/*
 * linux/drivers/video/backlight/pwm_bl.c
 *
 * simple PWM based backlight control, board code has to setup
 * 1) pin configuration so PWM waveforms can output
 * 2) platform_data being correctly configured
 *
 * 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/gpio/consumer.h>
#include <linux/gpio.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/fb.h>
#include <linux/backlight.h>
#include <linux/err.h>
#include <linux/pwm.h>
#include <linux/pwm_backlight.h>
#include <linux/regulator/consumer.h>
#include <linux/slab.h>

struct pwm_bl_data {
        struct pwm_device       *pwm;
        struct device           *dev;
        unsigned int            period;
        unsigned int            lth_brightness;
        unsigned int            *levels;
        bool                    enabled;
        struct regulator        *power_supply;
        struct gpio_desc        *enable_gpio;
        unsigned int            scale;
        bool                    legacy;
        int                     (*notify)(struct device *,
                                          int brightness);
        void                    (*notify_after)(struct device *,
                                        int brightness);
        int                     (*check_fb)(struct device *, struct fb_info *);
        void                    (*exit)(struct device *);
};

static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
{
        int err;

        if (pb->enabled)
                return;

        err = regulator_enable(pb->power_supply);
        if (err < 0)
                dev_err(pb->dev, "failed to enable power supply\n");

        if (pb->enable_gpio)
                gpiod_set_value_cansleep(pb->enable_gpio, 1);

        pwm_enable(pb->pwm);
        pb->enabled = true;
}

static void pwm_backlight_power_off(struct pwm_bl_data *pb)
{
        if (!pb->enabled)
                return;

        pwm_config(pb->pwm, 0, pb->period);
        pwm_disable(pb->pwm);

        if (pb->enable_gpio)
                gpiod_set_value_cansleep(pb->enable_gpio, 0);

        regulator_disable(pb->power_supply);
        pb->enabled = false;
}

static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
{
        unsigned int lth = pb->lth_brightness;
        u64 duty_cycle;

        if (pb->levels)
                duty_cycle = pb->levels[brightness];
        else
                duty_cycle = brightness;

        duty_cycle *= pb->period - lth;
        do_div(duty_cycle, pb->scale);

        return duty_cycle + lth;
}

static int pwm_backlight_update_status(struct backlight_device *bl)
{
        struct pwm_bl_data *pb = bl_get_data(bl);
        int brightness = bl->props.brightness;
        int duty_cycle;

        if (bl->props.power != FB_BLANK_UNBLANK ||
            bl->props.fb_blank != FB_BLANK_UNBLANK ||
            bl->props.state & BL_CORE_FBBLANK)
                brightness = 0;

        if (pb->notify)
                brightness = pb->notify(pb->dev, brightness);

        if (brightness > 0) {
                duty_cycle = compute_duty_cycle(pb, brightness);
                pwm_config(pb->pwm, duty_cycle, pb->period);
                pwm_backlight_power_on(pb, brightness);
        } else
                pwm_backlight_power_off(pb);

        if (pb->notify_after)
                pb->notify_after(pb->dev, brightness);

        return 0;
}

static int pwm_backlight_check_fb(struct backlight_device *bl,
                                  struct fb_info *info)
{
        struct pwm_bl_data *pb = bl_get_data(bl);

        return !pb->check_fb || pb->check_fb(pb->dev, info);
}

static const struct backlight_ops pwm_backlight_ops = {
        .update_status  = pwm_backlight_update_status,
        .check_fb       = pwm_backlight_check_fb,
};

#ifdef CONFIG_OF
static int pwm_backlight_parse_dt(struct device *dev,
                                  struct platform_pwm_backlight_data *data)
{
        struct device_node *node = dev->of_node;
        struct property *prop;
        int length;
        u32 value;
        int ret;

        if (!node)
                return -ENODEV;

        memset(data, 0, sizeof(*data));

        /* determine the number of brightness levels */
        prop = of_find_property(node, "brightness-levels", &length);
        if (!prop)
                return -EINVAL;

        data->max_brightness = length / sizeof(u32);

        /* read brightness levels from DT property */
        if (data->max_brightness > 0) {
                size_t size = sizeof(*data->levels) * data->max_brightness;

                data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
                if (!data->levels)
                        return -ENOMEM;

                ret = of_property_read_u32_array(node, "brightness-levels",
                                                 data->levels,
                                                 data->max_brightness);
                if (ret < 0)
                        return ret;

                ret = of_property_read_u32(node, "default-brightness-level",
                                           &value);
                if (ret < 0)
                        return ret;

                data->dft_brightness = value;
                data->max_brightness--;
        }

        data->enable_gpio = -EINVAL;
        return 0;
}

static const struct of_device_id pwm_backlight_of_match[] = {
        { .compatible = "pwm-backlight" },
        { }
};

MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
#else
static int pwm_backlight_parse_dt(struct device *dev,
                                  struct platform_pwm_backlight_data *data)
{
        return -ENODEV;
}
#endif

static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
{
        struct device_node *node = pb->dev->of_node;

        /* Not booted with device tree or no phandle link to the node */
        if (!node || !node->phandle)
                return FB_BLANK_UNBLANK;

        /*
         * If the driver is probed from the device tree and there is a
         * phandle link pointing to the backlight node, it is safe to
         * assume that another driver will enable the backlight at the
         * appropriate time. Therefore, if it is disabled, keep it so.
         */

        /* if the enable GPIO is disabled, do not enable the backlight */
        if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) == 0)
                return FB_BLANK_POWERDOWN;

        /* The regulator is disabled, do not enable the backlight */
        if (!regulator_is_enabled(pb->power_supply))
                return FB_BLANK_POWERDOWN;

        /* The PWM is disabled, keep it like this */
        if (!pwm_is_enabled(pb->pwm))
                return FB_BLANK_POWERDOWN;

        return FB_BLANK_UNBLANK;
}

static int pwm_backlight_probe(struct platform_device *pdev)
{
        struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
        struct platform_pwm_backlight_data defdata;
        struct backlight_properties props;
        struct backlight_device *bl;
        struct device_node *node = pdev->dev.of_node;
        struct pwm_bl_data *pb;
        struct pwm_args pargs;
        int ret;

        if (!data) {
                ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
                if (ret < 0) {
                        dev_err(&pdev->dev, "failed to find platform data\n");
                        return ret;
                }

                data = &defdata;
        }

        if (data->init) {
                ret = data->init(&pdev->dev);
                if (ret < 0)
                        return ret;
        }

        pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
        if (!pb) {
                ret = -ENOMEM;
                goto err_alloc;
        }

        if (data->levels) {
                unsigned int i;

                for (i = 0; i <= data->max_brightness; i++)
                        if (data->levels[i] > pb->scale)
                                pb->scale = data->levels[i];

                pb->levels = data->levels;
        } else
                pb->scale = data->max_brightness;

        pb->notify = data->notify;
        pb->notify_after = data->notify_after;
        pb->check_fb = data->check_fb;
        pb->exit = data->exit;
        pb->dev = &pdev->dev;
        pb->enabled = false;

        pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
                                                  GPIOD_ASIS);
        if (IS_ERR(pb->enable_gpio)) {
                ret = PTR_ERR(pb->enable_gpio);
                goto err_alloc;
        }

        /*
         * Compatibility fallback for drivers still using the integer GPIO
         * platform data. Must go away soon.
         */
        if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
                ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
                                            GPIOF_OUT_INIT_HIGH, "enable");
                if (ret < 0) {
                        dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
                                data->enable_gpio, ret);
                        goto err_alloc;
                }

                pb->enable_gpio = gpio_to_desc(data->enable_gpio);
        }

        /*
         * If the GPIO is not known to be already configured as output, that
         * is, if gpiod_get_direction returns either GPIOF_DIR_IN or -EINVAL,
         * change the direction to output and set the GPIO as active.
         * Do not force the GPIO to active when it was already output as it
         * could cause backlight flickering or we would enable the backlight too
         * early. Leave the decision of the initial backlight state for later.
         */
        if (pb->enable_gpio &&
            gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
                gpiod_direction_output(pb->enable_gpio, 1);

        pb->power_supply = devm_regulator_get(&pdev->dev, "power");
        if (IS_ERR(pb->power_supply)) {
                ret = PTR_ERR(pb->power_supply);
                goto err_alloc;
        }

        pb->pwm = devm_pwm_get(&pdev->dev, NULL);
        if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
                dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
                pb->legacy = true;
                pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
        }

        if (IS_ERR(pb->pwm)) {
                ret = PTR_ERR(pb->pwm);
                if (ret != -EPROBE_DEFER)
                        dev_err(&pdev->dev, "unable to request PWM\n");
                goto err_alloc;
        }

        dev_dbg(&pdev->dev, "got pwm for backlight\n");

        /*
         * FIXME: pwm_apply_args() should be removed when switching to
         * the atomic PWM API.
         */
        pwm_apply_args(pb->pwm);

        /*
         * The DT case will set the pwm_period_ns field to 0 and store the
         * period, parsed from the DT, in the PWM device. For the non-DT case,
         * set the period from platform data if it has not already been set
         * via the PWM lookup table.
         */
        pwm_get_args(pb->pwm, &pargs);
        pb->period = pargs.period;
        if (!pb->period && (data->pwm_period_ns > 0))
                pb->period = data->pwm_period_ns;

        pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);

        memset(&props, 0, sizeof(struct backlight_properties));
        props.type = BACKLIGHT_RAW;
        props.max_brightness = data->max_brightness;
        bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
                                       &pwm_backlight_ops, &props);
        if (IS_ERR(bl)) {
                dev_err(&pdev->dev, "failed to register backlight\n");
                ret = PTR_ERR(bl);
                if (pb->legacy)
                        pwm_free(pb->pwm);
                goto err_alloc;
        }

        if (data->dft_brightness > data->max_brightness) {
                dev_warn(&pdev->dev,
                         "invalid default brightness level: %u, using %u\n",
                         data->dft_brightness, data->max_brightness);
                data->dft_brightness = data->max_brightness;
        }

        bl->props.brightness = data->dft_brightness;
        bl->props.power = pwm_backlight_initial_power_state(pb);
        backlight_update_status(bl);

        platform_set_drvdata(pdev, bl);
        return 0;

err_alloc:
        if (data->exit)
                data->exit(&pdev->dev);
        return ret;
}

static int pwm_backlight_remove(struct platform_device *pdev)
{
        struct backlight_device *bl = platform_get_drvdata(pdev);
        struct pwm_bl_data *pb = bl_get_data(bl);

        backlight_device_unregister(bl);
        pwm_backlight_power_off(pb);

        if (pb->exit)
                pb->exit(&pdev->dev);
        if (pb->legacy)
                pwm_free(pb->pwm);

        return 0;
}

static void pwm_backlight_shutdown(struct platform_device *pdev)
{
        struct backlight_device *bl = platform_get_drvdata(pdev);
        struct pwm_bl_data *pb = bl_get_data(bl);

        pwm_backlight_power_off(pb);
}

#ifdef CONFIG_PM_SLEEP
static int pwm_backlight_suspend(struct device *dev)
{
        struct backlight_device *bl = dev_get_drvdata(dev);
        struct pwm_bl_data *pb = bl_get_data(bl);

        if (pb->notify)
                pb->notify(pb->dev, 0);

        pwm_backlight_power_off(pb);

        if (pb->notify_after)
                pb->notify_after(pb->dev, 0);

        return 0;
}

static int pwm_backlight_resume(struct device *dev)
{
        struct backlight_device *bl = dev_get_drvdata(dev);

        backlight_update_status(bl);

        return 0;
}
#endif

static const struct dev_pm_ops pwm_backlight_pm_ops = {
#ifdef CONFIG_PM_SLEEP
        .suspend = pwm_backlight_suspend,
        .resume = pwm_backlight_resume,
        .poweroff = pwm_backlight_suspend,
        .restore = pwm_backlight_resume,
#endif
};

static struct platform_driver pwm_backlight_driver = {
        .driver         = {
                .name           = "pwm-backlight",
                .pm             = &pwm_backlight_pm_ops,
                .of_match_table = of_match_ptr(pwm_backlight_of_match),
        },
        .probe          = pwm_backlight_probe,
        .remove         = pwm_backlight_remove,
        .shutdown       = pwm_backlight_shutdown,
};

module_platform_driver(pwm_backlight_driver);

MODULE_DESCRIPTION("PWM based Backlight Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:pwm-backlight");