// SPDX-License-Identifier: GPL-2.0-only
/*
 * Driver for Atmel Pulse Width Modulation Controller
 *
 * Copyright (C) 2013 Atmel Corporation
 *               Bo Shen <voice.shen@atmel.com>
 *
 * Links to reference manuals for the supported PWM chips can be found in
 * Documentation/arm/microchip.rst.
 *
 * Limitations:
 * - Periods start with the inactive level.
 * - Hardware has to be stopped in general to update settings.
 *
 * Software bugs/possible improvements:
 * - When atmel_pwm_apply() is called with state->enabled=false a change in
 *   state->polarity isn't honored.
 * - Instead of sleeping to wait for a completed period, the interrupt
 *   functionality could be used.
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/io.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/slab.h>

/* The following is global registers for PWM controller */
#define PWM_ENA                 0x04
#define PWM_DIS                 0x08
#define PWM_SR                  0x0C
#define PWM_ISR                 0x1C
/* Bit field in SR */
#define PWM_SR_ALL_CH_ON        0x0F

/* The following register is PWM channel related registers */
#define PWM_CH_REG_OFFSET       0x200
#define PWM_CH_REG_SIZE         0x20

#define PWM_CMR                 0x0
/* Bit field in CMR */
#define PWM_CMR_CPOL            (1 << 9)
#define PWM_CMR_UPD_CDTY        (1 << 10)
#define PWM_CMR_CPRE_MSK        0xF

/* The following registers for PWM v1 */
#define PWMV1_CDTY              0x04
#define PWMV1_CPRD              0x08
#define PWMV1_CUPD              0x10

/* The following registers for PWM v2 */
#define PWMV2_CDTY              0x04
#define PWMV2_CDTYUPD           0x08
#define PWMV2_CPRD              0x0C
#define PWMV2_CPRDUPD           0x10

#define PWM_MAX_PRES            10

struct atmel_pwm_registers {
        u8 period;
        u8 period_upd;
        u8 duty;
        u8 duty_upd;
};

struct atmel_pwm_config {
        u32 period_bits;
};

struct atmel_pwm_data {
        struct atmel_pwm_registers regs;
        struct atmel_pwm_config cfg;
};

struct atmel_pwm_chip {
        struct pwm_chip chip;
        struct clk *clk;
        void __iomem *base;
        const struct atmel_pwm_data *data;

        /*
         * The hardware supports a mechanism to update a channel's duty cycle at
         * the end of the currently running period. When such an update is
         * pending we delay disabling the PWM until the new configuration is
         * active because otherwise pmw_config(duty_cycle=0); pwm_disable();
         * might not result in an inactive output.
         * This bitmask tracks for which channels an update is pending in
         * hardware.
         */
        u32 update_pending;

        /* Protects .update_pending */
        spinlock_t lock;
};

static inline struct atmel_pwm_chip *to_atmel_pwm_chip(struct pwm_chip *chip)
{
        return container_of(chip, struct atmel_pwm_chip, chip);
}

static inline u32 atmel_pwm_readl(struct atmel_pwm_chip *chip,
                                  unsigned long offset)
{
        return readl_relaxed(chip->base + offset);
}

static inline void atmel_pwm_writel(struct atmel_pwm_chip *chip,
                                    unsigned long offset, unsigned long val)
{
        writel_relaxed(val, chip->base + offset);
}

static inline u32 atmel_pwm_ch_readl(struct atmel_pwm_chip *chip,
                                     unsigned int ch, unsigned long offset)
{
        unsigned long base = PWM_CH_REG_OFFSET + ch * PWM_CH_REG_SIZE;

        return atmel_pwm_readl(chip, base + offset);
}

static inline void atmel_pwm_ch_writel(struct atmel_pwm_chip *chip,
                                       unsigned int ch, unsigned long offset,
                                       unsigned long val)
{
        unsigned long base = PWM_CH_REG_OFFSET + ch * PWM_CH_REG_SIZE;

        atmel_pwm_writel(chip, base + offset, val);
}

static void atmel_pwm_update_pending(struct atmel_pwm_chip *chip)
{
        /*
         * Each channel that has its bit in ISR set started a new period since
         * ISR was cleared and so there is no more update pending.  Note that
         * reading ISR clears it, so this needs to handle all channels to not
         * loose information.
         */
        u32 isr = atmel_pwm_readl(chip, PWM_ISR);

        chip->update_pending &= ~isr;
}

static void atmel_pwm_set_pending(struct atmel_pwm_chip *chip, unsigned int ch)
{
        spin_lock(&chip->lock);

        /*
         * Clear pending flags in hardware because otherwise there might still
         * be a stale flag in ISR.
         */
        atmel_pwm_update_pending(chip);

        chip->update_pending |= (1 << ch);

        spin_unlock(&chip->lock);
}

static int atmel_pwm_test_pending(struct atmel_pwm_chip *chip, unsigned int ch)
{
        int ret = 0;

        spin_lock(&chip->lock);

        if (chip->update_pending & (1 << ch)) {
                atmel_pwm_update_pending(chip);

                if (chip->update_pending & (1 << ch))
                        ret = 1;
        }

        spin_unlock(&chip->lock);

        return ret;
}

static int atmel_pwm_wait_nonpending(struct atmel_pwm_chip *chip, unsigned int ch)
{
        unsigned long timeout = jiffies + 2 * HZ;
        int ret;

        while ((ret = atmel_pwm_test_pending(chip, ch)) &&
               time_before(jiffies, timeout))
                usleep_range(10, 100);

        return ret ? -ETIMEDOUT : 0;
}

static int atmel_pwm_calculate_cprd_and_pres(struct pwm_chip *chip,
                                             unsigned long clkrate,
                                             const struct pwm_state *state,
                                             unsigned long *cprd, u32 *pres)
{
        struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
        unsigned long long cycles = state->period;
        int shift;

        /* Calculate the period cycles and prescale value */
        cycles *= clkrate;
        do_div(cycles, NSEC_PER_SEC);

        /*
         * The register for the period length is cfg.period_bits bits wide.
         * So for each bit the number of clock cycles is wider divide the input
         * clock frequency by two using pres and shift cprd accordingly.
         */
        shift = fls(cycles) - atmel_pwm->data->cfg.period_bits;

        if (shift > PWM_MAX_PRES) {
                dev_err(chip->dev, "pres exceeds the maximum value\n");
                return -EINVAL;
        } else if (shift > 0) {
                *pres = shift;
                cycles >>= *pres;
        } else {
                *pres = 0;
        }

        *cprd = cycles;

        return 0;
}

static void atmel_pwm_calculate_cdty(const struct pwm_state *state,
                                     unsigned long clkrate, unsigned long cprd,
                                     u32 pres, unsigned long *cdty)
{
        unsigned long long cycles = state->duty_cycle;

        cycles *= clkrate;
        do_div(cycles, NSEC_PER_SEC);
        cycles >>= pres;
        *cdty = cprd - cycles;
}

static void atmel_pwm_update_cdty(struct pwm_chip *chip, struct pwm_device *pwm,
                                  unsigned long cdty)
{
        struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
        u32 val;

        if (atmel_pwm->data->regs.duty_upd ==
            atmel_pwm->data->regs.period_upd) {
                val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
                val &= ~PWM_CMR_UPD_CDTY;
                atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
        }

        atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm,
                            atmel_pwm->data->regs.duty_upd, cdty);
        atmel_pwm_set_pending(atmel_pwm, pwm->hwpwm);
}

static void atmel_pwm_set_cprd_cdty(struct pwm_chip *chip,
                                    struct pwm_device *pwm,
                                    unsigned long cprd, unsigned long cdty)
{
        struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);

        atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm,
                            atmel_pwm->data->regs.duty, cdty);
        atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm,
                            atmel_pwm->data->regs.period, cprd);
}

static void atmel_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm,
                              bool disable_clk)
{
        struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
        unsigned long timeout = jiffies + 2 * HZ;

        atmel_pwm_wait_nonpending(atmel_pwm, pwm->hwpwm);

        atmel_pwm_writel(atmel_pwm, PWM_DIS, 1 << pwm->hwpwm);

        /*
         * Wait for the PWM channel disable operation to be effective before
         * stopping the clock.
         */
        timeout = jiffies + 2 * HZ;

        while ((atmel_pwm_readl(atmel_pwm, PWM_SR) & (1 << pwm->hwpwm)) &&
               time_before(jiffies, timeout))
                usleep_range(10, 100);

        if (disable_clk)
                clk_disable(atmel_pwm->clk);
}

static int atmel_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
                           const struct pwm_state *state)
{
        struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
        struct pwm_state cstate;
        unsigned long cprd, cdty;
        u32 pres, val;
        int ret;

        pwm_get_state(pwm, &cstate);

        if (state->enabled) {
                unsigned long clkrate = clk_get_rate(atmel_pwm->clk);

                if (cstate.enabled &&
                    cstate.polarity == state->polarity &&
                    cstate.period == state->period) {
                        u32 cmr = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);

                        cprd = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm,
                                                  atmel_pwm->data->regs.period);
                        pres = cmr & PWM_CMR_CPRE_MSK;

                        atmel_pwm_calculate_cdty(state, clkrate, cprd, pres, &cdty);
                        atmel_pwm_update_cdty(chip, pwm, cdty);
                        return 0;
                }

                ret = atmel_pwm_calculate_cprd_and_pres(chip, clkrate, state, &cprd,
                                                        &pres);
                if (ret) {
                        dev_err(chip->dev,
                                "failed to calculate cprd and prescaler\n");
                        return ret;
                }

                atmel_pwm_calculate_cdty(state, clkrate, cprd, pres, &cdty);

                if (cstate.enabled) {
                        atmel_pwm_disable(chip, pwm, false);
                } else {
                        ret = clk_enable(atmel_pwm->clk);
                        if (ret) {
                                dev_err(chip->dev, "failed to enable clock\n");
                                return ret;
                        }
                }

                /* It is necessary to preserve CPOL, inside CMR */
                val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
                val = (val & ~PWM_CMR_CPRE_MSK) | (pres & PWM_CMR_CPRE_MSK);
                if (state->polarity == PWM_POLARITY_NORMAL)
                        val &= ~PWM_CMR_CPOL;
                else
                        val |= PWM_CMR_CPOL;
                atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
                atmel_pwm_set_cprd_cdty(chip, pwm, cprd, cdty);
                atmel_pwm_writel(atmel_pwm, PWM_ENA, 1 << pwm->hwpwm);
        } else if (cstate.enabled) {
                atmel_pwm_disable(chip, pwm, true);
        }

        return 0;
}

static void atmel_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
                                struct pwm_state *state)
{
        struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
        u32 sr, cmr;

        sr = atmel_pwm_readl(atmel_pwm, PWM_SR);
        cmr = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);

        if (sr & (1 << pwm->hwpwm)) {
                unsigned long rate = clk_get_rate(atmel_pwm->clk);
                u32 cdty, cprd, pres;
                u64 tmp;

                pres = cmr & PWM_CMR_CPRE_MSK;

                cprd = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm,
                                          atmel_pwm->data->regs.period);
                tmp = (u64)cprd * NSEC_PER_SEC;
                tmp <<= pres;
                state->period = DIV64_U64_ROUND_UP(tmp, rate);

                /* Wait for an updated duty_cycle queued in hardware */
                atmel_pwm_wait_nonpending(atmel_pwm, pwm->hwpwm);

                cdty = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm,
                                          atmel_pwm->data->regs.duty);
                tmp = (u64)(cprd - cdty) * NSEC_PER_SEC;
                tmp <<= pres;
                state->duty_cycle = DIV64_U64_ROUND_UP(tmp, rate);

                state->enabled = true;
        } else {
                state->enabled = false;
        }

        if (cmr & PWM_CMR_CPOL)
                state->polarity = PWM_POLARITY_INVERSED;
        else
                state->polarity = PWM_POLARITY_NORMAL;
}

static const struct pwm_ops atmel_pwm_ops = {
        .apply = atmel_pwm_apply,
        .get_state = atmel_pwm_get_state,
        .owner = THIS_MODULE,
};

static const struct atmel_pwm_data atmel_sam9rl_pwm_data = {
        .regs = {
                .period         = PWMV1_CPRD,
                .period_upd     = PWMV1_CUPD,
                .duty           = PWMV1_CDTY,
                .duty_upd       = PWMV1_CUPD,
        },
        .cfg = {
                /* 16 bits to keep period and duty. */
                .period_bits    = 16,
        },
};

static const struct atmel_pwm_data atmel_sama5_pwm_data = {
        .regs = {
                .period         = PWMV2_CPRD,
                .period_upd     = PWMV2_CPRDUPD,
                .duty           = PWMV2_CDTY,
                .duty_upd       = PWMV2_CDTYUPD,
        },
        .cfg = {
                /* 16 bits to keep period and duty. */
                .period_bits    = 16,
        },
};

static const struct atmel_pwm_data mchp_sam9x60_pwm_data = {
        .regs = {
                .period         = PWMV1_CPRD,
                .period_upd     = PWMV1_CUPD,
                .duty           = PWMV1_CDTY,
                .duty_upd       = PWMV1_CUPD,
        },
        .cfg = {
                /* 32 bits to keep period and duty. */
                .period_bits    = 32,
        },
};

static const struct of_device_id atmel_pwm_dt_ids[] = {
        {
                .compatible = "atmel,at91sam9rl-pwm",
                .data = &atmel_sam9rl_pwm_data,
        }, {
                .compatible = "atmel,sama5d3-pwm",
                .data = &atmel_sama5_pwm_data,
        }, {
                .compatible = "atmel,sama5d2-pwm",
                .data = &atmel_sama5_pwm_data,
        }, {
                .compatible = "microchip,sam9x60-pwm",
                .data = &mchp_sam9x60_pwm_data,
        }, {
                /* sentinel */
        },
};
MODULE_DEVICE_TABLE(of, atmel_pwm_dt_ids);

static int atmel_pwm_probe(struct platform_device *pdev)
{
        struct atmel_pwm_chip *atmel_pwm;
        int ret;

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

        atmel_pwm->data = of_device_get_match_data(&pdev->dev);

        atmel_pwm->update_pending = 0;
        spin_lock_init(&atmel_pwm->lock);

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

        atmel_pwm->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(atmel_pwm->clk))
                return PTR_ERR(atmel_pwm->clk);

        ret = clk_prepare(atmel_pwm->clk);
        if (ret) {
                dev_err(&pdev->dev, "failed to prepare PWM clock\n");
                return ret;
        }

        atmel_pwm->chip.dev = &pdev->dev;
        atmel_pwm->chip.ops = &atmel_pwm_ops;
        atmel_pwm->chip.npwm = 4;

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

        platform_set_drvdata(pdev, atmel_pwm);

        return ret;

unprepare_clk:
        clk_unprepare(atmel_pwm->clk);
        return ret;
}

static int atmel_pwm_remove(struct platform_device *pdev)
{
        struct atmel_pwm_chip *atmel_pwm = platform_get_drvdata(pdev);

        pwmchip_remove(&atmel_pwm->chip);

        clk_unprepare(atmel_pwm->clk);

        return 0;
}

static struct platform_driver atmel_pwm_driver = {
        .driver = {
                .name = "atmel-pwm",
                .of_match_table = of_match_ptr(atmel_pwm_dt_ids),
        },
        .probe = atmel_pwm_probe,
        .remove = atmel_pwm_remove,
};
module_platform_driver(atmel_pwm_driver);

MODULE_ALIAS("platform:atmel-pwm");
MODULE_AUTHOR("Bo Shen <voice.shen@atmel.com>");
MODULE_DESCRIPTION("Atmel PWM driver");
MODULE_LICENSE("GPL v2");