pwm-mxs.c

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/*
 * Copyright 2012 Freescale Semiconductor, Inc.
 *
 * The code contained herein is licensed under the GNU General Public
 * License. You may obtain a copy of the GNU General Public License
 * Version 2 or later at the following locations:
 *
 * http://www.opensource.org/licenses/gpl-license.html
 * http://www.gnu.org/copyleft/gpl.html
 */

#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/pinctrl/consumer.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>
#include <linux/stmp_device.h>

#define SET 0x4
#define CLR 0x8
#define TOG 0xc

#define PWM_CTRL        0x0
#define PWM_ACTIVE0     0x10
#define PWM_PERIOD0     0x20
#define  PERIOD_PERIOD(p)   ((p) & 0xffff)
#define  PERIOD_PERIOD_MAX  0x10000
#define  PERIOD_ACTIVE_HIGH (3 << 16)
#define  PERIOD_INACTIVE_LOW    (2 << 18)
#define  PERIOD_CDIV(div)   (((div) & 0x7) << 20)
#define  PERIOD_CDIV_MAX    8

struct mxs_pwm_chip {
    struct pwm_chip chip;
    struct device *dev;
    struct clk *clk;
    void __iomem *base;
};

#define to_mxs_pwm_chip(_chip) container_of(_chip, struct mxs_pwm_chip, chip)

static int mxs_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
              int duty_ns, int period_ns)
{
    struct mxs_pwm_chip *mxs = to_mxs_pwm_chip(chip);
    int ret, div = 0;
    unsigned int period_cycles, duty_cycles;
    unsigned long rate;
    unsigned long long c;

    rate = clk_get_rate(mxs->clk);
    while (1) {
        c = rate / (1 << div);
        c = c * period_ns;
        do_div(c, 1000000000);
        if (c < PERIOD_PERIOD_MAX)
            break;
        div++;
        if (div > PERIOD_CDIV_MAX)
            return -EINVAL;
    }

    period_cycles = c;
    c *= duty_ns;
    do_div(c, period_ns);
    duty_cycles = c;

    /*
     * If the PWM channel is disabled, make sure to turn on the clock
     * before writing the register. Otherwise, keep it enabled.
     */
    if (!test_bit(PWMF_ENABLED, &pwm->flags)) {
        ret = clk_prepare_enable(mxs->clk);
        if (ret)
            return ret;
    }

    writel(duty_cycles << 16,
            mxs->base + PWM_ACTIVE0 + pwm->hwpwm * 0x20);
    writel(PERIOD_PERIOD(period_cycles) | PERIOD_ACTIVE_HIGH |
           PERIOD_INACTIVE_LOW | PERIOD_CDIV(div),
            mxs->base + PWM_PERIOD0 + pwm->hwpwm * 0x20);

    /*
     * If the PWM is not enabled, turn the clock off again to save power.
     */
    if (!test_bit(PWMF_ENABLED, &pwm->flags))
        clk_disable_unprepare(mxs->clk);

    return 0;
}

static int mxs_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
    struct mxs_pwm_chip *mxs = to_mxs_pwm_chip(chip);
    int ret;

    ret = clk_prepare_enable(mxs->clk);
    if (ret)
        return ret;

    writel(1 << pwm->hwpwm, mxs->base + PWM_CTRL + SET);

    return 0;
}

static void mxs_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
    struct mxs_pwm_chip *mxs = to_mxs_pwm_chip(chip);

    writel(1 << pwm->hwpwm, mxs->base + PWM_CTRL + CLR);

    clk_disable_unprepare(mxs->clk);
}

static const struct pwm_ops mxs_pwm_ops = {
    .config = mxs_pwm_config,
    .enable = mxs_pwm_enable,
    .disable = mxs_pwm_disable,
    .owner = THIS_MODULE,
};

static int mxs_pwm_probe(struct platform_device *pdev)
{
    struct device_node *np = pdev->dev.of_node;
    struct mxs_pwm_chip *mxs;
    struct resource *res;
    struct pinctrl *pinctrl;
    int ret;

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

    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    mxs->base = devm_request_and_ioremap(&pdev->dev, res);
    if (!mxs->base)
        return -EADDRNOTAVAIL;

    pinctrl = devm_pinctrl_get_select_default(&pdev->dev);
    if (IS_ERR(pinctrl))
        return PTR_ERR(pinctrl);

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

    mxs->chip.dev = &pdev->dev;
    mxs->chip.ops = &mxs_pwm_ops;
    mxs->chip.base = -1;
    ret = of_property_read_u32(np, "fsl,pwm-number", &mxs->chip.npwm);
    if (ret < 0) {
        dev_err(&pdev->dev, "failed to get pwm number: %d\n", ret);
        return ret;
    }

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

    mxs->dev = &pdev->dev;
    platform_set_drvdata(pdev, mxs);

    stmp_reset_block(mxs->base);

    return 0;
}

static int __devexit mxs_pwm_remove(struct platform_device *pdev)
{
    struct mxs_pwm_chip *mxs = platform_get_drvdata(pdev);

    return pwmchip_remove(&mxs->chip);
}

static struct of_device_id mxs_pwm_dt_ids[] = {
    { .compatible = "fsl,imx23-pwm", },
    { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, mxs_pwm_dt_ids);

static struct platform_driver mxs_pwm_driver = {
    .driver = {
        .name = "mxs-pwm",
        .of_match_table = of_match_ptr(mxs_pwm_dt_ids),
    },
    .probe = mxs_pwm_probe,
    .remove = __devexit_p(mxs_pwm_remove),
};
module_platform_driver(mxs_pwm_driver);

MODULE_ALIAS("platform:mxs-pwm");
MODULE_AUTHOR("Shawn Guo <[email protected]>");
MODULE_DESCRIPTION("Freescale MXS PWM Driver");
MODULE_LICENSE("GPL v2");