/*
 * Copyright (C) 2016 Google, Inc
 *
 * 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.
 *
 * Expose a PWM controlled by the ChromeOS EC to the host processor.
 */

#include <linux/module.h>
#include <linux/mfd/cros_ec.h>
#include <linux/mfd/cros_ec_commands.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>

/**
 * struct cros_ec_pwm_device - Driver data for EC PWM
 *
 * @dev: Device node
 * @ec: Pointer to EC device
 * @chip: PWM controller chip
 */
struct cros_ec_pwm_device {
        struct device *dev;
        struct cros_ec_device *ec;
        struct pwm_chip chip;
};

static inline struct cros_ec_pwm_device *pwm_to_cros_ec_pwm(struct pwm_chip *c)
{
        return container_of(c, struct cros_ec_pwm_device, chip);
}

static int cros_ec_pwm_set_duty(struct cros_ec_device *ec, u8 index, u16 duty)
{
        struct {
                struct cros_ec_command msg;
                struct ec_params_pwm_set_duty params;
        } __packed buf;
        struct ec_params_pwm_set_duty *params = &buf.params;
        struct cros_ec_command *msg = &buf.msg;

        memset(&buf, 0, sizeof(buf));

        msg->version = 0;
        msg->command = EC_CMD_PWM_SET_DUTY;
        msg->insize = 0;
        msg->outsize = sizeof(*params);

        params->duty = duty;
        params->pwm_type = EC_PWM_TYPE_GENERIC;
        params->index = index;

        return cros_ec_cmd_xfer_status(ec, msg);
}

static int __cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index,
                                  u32 *result)
{
        struct {
                struct cros_ec_command msg;
                union {
                        struct ec_params_pwm_get_duty params;
                        struct ec_response_pwm_get_duty resp;
                };
        } __packed buf;
        struct ec_params_pwm_get_duty *params = &buf.params;
        struct ec_response_pwm_get_duty *resp = &buf.resp;
        struct cros_ec_command *msg = &buf.msg;
        int ret;

        memset(&buf, 0, sizeof(buf));

        msg->version = 0;
        msg->command = EC_CMD_PWM_GET_DUTY;
        msg->insize = sizeof(*resp);
        msg->outsize = sizeof(*params);

        params->pwm_type = EC_PWM_TYPE_GENERIC;
        params->index = index;

        ret = cros_ec_cmd_xfer_status(ec, msg);
        if (result)
                *result = msg->result;
        if (ret < 0)
                return ret;

        return resp->duty;
}

static int cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index)
{
        return __cros_ec_pwm_get_duty(ec, index, NULL);
}

static int cros_ec_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
                             struct pwm_state *state)
{
        struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
        int duty_cycle;

        /* The EC won't let us change the period */
        if (state->period != EC_PWM_MAX_DUTY)
                return -EINVAL;

        /*
         * EC doesn't separate the concept of duty cycle and enabled, but
         * kernel does. Translate.
         */
        duty_cycle = state->enabled ? state->duty_cycle : 0;

        return cros_ec_pwm_set_duty(ec_pwm->ec, pwm->hwpwm, duty_cycle);
}

static void cros_ec_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
                                  struct pwm_state *state)
{
        struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
        int ret;

        ret = cros_ec_pwm_get_duty(ec_pwm->ec, pwm->hwpwm);
        if (ret < 0) {
                dev_err(chip->dev, "error getting initial duty: %d\n", ret);
                return;
        }

        state->enabled = (ret > 0);
        state->period = EC_PWM_MAX_DUTY;

        /* Note that "disabled" and "duty cycle == 0" are treated the same */
        state->duty_cycle = ret;
}

static struct pwm_device *
cros_ec_pwm_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
{
        struct pwm_device *pwm;

        if (args->args[0] >= pc->npwm)
                return ERR_PTR(-EINVAL);

        pwm = pwm_request_from_chip(pc, args->args[0], NULL);
        if (IS_ERR(pwm))
                return pwm;

        /* The EC won't let us change the period */
        pwm->args.period = EC_PWM_MAX_DUTY;

        return pwm;
}

static const struct pwm_ops cros_ec_pwm_ops = {
        .get_state      = cros_ec_pwm_get_state,
        .apply          = cros_ec_pwm_apply,
        .owner          = THIS_MODULE,
};

static int cros_ec_num_pwms(struct cros_ec_device *ec)
{
        int i, ret;

        /* The index field is only 8 bits */
        for (i = 0; i <= U8_MAX; i++) {
                u32 result = 0;

                ret = __cros_ec_pwm_get_duty(ec, i, &result);
                /* We want to parse EC protocol errors */
                if (ret < 0 && !(ret == -EPROTO && result))
                        return ret;

                /*
                 * We look for SUCCESS, INVALID_COMMAND, or INVALID_PARAM
                 * responses; everything else is treated as an error.
                 */
                if (result == EC_RES_INVALID_COMMAND)
                        return -ENODEV;
                else if (result == EC_RES_INVALID_PARAM)
                        return i;
                else if (result)
                        return -EPROTO;
        }

        return U8_MAX;
}

static int cros_ec_pwm_probe(struct platform_device *pdev)
{
        struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
        struct device *dev = &pdev->dev;
        struct cros_ec_pwm_device *ec_pwm;
        struct pwm_chip *chip;
        int ret;

        if (!ec) {
                dev_err(dev, "no parent EC device\n");
                return -EINVAL;
        }

        ec_pwm = devm_kzalloc(dev, sizeof(*ec_pwm), GFP_KERNEL);
        if (!ec_pwm)
                return -ENOMEM;
        chip = &ec_pwm->chip;
        ec_pwm->ec = ec;

        /* PWM chip */
        chip->dev = dev;
        chip->ops = &cros_ec_pwm_ops;
        chip->of_xlate = cros_ec_pwm_xlate;
        chip->of_pwm_n_cells = 1;
        chip->base = -1;
        ret = cros_ec_num_pwms(ec);
        if (ret < 0) {
                dev_err(dev, "Couldn't find PWMs: %d\n", ret);
                return ret;
        }
        chip->npwm = ret;
        dev_dbg(dev, "Probed %u PWMs\n", chip->npwm);

        ret = pwmchip_add(chip);
        if (ret < 0) {
                dev_err(dev, "cannot register PWM: %d\n", ret);
                return ret;
        }

        platform_set_drvdata(pdev, ec_pwm);

        return ret;
}

static int cros_ec_pwm_remove(struct platform_device *dev)
{
        struct cros_ec_pwm_device *ec_pwm = platform_get_drvdata(dev);
        struct pwm_chip *chip = &ec_pwm->chip;

        return pwmchip_remove(chip);
}

#ifdef CONFIG_OF
static const struct of_device_id cros_ec_pwm_of_match[] = {
        { .compatible = "google,cros-ec-pwm" },
        {},
};
MODULE_DEVICE_TABLE(of, cros_ec_pwm_of_match);
#endif

static struct platform_driver cros_ec_pwm_driver = {
        .probe = cros_ec_pwm_probe,
        .remove = cros_ec_pwm_remove,
        .driver = {
                .name = "cros-ec-pwm",
                .of_match_table = of_match_ptr(cros_ec_pwm_of_match),
        },
};
module_platform_driver(cros_ec_pwm_driver);

MODULE_ALIAS("platform:cros-ec-pwm");
MODULE_DESCRIPTION("ChromeOS EC PWM driver");
MODULE_LICENSE("GPL v2");