// SPDX-License-Identifier: GPL-2.0-only
/*
 * drivers/pwm/pwm-vt8500.c
 *
 * Copyright (C) 2012 Tony Prisk <linux@prisktech.co.nz>
 * Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
 */

#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/pwm.h>
#include <linux/delay.h>
#include <linux/clk.h>

#include <asm/div64.h>

/*
 * SoC architecture allocates register space for 4 PWMs but only
 * 2 are currently implemented.
 */
#define VT8500_NR_PWMS  2

#define REG_CTRL(pwm)           (((pwm) << 4) + 0x00)
#define REG_SCALAR(pwm)         (((pwm) << 4) + 0x04)
#define REG_PERIOD(pwm)         (((pwm) << 4) + 0x08)
#define REG_DUTY(pwm)           (((pwm) << 4) + 0x0C)
#define REG_STATUS              0x40

#define CTRL_ENABLE             BIT(0)
#define CTRL_INVERT             BIT(1)
#define CTRL_AUTOLOAD           BIT(2)
#define CTRL_STOP_IMM           BIT(3)
#define CTRL_LOAD_PRESCALE      BIT(4)
#define CTRL_LOAD_PERIOD        BIT(5)

#define STATUS_CTRL_UPDATE      BIT(0)
#define STATUS_SCALAR_UPDATE    BIT(1)
#define STATUS_PERIOD_UPDATE    BIT(2)
#define STATUS_DUTY_UPDATE      BIT(3)
#define STATUS_ALL_UPDATE       0x0F

struct vt8500_chip {
        void __iomem *base;
        struct clk *clk;
};

static inline struct vt8500_chip *to_vt8500_chip(struct pwm_chip *chip)
{
        return pwmchip_get_drvdata(chip);
}

#define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
static inline void vt8500_pwm_busy_wait(struct pwm_chip *chip, int nr, u8 bitmask)
{
        struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
        int loops = msecs_to_loops(10);
        u32 mask = bitmask << (nr << 8);

        while ((readl(vt8500->base + REG_STATUS) & mask) && --loops)
                cpu_relax();

        if (unlikely(!loops))
                dev_warn(pwmchip_parent(chip), "Waiting for status bits 0x%x to clear timed out\n",
                         mask);
}

static int vt8500_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
                u64 duty_ns, u64 period_ns)
{
        struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
        unsigned long long c;
        unsigned long period_cycles, prescale, pv, dc;
        int err;
        u32 val;

        err = clk_enable(vt8500->clk);
        if (err < 0) {
                dev_err(pwmchip_parent(chip), "failed to enable clock\n");
                return err;
        }

        c = clk_get_rate(vt8500->clk);
        c = c * period_ns;
        do_div(c, 1000000000);
        period_cycles = c;

        if (period_cycles < 1)
                period_cycles = 1;
        prescale = (period_cycles - 1) / 4096;
        pv = period_cycles / (prescale + 1) - 1;
        if (pv > 4095)
                pv = 4095;

        if (prescale > 1023) {
                clk_disable(vt8500->clk);
                return -EINVAL;
        }

        c = (unsigned long long)pv * duty_ns;

        dc = div64_u64(c, period_ns);

        writel(prescale, vt8500->base + REG_SCALAR(pwm->hwpwm));
        vt8500_pwm_busy_wait(chip, pwm->hwpwm, STATUS_SCALAR_UPDATE);

        writel(pv, vt8500->base + REG_PERIOD(pwm->hwpwm));
        vt8500_pwm_busy_wait(chip, pwm->hwpwm, STATUS_PERIOD_UPDATE);

        writel(dc, vt8500->base + REG_DUTY(pwm->hwpwm));
        vt8500_pwm_busy_wait(chip, pwm->hwpwm, STATUS_DUTY_UPDATE);

        val = readl(vt8500->base + REG_CTRL(pwm->hwpwm));
        val |= CTRL_AUTOLOAD;
        writel(val, vt8500->base + REG_CTRL(pwm->hwpwm));
        vt8500_pwm_busy_wait(chip, pwm->hwpwm, STATUS_CTRL_UPDATE);

        clk_disable(vt8500->clk);
        return 0;
}

static int vt8500_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
        int err;
        u32 val;

        err = clk_enable(vt8500->clk);
        if (err < 0) {
                dev_err(pwmchip_parent(chip), "failed to enable clock\n");
                return err;
        }

        val = readl(vt8500->base + REG_CTRL(pwm->hwpwm));
        val |= CTRL_ENABLE;
        writel(val, vt8500->base + REG_CTRL(pwm->hwpwm));
        vt8500_pwm_busy_wait(chip, pwm->hwpwm, STATUS_CTRL_UPDATE);

        return 0;
}

static void vt8500_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
        u32 val;

        val = readl(vt8500->base + REG_CTRL(pwm->hwpwm));
        val &= ~CTRL_ENABLE;
        writel(val, vt8500->base + REG_CTRL(pwm->hwpwm));
        vt8500_pwm_busy_wait(chip, pwm->hwpwm, STATUS_CTRL_UPDATE);

        clk_disable(vt8500->clk);
}

static int vt8500_pwm_set_polarity(struct pwm_chip *chip,
                                   struct pwm_device *pwm,
                                   enum pwm_polarity polarity)
{
        struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
        u32 val;

        val = readl(vt8500->base + REG_CTRL(pwm->hwpwm));

        if (polarity == PWM_POLARITY_INVERSED)
                val |= CTRL_INVERT;
        else
                val &= ~CTRL_INVERT;

        writel(val, vt8500->base + REG_CTRL(pwm->hwpwm));
        vt8500_pwm_busy_wait(chip, pwm->hwpwm, STATUS_CTRL_UPDATE);

        return 0;
}

static int vt8500_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
                            const struct pwm_state *state)
{
        int err;
        bool enabled = pwm->state.enabled;

        if (state->polarity != pwm->state.polarity) {
                /*
                 * Changing the polarity of a running PWM is only allowed when
                 * the PWM driver implements ->apply().
                 */
                if (enabled) {
                        vt8500_pwm_disable(chip, pwm);

                        enabled = false;
                }

                err = vt8500_pwm_set_polarity(chip, pwm, state->polarity);
                if (err)
                        return err;
        }

        if (!state->enabled) {
                if (enabled)
                        vt8500_pwm_disable(chip, pwm);

                return 0;
        }

        /*
         * We cannot skip calling ->config even if state->period ==
         * pwm->state.period && state->duty_cycle == pwm->state.duty_cycle
         * because we might have exited early in the last call to
         * pwm_apply_might_sleep because of !state->enabled and so the two values in
         * pwm->state might not be configured in hardware.
         */
        err = vt8500_pwm_config(chip, pwm, state->duty_cycle, state->period);
        if (err)
                return err;

        if (!enabled)
                err = vt8500_pwm_enable(chip, pwm);

        return err;
}

static const struct pwm_ops vt8500_pwm_ops = {
        .apply = vt8500_pwm_apply,
};

static const struct of_device_id vt8500_pwm_dt_ids[] = {
        { .compatible = "via,vt8500-pwm", },
        { /* Sentinel */ }
};
MODULE_DEVICE_TABLE(of, vt8500_pwm_dt_ids);

static int vt8500_pwm_probe(struct platform_device *pdev)
{
        struct pwm_chip *chip;
        struct vt8500_chip *vt8500;
        struct device_node *np = pdev->dev.of_node;
        int ret;

        if (!np)
                return dev_err_probe(&pdev->dev, -EINVAL, "invalid devicetree node\n");

        chip = devm_pwmchip_alloc(&pdev->dev, VT8500_NR_PWMS, sizeof(*vt8500));
        if (IS_ERR(chip))
                return PTR_ERR(chip);
        vt8500 = to_vt8500_chip(chip);

        chip->ops = &vt8500_pwm_ops;

        vt8500->clk = devm_clk_get_prepared(&pdev->dev, NULL);
        if (IS_ERR(vt8500->clk))
                return dev_err_probe(&pdev->dev, PTR_ERR(vt8500->clk), "clock source not specified\n");

        vt8500->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(vt8500->base))
                return PTR_ERR(vt8500->base);

        ret = devm_pwmchip_add(&pdev->dev, chip);
        if (ret < 0)
                return dev_err_probe(&pdev->dev, ret, "failed to add PWM chip\n");

        return 0;
}

static struct platform_driver vt8500_pwm_driver = {
        .probe          = vt8500_pwm_probe,
        .driver         = {
                .name   = "vt8500-pwm",
                .of_match_table = vt8500_pwm_dt_ids,
        },
};
module_platform_driver(vt8500_pwm_driver);

MODULE_DESCRIPTION("VT8500 PWM Driver");
MODULE_AUTHOR("Tony Prisk <linux@prisktech.co.nz>");
MODULE_LICENSE("GPL v2");