// SPDX-License-Identifier: GPL-2.0
/*
 * Intel Keem Bay PWM driver
 *
 * Copyright (C) 2020 Intel Corporation
 * Authors: Lai Poey Seng <poey.seng.lai@intel.com>
 *          Vineetha G. Jaya Kumaran <vineetha.g.jaya.kumaran@intel.com>
 *
 * Limitations:
 * - Upon disabling a channel, the currently running
 *   period will not be completed. However, upon
 *   reconfiguration of the duty cycle/period, the
 *   currently running period will be completed first.
 */

#include <linux/bitfield.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/regmap.h>

#define KMB_TOTAL_PWM_CHANNELS          6
#define KMB_PWM_COUNT_MAX               U16_MAX
#define KMB_PWM_EN_BIT                  BIT(31)

/* Mask */
#define KMB_PWM_HIGH_MASK               GENMASK(31, 16)
#define KMB_PWM_LOW_MASK                GENMASK(15, 0)
#define KMB_PWM_LEADIN_MASK             GENMASK(30, 0)

/* PWM Register offset */
#define KMB_PWM_LEADIN_OFFSET(ch)       (0x00 + 4 * (ch))
#define KMB_PWM_HIGHLOW_OFFSET(ch)      (0x20 + 4 * (ch))

struct keembay_pwm {
        struct pwm_chip chip;
        struct device *dev;
        struct clk *clk;
        void __iomem *base;
};

static inline struct keembay_pwm *to_keembay_pwm_dev(struct pwm_chip *chip)
{
        return container_of(chip, struct keembay_pwm, chip);
}

static void keembay_clk_unprepare(void *data)
{
        clk_disable_unprepare(data);
}

static int keembay_clk_enable(struct device *dev, struct clk *clk)
{
        int ret;

        ret = clk_prepare_enable(clk);
        if (ret)
                return ret;

        return devm_add_action_or_reset(dev, keembay_clk_unprepare, clk);
}

/*
 * With gcc 10, CONFIG_CC_OPTIMIZE_FOR_SIZE and only "inline" instead of
 * "__always_inline" this fails to compile because the compiler doesn't notice
 * for all valid masks (e.g. KMB_PWM_LEADIN_MASK) that they are ok.
 */
static __always_inline void keembay_pwm_update_bits(struct keembay_pwm *priv, u32 mask,
                                           u32 val, u32 offset)
{
        u32 buff = readl(priv->base + offset);

        buff = u32_replace_bits(buff, val, mask);
        writel(buff, priv->base + offset);
}

static void keembay_pwm_enable(struct keembay_pwm *priv, int ch)
{
        keembay_pwm_update_bits(priv, KMB_PWM_EN_BIT, 1,
                                KMB_PWM_LEADIN_OFFSET(ch));
}

static void keembay_pwm_disable(struct keembay_pwm *priv, int ch)
{
        keembay_pwm_update_bits(priv, KMB_PWM_EN_BIT, 0,
                                KMB_PWM_LEADIN_OFFSET(ch));
}

static void keembay_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
                                  struct pwm_state *state)
{
        struct keembay_pwm *priv = to_keembay_pwm_dev(chip);
        unsigned long long high, low;
        unsigned long clk_rate;
        u32 highlow;

        clk_rate = clk_get_rate(priv->clk);

        /* Read channel enabled status */
        highlow = readl(priv->base + KMB_PWM_LEADIN_OFFSET(pwm->hwpwm));
        if (highlow & KMB_PWM_EN_BIT)
                state->enabled = true;
        else
                state->enabled = false;

        /* Read period and duty cycle */
        highlow = readl(priv->base + KMB_PWM_HIGHLOW_OFFSET(pwm->hwpwm));
        low = FIELD_GET(KMB_PWM_LOW_MASK, highlow) * NSEC_PER_SEC;
        high = FIELD_GET(KMB_PWM_HIGH_MASK, highlow) * NSEC_PER_SEC;
        state->duty_cycle = DIV_ROUND_UP_ULL(high, clk_rate);
        state->period = DIV_ROUND_UP_ULL(high + low, clk_rate);
        state->polarity = PWM_POLARITY_NORMAL;
}

static int keembay_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
                             const struct pwm_state *state)
{
        struct keembay_pwm *priv = to_keembay_pwm_dev(chip);
        struct pwm_state current_state;
        unsigned long long div;
        unsigned long clk_rate;
        u32 pwm_count = 0;
        u16 high, low;

        if (state->polarity != PWM_POLARITY_NORMAL)
                return -EINVAL;

        /*
         * Configure the pwm repeat count as infinite at (15:0) and leadin
         * low time as 0 at (30:16), which is in terms of clock cycles.
         */
        keembay_pwm_update_bits(priv, KMB_PWM_LEADIN_MASK, 0,
                                KMB_PWM_LEADIN_OFFSET(pwm->hwpwm));

        keembay_pwm_get_state(chip, pwm, &current_state);

        if (!state->enabled) {
                if (current_state.enabled)
                        keembay_pwm_disable(priv, pwm->hwpwm);
                return 0;
        }

        /*
         * The upper 16 bits and lower 16 bits of the KMB_PWM_HIGHLOW_OFFSET
         * register contain the high time and low time of waveform accordingly.
         * All the values are in terms of clock cycles.
         */

        clk_rate = clk_get_rate(priv->clk);
        div = clk_rate * state->duty_cycle;
        div = DIV_ROUND_DOWN_ULL(div, NSEC_PER_SEC);
        if (div > KMB_PWM_COUNT_MAX)
                return -ERANGE;

        high = div;
        div = clk_rate * state->period;
        div = DIV_ROUND_DOWN_ULL(div, NSEC_PER_SEC);
        div = div - high;
        if (div > KMB_PWM_COUNT_MAX)
                return -ERANGE;

        low = div;

        pwm_count = FIELD_PREP(KMB_PWM_HIGH_MASK, high) |
                    FIELD_PREP(KMB_PWM_LOW_MASK, low);

        writel(pwm_count, priv->base + KMB_PWM_HIGHLOW_OFFSET(pwm->hwpwm));

        if (state->enabled && !current_state.enabled)
                keembay_pwm_enable(priv, pwm->hwpwm);

        return 0;
}

static const struct pwm_ops keembay_pwm_ops = {
        .owner = THIS_MODULE,
        .apply = keembay_pwm_apply,
        .get_state = keembay_pwm_get_state,
};

static int keembay_pwm_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct keembay_pwm *priv;
        int ret;

        priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        priv->clk = devm_clk_get(dev, NULL);
        if (IS_ERR(priv->clk))
                return dev_err_probe(dev, PTR_ERR(priv->clk), "Failed to get clock\n");

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

        ret = keembay_clk_enable(dev, priv->clk);
        if (ret)
                return ret;

        priv->chip.dev = dev;
        priv->chip.ops = &keembay_pwm_ops;
        priv->chip.npwm = KMB_TOTAL_PWM_CHANNELS;

        ret = devm_pwmchip_add(dev, &priv->chip);
        if (ret)
                return dev_err_probe(dev, ret, "Failed to add PWM chip\n");

        return 0;
}

static const struct of_device_id keembay_pwm_of_match[] = {
        { .compatible = "intel,keembay-pwm" },
        { }
};
MODULE_DEVICE_TABLE(of, keembay_pwm_of_match);

static struct platform_driver keembay_pwm_driver = {
        .probe  = keembay_pwm_probe,
        .driver = {
                .name = "pwm-keembay",
                .of_match_table = keembay_pwm_of_match,
        },
};
module_platform_driver(keembay_pwm_driver);

MODULE_ALIAS("platform:pwm-keembay");
MODULE_DESCRIPTION("Intel Keem Bay PWM driver");
MODULE_LICENSE("GPL v2");