/*
 * Copyright (C) 2016 Linaro Ltd.
 *
 * Author: Linus Walleij <linus.walleij@linaro.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2, as
 * published by the Free Software Foundation.
 *
 */

#include <linux/bitops.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/mfd/stmpe.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>

#define STMPE24XX_PWMCS         0x30
#define PWMCS_EN_PWM0           BIT(0)
#define PWMCS_EN_PWM1           BIT(1)
#define PWMCS_EN_PWM2           BIT(2)
#define STMPE24XX_PWMIC0        0x38
#define STMPE24XX_PWMIC1        0x39
#define STMPE24XX_PWMIC2        0x3a

#define STMPE_PWM_24XX_PINBASE  21

struct stmpe_pwm {
        struct stmpe *stmpe;
        struct pwm_chip chip;
        u8 last_duty;
};

static inline struct stmpe_pwm *to_stmpe_pwm(struct pwm_chip *chip)
{
        return container_of(chip, struct stmpe_pwm, chip);
}

static int stmpe_24xx_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip);
        u8 value;
        int ret;

        ret = stmpe_reg_read(stmpe_pwm->stmpe, STMPE24XX_PWMCS);
        if (ret < 0) {
                dev_err(chip->dev, "error reading PWM#%u control\n",
                        pwm->hwpwm);
                return ret;
        }

        value = ret | BIT(pwm->hwpwm);

        ret = stmpe_reg_write(stmpe_pwm->stmpe, STMPE24XX_PWMCS, value);
        if (ret) {
                dev_err(chip->dev, "error writing PWM#%u control\n",
                        pwm->hwpwm);
                return ret;
        }

        return 0;
}

static void stmpe_24xx_pwm_disable(struct pwm_chip *chip,
                                   struct pwm_device *pwm)
{
        struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip);
        u8 value;
        int ret;

        ret = stmpe_reg_read(stmpe_pwm->stmpe, STMPE24XX_PWMCS);
        if (ret < 0) {
                dev_err(chip->dev, "error reading PWM#%u control\n",
                        pwm->hwpwm);
                return;
        }

        value = ret & ~BIT(pwm->hwpwm);

        ret = stmpe_reg_write(stmpe_pwm->stmpe, STMPE24XX_PWMCS, value);
        if (ret) {
                dev_err(chip->dev, "error writing PWM#%u control\n",
                        pwm->hwpwm);
                return;
        }
}

/* STMPE 24xx PWM instructions */
#define SMAX            0x007f
#define SMIN            0x00ff
#define GTS             0x0000
#define LOAD            BIT(14) /* Only available on 2403 */
#define RAMPUP          0x0000
#define RAMPDOWN        BIT(7)
#define PRESCALE_512    BIT(14)
#define STEPTIME_1      BIT(8)
#define BRANCH          (BIT(15) | BIT(13))

static int stmpe_24xx_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
                                 int duty_ns, int period_ns)
{
        struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip);
        unsigned int i, pin;
        u16 program[3] = {
                SMAX,
                GTS,
                GTS,
        };
        u8 offset;
        int ret;

        /* Make sure we are disabled */
        if (pwm_is_enabled(pwm)) {
                stmpe_24xx_pwm_disable(chip, pwm);
        } else {
                /* Connect the PWM to the pin */
                pin = pwm->hwpwm;

                /* On STMPE2401 and 2403 pins 21,22,23 are used */
                if (stmpe_pwm->stmpe->partnum == STMPE2401 ||
                    stmpe_pwm->stmpe->partnum == STMPE2403)
                        pin += STMPE_PWM_24XX_PINBASE;

                ret = stmpe_set_altfunc(stmpe_pwm->stmpe, BIT(pin),
                                        STMPE_BLOCK_PWM);
                if (ret) {
                        dev_err(chip->dev, "unable to connect PWM#%u to pin\n",
                                pwm->hwpwm);
                        return ret;
                }
        }

        /* STMPE24XX */
        switch (pwm->hwpwm) {
        case 0:
                offset = STMPE24XX_PWMIC0;
                break;

        case 1:
                offset = STMPE24XX_PWMIC1;
                break;

        case 2:
                offset = STMPE24XX_PWMIC2;
                break;

        default:
                /* Should not happen as npwm is 3 */
                return -ENODEV;
        }

        dev_dbg(chip->dev, "PWM#%u: config duty %d ns, period %d ns\n",
                pwm->hwpwm, duty_ns, period_ns);

        if (duty_ns == 0) {
                if (stmpe_pwm->stmpe->partnum == STMPE2401)
                        program[0] = SMAX; /* off all the time */

                if (stmpe_pwm->stmpe->partnum == STMPE2403)
                        program[0] = LOAD | 0xff; /* LOAD 0xff */

                stmpe_pwm->last_duty = 0x00;
        } else if (duty_ns == period_ns) {
                if (stmpe_pwm->stmpe->partnum == STMPE2401)
                        program[0] = SMIN; /* on all the time */

                if (stmpe_pwm->stmpe->partnum == STMPE2403)
                        program[0] = LOAD | 0x00; /* LOAD 0x00 */

                stmpe_pwm->last_duty = 0xff;
        } else {
                u8 value, last = stmpe_pwm->last_duty;
                unsigned long duty;

                /*
                 * Counter goes from 0x00 to 0xff repeatedly at 32768 Hz,
                 * (means a period of 30517 ns) then this is compared to the
                 * counter from the ramp, if this is >= PWM counter the output
                 * is high. With LOAD we can define how much of the cycle it
                 * is on.
                 *
                 * Prescale = 0 -> 2 kHz -> T = 1/f = 488281.25 ns
                 */

                /* Scale to 0..0xff */
                duty = duty_ns * 256;
                duty = DIV_ROUND_CLOSEST(duty, period_ns);
                value = duty;

                if (value == last) {
                        /* Run the old program */
                        if (pwm_is_enabled(pwm))
                                stmpe_24xx_pwm_enable(chip, pwm);

                        return 0;
                } else if (stmpe_pwm->stmpe->partnum == STMPE2403) {
                        /* STMPE2403 can simply set the right PWM value */
                        program[0] = LOAD | value;
                        program[1] = 0x0000;
                } else if (stmpe_pwm->stmpe->partnum == STMPE2401) {
                        /* STMPE2401 need a complex program */
                        u16 incdec = 0x0000;

                        if (last < value)
                                /* Count up */
                                incdec = RAMPUP | (value - last);
                        else
                                /* Count down */
                                incdec = RAMPDOWN | (last - value);

                        /* Step to desired value, smoothly */
                        program[0] = PRESCALE_512 | STEPTIME_1 | incdec;

                        /* Loop eternally to 0x00 */
                        program[1] = BRANCH;
                }

                dev_dbg(chip->dev,
                        "PWM#%u: value = %02x, last_duty = %02x, program=%04x,%04x,%04x\n",
                        pwm->hwpwm, value, last, program[0], program[1],
                        program[2]);
                stmpe_pwm->last_duty = value;
        }

        /*
         * We can write programs of up to 64 16-bit words into this channel.
         */
        for (i = 0; i < ARRAY_SIZE(program); i++) {
                u8 value;

                value = (program[i] >> 8) & 0xff;

                ret = stmpe_reg_write(stmpe_pwm->stmpe, offset, value);
                if (ret) {
                        dev_err(chip->dev, "error writing register %02x: %d\n",
                                offset, ret);
                        return ret;
                }

                value = program[i] & 0xff;

                ret = stmpe_reg_write(stmpe_pwm->stmpe, offset, value);
                if (ret) {
                        dev_err(chip->dev, "error writing register %02x: %d\n",
                                offset, ret);
                        return ret;
                }
        }

        /* If we were enabled, re-enable this PWM */
        if (pwm_is_enabled(pwm))
                stmpe_24xx_pwm_enable(chip, pwm);

        /* Sleep for 200ms so we're sure it will take effect */
        msleep(200);

        dev_dbg(chip->dev, "programmed PWM#%u, %u bytes\n", pwm->hwpwm, i);

        return 0;
}

static const struct pwm_ops stmpe_24xx_pwm_ops = {
        .config = stmpe_24xx_pwm_config,
        .enable = stmpe_24xx_pwm_enable,
        .disable = stmpe_24xx_pwm_disable,
        .owner = THIS_MODULE,
};

static int __init stmpe_pwm_probe(struct platform_device *pdev)
{
        struct stmpe *stmpe = dev_get_drvdata(pdev->dev.parent);
        struct stmpe_pwm *pwm;
        int ret;

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

        pwm->stmpe = stmpe;
        pwm->chip.dev = &pdev->dev;
        pwm->chip.base = -1;

        if (stmpe->partnum == STMPE2401 || stmpe->partnum == STMPE2403) {
                pwm->chip.ops = &stmpe_24xx_pwm_ops;
                pwm->chip.npwm = 3;
        } else {
                if (stmpe->partnum == STMPE1601)
                        dev_err(&pdev->dev, "STMPE1601 not yet supported\n");
                else
                        dev_err(&pdev->dev, "Unknown STMPE PWM\n");

                return -ENODEV;
        }

        ret = stmpe_enable(stmpe, STMPE_BLOCK_PWM);
        if (ret)
                return ret;

        ret = pwmchip_add(&pwm->chip);
        if (ret) {
                stmpe_disable(stmpe, STMPE_BLOCK_PWM);
                return ret;
        }

        platform_set_drvdata(pdev, pwm);

        return 0;
}

static struct platform_driver stmpe_pwm_driver = {
        .driver = {
                .name = "stmpe-pwm",
        },
};
builtin_platform_driver_probe(stmpe_pwm_driver, stmpe_pwm_probe);