// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Allwinner sun4i low res adc attached tablet keys driver
 *
 * Copyright (C) 2014 Hans de Goede <hdegoede@redhat.com>
 */

/*
 * Allwinnner sunxi SoCs have a lradc which is specifically designed to have
 * various (tablet) keys (ie home, back, search, etc). attached to it using
 * a resistor network. This driver is for the keys on such boards.
 *
 * There are 2 channels, currently this driver only supports channel 0 since
 * there are no boards known to use channel 1.
 */

#include <linux/clk.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/input.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm_wakeirq.h>
#include <linux/property.h>
#include <linux/regulator/consumer.h>
#include <linux/reset.h>
#include <linux/slab.h>

#define LRADC_CTRL              0x00
#define LRADC_INTC              0x04
#define LRADC_INTS              0x08
#define LRADC_DATA0             0x0c
#define LRADC_DATA1             0x10

/* LRADC_CTRL bits */
#define FIRST_CONVERT_DLY(x)    ((x) << 24) /* 8 bits */
#define CHAN_SELECT(x)          ((x) << 22) /* 2 bits */
#define CONTINUE_TIME_SEL(x)    ((x) << 16) /* 4 bits */
#define KEY_MODE_SEL(x)         ((x) << 12) /* 2 bits */
#define LEVELA_B_CNT(x)         ((x) << 8)  /* 4 bits */
#define HOLD_KEY_EN(x)          ((x) << 7)
#define HOLD_EN(x)              ((x) << 6)
#define LEVELB_VOL(x)           ((x) << 4)  /* 2 bits */
#define SAMPLE_RATE(x)          ((x) << 2)  /* 2 bits */
#define ENABLE(x)               ((x) << 0)

/* LRADC_INTC and LRADC_INTS bits */
#define CHAN1_KEYUP_IRQ         BIT(12)
#define CHAN1_ALRDY_HOLD_IRQ    BIT(11)
#define CHAN1_HOLD_IRQ          BIT(10)
#define CHAN1_KEYDOWN_IRQ       BIT(9)
#define CHAN1_DATA_IRQ          BIT(8)
#define CHAN0_KEYUP_IRQ         BIT(4)
#define CHAN0_ALRDY_HOLD_IRQ    BIT(3)
#define CHAN0_HOLD_IRQ          BIT(2)
#define CHAN0_KEYDOWN_IRQ       BIT(1)
#define CHAN0_DATA_IRQ          BIT(0)

/* struct lradc_variant - Describe sun4i-a10-lradc-keys hardware variant
 * @divisor_numerator:          The numerator of lradc Vref internally divisor
 * @divisor_denominator:        The denominator of lradc Vref internally divisor
 * @has_clock_reset:            If the binding requires a clock and reset
 */
struct lradc_variant {
        u8 divisor_numerator;
        u8 divisor_denominator;
        bool has_clock_reset;
};

static const struct lradc_variant lradc_variant_a10 = {
        .divisor_numerator = 2,
        .divisor_denominator = 3
};

static const struct lradc_variant r_lradc_variant_a83t = {
        .divisor_numerator = 3,
        .divisor_denominator = 4
};

static const struct lradc_variant lradc_variant_r329 = {
        .divisor_numerator = 3,
        .divisor_denominator = 4,
        .has_clock_reset = true,
};

struct sun4i_lradc_keymap {
        u32 voltage;
        u32 keycode;
};

struct sun4i_lradc_data {
        struct device *dev;
        struct input_dev *input;
        void __iomem *base;
        struct clk *clk;
        struct reset_control *reset;
        struct regulator *vref_supply;
        struct sun4i_lradc_keymap *chan0_map;
        const struct lradc_variant *variant;
        u32 chan0_map_count;
        u32 chan0_keycode;
        u32 vref;
};

static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
{
        struct sun4i_lradc_data *lradc = dev_id;
        u32 i, ints, val, voltage, diff, keycode = 0, closest = 0xffffffff;

        ints  = readl(lradc->base + LRADC_INTS);

        /*
         * lradc supports only one keypress at a time, release does not give
         * any info as to which key was released, so we cache the keycode.
         */

        if (ints & CHAN0_KEYUP_IRQ) {
                input_report_key(lradc->input, lradc->chan0_keycode, 0);
                lradc->chan0_keycode = 0;
        }

        if ((ints & CHAN0_KEYDOWN_IRQ) && lradc->chan0_keycode == 0) {
                val = readl(lradc->base + LRADC_DATA0) & 0x3f;
                voltage = val * lradc->vref / 63;

                for (i = 0; i < lradc->chan0_map_count; i++) {
                        diff = abs(lradc->chan0_map[i].voltage - voltage);
                        if (diff < closest) {
                                closest = diff;
                                keycode = lradc->chan0_map[i].keycode;
                        }
                }

                lradc->chan0_keycode = keycode;
                input_report_key(lradc->input, lradc->chan0_keycode, 1);
        }

        input_sync(lradc->input);

        writel(ints, lradc->base + LRADC_INTS);

        return IRQ_HANDLED;
}

static int sun4i_lradc_open(struct input_dev *dev)
{
        struct sun4i_lradc_data *lradc = input_get_drvdata(dev);
        int error;

        error = regulator_enable(lradc->vref_supply);
        if (error)
                return error;

        error = reset_control_deassert(lradc->reset);
        if (error)
                goto err_disable_reg;

        error = clk_prepare_enable(lradc->clk);
        if (error)
                goto err_assert_reset;

        lradc->vref = regulator_get_voltage(lradc->vref_supply) *
                      lradc->variant->divisor_numerator /
                      lradc->variant->divisor_denominator;
        /*
         * Set sample time to 4 ms / 250 Hz. Wait 2 * 4 ms for key to
         * stabilize on press, wait (1 + 1) * 4 ms for key release
         */
        writel(FIRST_CONVERT_DLY(2) | LEVELA_B_CNT(1) | HOLD_EN(1) |
                SAMPLE_RATE(0) | ENABLE(1), lradc->base + LRADC_CTRL);

        writel(CHAN0_KEYUP_IRQ | CHAN0_KEYDOWN_IRQ, lradc->base + LRADC_INTC);

        return 0;

err_assert_reset:
        reset_control_assert(lradc->reset);
err_disable_reg:
        regulator_disable(lradc->vref_supply);

        return error;
}

static void sun4i_lradc_close(struct input_dev *dev)
{
        struct sun4i_lradc_data *lradc = input_get_drvdata(dev);

        /* Disable lradc, leave other settings unchanged */
        writel(FIRST_CONVERT_DLY(2) | LEVELA_B_CNT(1) | HOLD_EN(1) |
                SAMPLE_RATE(2), lradc->base + LRADC_CTRL);
        writel(0, lradc->base + LRADC_INTC);

        clk_disable_unprepare(lradc->clk);
        reset_control_assert(lradc->reset);
        regulator_disable(lradc->vref_supply);
}

static int sun4i_lradc_load_dt_keymap(struct device *dev,
                                      struct sun4i_lradc_data *lradc)
{
        struct device_node *np;
        int i;
        int error;

        np = dev->of_node;
        if (!np)
                return -EINVAL;

        lradc->chan0_map_count = of_get_child_count(np);
        if (lradc->chan0_map_count == 0) {
                dev_err(dev, "keymap is missing in device tree\n");
                return -EINVAL;
        }

        lradc->chan0_map = devm_kmalloc_array(dev, lradc->chan0_map_count,
                                              sizeof(struct sun4i_lradc_keymap),
                                              GFP_KERNEL);
        if (!lradc->chan0_map)
                return -ENOMEM;

        i = 0;
        for_each_child_of_node_scoped(np, pp) {
                struct sun4i_lradc_keymap *map = &lradc->chan0_map[i];
                u32 channel;

                error = of_property_read_u32(pp, "channel", &channel);
                if (error || channel != 0) {
                        dev_err(dev, "%pOFn: Inval channel prop\n", pp);
                        return -EINVAL;
                }

                error = of_property_read_u32(pp, "voltage", &map->voltage);
                if (error) {
                        dev_err(dev, "%pOFn: Inval voltage prop\n", pp);
                        return -EINVAL;
                }

                error = of_property_read_u32(pp, "linux,code", &map->keycode);
                if (error) {
                        dev_err(dev, "%pOFn: Inval linux,code prop\n", pp);
                        return -EINVAL;
                }

                i++;
        }

        return 0;
}

static int sun4i_lradc_probe(struct platform_device *pdev)
{
        struct sun4i_lradc_data *lradc;
        struct device *dev = &pdev->dev;
        int error, i, irq;

        lradc = devm_kzalloc(dev, sizeof(struct sun4i_lradc_data), GFP_KERNEL);
        if (!lradc)
                return -ENOMEM;

        error = sun4i_lradc_load_dt_keymap(dev, lradc);
        if (error)
                return error;

        lradc->variant = of_device_get_match_data(&pdev->dev);
        if (!lradc->variant) {
                dev_err(&pdev->dev, "Missing sun4i-a10-lradc-keys variant\n");
                return -EINVAL;
        }

        if (lradc->variant->has_clock_reset) {
                lradc->clk = devm_clk_get(dev, NULL);
                if (IS_ERR(lradc->clk))
                        return PTR_ERR(lradc->clk);

                lradc->reset = devm_reset_control_get_exclusive(dev, NULL);
                if (IS_ERR(lradc->reset))
                        return PTR_ERR(lradc->reset);
        }

        lradc->vref_supply = devm_regulator_get(dev, "vref");
        if (IS_ERR(lradc->vref_supply))
                return PTR_ERR(lradc->vref_supply);

        lradc->dev = dev;
        lradc->input = devm_input_allocate_device(dev);
        if (!lradc->input)
                return -ENOMEM;

        lradc->input->name = pdev->name;
        lradc->input->phys = "sun4i_lradc/input0";
        lradc->input->open = sun4i_lradc_open;
        lradc->input->close = sun4i_lradc_close;
        lradc->input->id.bustype = BUS_HOST;
        lradc->input->id.vendor = 0x0001;
        lradc->input->id.product = 0x0001;
        lradc->input->id.version = 0x0100;

        __set_bit(EV_KEY, lradc->input->evbit);
        for (i = 0; i < lradc->chan0_map_count; i++)
                __set_bit(lradc->chan0_map[i].keycode, lradc->input->keybit);

        input_set_drvdata(lradc->input, lradc);

        lradc->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(lradc->base))
                return PTR_ERR(lradc->base);

        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                return irq;

        error = devm_request_irq(dev, irq, sun4i_lradc_irq, 0,
                                 "sun4i-a10-lradc-keys", lradc);
        if (error)
                return error;

        error = input_register_device(lradc->input);
        if (error)
                return error;

        if (device_property_read_bool(dev, "wakeup-source")) {
                error = dev_pm_set_wake_irq(dev, irq);
                if (error)
                        dev_warn(dev,
                                 "Failed to set IRQ %d as a wake IRQ: %d\n",
                                 irq, error);
                else
                        device_set_wakeup_capable(dev, true);
        }

        return 0;
}

static const struct of_device_id sun4i_lradc_of_match[] = {
        { .compatible = "allwinner,sun4i-a10-lradc-keys",
                .data = &lradc_variant_a10 },
        { .compatible = "allwinner,sun8i-a83t-r-lradc",
                .data = &r_lradc_variant_a83t },
        { .compatible = "allwinner,sun50i-r329-lradc",
                .data = &lradc_variant_r329 },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, sun4i_lradc_of_match);

static struct platform_driver sun4i_lradc_driver = {
        .driver = {
                .name   = "sun4i-a10-lradc-keys",
                .of_match_table = of_match_ptr(sun4i_lradc_of_match),
        },
        .probe  = sun4i_lradc_probe,
};

module_platform_driver(sun4i_lradc_driver);

MODULE_DESCRIPTION("Allwinner sun4i low res adc attached tablet keys driver");
MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
MODULE_LICENSE("GPL");