// SPDX-License-Identifier: GPL-2.0-only
/*
 * Driver for Allwinner sun4i Pulse Width Modulation Controller
 *
 * Copyright (C) 2014 Alexandre Belloni <alexandre.belloni@free-electrons.com>
 *
 * Limitations:
 * - When outputing the source clock directly, the PWM logic will be bypassed
 *   and the currently running period is not guaranteed to be completed
 */

#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/reset.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/time.h>

#define PWM_CTRL_REG            0x0

#define PWM_CH_PRD_BASE         0x4
#define PWM_CH_PRD_OFFSET       0x4
#define PWM_CH_PRD(ch)          (PWM_CH_PRD_BASE + PWM_CH_PRD_OFFSET * (ch))

#define PWMCH_OFFSET            15
#define PWM_PRESCAL_MASK        GENMASK(3, 0)
#define PWM_PRESCAL_OFF         0
#define PWM_EN                  BIT(4)
#define PWM_ACT_STATE           BIT(5)
#define PWM_CLK_GATING          BIT(6)
#define PWM_MODE                BIT(7)
#define PWM_PULSE               BIT(8)
#define PWM_BYPASS              BIT(9)

#define PWM_RDY_BASE            28
#define PWM_RDY_OFFSET          1
#define PWM_RDY(ch)             BIT(PWM_RDY_BASE + PWM_RDY_OFFSET * (ch))

#define PWM_PRD(prd)            (((prd) - 1) << 16)
#define PWM_PRD_MASK            GENMASK(15, 0)

#define PWM_DTY_MASK            GENMASK(15, 0)

#define PWM_REG_PRD(reg)        ((((reg) >> 16) & PWM_PRD_MASK) + 1)
#define PWM_REG_DTY(reg)        ((reg) & PWM_DTY_MASK)
#define PWM_REG_PRESCAL(reg, chan)      (((reg) >> ((chan) * PWMCH_OFFSET)) & PWM_PRESCAL_MASK)

#define BIT_CH(bit, chan)       ((bit) << ((chan) * PWMCH_OFFSET))

static const u32 prescaler_table[] = {
        120,
        180,
        240,
        360,
        480,
        0,
        0,
        0,
        12000,
        24000,
        36000,
        48000,
        72000,
        0,
        0,
        0, /* Actually 1 but tested separately */
};

struct sun4i_pwm_data {
        bool has_prescaler_bypass;
        bool has_direct_mod_clk_output;
        unsigned int npwm;
};

struct sun4i_pwm_chip {
        struct pwm_chip chip;
        struct clk *bus_clk;
        struct clk *clk;
        struct reset_control *rst;
        void __iomem *base;
        spinlock_t ctrl_lock;
        const struct sun4i_pwm_data *data;
        unsigned long next_period[2];
};

static inline struct sun4i_pwm_chip *to_sun4i_pwm_chip(struct pwm_chip *chip)
{
        return container_of(chip, struct sun4i_pwm_chip, chip);
}

static inline u32 sun4i_pwm_readl(struct sun4i_pwm_chip *chip,
                                  unsigned long offset)
{
        return readl(chip->base + offset);
}

static inline void sun4i_pwm_writel(struct sun4i_pwm_chip *chip,
                                    u32 val, unsigned long offset)
{
        writel(val, chip->base + offset);
}

static void sun4i_pwm_get_state(struct pwm_chip *chip,
                                struct pwm_device *pwm,
                                struct pwm_state *state)
{
        struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
        u64 clk_rate, tmp;
        u32 val;
        unsigned int prescaler;

        clk_rate = clk_get_rate(sun4i_pwm->clk);

        val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);

        /*
         * PWM chapter in H6 manual has a diagram which explains that if bypass
         * bit is set, no other setting has any meaning. Even more, experiment
         * proved that also enable bit is ignored in this case.
         */
        if ((val & BIT_CH(PWM_BYPASS, pwm->hwpwm)) &&
            sun4i_pwm->data->has_direct_mod_clk_output) {
                state->period = DIV_ROUND_UP_ULL(NSEC_PER_SEC, clk_rate);
                state->duty_cycle = DIV_ROUND_UP_ULL(state->period, 2);
                state->polarity = PWM_POLARITY_NORMAL;
                state->enabled = true;
                return;
        }

        if ((PWM_REG_PRESCAL(val, pwm->hwpwm) == PWM_PRESCAL_MASK) &&
            sun4i_pwm->data->has_prescaler_bypass)
                prescaler = 1;
        else
                prescaler = prescaler_table[PWM_REG_PRESCAL(val, pwm->hwpwm)];

        if (prescaler == 0)
                return;

        if (val & BIT_CH(PWM_ACT_STATE, pwm->hwpwm))
                state->polarity = PWM_POLARITY_NORMAL;
        else
                state->polarity = PWM_POLARITY_INVERSED;

        if ((val & BIT_CH(PWM_CLK_GATING | PWM_EN, pwm->hwpwm)) ==
            BIT_CH(PWM_CLK_GATING | PWM_EN, pwm->hwpwm))
                state->enabled = true;
        else
                state->enabled = false;

        val = sun4i_pwm_readl(sun4i_pwm, PWM_CH_PRD(pwm->hwpwm));

        tmp = (u64)prescaler * NSEC_PER_SEC * PWM_REG_DTY(val);
        state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, clk_rate);

        tmp = (u64)prescaler * NSEC_PER_SEC * PWM_REG_PRD(val);
        state->period = DIV_ROUND_CLOSEST_ULL(tmp, clk_rate);
}

static int sun4i_pwm_calculate(struct sun4i_pwm_chip *sun4i_pwm,
                               const struct pwm_state *state,
                               u32 *dty, u32 *prd, unsigned int *prsclr,
                               bool *bypass)
{
        u64 clk_rate, div = 0;
        unsigned int prescaler = 0;

        clk_rate = clk_get_rate(sun4i_pwm->clk);

        *bypass = sun4i_pwm->data->has_direct_mod_clk_output &&
                  state->enabled &&
                  (state->period * clk_rate >= NSEC_PER_SEC) &&
                  (state->period * clk_rate < 2 * NSEC_PER_SEC) &&
                  (state->duty_cycle * clk_rate * 2 >= NSEC_PER_SEC);

        /* Skip calculation of other parameters if we bypass them */
        if (*bypass)
                return 0;

        if (sun4i_pwm->data->has_prescaler_bypass) {
                /* First, test without any prescaler when available */
                prescaler = PWM_PRESCAL_MASK;
                /*
                 * When not using any prescaler, the clock period in nanoseconds
                 * is not an integer so round it half up instead of
                 * truncating to get less surprising values.
                 */
                div = clk_rate * state->period + NSEC_PER_SEC / 2;
                do_div(div, NSEC_PER_SEC);
                if (div - 1 > PWM_PRD_MASK)
                        prescaler = 0;
        }

        if (prescaler == 0) {
                /* Go up from the first divider */
                for (prescaler = 0; prescaler < PWM_PRESCAL_MASK; prescaler++) {
                        unsigned int pval = prescaler_table[prescaler];

                        if (!pval)
                                continue;

                        div = clk_rate;
                        do_div(div, pval);
                        div = div * state->period;
                        do_div(div, NSEC_PER_SEC);
                        if (div - 1 <= PWM_PRD_MASK)
                                break;
                }

                if (div - 1 > PWM_PRD_MASK)
                        return -EINVAL;
        }

        *prd = div;
        div *= state->duty_cycle;
        do_div(div, state->period);
        *dty = div;
        *prsclr = prescaler;

        return 0;
}

static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
                           const struct pwm_state *state)
{
        struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
        struct pwm_state cstate;
        u32 ctrl, duty = 0, period = 0, val;
        int ret;
        unsigned int delay_us, prescaler = 0;
        unsigned long now;
        bool bypass;

        pwm_get_state(pwm, &cstate);

        if (!cstate.enabled) {
                ret = clk_prepare_enable(sun4i_pwm->clk);
                if (ret) {
                        dev_err(chip->dev, "failed to enable PWM clock\n");
                        return ret;
                }
        }

        ret = sun4i_pwm_calculate(sun4i_pwm, state, &duty, &period, &prescaler,
                                  &bypass);
        if (ret) {
                dev_err(chip->dev, "period exceeds the maximum value\n");
                if (!cstate.enabled)
                        clk_disable_unprepare(sun4i_pwm->clk);
                return ret;
        }

        spin_lock(&sun4i_pwm->ctrl_lock);
        ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);

        if (sun4i_pwm->data->has_direct_mod_clk_output) {
                if (bypass) {
                        ctrl |= BIT_CH(PWM_BYPASS, pwm->hwpwm);
                        /* We can skip other parameter */
                        sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
                        spin_unlock(&sun4i_pwm->ctrl_lock);
                        return 0;
                }

                ctrl &= ~BIT_CH(PWM_BYPASS, pwm->hwpwm);
        }

        if (PWM_REG_PRESCAL(ctrl, pwm->hwpwm) != prescaler) {
                /* Prescaler changed, the clock has to be gated */
                ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
                sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);

                ctrl &= ~BIT_CH(PWM_PRESCAL_MASK, pwm->hwpwm);
                ctrl |= BIT_CH(prescaler, pwm->hwpwm);
        }

        val = (duty & PWM_DTY_MASK) | PWM_PRD(period);
        sun4i_pwm_writel(sun4i_pwm, val, PWM_CH_PRD(pwm->hwpwm));
        sun4i_pwm->next_period[pwm->hwpwm] = jiffies +
                nsecs_to_jiffies(cstate.period + 1000);

        if (state->polarity != PWM_POLARITY_NORMAL)
                ctrl &= ~BIT_CH(PWM_ACT_STATE, pwm->hwpwm);
        else
                ctrl |= BIT_CH(PWM_ACT_STATE, pwm->hwpwm);

        ctrl |= BIT_CH(PWM_CLK_GATING, pwm->hwpwm);

        if (state->enabled)
                ctrl |= BIT_CH(PWM_EN, pwm->hwpwm);

        sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);

        spin_unlock(&sun4i_pwm->ctrl_lock);

        if (state->enabled)
                return 0;

        /* We need a full period to elapse before disabling the channel. */
        now = jiffies;
        if (time_before(now, sun4i_pwm->next_period[pwm->hwpwm])) {
                delay_us = jiffies_to_usecs(sun4i_pwm->next_period[pwm->hwpwm] -
                                           now);
                if ((delay_us / 500) > MAX_UDELAY_MS)
                        msleep(delay_us / 1000 + 1);
                else
                        usleep_range(delay_us, delay_us * 2);
        }

        spin_lock(&sun4i_pwm->ctrl_lock);
        ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
        ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
        ctrl &= ~BIT_CH(PWM_EN, pwm->hwpwm);
        sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
        spin_unlock(&sun4i_pwm->ctrl_lock);

        clk_disable_unprepare(sun4i_pwm->clk);

        return 0;
}

static const struct pwm_ops sun4i_pwm_ops = {
        .apply = sun4i_pwm_apply,
        .get_state = sun4i_pwm_get_state,
        .owner = THIS_MODULE,
};

static const struct sun4i_pwm_data sun4i_pwm_dual_nobypass = {
        .has_prescaler_bypass = false,
        .npwm = 2,
};

static const struct sun4i_pwm_data sun4i_pwm_dual_bypass = {
        .has_prescaler_bypass = true,
        .npwm = 2,
};

static const struct sun4i_pwm_data sun4i_pwm_single_bypass = {
        .has_prescaler_bypass = true,
        .npwm = 1,
};

static const struct sun4i_pwm_data sun50i_a64_pwm_data = {
        .has_prescaler_bypass = true,
        .has_direct_mod_clk_output = true,
        .npwm = 1,
};

static const struct sun4i_pwm_data sun50i_h6_pwm_data = {
        .has_prescaler_bypass = true,
        .has_direct_mod_clk_output = true,
        .npwm = 2,
};

static const struct of_device_id sun4i_pwm_dt_ids[] = {
        {
                .compatible = "allwinner,sun4i-a10-pwm",
                .data = &sun4i_pwm_dual_nobypass,
        }, {
                .compatible = "allwinner,sun5i-a10s-pwm",
                .data = &sun4i_pwm_dual_bypass,
        }, {
                .compatible = "allwinner,sun5i-a13-pwm",
                .data = &sun4i_pwm_single_bypass,
        }, {
                .compatible = "allwinner,sun7i-a20-pwm",
                .data = &sun4i_pwm_dual_bypass,
        }, {
                .compatible = "allwinner,sun8i-h3-pwm",
                .data = &sun4i_pwm_single_bypass,
        }, {
                .compatible = "allwinner,sun50i-a64-pwm",
                .data = &sun50i_a64_pwm_data,
        }, {
                .compatible = "allwinner,sun50i-h6-pwm",
                .data = &sun50i_h6_pwm_data,
        }, {
                /* sentinel */
        },
};
MODULE_DEVICE_TABLE(of, sun4i_pwm_dt_ids);

static int sun4i_pwm_probe(struct platform_device *pdev)
{
        struct sun4i_pwm_chip *pwm;
        int ret;

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

        pwm->data = of_device_get_match_data(&pdev->dev);
        if (!pwm->data)
                return -ENODEV;

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

        /*
         * All hardware variants need a source clock that is divided and
         * then feeds the counter that defines the output wave form. In the
         * device tree this clock is either unnamed or called "mod".
         * Some variants (e.g. H6) need another clock to access the
         * hardware registers; this is called "bus".
         * So we request "mod" first (and ignore the corner case that a
         * parent provides a "mod" clock while the right one would be the
         * unnamed one of the PWM device) and if this is not found we fall
         * back to the first clock of the PWM.
         */
        pwm->clk = devm_clk_get_optional(&pdev->dev, "mod");
        if (IS_ERR(pwm->clk))
                return dev_err_probe(&pdev->dev, PTR_ERR(pwm->clk),
                                     "get mod clock failed\n");

        if (!pwm->clk) {
                pwm->clk = devm_clk_get(&pdev->dev, NULL);
                if (IS_ERR(pwm->clk))
                        return dev_err_probe(&pdev->dev, PTR_ERR(pwm->clk),
                                             "get unnamed clock failed\n");
        }

        pwm->bus_clk = devm_clk_get_optional(&pdev->dev, "bus");
        if (IS_ERR(pwm->bus_clk))
                return dev_err_probe(&pdev->dev, PTR_ERR(pwm->bus_clk),
                                     "get bus clock failed\n");

        pwm->rst = devm_reset_control_get_optional_shared(&pdev->dev, NULL);
        if (IS_ERR(pwm->rst))
                return dev_err_probe(&pdev->dev, PTR_ERR(pwm->rst),
                                     "get reset failed\n");

        /* Deassert reset */
        ret = reset_control_deassert(pwm->rst);
        if (ret) {
                dev_err(&pdev->dev, "cannot deassert reset control: %pe\n",
                        ERR_PTR(ret));
                return ret;
        }

        /*
         * We're keeping the bus clock on for the sake of simplicity.
         * Actually it only needs to be on for hardware register accesses.
         */
        ret = clk_prepare_enable(pwm->bus_clk);
        if (ret) {
                dev_err(&pdev->dev, "cannot prepare and enable bus_clk %pe\n",
                        ERR_PTR(ret));
                goto err_bus;
        }

        pwm->chip.dev = &pdev->dev;
        pwm->chip.ops = &sun4i_pwm_ops;
        pwm->chip.npwm = pwm->data->npwm;

        spin_lock_init(&pwm->ctrl_lock);

        ret = pwmchip_add(&pwm->chip);
        if (ret < 0) {
                dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
                goto err_pwm_add;
        }

        platform_set_drvdata(pdev, pwm);

        return 0;

err_pwm_add:
        clk_disable_unprepare(pwm->bus_clk);
err_bus:
        reset_control_assert(pwm->rst);

        return ret;
}

static int sun4i_pwm_remove(struct platform_device *pdev)
{
        struct sun4i_pwm_chip *pwm = platform_get_drvdata(pdev);

        pwmchip_remove(&pwm->chip);

        clk_disable_unprepare(pwm->bus_clk);
        reset_control_assert(pwm->rst);

        return 0;
}

static struct platform_driver sun4i_pwm_driver = {
        .driver = {
                .name = "sun4i-pwm",
                .of_match_table = sun4i_pwm_dt_ids,
        },
        .probe = sun4i_pwm_probe,
        .remove = sun4i_pwm_remove,
};
module_platform_driver(sun4i_pwm_driver);

MODULE_ALIAS("platform:sun4i-pwm");
MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
MODULE_DESCRIPTION("Allwinner sun4i PWM driver");
MODULE_LICENSE("GPL v2");