// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Touch Screen driver for EETI's I2C connected touch screen panels
 *   Copyright (c) 2009,2018 Daniel Mack <daniel@zonque.org>
 *
 * See EETI's software guide for the protocol specification:
 *   http://home.eeti.com.tw/documentation.html
 *
 * Based on migor_ts.c
 *   Copyright (c) 2008 Magnus Damm
 *   Copyright (c) 2007 Ujjwal Pande <ujjwal@kenati.com>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/input.h>
#include <linux/input/touchscreen.h>
#include <linux/interrupt.h>
#include <linux/i2c.h>
#include <linux/timer.h>
#include <linux/gpio/consumer.h>
#include <linux/of.h>
#include <linux/slab.h>
#include <asm/unaligned.h>

struct eeti_ts {
        struct i2c_client *client;
        struct input_dev *input;
        struct gpio_desc *attn_gpio;
        struct touchscreen_properties props;
        struct mutex mutex;
        bool running;
};

#define EETI_TS_BITDEPTH        (11)
#define EETI_MAXVAL             ((1 << (EETI_TS_BITDEPTH + 1)) - 1)

#define REPORT_BIT_PRESSED      BIT(0)
#define REPORT_BIT_AD0          BIT(1)
#define REPORT_BIT_AD1          BIT(2)
#define REPORT_BIT_HAS_PRESSURE BIT(6)
#define REPORT_RES_BITS(v)      (((v) >> 1) + EETI_TS_BITDEPTH)

static void eeti_ts_report_event(struct eeti_ts *eeti, u8 *buf)
{
        unsigned int res;
        u16 x, y;

        res = REPORT_RES_BITS(buf[0] & (REPORT_BIT_AD0 | REPORT_BIT_AD1));

        x = get_unaligned_be16(&buf[1]);
        y = get_unaligned_be16(&buf[3]);

        /* fix the range to 11 bits */
        x >>= res - EETI_TS_BITDEPTH;
        y >>= res - EETI_TS_BITDEPTH;

        if (buf[0] & REPORT_BIT_HAS_PRESSURE)
                input_report_abs(eeti->input, ABS_PRESSURE, buf[5]);

        touchscreen_report_pos(eeti->input, &eeti->props, x, y, false);
        input_report_key(eeti->input, BTN_TOUCH, buf[0] & REPORT_BIT_PRESSED);
        input_sync(eeti->input);
}

static int eeti_ts_read(struct eeti_ts *eeti)
{
        int len, error;
        char buf[6];

        len = i2c_master_recv(eeti->client, buf, sizeof(buf));
        if (len != sizeof(buf)) {
                error = len < 0 ? len : -EIO;
                dev_err(&eeti->client->dev,
                        "failed to read touchscreen data: %d\n",
                        error);
                return error;
        }

        /* Motion packet */
        if (buf[0] & 0x80)
                eeti_ts_report_event(eeti, buf);

        return 0;
}

static irqreturn_t eeti_ts_isr(int irq, void *dev_id)
{
        struct eeti_ts *eeti = dev_id;
        int error;

        mutex_lock(&eeti->mutex);

        do {
                /*
                 * If we have attention GPIO, trust it. Otherwise we'll read
                 * once and exit. We assume that in this case we are using
                 * level triggered interrupt and it will get raised again
                 * if/when there is more data.
                 */
                if (eeti->attn_gpio &&
                    !gpiod_get_value_cansleep(eeti->attn_gpio)) {
                        break;
                }

                error = eeti_ts_read(eeti);
                if (error)
                        break;

        } while (eeti->running && eeti->attn_gpio);

        mutex_unlock(&eeti->mutex);
        return IRQ_HANDLED;
}

static void eeti_ts_start(struct eeti_ts *eeti)
{
        mutex_lock(&eeti->mutex);

        eeti->running = true;
        enable_irq(eeti->client->irq);

        /*
         * Kick the controller in case we are using edge interrupt and
         * we missed our edge while interrupt was disabled. We expect
         * the attention GPIO to be wired in this case.
         */
        if (eeti->attn_gpio && gpiod_get_value_cansleep(eeti->attn_gpio))
                eeti_ts_read(eeti);

        mutex_unlock(&eeti->mutex);
}

static void eeti_ts_stop(struct eeti_ts *eeti)
{
        /*
         * Not locking here, just setting a flag and expect that the
         * interrupt thread will notice the flag eventually.
         */
        eeti->running = false;
        wmb();
        disable_irq(eeti->client->irq);
}

static int eeti_ts_open(struct input_dev *dev)
{
        struct eeti_ts *eeti = input_get_drvdata(dev);

        eeti_ts_start(eeti);

        return 0;
}

static void eeti_ts_close(struct input_dev *dev)
{
        struct eeti_ts *eeti = input_get_drvdata(dev);

        eeti_ts_stop(eeti);
}

static int eeti_ts_probe(struct i2c_client *client,
                         const struct i2c_device_id *idp)
{
        struct device *dev = &client->dev;
        struct eeti_ts *eeti;
        struct input_dev *input;
        int error;

        /*
         * In contrast to what's described in the datasheet, there seems
         * to be no way of probing the presence of that device using I2C
         * commands. So we need to blindly believe it is there, and wait
         * for interrupts to occur.
         */

        eeti = devm_kzalloc(dev, sizeof(*eeti), GFP_KERNEL);
        if (!eeti) {
                dev_err(dev, "failed to allocate driver data\n");
                return -ENOMEM;
        }

        mutex_init(&eeti->mutex);

        input = devm_input_allocate_device(dev);
        if (!input) {
                dev_err(dev, "Failed to allocate input device.\n");
                return -ENOMEM;
        }

        input_set_capability(input, EV_KEY, BTN_TOUCH);

        input_set_abs_params(input, ABS_X, 0, EETI_MAXVAL, 0, 0);
        input_set_abs_params(input, ABS_Y, 0, EETI_MAXVAL, 0, 0);
        input_set_abs_params(input, ABS_PRESSURE, 0, 0xff, 0, 0);

        touchscreen_parse_properties(input, false, &eeti->props);

        input->name = client->name;
        input->id.bustype = BUS_I2C;
        input->open = eeti_ts_open;
        input->close = eeti_ts_close;

        eeti->client = client;
        eeti->input = input;

        eeti->attn_gpio = devm_gpiod_get_optional(dev, "attn", GPIOD_IN);
        if (IS_ERR(eeti->attn_gpio))
                return PTR_ERR(eeti->attn_gpio);

        i2c_set_clientdata(client, eeti);
        input_set_drvdata(input, eeti);

        error = devm_request_threaded_irq(dev, client->irq,
                                          NULL, eeti_ts_isr,
                                          IRQF_ONESHOT,
                                          client->name, eeti);
        if (error) {
                dev_err(dev, "Unable to request touchscreen IRQ: %d\n",
                        error);
                return error;
        }

        /*
         * Disable the device for now. It will be enabled once the
         * input device is opened.
         */
        eeti_ts_stop(eeti);

        error = input_register_device(input);
        if (error)
                return error;

        return 0;
}

static int __maybe_unused eeti_ts_suspend(struct device *dev)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct eeti_ts *eeti = i2c_get_clientdata(client);
        struct input_dev *input_dev = eeti->input;

        mutex_lock(&input_dev->mutex);

        if (input_dev->users)
                eeti_ts_stop(eeti);

        mutex_unlock(&input_dev->mutex);

        if (device_may_wakeup(&client->dev))
                enable_irq_wake(client->irq);

        return 0;
}

static int __maybe_unused eeti_ts_resume(struct device *dev)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct eeti_ts *eeti = i2c_get_clientdata(client);
        struct input_dev *input_dev = eeti->input;

        if (device_may_wakeup(&client->dev))
                disable_irq_wake(client->irq);

        mutex_lock(&input_dev->mutex);

        if (input_dev->users)
                eeti_ts_start(eeti);

        mutex_unlock(&input_dev->mutex);

        return 0;
}

static SIMPLE_DEV_PM_OPS(eeti_ts_pm, eeti_ts_suspend, eeti_ts_resume);

static const struct i2c_device_id eeti_ts_id[] = {
        { "eeti_ts", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, eeti_ts_id);

#ifdef CONFIG_OF
static const struct of_device_id of_eeti_ts_match[] = {
        { .compatible = "eeti,exc3000-i2c", },
        { }
};
#endif

static struct i2c_driver eeti_ts_driver = {
        .driver = {
                .name = "eeti_ts",
                .pm = &eeti_ts_pm,
                .of_match_table = of_match_ptr(of_eeti_ts_match),
        },
        .probe = eeti_ts_probe,
        .id_table = eeti_ts_id,
};

module_i2c_driver(eeti_ts_driver);

MODULE_DESCRIPTION("EETI Touchscreen driver");
MODULE_AUTHOR("Daniel Mack <daniel@zonque.org>");
MODULE_LICENSE("GPL");