.prev, struct spi_transfer, transfer_list);

    if (ts->model == 7845) {
        return be16_to_cpup((__be16 *)&(((char*)t->rx_buf)[1])) >> 3;
    } else {
        /*
         * adjust:  on-wire is a must-ignore bit, a BE12 value, then
         * padding; built from two 8 bit values written msb-first.
         */
        return be16_to_cpup((__be16 *)t->rx_buf) >> 3;
    }
}

static void ads7846_update_value(struct spi_message *m, int val)
{
    struct spi_transfer *t =
        list_entry(m->transfers.prev, struct spi_transfer, transfer_list);

    *(u16 *)t->rx_buf = val;
}

static void ads7846_read_state(struct ads7846 *ts)
{
    struct ads7846_packet *packet = ts->packet;
    struct spi_message *m;
    int msg_idx = 0;
    int val;
    int action;
    int error;

    while (msg_idx < ts->msg_count) {

        ts->wait_for_sync();

        m = &ts->msg[msg_idx];
        error = spi_sync(ts->spi, m);
        if (error) {
            dev_err(&ts->spi->dev, "spi_async --> %d\n", error);
            packet->tc.ignore = true;
            return;
        }

        /*
         * Last message is power down request, no need to convert
         * or filter the value.
         */
        if (msg_idx < ts->msg_count - 1) {

            val = ads7846_get_value(ts, m);

            action = ts->filter(ts->filter_data, msg_idx, &val);
            switch (action) {
            case ADS7846_FILTER_REPEAT:
                continue;

            case ADS7846_FILTER_IGNORE:
                packet->tc.ignore = true;
                msg_idx = ts->msg_count - 1;
                continue;

            case ADS7846_FILTER_OK:
                ads7846_update_value(m, val);
                packet->tc.ignore = false;
                msg_idx++;
                break;

            default:
                BUG();
            }
        } else {
            msg_idx++;
        }
    }
}

static void ads7846_report_state(struct ads7846 *ts)
{
    struct ads7846_packet *packet = ts->packet;
    unsigned int Rt;
    u16 x, y, z1, z2;

    /*
     * ads7846_get_value() does in-place conversion (including byte swap)
     * from on-the-wire format as part of debouncing to get stable
     * readings.
     */
    if (ts->model == 7845) {
        x = *(u16 *)packet->tc.x_buf;
        y = *(u16 *)packet->tc.y_buf;
        z1 = 0;
        z2 = 0;
    } else {
        x = packet->tc.x;
        y = packet->tc.y;
        z1 = packet->tc.z1;
        z2 = packet->tc.z2;
    }

    /* range filtering */
    if (x == MAX_12BIT)
        x = 0;

    if (ts->model == 7843) {
        Rt = ts->pressure_max / 2;
    } else if (ts->model == 7845) {
        if (get_pendown_state(ts))
            Rt = ts->pressure_max / 2;
        else
            Rt = 0;
        dev_vdbg(&ts->spi->dev, "x/y: %d/%d, PD %d\n", x, y, Rt);
    } else if (likely(x && z1)) {
        /* compute touch pressure resistance using equation #2 */
        Rt = z2;
        Rt -= z1;
        Rt *= x;
        Rt *= ts->x_plate_ohms;
        Rt /= z1;
        Rt = (Rt + 2047) >> 12;
    } else {
        Rt = 0;
    }

    /*
     * Sample found inconsistent by debouncing or pressure is beyond
     * the maximum. Don't report it to user space, repeat at least
     * once more the measurement
     */
    if (packet->tc.ignore || Rt > ts->pressure_max) {
        dev_vdbg(&ts->spi->dev, "ignored %d pressure %d\n",
             packet->tc.ignore, Rt);
        return;
    }

    /*
     * Maybe check the pendown state before reporting. This discards
     * false readings when the pen is lifted.
     */
    if (ts->penirq_recheck_delay_usecs) {
        udelay(ts->penirq_recheck_delay_usecs);
        if (!get_pendown_state(ts))
            Rt = 0;
    }

    /*
     * NOTE: We can't rely on the pressure to determine the pen down
     * state, even this controller has a pressure sensor. The pressure
     * value can fluctuate for quite a while after lifting the pen and
     * in some cases may not even settle at the expected value.
     *
     * The only safe way to check for the pen up condition is in the
     * timer by reading the pen signal state (it's a GPIO _and_ IRQ).
     */
    if (Rt) {
        struct input_dev *input = ts->input;

        if (ts->swap_xy)
            swap(x, y);

        if (!ts->pendown) {
            input_report_key(input, BTN_TOUCH, 1);
            ts->pendown = true;
            dev_vdbg(&ts->spi->dev, "DOWN\n");
        }

        input_report_abs(input, ABS_X, x);
        input_report_abs(input, ABS_Y, y);
        input_report_abs(input, ABS_PRESSURE, ts->pressure_max - Rt);

        input_sync(input);
        dev_vdbg(&ts->spi->dev, "%4d/%4d/%4d\n", x, y, Rt);
    }
}

static irqreturn_t ads7846_hard_irq(int irq, void *handle)
{
    struct ads7846 *ts = handle;

    return get_pendown_state(ts) ? IRQ_WAKE_THREAD : IRQ_HANDLED;
}


static irqreturn_t ads7846_irq(int irq, void *handle)
{
    struct ads7846 *ts = handle;

    /* Start with a small delay before checking pendown state */
    msleep(TS_POLL_DELAY);

    while (!ts->stopped && get_pendown_state(ts)) {

        /* pen is down, continue with the measurement */
        ads7846_read_state(ts);

        if (!ts->stopped)
            ads7846_report_state(ts);

        wait_event_timeout(ts->wait, ts->stopped,
                   msecs_to_jiffies(TS_POLL_PERIOD));
    }

    if (ts->pendown) {
        struct input_dev *input = ts->input;

        input_report_key(input, BTN_TOUCH, 0);
        input_report_abs(input, ABS_PRESSURE, 0);
        input_sync(input);

        ts->pendown = false;
        dev_vdbg(&ts->spi->dev, "UP\n");
    }

    return IRQ_HANDLED;
}

#ifdef CONFIG_PM_SLEEP
static int ads7846_suspend(struct device *dev)
{
    struct ads7846 *ts = dev_get_drvdata(dev);

    mutex_lock(&ts->lock);

    if (!ts->suspended) {

        if (!ts->disabled)
            __ads7846_disable(ts);

        if (device_may_wakeup(&ts->spi->dev))
            enable_irq_wake(ts->spi->irq);

        ts->suspended = true;
    }

    mutex_unlock(&ts->lock);

    return 0;
}

static int ads7846_resume(struct device *dev)
{
    struct ads7846 *ts = dev_get_drvdata(dev);

    mutex_lock(&ts->lock);

    if (ts->suspended) {

        ts->suspended = false;

        if (device_may_wakeup(&ts->spi->dev))
            disable_irq_wake(ts->spi->irq);

        if (!ts->disabled)
            __ads7846_enable(ts);
    }

    mutex_unlock(&ts->lock);

    return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(ads7846_pm, ads7846_suspend, ads7846_resume);

static int __devinit ads7846_setup_pendown(struct spi_device *spi,
                       struct ads7846 *ts)
{
    struct ads7846_platform_data *pdata = spi->dev.platform_data;
    int err;

    /*
     * REVISIT when the irq can be triggered active-low, or if for some
     * reason the touchscreen isn't hooked up, we don't need to access
     * the pendown state.
     */

    if (pdata->get_pendown_state) {
        ts->get_pendown_state = pdata->get_pendown_state;
    } else if (gpio_is_valid(pdata->gpio_pendown)) {

        err = gpio_request_one(pdata->gpio_pendown, GPIOF_IN,
                       "ads7846_pendown");
        if (err) {
            dev_err(&spi->dev,
                "failed to request/setup pendown GPIO%d: %d\n",
                pdata->gpio_pendown, err);
            return err;
        }

        ts->gpio_pendown = pdata->gpio_pendown;

        if (pdata->gpio_pendown_debounce)
            gpio_set_debounce(pdata->gpio_pendown,
                      pdata->gpio_pendown_debounce);
    } else {
        dev_err(&spi->dev, "no get_pendown_state nor gpio_pendown?\n");
        return -EINVAL;
    }

    return 0;
}

/*
 * Set up the transfers to read touchscreen state; this assumes we
 * use formula #2 for pressure, not #3.
 */
static void __devinit ads7846_setup_spi_msg(struct ads7846 *ts,
                const struct ads7846_platform_data *pdata)
{
    struct spi_message *m = &ts->msg[0];
    struct spi_transfer *x = ts->xfer;
    struct ads7846_packet *packet = ts->packet;
    int vref = pdata->keep_vref_on;

    if (ts->model == 7873) {
        /*
         * The AD7873 is almost identical to the ADS7846
         * keep VREF off during differential/ratiometric
         * conversion modes.
         */
        ts->model = 7846;
        vref = 0;
    }

    ts->msg_count = 1;
    spi_message_init(m);
    m->context = ts;

    if (ts->model == 7845) {
        packet->read_y_cmd[0] = READ_Y(vref);
        packet->read_y_cmd[1] = 0;
        packet->read_y_cmd[2] = 0;
        x->tx_buf = &packet->read_y_cmd[0];
        x->rx_buf = &packet->tc.y_buf[0];
        x->len = 3;
        spi_message_add_tail(x, m);
    } else {
        /* y- still on; turn on only y+ (and ADC) */
        packet->read_y = READ_Y(vref);
        x->tx_buf = &packet->read_y;
        x->len = 1;
        spi_message_add_tail(x, m);

        x++;
        x->rx_buf = &packet->tc.y;
        x->len = 2;
        spi_message_add_tail(x, m);
    }

    /*
     * The first sample after switching drivers can be low quality;
     * optionally discard it, using a second one after the signals
     * have had enough time to stabilize.
     */
    if (pdata->settle_delay_usecs) {
        x->delay_usecs = pdata->settle_delay_usecs;

        x++;
        x->tx_buf = &packet->read_y;
        x->len = 1;
        spi_message_add_tail(x, m);

        x++;
        x->rx_buf = &packet->tc.y;
        x->len = 2;
        spi_message_add_tail(x, m);
    }

    ts->msg_count++;
    m++;
    spi_message_init(m);
    m->context = ts;

    if (ts->model == 7845) {
        x++;
        packet->read_x_cmd[0] = READ_X(vref);
        packet->read_x_cmd[1] = 0;
        packet->read_x_cmd[2] = 0;
        x->tx_buf = &packet->read_x_cmd[0];
        x->rx_buf = &packet->tc.x_buf[0];
        x->len = 3;
        spi_message_add_tail(x, m);
    } else {
        /* turn y- off, x+ on, then leave in lowpower */
        x++;
        packet->read_x = READ_X(vref);
        x->tx_buf = &packet->read_x;
        x->len = 1;
        spi_message_add_tail(x, m);

        x++;
        x->rx_buf = &packet->tc.x;
        x->len = 2;
        spi_message_add_tail(x, m);
    }

    /* ... maybe discard first sample ... */
    if (pdata->settle_delay_usecs) {
        x->delay_usecs = pdata->settle_delay_usecs;

        x++;
        x->tx_buf = &packet->read_x;
        x->len = 1;
        spi_message_add_tail(x, m);

        x++;
        x->rx_buf = &packet->tc.x;
        x->len = 2;
        spi_message_add_tail(x, m);
    }

    /* turn y+ off, x- on; we'll use formula #2 */
    if (ts->model == 7846) {
        ts->msg_count++;
        m++;
        spi_message_init(m);
        m->context = ts;

        x++;
        packet->read_z1 = READ_Z1(vref);
        x->tx_buf = &packet->read_z1;
        x->len = 1;
        spi_message_add_tail(x, m);

        x++;
        x->rx_buf = &packet->tc.z1;
        x->len = 2;
        spi_message_add_tail(x, m);

        /* ... maybe discard first sample ... */
        if (pdata->settle_delay_usecs) {
            x->delay_usecs = pdata->settle_delay_usecs;

            x++;
            x->tx_buf = &packet->read_z1;
            x->len = 1;
            spi_message_add_tail(x, m);

            x++;
            x->rx_buf = &packet->tc.z1;
            x->len = 2;
            spi_message_add_tail(x, m);
        }

        ts->msg_count++;
        m++;
        spi_message_init(m);
        m->context = ts;

        x++;
        packet->read_z2 = READ_Z2(vref);
        x->tx_buf = &packet->read_z2;
        x->len = 1;
        spi_message_add_tail(x, m);

        x++;
        x->rx_buf = &packet->tc.z2;
        x->len = 2;
        spi_message_add_tail(x, m);

        /* ... maybe discard first sample ... */
        if (pdata->settle_delay_usecs) {
            x->delay_usecs = pdata->settle_delay_usecs;

            x++;
            x->tx_buf = &packet->read_z2;
            x->len = 1;
            spi_message_add_tail(x, m);

            x++;
            x->rx_buf = &packet->tc.z2;
            x->len = 2;
            spi_message_add_tail(x, m);
        }
    }

    /* power down */
    ts->msg_count++;
    m++;
    spi_message_init(m);
    m->context = ts;

    if (ts->model == 7845) {
        x++;
        packet->pwrdown_cmd[0] = PWRDOWN;
        packet->pwrdown_cmd[1] = 0;
        packet->pwrdown_cmd[2] = 0;
        x->tx_buf = &packet->pwrdown_cmd[0];
        x->len = 3;
    } else {
        x++;
        packet->pwrdown = PWRDOWN;
        x->tx_buf = &packet->pwrdown;
        x->len = 1;
        spi_message_add_tail(x, m);

        x++;
        x->rx_buf = &packet->dummy;
        x->len = 2;
    }

    CS_CHANGE(*x);
    spi_message_add_tail(x, m);
}

static int __devinit ads7846_probe(struct spi_device *spi)
{
    struct ads7846 *ts;
    struct ads7846_packet *packet;
    struct input_dev *input_dev;
    struct ads7846_platform_data *pdata = spi->dev.platform_data;
    unsigned long irq_flags;
    int err;

    if (!spi->irq) {
        dev_dbg(&spi->dev, "no IRQ?\n");
        return -ENODEV;
    }

    if (!pdata) {
        dev_dbg(&spi->dev, "no platform data?\n");
        return -ENODEV;
    }

    /* don't exceed max specified sample rate */
    if (spi->max_speed_hz > (125000 * SAMPLE_BITS)) {
        dev_dbg(&spi->dev, "f(sample) %d KHz?\n",
                (spi->max_speed_hz/SAMPLE_BITS)/1000);
        return -EINVAL;
    }

    /* We'd set TX word size 8 bits and RX word size to 13 bits ... except
     * that even if the hardware can do that, the SPI controller driver
     * may not.  So we stick to very-portable 8 bit words, both RX and TX.
     */
    spi->bits_per_word = 8;
    spi->mode = SPI_MODE_0;
    err = spi_setup(spi);
    if (err < 0)
        return err;

    ts = kzalloc(sizeof(struct ads7846), GFP_KERNEL);
    packet = kzalloc(sizeof(struct ads7846_packet), GFP_KERNEL);
    input_dev = input_allocate_device();
    if (!ts || !packet || !input_dev) {
        err = -ENOMEM;
        goto err_free_mem;
    }

    dev_set_drvdata(&spi->dev, ts);

    ts->packet = packet;
    ts->spi = spi;
    ts->input = input_dev;
    ts->vref_mv = pdata->vref_mv;
    ts->swap_xy = pdata->swap_xy;

    mutex_init(&ts->lock);
    init_waitqueue_head(&ts->wait);

    ts->model = pdata->model ? : 7846;
    ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
    ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
    ts->pressure_max = pdata->pressure_max ? : ~0;

    if (pdata->filter != NULL) {
        if (pdata->filter_init != NULL) {
            err = pdata->filter_init(pdata, &ts->filter_data);
            if (err < 0)
                goto err_free_mem;
        }
        ts->filter = pdata->filter;
        ts->filter_cleanup = pdata->filter_cleanup;
    } else if (pdata->debounce_max) {
        ts->debounce_max = pdata->debounce_max;
        if (ts->debounce_max < 2)
            ts->debounce_max = 2;
        ts->debounce_tol = pdata->debounce_tol;
        ts->debounce_rep = pdata->debounce_rep;
        ts->filter = ads7846_debounce_filter;
        ts->filter_data = ts;
    } else {
        ts->filter = ads7846_no_filter;
    }

    err = ads7846_setup_pendown(spi, ts);
    if (err)
        goto err_cleanup_filter;

    if (pdata->penirq_recheck_delay_usecs)
        ts->penirq_recheck_delay_usecs =
                pdata->penirq_recheck_delay_usecs;

    ts->wait_for_sync = pdata->wait_for_sync ? : null_wait_for_sync;

    snprintf(ts->phys, sizeof(ts->phys), "%s/input0", dev_name(&spi->dev));
    snprintf(ts->name, sizeof(ts->name), "ADS%d Touchscreen", ts->model);

    input_dev->name = ts->name;
    input_dev->phys = ts->phys;
    input_dev->dev.parent = &spi->dev;

    input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
    input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
    input_set_abs_params(input_dev, ABS_X,
            pdata->x_min ? : 0,
            pdata->x_max ? : MAX_12BIT,
            0, 0);
    input_set_abs_params(input_dev, ABS_Y,
            pdata->y_min ? : 0,
            pdata->y_max ? : MAX_12BIT,
            0, 0);
    input_set_abs_params(input_dev, ABS_PRESSURE,
            pdata->pressure_min, pdata->pressure_max, 0, 0);

    ads7846_setup_spi_msg(ts, pdata);

    ts->reg = regulator_get(&spi->dev, "vcc");
    if (IS_ERR(ts->reg)) {
        err = PTR_ERR(ts->reg);
        dev_err(&spi->dev, "unable to get regulator: %d\n", err);
        goto err_free_gpio;
    }

    err = regulator_enable(ts->reg);
    if (err) {
        dev_err(&spi->dev, "unable to enable regulator: %d\n", err);
        goto err_put_regulator;
    }

    irq_flags = pdata->irq_flags ? : IRQF_TRIGGER_FALLING;
    irq_flags |= IRQF_ONESHOT;

    err = request_threaded_irq(spi->irq, ads7846_hard_irq, ads7846_irq,
                   irq_flags, spi->dev.driver->name, ts);
    if (err && !pdata->irq_flags) {
        dev_info(&spi->dev,
            "trying pin change workaround on irq %d\n", spi->irq);
        irq_flags |= IRQF_TRIGGER_RISING;
        err = request_threaded_irq(spi->irq,
                  ads7846_hard_irq, ads7846_irq,
                  irq_flags, spi->dev.driver->name, ts);
    }

    if (err) {
        dev_dbg(&spi->dev, "irq %d busy?\n", spi->irq);
        goto err_disable_regulator;
    }

    err = ads784x_hwmon_register(spi, ts);
    if (err)
        goto err_free_irq;

    dev_info(&spi->dev, "touchscreen, irq %d\n", spi->irq);

    /*
     * Take a first sample, leaving nPENIRQ active and vREF off; avoid
     * the touchscreen, in case it's not connected.
     */
    if (ts->model == 7845)
        ads7845_read12_ser(&spi->dev, PWRDOWN);
    else
        (void) ads7846_read12_ser(&spi->dev, READ_12BIT_SER(vaux));

    err = sysfs_create_group(&spi->dev.kobj, &ads784x_attr_group);
    if (err)
        goto err_remove_hwmon;

    err = input_register_device(input_dev);
    if (err)
        goto err_remove_attr_group;

    device_init_wakeup(&spi->dev, pdata->wakeup);

    return 0;

 err_remove_attr_group:
    sysfs_remove_group(&spi->dev.kobj, &ads784x_attr_group);
 err_remove_hwmon:
    ads784x_hwmon_unregister(spi, ts);
 err_free_irq:
    free_irq(spi->irq, ts);
 err_disable_regulator:
    regulator_disable(ts->reg);
 err_put_regulator:
    regulator_put(ts->reg);
 err_free_gpio:
    if (!ts->get_pendown_state)
        gpio_free(ts->gpio_pendown);
 err_cleanup_filter:
    if (ts->filter_cleanup)
        ts->filter_cleanup(ts->filter_data);
 err_free_mem:
    input_free_device(input_dev);
    kfree(packet);
    kfree(ts);
    return err;
}

static int __devexit ads7846_remove(struct spi_device *spi)
{
    struct ads7846 *ts = dev_get_drvdata(&spi->dev);

    device_init_wakeup(&spi->dev, false);

    sysfs_remove_group(&spi->dev.kobj, &ads784x_attr_group);

    ads7846_disable(ts);
    free_irq(ts->spi->irq, ts);

    input_unregister_device(ts->input);

    ads784x_hwmon_unregister(spi, ts);

    regulator_disable(ts->reg);
    regulator_put(ts->reg);

    if (!ts->get_pendown_state) {
        /*
         * If we are not using specialized pendown method we must
         * have been relying on gpio we set up ourselves.
         */
        gpio_free(ts->gpio_pendown);
    }

    if (ts->filter_cleanup)
        ts->filter_cleanup(ts->filter_data);

    kfree(ts->packet);
    kfree(ts);

    dev_dbg(&spi->dev, "unregistered touchscreen\n");

    return 0;
}

static struct spi_driver ads7846_driver = {
    .driver = {
        .name   = "ads7846",
        .owner  = THIS_MODULE,
        .pm = &ads7846_pm,
    },
    .probe      = ads7846_probe,
    .remove     = __devexit_p(ads7846_remove),
};

module_spi_driver(ads7846_driver);

MODULE_DESCRIPTION("ADS7846 TouchScreen Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:ads7846");