// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2020 Marek Vasut <marex@denx.de>
 *
 * Based on rpi_touchscreen.c by Eric Anholt <eric@anholt.net>
 */

#include <linux/backlight.h>
#include <linux/cleanup.h>
#include <linux/err.h>
#include <linux/gpio/driver.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/regmap.h>
#include <linux/regulator/driver.h>
#include <linux/regulator/machine.h>
#include <linux/regulator/of_regulator.h>
#include <linux/slab.h>

/* I2C registers of the Atmel microcontroller. */
#define REG_ID          0x80
#define REG_PORTA       0x81
#define REG_PORTB       0x82
#define REG_PORTC       0x83
#define REG_POWERON     0x85
#define REG_PWM         0x86
#define REG_ADDR_L      0x8c
#define REG_ADDR_H      0x8d
#define REG_WRITE_DATA_H        0x90
#define REG_WRITE_DATA_L        0x91

#define PA_LCD_DITHB            BIT(0)
#define PA_LCD_MODE             BIT(1)
#define PA_LCD_LR               BIT(2)
#define PA_LCD_UD               BIT(3)

#define PB_BRIDGE_PWRDNX_N      BIT(0)
#define PB_LCD_VCC_N            BIT(1)
#define PB_LCD_MAIN             BIT(7)

#define PC_LED_EN               BIT(0)
#define PC_RST_TP_N             BIT(1)
#define PC_RST_LCD_N            BIT(2)
#define PC_RST_BRIDGE_N         BIT(3)

enum gpio_signals {
        RST_BRIDGE_N,   /* TC358762 bridge reset */
        RST_TP_N,       /* Touch controller reset */
        NUM_GPIO
};

struct gpio_signal_mappings {
        unsigned int reg;
        unsigned int mask;
};

static const struct gpio_signal_mappings mappings[NUM_GPIO] = {
        [RST_BRIDGE_N] = { REG_PORTC, PC_RST_BRIDGE_N | PC_RST_LCD_N  },
        [RST_TP_N] = { REG_PORTC, PC_RST_TP_N },
};

struct attiny_lcd {
        /* lock to serialise overall accesses to the Atmel */
        struct mutex    lock;
        struct regmap   *regmap;
        bool gpio_states[NUM_GPIO];
        u8 port_states[3];

        struct gpio_chip gc;
};

static const struct regmap_config attiny_regmap_config = {
        .reg_bits = 8,
        .val_bits = 8,
        .disable_locking = 1,
        .max_register = REG_WRITE_DATA_L,
        .cache_type = REGCACHE_MAPLE,
};

static int attiny_set_port_state(struct attiny_lcd *state, int reg, u8 val)
{
        state->port_states[reg - REG_PORTA] = val;
        return regmap_write(state->regmap, reg, val);
};

static u8 attiny_get_port_state(struct attiny_lcd *state, int reg)
{
        return state->port_states[reg - REG_PORTA];
};

static int attiny_lcd_power_enable(struct regulator_dev *rdev)
{
        struct attiny_lcd *state = rdev_get_drvdata(rdev);

        guard(mutex)(&state->lock);

        /* Ensure bridge, and tp stay in reset */
        attiny_set_port_state(state, REG_PORTC, 0);
        usleep_range(5000, 10000);

        /* Default to the same orientation as the closed source
         * firmware used for the panel.  Runtime rotation
         * configuration will be supported using VC4's plane
         * orientation bits.
         */
        attiny_set_port_state(state, REG_PORTA, PA_LCD_LR);
        usleep_range(5000, 10000);
        /* Main regulator on, and power to the panel (LCD_VCC_N) */
        attiny_set_port_state(state, REG_PORTB, PB_LCD_MAIN);
        usleep_range(5000, 10000);
        /* Bring controllers out of reset */
        attiny_set_port_state(state, REG_PORTC, PC_LED_EN);

        msleep(80);

        return 0;
}

static int attiny_lcd_power_disable(struct regulator_dev *rdev)
{
        struct attiny_lcd *state = rdev_get_drvdata(rdev);

        guard(mutex)(&state->lock);

        regmap_write(rdev->regmap, REG_PWM, 0);
        usleep_range(5000, 10000);

        attiny_set_port_state(state, REG_PORTA, 0);
        usleep_range(5000, 10000);
        attiny_set_port_state(state, REG_PORTB, PB_LCD_VCC_N);
        usleep_range(5000, 10000);
        attiny_set_port_state(state, REG_PORTC, 0);
        msleep(30);

        return 0;
}

static int attiny_lcd_power_is_enabled(struct regulator_dev *rdev)
{
        struct attiny_lcd *state = rdev_get_drvdata(rdev);
        unsigned int data;
        int ret = 0, i;

        scoped_guard(mutex, &state->lock) {
                for (i = 0; i < 10; i++) {
                        ret = regmap_read(rdev->regmap, REG_PORTC, &data);
                        if (!ret)
                                break;
                        usleep_range(10000, 12000);
                }
        }

        if (ret < 0)
                return ret;

        return data & PC_RST_BRIDGE_N;
}

static const struct regulator_init_data attiny_regulator_default = {
        .constraints = {
                .valid_ops_mask = REGULATOR_CHANGE_STATUS,
        },
};

static const struct regulator_ops attiny_regulator_ops = {
        .enable = attiny_lcd_power_enable,
        .disable = attiny_lcd_power_disable,
        .is_enabled = attiny_lcd_power_is_enabled,
};

static const struct regulator_desc attiny_regulator = {
        .name   = "tc358762-power",
        .ops    = &attiny_regulator_ops,
        .type   = REGULATOR_VOLTAGE,
        .owner  = THIS_MODULE,
};

static int attiny_update_status(struct backlight_device *bl)
{
        struct attiny_lcd *state = bl_get_data(bl);
        struct regmap *regmap = state->regmap;
        int brightness = backlight_get_brightness(bl);
        int ret, i;

        guard(mutex)(&state->lock);

        for (i = 0; i < 10; i++) {
                ret = regmap_write(regmap, REG_PWM, brightness);
                if (!ret)
                        break;
        }

        return ret;
}

static const struct backlight_ops attiny_bl = {
        .update_status  = attiny_update_status,
};

static int attiny_gpio_get_direction(struct gpio_chip *gc, unsigned int off)
{
        return GPIO_LINE_DIRECTION_OUT;
}

static int attiny_gpio_set(struct gpio_chip *gc, unsigned int off, int val)
{
        struct attiny_lcd *state = gpiochip_get_data(gc);
        u8 last_val;

        guard(mutex)(&state->lock);

        last_val = attiny_get_port_state(state, mappings[off].reg);
        if (val)
                last_val |= mappings[off].mask;
        else
                last_val &= ~mappings[off].mask;

        attiny_set_port_state(state, mappings[off].reg, last_val);

        if (off == RST_BRIDGE_N && val) {
                usleep_range(5000, 8000);
                regmap_write(state->regmap, REG_ADDR_H, 0x04);
                usleep_range(5000, 8000);
                regmap_write(state->regmap, REG_ADDR_L, 0x7c);
                usleep_range(5000, 8000);
                regmap_write(state->regmap, REG_WRITE_DATA_H, 0x00);
                usleep_range(5000, 8000);
                regmap_write(state->regmap, REG_WRITE_DATA_L, 0x00);

                msleep(100);
        }

        return 0;
}

static int attiny_i2c_read(struct i2c_client *client, u8 reg, unsigned int *buf)
{
        struct i2c_msg msgs[1];
        u8 addr_buf[1] = { reg };
        u8 data_buf[1] = { 0, };
        int ret;

        /* Write register address */
        msgs[0].addr = client->addr;
        msgs[0].flags = 0;
        msgs[0].len = ARRAY_SIZE(addr_buf);
        msgs[0].buf = addr_buf;

        ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
        if (ret != ARRAY_SIZE(msgs))
                return -EIO;

        usleep_range(5000, 10000);

        /* Read data from register */
        msgs[0].addr = client->addr;
        msgs[0].flags = I2C_M_RD;
        msgs[0].len = 1;
        msgs[0].buf = data_buf;

        ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
        if (ret != ARRAY_SIZE(msgs))
                return -EIO;

        *buf = data_buf[0];
        return 0;
}

/*
 * I2C driver interface functions
 */
static int attiny_i2c_probe(struct i2c_client *i2c)
{
        struct backlight_properties props = { };
        struct regulator_config config = { };
        struct backlight_device *bl;
        struct regulator_dev *rdev;
        struct attiny_lcd *state;
        struct regmap *regmap;
        unsigned int data;
        int ret;

        state = devm_kzalloc(&i2c->dev, sizeof(*state), GFP_KERNEL);
        if (!state)
                return -ENOMEM;

        ret = devm_mutex_init(&i2c->dev, &state->lock);
        if (ret)
                return ret;

        i2c_set_clientdata(i2c, state);

        regmap = devm_regmap_init_i2c(i2c, &attiny_regmap_config);
        if (IS_ERR(regmap)) {
                ret = PTR_ERR(regmap);
                dev_err(&i2c->dev, "Failed to allocate register map: %d\n",
                        ret);
                return ret;
        }

        ret = attiny_i2c_read(i2c, REG_ID, &data);
        if (ret < 0) {
                dev_err(&i2c->dev, "Failed to read REG_ID reg: %d\n", ret);
                return ret;
        }

        switch (data) {
        case 0xde: /* ver 1 */
        case 0xc3: /* ver 2 */
                break;
        default:
                dev_err(&i2c->dev, "Unknown Atmel firmware revision: 0x%02x\n", data);
                return -ENODEV;
        }

        regmap_write(regmap, REG_POWERON, 0);
        msleep(30);
        regmap_write(regmap, REG_PWM, 0);

        config.dev = &i2c->dev;
        config.regmap = regmap;
        config.of_node = i2c->dev.of_node;
        config.init_data = &attiny_regulator_default;
        config.driver_data = state;

        rdev = devm_regulator_register(&i2c->dev, &attiny_regulator, &config);
        if (IS_ERR(rdev)) {
                dev_err(&i2c->dev, "Failed to register ATTINY regulator\n");
                return PTR_ERR(rdev);
        }

        props.type = BACKLIGHT_RAW;
        props.max_brightness = 0xff;

        state->regmap = regmap;

        bl = devm_backlight_device_register(&i2c->dev, dev_name(&i2c->dev),
                                            &i2c->dev, state, &attiny_bl,
                                            &props);
        if (IS_ERR(bl))
                return PTR_ERR(bl);

        bl->props.brightness = 0xff;

        state->gc.parent = &i2c->dev;
        state->gc.label = i2c->name;
        state->gc.owner = THIS_MODULE;
        state->gc.base = -1;
        state->gc.ngpio = NUM_GPIO;

        state->gc.set = attiny_gpio_set;
        state->gc.get_direction = attiny_gpio_get_direction;
        state->gc.can_sleep = true;

        ret = devm_gpiochip_add_data(&i2c->dev, &state->gc, state);
        if (ret)
                dev_err(&i2c->dev, "Failed to create gpiochip: %d\n", ret);

        return ret;
}

static const struct of_device_id attiny_dt_ids[] = {
        { .compatible = "raspberrypi,7inch-touchscreen-panel-regulator" },
        {},
};
MODULE_DEVICE_TABLE(of, attiny_dt_ids);

static struct i2c_driver attiny_regulator_driver = {
        .driver = {
                .name = "rpi_touchscreen_attiny",
                .probe_type = PROBE_PREFER_ASYNCHRONOUS,
                .of_match_table = attiny_dt_ids,
        },
        .probe = attiny_i2c_probe,
};

module_i2c_driver(attiny_regulator_driver);

MODULE_AUTHOR("Marek Vasut <marex@denx.de>");
MODULE_DESCRIPTION("Regulator device driver for Raspberry Pi 7-inch touchscreen");
MODULE_LICENSE("GPL v2");