/*
 * ECAP PWM driver
 *
 * Copyright (C) 2012 Texas Instruments, Inc. - http://www.ti.com/
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

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

/* ECAP registers and bits definitions */
#define CAP1                    0x08
#define CAP2                    0x0C
#define CAP3                    0x10
#define CAP4                    0x14
#define ECCTL2                  0x2A
#define ECCTL2_APWM_POL_LOW     BIT(10)
#define ECCTL2_APWM_MODE        BIT(9)
#define ECCTL2_SYNC_SEL_DISA    (BIT(7) | BIT(6))
#define ECCTL2_TSCTR_FREERUN    BIT(4)

struct ecap_pwm_chip {
        struct pwm_chip chip;
        unsigned int    clk_rate;
        void __iomem    *mmio_base;
};

static inline struct ecap_pwm_chip *to_ecap_pwm_chip(struct pwm_chip *chip)
{
        return container_of(chip, struct ecap_pwm_chip, chip);
}

/*
 * period_ns = 10^9 * period_cycles / PWM_CLK_RATE
 * duty_ns   = 10^9 * duty_cycles / PWM_CLK_RATE
 */
static int ecap_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
                int duty_ns, int period_ns)
{
        struct ecap_pwm_chip *pc = to_ecap_pwm_chip(chip);
        unsigned long long c;
        unsigned long period_cycles, duty_cycles;
        unsigned int reg_val;

        if (period_ns > NSEC_PER_SEC)
                return -ERANGE;

        c = pc->clk_rate;
        c = c * period_ns;
        do_div(c, NSEC_PER_SEC);
        period_cycles = (unsigned long)c;

        if (period_cycles < 1) {
                period_cycles = 1;
                duty_cycles = 1;
        } else {
                c = pc->clk_rate;
                c = c * duty_ns;
                do_div(c, NSEC_PER_SEC);
                duty_cycles = (unsigned long)c;
        }

        pm_runtime_get_sync(pc->chip.dev);

        reg_val = readw(pc->mmio_base + ECCTL2);

        /* Configure APWM mode & disable sync option */
        reg_val |= ECCTL2_APWM_MODE | ECCTL2_SYNC_SEL_DISA;

        writew(reg_val, pc->mmio_base + ECCTL2);

        if (!test_bit(PWMF_ENABLED, &pwm->flags)) {
                /* Update active registers if not running */
                writel(duty_cycles, pc->mmio_base + CAP2);
                writel(period_cycles, pc->mmio_base + CAP1);
        } else {
                /*
                 * Update shadow registers to configure period and
                 * compare values. This helps current PWM period to
                 * complete on reconfiguring
                 */
                writel(duty_cycles, pc->mmio_base + CAP4);
                writel(period_cycles, pc->mmio_base + CAP3);
        }

        if (!test_bit(PWMF_ENABLED, &pwm->flags)) {
                reg_val = readw(pc->mmio_base + ECCTL2);
                /* Disable APWM mode to put APWM output Low */
                reg_val &= ~ECCTL2_APWM_MODE;
                writew(reg_val, pc->mmio_base + ECCTL2);
        }

        pm_runtime_put_sync(pc->chip.dev);
        return 0;
}

static int ecap_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
                enum pwm_polarity polarity)
{
        struct ecap_pwm_chip *pc = to_ecap_pwm_chip(chip);
        unsigned short reg_val;

        pm_runtime_get_sync(pc->chip.dev);
        reg_val = readw(pc->mmio_base + ECCTL2);
        if (polarity == PWM_POLARITY_INVERSED)
                /* Duty cycle defines LOW period of PWM */
                reg_val |= ECCTL2_APWM_POL_LOW;
        else
                /* Duty cycle defines HIGH period of PWM */
                reg_val &= ~ECCTL2_APWM_POL_LOW;

        writew(reg_val, pc->mmio_base + ECCTL2);
        pm_runtime_put_sync(pc->chip.dev);
        return 0;
}

static int ecap_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct ecap_pwm_chip *pc = to_ecap_pwm_chip(chip);
        unsigned int reg_val;

        /* Leave clock enabled on enabling PWM */
        pm_runtime_get_sync(pc->chip.dev);

        /*
         * Enable 'Free run Time stamp counter mode' to start counter
         * and  'APWM mode' to enable APWM output
         */
        reg_val = readw(pc->mmio_base + ECCTL2);
        reg_val |= ECCTL2_TSCTR_FREERUN | ECCTL2_APWM_MODE;
        writew(reg_val, pc->mmio_base + ECCTL2);
        return 0;
}

static void ecap_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct ecap_pwm_chip *pc = to_ecap_pwm_chip(chip);
        unsigned int reg_val;

        /*
         * Disable 'Free run Time stamp counter mode' to stop counter
         * and 'APWM mode' to put APWM output to low
         */
        reg_val = readw(pc->mmio_base + ECCTL2);
        reg_val &= ~(ECCTL2_TSCTR_FREERUN | ECCTL2_APWM_MODE);
        writew(reg_val, pc->mmio_base + ECCTL2);

        /* Disable clock on PWM disable */
        pm_runtime_put_sync(pc->chip.dev);
}

static void ecap_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
{
        if (test_bit(PWMF_ENABLED, &pwm->flags)) {
                dev_warn(chip->dev, "Removing PWM device without disabling\n");
                pm_runtime_put_sync(chip->dev);
        }
}

static const struct pwm_ops ecap_pwm_ops = {
        .free           = ecap_pwm_free,
        .config         = ecap_pwm_config,
        .set_polarity   = ecap_pwm_set_polarity,
        .enable         = ecap_pwm_enable,
        .disable        = ecap_pwm_disable,
        .owner          = THIS_MODULE,
};

static int __devinit ecap_pwm_probe(struct platform_device *pdev)
{
        int ret;
        struct resource *r;
        struct clk *clk;
        struct ecap_pwm_chip *pc;

        pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
        if (!pc) {
                dev_err(&pdev->dev, "failed to allocate memory\n");
                return -ENOMEM;
        }

        clk = devm_clk_get(&pdev->dev, "fck");
        if (IS_ERR(clk)) {
                dev_err(&pdev->dev, "failed to get clock\n");
                return PTR_ERR(clk);
        }

        pc->clk_rate = clk_get_rate(clk);
        if (!pc->clk_rate) {
                dev_err(&pdev->dev, "failed to get clock rate\n");
                return -EINVAL;
        }

        pc->chip.dev = &pdev->dev;
        pc->chip.ops = &ecap_pwm_ops;
        pc->chip.base = -1;
        pc->chip.npwm = 1;

        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!r) {
                dev_err(&pdev->dev, "no memory resource defined\n");
                return -ENODEV;
        }

        pc->mmio_base = devm_request_and_ioremap(&pdev->dev, r);
        if (!pc->mmio_base)
                return -EADDRNOTAVAIL;

        ret = pwmchip_add(&pc->chip);
        if (ret < 0) {
                dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
                return ret;
        }

        pm_runtime_enable(&pdev->dev);
        platform_set_drvdata(pdev, pc);
        return 0;
}

static int __devexit ecap_pwm_remove(struct platform_device *pdev)
{
        struct ecap_pwm_chip *pc = platform_get_drvdata(pdev);

        pm_runtime_put_sync(&pdev->dev);
        pm_runtime_disable(&pdev->dev);
        return pwmchip_remove(&pc->chip);
}

static struct platform_driver ecap_pwm_driver = {
        .driver = {
                .name = "ecap",
        },
        .probe = ecap_pwm_probe,
        .remove = __devexit_p(ecap_pwm_remove),
};

module_platform_driver(ecap_pwm_driver);

MODULE_DESCRIPTION("ECAP PWM driver");
MODULE_AUTHOR("Texas Instruments");
MODULE_LICENSE("GPL");