// SPDX-License-Identifier: GPL-2.0-only
/*
 * ADS7846 based touchscreen and sensor driver
 *
 * Copyright (c) 2005 David Brownell
 * Copyright (c) 2006 Nokia Corporation
 * Various changes: Imre Deak <imre.deak@nokia.com>
 *
 * 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
 */
#include <linux/types.h>
#include <linux/hwmon.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/input.h>
#include <linux/input/touchscreen.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/pm.h>
#include <linux/property.h>
#include <linux/gpio/consumer.h>
#include <linux/spi/spi.h>
#include <linux/spi/ads7846.h>
#include <linux/regulator/consumer.h>
#include <linux/module.h>
#include <linux/unaligned.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 ads7846_buf {
        u8 cmd;
        __be16 data;
} __packed;

struct ads7846_buf_layout {
        unsigned int offset;
        unsigned int count;
        unsigned int skip;
};

/*
 * 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 {
        unsigned int count;
        unsigned int count_skip;
        unsigned int cmds;
        unsigned int last_cmd_idx;
        struct ads7846_buf_layout l[5];
        struct ads7846_buf *rx;
        struct ads7846_buf *tx;

        struct ads7846_buf pwrdown_cmd;

        bool ignore;
        u16 x, y, z1, z2;
};

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

        struct spi_device       *spi;
        struct regulator        *reg;

        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 touchscreen_properties core_prop;

        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;
        int                     (*get_pendown_state)(void);
        struct gpio_desc        *gpio_pendown;
        struct gpio_desc        *gpio_hsync;

        void                    (*wait_for_sync)(void);
};

enum ads7846_filter {
        ADS7846_FILTER_OK,
        ADS7846_FILTER_REPEAT,
        ADS7846_FILTER_IGNORE,
};

/* 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))

/* Order commands in the most optimal way to reduce Vref switching and
 * settling time:
 * Measure:  X; Vref: X+, X-; IN: Y+
 * Measure:  Y; Vref: Y+, Y-; IN: X+
 * Measure: Z1; Vref: Y+, X-; IN: X+
 * Measure: Z2; Vref: Y+, X-; IN: Y-
 */
enum ads7846_cmds {
        ADS7846_X,
        ADS7846_Y,
        ADS7846_Z1,
        ADS7846_Z2,
        ADS7846_PWDOWN,
};

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

        return gpiod_get_value(ts->gpio_pendown);
}

static void ads7846_report_pen_up(struct ads7846 *ts)
{
        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");
}

/* 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) {
                /* Check if pen was released since last stop */
                if (ts->pendown && !get_pendown_state(ts))
                        ads7846_report_pen_up(ts);

                /* 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)
{
        int error;

        error = regulator_enable(ts->reg);
        if (error != 0)
                dev_err(&ts->spi->dev, "Failed to enable supply: %d\n", error);

        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[8];
        /*
         * 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_obj(*req);
        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.value = ts->vref_delay_usecs;
                req->xfer[1].delay.unit = SPI_DELAY_UNIT_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;
        spi_message_add_tail(&req->xfer[5], &req->msg);

        /* clear the command register */
        req->scratch = 0;
        req->xfer[6].tx_buf = &req->scratch;
        req->xfer[6].len = 1;
        spi_message_add_tail(&req->xfer[6], &req->msg);

        req->xfer[7].rx_buf = &req->scratch;
        req->xfer[7].len = 2;
        CS_CHANGE(req->xfer[7]);
        spi_message_add_tail(&req->xfer[7], &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_obj(*req);
        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 = get_unaligned_be16(&req->sample[1]);
                status = status >> 3;
                status &= 0x0fff;
        }

        kfree(req);
        return status;
}

#if IS_ENABLED(CONFIG_HWMON)

#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(&ts->spi->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 umode_t ads7846_is_visible(struct kobject *kobj, struct attribute *attr,
                                  int index)
{
        struct device *dev = kobj_to_dev(kobj);
        struct ads7846 *ts = dev_get_drvdata(dev);

        if (ts->model == 7843 && index < 2)     /* in0, in1 */
                return 0;
        if (ts->model == 7845 && index != 2)    /* in0 */
                return 0;

        return attr->mode;
}

static struct attribute *ads7846_attributes[] = {
        &dev_attr_temp0.attr,           /* 0 */
        &dev_attr_temp1.attr,           /* 1 */
        &dev_attr_in0_input.attr,       /* 2 */
        &dev_attr_in1_input.attr,       /* 3 */
        NULL,
};

static const struct attribute_group ads7846_attr_group = {
        .attrs = ads7846_attributes,
        .is_visible = ads7846_is_visible,
};
__ATTRIBUTE_GROUPS(ads7846_attr);

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

        /* 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;
        }

        hwmon = devm_hwmon_device_register_with_groups(&spi->dev,
                                                       spi->modalias, ts,
                                                       ads7846_attr_groups);

        return PTR_ERR_OR_ZERO(hwmon);
}

#else
static inline int ads784x_hwmon_register(struct spi_device *spi,
                                         struct ads7846 *ts)
{
        return 0;
}
#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_attrs[] = {
        &dev_attr_pen_down.attr,
        &dev_attr_disable.attr,
        NULL,
};
ATTRIBUTE_GROUPS(ads784x);

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

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_buf *buf)
{
        int value;

        value = be16_to_cpup(&buf->data);

        /* enforce ADC output is 12 bits width */
        return (value >> 3) & 0xfff;
}

static void ads7846_set_cmd_val(struct ads7846 *ts, enum ads7846_cmds cmd_idx,
                                u16 val)
{
        struct ads7846_packet *packet = ts->packet;

        switch (cmd_idx) {
        case ADS7846_Y:
                packet->y = val;
                break;
        case ADS7846_X:
                packet->x = val;
                break;
        case ADS7846_Z1:
                packet->z1 = val;
                break;
        case ADS7846_Z2:
                packet->z2 = val;
                break;
        default:
                WARN_ON_ONCE(1);
        }
}

static u8 ads7846_get_cmd(enum ads7846_cmds cmd_idx, int vref)
{
        switch (cmd_idx) {
        case ADS7846_Y:
                return READ_Y(vref);
        case ADS7846_X:
                return READ_X(vref);

        /* 7846 specific commands  */
        case ADS7846_Z1:
                return READ_Z1(vref);
        case ADS7846_Z2:
                return READ_Z2(vref);
        case ADS7846_PWDOWN:
                return PWRDOWN;
        default:
                WARN_ON_ONCE(1);
        }

        return 0;
}

static bool ads7846_cmd_need_settle(enum ads7846_cmds cmd_idx)
{
        switch (cmd_idx) {
        case ADS7846_X:
        case ADS7846_Y:
        case ADS7846_Z1:
        case ADS7846_Z2:
                return true;
        case ADS7846_PWDOWN:
                return false;
        default:
                WARN_ON_ONCE(1);
        }

        return false;
}

static int ads7846_filter(struct ads7846 *ts)
{
        struct ads7846_packet *packet = ts->packet;
        int action;
        int val;
        unsigned int cmd_idx, b;

        packet->ignore = false;
        for (cmd_idx = packet->last_cmd_idx; cmd_idx < packet->cmds - 1; cmd_idx++) {
                struct ads7846_buf_layout *l = &packet->l[cmd_idx];

                packet->last_cmd_idx = cmd_idx;

                for (b = l->skip; b < l->count; b++) {
                        val = ads7846_get_value(&packet->rx[l->offset + b]);

                        action = ts->filter(ts->filter_data, cmd_idx, &val);
                        if (action == ADS7846_FILTER_REPEAT) {
                                if (b == l->count - 1)
                                        return -EAGAIN;
                        } else if (action == ADS7846_FILTER_OK) {
                                ads7846_set_cmd_val(ts, cmd_idx, val);
                                break;
                        } else {
                                packet->ignore = true;
                                return 0;
                        }
                }
        }

        return 0;
}

static void ads7846_wait_for_hsync(struct ads7846 *ts)
{
        if (ts->wait_for_sync) {
                ts->wait_for_sync();
                return;
        }

        if (!ts->gpio_hsync)
                return;

        /*
         * Wait for HSYNC to assert the line should be flagged
         * as active low so here we are waiting for it to assert
         */
        while (!gpiod_get_value(ts->gpio_hsync))
                cpu_relax();

        /* Then we wait for it do de-assert */
        while (gpiod_get_value(ts->gpio_hsync))
                cpu_relax();
}

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

        packet->last_cmd_idx = 0;

        while (true) {
                ads7846_wait_for_hsync(ts);

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

                error = ads7846_filter(ts);
                if (error)
                        continue;

                return;
        }
}

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

        x = packet->x;
        y = packet->y;
        if (ts->model == 7845) {
                z1 = 0;
                z2 = 0;
        } else {
                z1 = packet->z1;
                z2 = packet->z2;
        }

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

        if (ts->model == 7843 || ts->model == 7845) {
                Rt = ts->pressure_max / 2;
        } else if (likely(x && z1)) {
                /* compute touch pressure resistance using equation #2 */
                Rt = z2;
                Rt -= z1;
                Rt *= ts->x_plate_ohms;
                Rt = DIV_ROUND_CLOSEST(Rt, 16);
                Rt *= x;
                Rt /= z1;
                Rt = DIV_ROUND_CLOSEST(Rt, 256);
        } 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->ignore || Rt > ts->pressure_max) {
                dev_vdbg(&ts->spi->dev, "ignored %d pressure %d\n",
                         packet->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->pendown) {
                        input_report_key(input, BTN_TOUCH, 1);
                        ts->pendown = true;
                        dev_vdbg(&ts->spi->dev, "DOWN\n");
                }

                touchscreen_report_pos(input, &ts->core_prop, x, y, false);
                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 && !ts->stopped)
                ads7846_report_pen_up(ts);

        return IRQ_HANDLED;
}

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;
}

static DEFINE_SIMPLE_DEV_PM_OPS(ads7846_pm, ads7846_suspend, ads7846_resume);

static int ads7846_setup_pendown(struct spi_device *spi,
                                 struct ads7846 *ts,
                                 const struct ads7846_platform_data *pdata)
{
        /*
         * 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 {
                ts->gpio_pendown = devm_gpiod_get(&spi->dev, "pendown", GPIOD_IN);
                if (IS_ERR(ts->gpio_pendown)) {
                        dev_err(&spi->dev, "failed to request pendown GPIO\n");
                        return PTR_ERR(ts->gpio_pendown);
                }
                if (pdata->gpio_pendown_debounce)
                        gpiod_set_debounce(ts->gpio_pendown,
                                           pdata->gpio_pendown_debounce);
        }

        return 0;
}

/*
 * Set up the transfers to read touchscreen state; this assumes we
 * use formula #2 for pressure, not #3.
 */
static int 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;
        unsigned int count, offset = 0;
        unsigned int cmd_idx, b;
        unsigned long time;
        size_t size = 0;

        /* time per bit */
        time = NSEC_PER_SEC / ts->spi->max_speed_hz;

        count = pdata->settle_delay_usecs * NSEC_PER_USEC / time;
        packet->count_skip = DIV_ROUND_UP(count, 24);

        if (ts->debounce_max && ts->debounce_rep)
                /* ads7846_debounce_filter() is making ts->debounce_rep + 2
                 * reads. So we need to get all samples for normal case. */
                packet->count = ts->debounce_rep + 2;
        else
                packet->count = 1;

        if (ts->model == 7846)
                packet->cmds = 5; /* x, y, z1, z2, pwdown */
        else
                packet->cmds = 3; /* x, y, pwdown */

        for (cmd_idx = 0; cmd_idx < packet->cmds; cmd_idx++) {
                struct ads7846_buf_layout *l = &packet->l[cmd_idx];
                unsigned int max_count;

                if (cmd_idx == packet->cmds - 1)
                        cmd_idx = ADS7846_PWDOWN;

                if (ads7846_cmd_need_settle(cmd_idx))
                        max_count = packet->count + packet->count_skip;
                else
                        max_count = packet->count;

                l->offset = offset;
                offset += max_count;
                l->count = max_count;
                l->skip = packet->count_skip;
                size += sizeof(*packet->tx) * max_count;
        }

        packet->tx = devm_kzalloc(&ts->spi->dev, size, GFP_KERNEL);
        if (!packet->tx)
                return -ENOMEM;

        packet->rx = devm_kzalloc(&ts->spi->dev, size, GFP_KERNEL);
        if (!packet->rx)
                return -ENOMEM;

        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;

        for (cmd_idx = 0; cmd_idx < packet->cmds; cmd_idx++) {
                struct ads7846_buf_layout *l = &packet->l[cmd_idx];
                u8 cmd;

                if (cmd_idx == packet->cmds - 1)
                        cmd_idx = ADS7846_PWDOWN;

                cmd = ads7846_get_cmd(cmd_idx, vref);

                for (b = 0; b < l->count; b++)
                        packet->tx[l->offset + b].cmd = cmd;
        }

        x->tx_buf = packet->tx;
        x->rx_buf = packet->rx;
        x->len = size;
        spi_message_add_tail(x, m);

        return 0;
}

static const struct of_device_id ads7846_dt_ids[] = {
        { .compatible = "ti,tsc2046",   .data = (void *) 7846 },
        { .compatible = "ti,ads7843",   .data = (void *) 7843 },
        { .compatible = "ti,ads7845",   .data = (void *) 7845 },
        { .compatible = "ti,ads7846",   .data = (void *) 7846 },
        { .compatible = "ti,ads7873",   .data = (void *) 7873 },
        { }
};
MODULE_DEVICE_TABLE(of, ads7846_dt_ids);

static const struct spi_device_id ads7846_spi_ids[] = {
        { "tsc2046", 7846 },
        { "ads7843", 7843 },
        { "ads7845", 7845 },
        { "ads7846", 7846 },
        { "ads7873", 7873 },
        { },
};
MODULE_DEVICE_TABLE(spi, ads7846_spi_ids);

static const struct ads7846_platform_data *ads7846_get_props(struct device *dev)
{
        struct ads7846_platform_data *pdata;
        u32 value;

        pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
        if (!pdata)
                return ERR_PTR(-ENOMEM);

        pdata->model = (uintptr_t)device_get_match_data(dev);

        device_property_read_u16(dev, "ti,vref-delay-usecs",
                                 &pdata->vref_delay_usecs);
        device_property_read_u16(dev, "ti,vref-mv", &pdata->vref_mv);
        pdata->keep_vref_on = device_property_read_bool(dev, "ti,keep-vref-on");

        pdata->swap_xy = device_property_read_bool(dev, "ti,swap-xy");

        device_property_read_u16(dev, "ti,settle-delay-usec",
                                 &pdata->settle_delay_usecs);
        device_property_read_u16(dev, "ti,penirq-recheck-delay-usecs",
                                 &pdata->penirq_recheck_delay_usecs);

        device_property_read_u16(dev, "ti,x-plate-ohms", &pdata->x_plate_ohms);
        device_property_read_u16(dev, "ti,y-plate-ohms", &pdata->y_plate_ohms);

        device_property_read_u16(dev, "ti,x-min", &pdata->x_min);
        device_property_read_u16(dev, "ti,y-min", &pdata->y_min);
        device_property_read_u16(dev, "ti,x-max", &pdata->x_max);
        device_property_read_u16(dev, "ti,y-max", &pdata->y_max);

        /*
         * touchscreen-max-pressure gets parsed during
         * touchscreen_parse_properties()
         */
        device_property_read_u16(dev, "ti,pressure-min", &pdata->pressure_min);
        if (!device_property_read_u32(dev, "touchscreen-min-pressure", &value))
                pdata->pressure_min = (u16) value;
        device_property_read_u16(dev, "ti,pressure-max", &pdata->pressure_max);

        device_property_read_u16(dev, "ti,debounce-max", &pdata->debounce_max);
        if (!device_property_read_u32(dev, "touchscreen-average-samples", &value))
                pdata->debounce_max = (u16) value;
        device_property_read_u16(dev, "ti,debounce-tol", &pdata->debounce_tol);
        device_property_read_u16(dev, "ti,debounce-rep", &pdata->debounce_rep);

        device_property_read_u32(dev, "ti,pendown-gpio-debounce",
                             &pdata->gpio_pendown_debounce);

        pdata->wakeup = device_property_read_bool(dev, "wakeup-source") ||
                        device_property_read_bool(dev, "linux,wakeup");

        return pdata;
}

static void ads7846_regulator_disable(void *regulator)
{
        regulator_disable(regulator);
}

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

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

        /* don't exceed max specified sample rate */
        if (spi->max_speed_hz > (125000 * SAMPLE_BITS)) {
                dev_err(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_X_MASK;
        spi->mode |= SPI_MODE_0;
        err = spi_setup(spi);
        if (err < 0)
                return err;

        ts = devm_kzalloc(dev, sizeof(struct ads7846), GFP_KERNEL);
        if (!ts)
                return -ENOMEM;

        packet = devm_kzalloc(dev, sizeof(struct ads7846_packet), GFP_KERNEL);
        if (!packet)
                return -ENOMEM;

        input_dev = devm_input_allocate_device(dev);
        if (!input_dev)
                return -ENOMEM;

        spi_set_drvdata(spi, ts);

        ts->packet = packet;
        ts->spi = spi;
        ts->input = input_dev;

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

        pdata = dev_get_platdata(dev);
        if (!pdata) {
                pdata = ads7846_get_props(dev);
                if (IS_ERR(pdata))
                        return PTR_ERR(pdata);
        }

        ts->model = pdata->model ? : 7846;
        ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
        ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
        ts->vref_mv = pdata->vref_mv;

        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, pdata);
        if (err)
                return err;

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

        ts->wait_for_sync = pdata->wait_for_sync;

        ts->gpio_hsync = devm_gpiod_get_optional(dev, "ti,hsync", GPIOD_IN);
        if (IS_ERR(ts->gpio_hsync))
                return PTR_ERR(ts->gpio_hsync);

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

        input_dev->name = ts->name;
        input_dev->phys = ts->phys;

        input_dev->id.bustype = BUS_SPI;
        input_dev->id.product = pdata->model;

        input_set_capability(input_dev, EV_KEY, 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);
        if (ts->model != 7845)
                input_set_abs_params(input_dev, ABS_PRESSURE,
                                pdata->pressure_min, pdata->pressure_max, 0, 0);

        /*
         * Parse common framework properties. Must be done here to ensure the
         * correct behaviour in case of using the legacy vendor bindings. The
         * general binding value overrides the vendor specific one.
         */
        touchscreen_parse_properties(ts->input, false, &ts->core_prop);
        ts->pressure_max = input_abs_get_max(input_dev, ABS_PRESSURE) ? : ~0;

        /*
         * Check if legacy ti,swap-xy binding is used instead of
         * touchscreen-swapped-x-y
         */
        if (!ts->core_prop.swap_x_y && pdata->swap_xy) {
                swap(input_dev->absinfo[ABS_X], input_dev->absinfo[ABS_Y]);
                ts->core_prop.swap_x_y = true;
        }

        ads7846_setup_spi_msg(ts, pdata);

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

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

        err = devm_add_action_or_reset(dev, ads7846_regulator_disable, ts->reg);
        if (err)
                return err;

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

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

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

        err = ads784x_hwmon_register(spi, ts);
        if (err)
                return err;

        dev_info(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(dev, PWRDOWN);
        else
                (void) ads7846_read12_ser(dev, READ_12BIT_SER(vaux));

        err = input_register_device(input_dev);
        if (err)
                return err;

        device_init_wakeup(dev, pdata->wakeup);

        /*
         * If device does not carry platform data we must have allocated it
         * when parsing DT data.
         */
        if (!dev_get_platdata(dev))
                devm_kfree(dev, (void *)pdata);

        return 0;
}

static void ads7846_remove(struct spi_device *spi)
{
        struct ads7846 *ts = spi_get_drvdata(spi);

        ads7846_stop(ts);
}

static struct spi_driver ads7846_driver = {
        .driver = {
                .name           = "ads7846",
                .dev_groups     = ads784x_groups,
                .pm             = pm_sleep_ptr(&ads7846_pm),
                .of_match_table = ads7846_dt_ids,
        },
        .probe          = ads7846_probe,
        .remove         = ads7846_remove,
        .id_table       = ads7846_spi_ids,
};

module_spi_driver(ads7846_driver);

MODULE_DESCRIPTION("ADS7846 TouchScreen Driver");
MODULE_LICENSE("GPL");