// SPDX-License-Identifier: GPL-2.0-only
/*
 * Toshiba Visconti pulse-width-modulation controller driver
 *
 * Copyright (c) 2020 - 2021 TOSHIBA CORPORATION
 * Copyright (c) 2020 - 2021 Toshiba Electronic Devices & Storage Corporation
 *
 * Authors: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
 *
 * Limitations:
 * - The fixed input clock is running at 1 MHz and is divided by either 1,
 *   2, 4 or 8.
 * - When the settings of the PWM are modified, the new values are shadowed
 *   in hardware until the PIPGM_PCSR register is written and the currently
 *   running period is completed. This way the hardware switches atomically
 *   from the old setting to the new.
 * - Disabling the hardware completes the currently running period and keeps
 *   the output at low level at all times.
 */

#include <linux/err.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>

#define PIPGM_PCSR(ch) (0x400 + 4 * (ch))
#define PIPGM_PDUT(ch) (0x420 + 4 * (ch))
#define PIPGM_PWMC(ch) (0x440 + 4 * (ch))

#define PIPGM_PWMC_PWMACT               BIT(5)
#define PIPGM_PWMC_CLK_MASK             GENMASK(1, 0)
#define PIPGM_PWMC_POLARITY_MASK        GENMASK(5, 5)

struct visconti_pwm_chip {
        void __iomem *base;
};

static inline struct visconti_pwm_chip *visconti_pwm_from_chip(struct pwm_chip *chip)
{
        return pwmchip_get_drvdata(chip);
}

static int visconti_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
                              const struct pwm_state *state)
{
        struct visconti_pwm_chip *priv = visconti_pwm_from_chip(chip);
        u32 period, duty_cycle, pwmc0;

        if (!state->enabled) {
                writel(0, priv->base + PIPGM_PCSR(pwm->hwpwm));
                return 0;
        }

        /*
         * The biggest period the hardware can provide is
         *      (0xffff << 3) * 1000 ns
         * This value fits easily in an u32, so simplify the maths by
         * capping the values to 32 bit integers.
         */
        if (state->period > (0xffff << 3) * 1000)
                period = (0xffff << 3) * 1000;
        else
                period = state->period;

        if (state->duty_cycle > period)
                duty_cycle = period;
        else
                duty_cycle = state->duty_cycle;

        /*
         * The input clock runs fixed at 1 MHz, so we have only
         * microsecond resolution and so can divide by
         * NSEC_PER_SEC / CLKFREQ = 1000 without losing precision.
         */
        period /= 1000;
        duty_cycle /= 1000;

        if (!period)
                return -ERANGE;

        /*
         * PWMC controls a divider that divides the input clk by a power of two
         * between 1 and 8. As a smaller divider yields higher precision, pick
         * the smallest possible one. As period is at most 0xffff << 3, pwmc0 is
         * in the intended range [0..3].
         */
        pwmc0 = fls(period >> 16);
        if (WARN_ON(pwmc0 > 3))
                return -EINVAL;

        period >>= pwmc0;
        duty_cycle >>= pwmc0;

        if (state->polarity == PWM_POLARITY_INVERSED)
                pwmc0 |= PIPGM_PWMC_PWMACT;
        writel(pwmc0, priv->base + PIPGM_PWMC(pwm->hwpwm));
        writel(duty_cycle, priv->base + PIPGM_PDUT(pwm->hwpwm));
        writel(period, priv->base + PIPGM_PCSR(pwm->hwpwm));

        return 0;
}

static int visconti_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
                                  struct pwm_state *state)
{
        struct visconti_pwm_chip *priv = visconti_pwm_from_chip(chip);
        u32 period, duty, pwmc0, pwmc0_clk;

        period = readl(priv->base + PIPGM_PCSR(pwm->hwpwm));
        duty = readl(priv->base + PIPGM_PDUT(pwm->hwpwm));
        pwmc0 = readl(priv->base + PIPGM_PWMC(pwm->hwpwm));
        pwmc0_clk = pwmc0 & PIPGM_PWMC_CLK_MASK;

        state->period = (period << pwmc0_clk) * NSEC_PER_USEC;
        state->duty_cycle = (duty << pwmc0_clk) * NSEC_PER_USEC;
        if (pwmc0 & PIPGM_PWMC_POLARITY_MASK)
                state->polarity = PWM_POLARITY_INVERSED;
        else
                state->polarity = PWM_POLARITY_NORMAL;

        state->enabled = true;

        return 0;
}

static const struct pwm_ops visconti_pwm_ops = {
        .apply = visconti_pwm_apply,
        .get_state = visconti_pwm_get_state,
};

static int visconti_pwm_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct pwm_chip *chip;
        struct visconti_pwm_chip *priv;
        int ret;

        chip = devm_pwmchip_alloc(dev, 4, sizeof(*priv));
        if (IS_ERR(chip))
                return PTR_ERR(chip);
        priv = visconti_pwm_from_chip(chip);

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

        chip->ops = &visconti_pwm_ops;

        ret = devm_pwmchip_add(&pdev->dev, chip);
        if (ret < 0)
                return dev_err_probe(&pdev->dev, ret, "Cannot register visconti PWM\n");

        return 0;
}

static const struct of_device_id visconti_pwm_of_match[] = {
        { .compatible = "toshiba,visconti-pwm", },
        { }
};
MODULE_DEVICE_TABLE(of, visconti_pwm_of_match);

static struct platform_driver visconti_pwm_driver = {
        .driver = {
                .name = "pwm-visconti",
                .of_match_table = visconti_pwm_of_match,
        },
        .probe = visconti_pwm_probe,
};
module_platform_driver(visconti_pwm_driver);

MODULE_DESCRIPTION("Toshiba Visconti Pulse Width Modulator driver");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>");
MODULE_ALIAS("platform:pwm-visconti");