pwm-imx.c

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/*
 * simple driver for PWM (Pulse Width Modulator) controller
 *
 * 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.
 *
 * Derived from pxa PWM driver by eric miao <[email protected]>
 */

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

/* i.MX1 and i.MX21 share the same PWM function block: */

#define MX1_PWMC    0x00   /* PWM Control Register */
#define MX1_PWMS    0x04   /* PWM Sample Register */
#define MX1_PWMP    0x08   /* PWM Period Register */

#define MX1_PWMC_EN     (1 << 4)

/* i.MX27, i.MX31, i.MX35 share the same PWM function block: */

#define MX3_PWMCR                 0x00    /* PWM Control Register */
#define MX3_PWMSAR                0x0C    /* PWM Sample Register */
#define MX3_PWMPR                 0x10    /* PWM Period Register */
#define MX3_PWMCR_PRESCALER(x)    (((x - 1) & 0xFFF) << 4)
#define MX3_PWMCR_DOZEEN                (1 << 24)
#define MX3_PWMCR_WAITEN                (1 << 23)
#define MX3_PWMCR_DBGEN         (1 << 22)
#define MX3_PWMCR_CLKSRC_IPG_HIGH (2 << 16)
#define MX3_PWMCR_CLKSRC_IPG      (1 << 16)
#define MX3_PWMCR_EN              (1 << 0)

struct imx_chip {
    struct clk  *clk_per;
    struct clk  *clk_ipg;

    int     enabled;
    void __iomem    *mmio_base;

    struct pwm_chip chip;

    int (*config)(struct pwm_chip *chip,
        struct pwm_device *pwm, int duty_ns, int period_ns);
    void (*set_enable)(struct pwm_chip *chip, bool enable);
};

#define to_imx_chip(chip)   container_of(chip, struct imx_chip, chip)

static int imx_pwm_config_v1(struct pwm_chip *chip,
        struct pwm_device *pwm, int duty_ns, int period_ns)
{
    struct imx_chip *imx = to_imx_chip(chip);

    /*
     * The PWM subsystem allows for exact frequencies. However,
     * I cannot connect a scope on my device to the PWM line and
     * thus cannot provide the program the PWM controller
     * exactly. Instead, I'm relying on the fact that the
     * Bootloader (u-boot or WinCE+haret) has programmed the PWM
     * function group already. So I'll just modify the PWM sample
     * register to follow the ratio of duty_ns vs. period_ns
     * accordingly.
     *
     * This is good enough for programming the brightness of
     * the LCD backlight.
     *
     * The real implementation would divide PERCLK[0] first by
     * both the prescaler (/1 .. /128) and then by CLKSEL
     * (/2 .. /16).
     */
    u32 max = readl(imx->mmio_base + MX1_PWMP);
    u32 p = max * duty_ns / period_ns;
    writel(max - p, imx->mmio_base + MX1_PWMS);

    return 0;
}

static void imx_pwm_set_enable_v1(struct pwm_chip *chip, bool enable)
{
    struct imx_chip *imx = to_imx_chip(chip);
    u32 val;

    val = readl(imx->mmio_base + MX1_PWMC);

    if (enable)
        val |= MX1_PWMC_EN;
    else
        val &= ~MX1_PWMC_EN;

    writel(val, imx->mmio_base + MX1_PWMC);
}

static int imx_pwm_config_v2(struct pwm_chip *chip,
        struct pwm_device *pwm, int duty_ns, int period_ns)
{
    struct imx_chip *imx = to_imx_chip(chip);
    unsigned long long c;
    unsigned long period_cycles, duty_cycles, prescale;
    u32 cr;

    c = clk_get_rate(imx->clk_per);
    c = c * period_ns;
    do_div(c, 1000000000);
    period_cycles = c;

    prescale = period_cycles / 0x10000 + 1;

    period_cycles /= prescale;
    c = (unsigned long long)period_cycles * duty_ns;
    do_div(c, period_ns);
    duty_cycles = c;

    /*
     * according to imx pwm RM, the real period value should be
     * PERIOD value in PWMPR plus 2.
     */
    if (period_cycles > 2)
        period_cycles -= 2;
    else
        period_cycles = 0;

    writel(duty_cycles, imx->mmio_base + MX3_PWMSAR);
    writel(period_cycles, imx->mmio_base + MX3_PWMPR);

    cr = MX3_PWMCR_PRESCALER(prescale) |
        MX3_PWMCR_DOZEEN | MX3_PWMCR_WAITEN |
        MX3_PWMCR_DBGEN | MX3_PWMCR_CLKSRC_IPG_HIGH;

    if (imx->enabled)
        cr |= MX3_PWMCR_EN;

    writel(cr, imx->mmio_base + MX3_PWMCR);

    return 0;
}

static void imx_pwm_set_enable_v2(struct pwm_chip *chip, bool enable)
{
    struct imx_chip *imx = to_imx_chip(chip);
    u32 val;

    val = readl(imx->mmio_base + MX3_PWMCR);

    if (enable)
        val |= MX3_PWMCR_EN;
    else
        val &= ~MX3_PWMCR_EN;

    writel(val, imx->mmio_base + MX3_PWMCR);
}

static int imx_pwm_config(struct pwm_chip *chip,
        struct pwm_device *pwm, int duty_ns, int period_ns)
{
    struct imx_chip *imx = to_imx_chip(chip);
    int ret;

    ret = clk_prepare_enable(imx->clk_ipg);
    if (ret)
        return ret;

    ret = imx->config(chip, pwm, duty_ns, period_ns);

    clk_disable_unprepare(imx->clk_ipg);

    return ret;
}

static int imx_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
    struct imx_chip *imx = to_imx_chip(chip);
    int ret;

    ret = clk_prepare_enable(imx->clk_per);
    if (ret)
        return ret;

    imx->set_enable(chip, true);

    imx->enabled = 1;

    return 0;
}

static void imx_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
    struct imx_chip *imx = to_imx_chip(chip);

    imx->set_enable(chip, false);

    clk_disable_unprepare(imx->clk_per);
    imx->enabled = 0;
}

static struct pwm_ops imx_pwm_ops = {
    .enable = imx_pwm_enable,
    .disable = imx_pwm_disable,
    .config = imx_pwm_config,
    .owner = THIS_MODULE,
};

struct imx_pwm_data {
    int (*config)(struct pwm_chip *chip,
        struct pwm_device *pwm, int duty_ns, int period_ns);
    void (*set_enable)(struct pwm_chip *chip, bool enable);
};

static struct imx_pwm_data imx_pwm_data_v1 = {
    .config = imx_pwm_config_v1,
    .set_enable = imx_pwm_set_enable_v1,
};

static struct imx_pwm_data imx_pwm_data_v2 = {
    .config = imx_pwm_config_v2,
    .set_enable = imx_pwm_set_enable_v2,
};

static const struct of_device_id imx_pwm_dt_ids[] = {
    { .compatible = "fsl,imx1-pwm", .data = &imx_pwm_data_v1, },
    { .compatible = "fsl,imx27-pwm", .data = &imx_pwm_data_v2, },
    { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, imx_pwm_dt_ids);

static int __devinit imx_pwm_probe(struct platform_device *pdev)
{
    const struct of_device_id *of_id =
            of_match_device(imx_pwm_dt_ids, &pdev->dev);
    struct imx_pwm_data *data;
    struct imx_chip *imx;
    struct resource *r;
    int ret = 0;

    if (!of_id)
        return -ENODEV;

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

    imx->clk_per = devm_clk_get(&pdev->dev, "per");
    if (IS_ERR(imx->clk_per)) {
        dev_err(&pdev->dev, "getting per clock failed with %ld\n",
                PTR_ERR(imx->clk_per));
        return PTR_ERR(imx->clk_per);
    }

    imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg");
    if (IS_ERR(imx->clk_ipg)) {
        dev_err(&pdev->dev, "getting ipg clock failed with %ld\n",
                PTR_ERR(imx->clk_ipg));
        return PTR_ERR(imx->clk_ipg);
    }

    imx->chip.ops = &imx_pwm_ops;
    imx->chip.dev = &pdev->dev;
    imx->chip.base = -1;
    imx->chip.npwm = 1;

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

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

    data = of_id->data;
    imx->config = data->config;
    imx->set_enable = data->set_enable;

    ret = pwmchip_add(&imx->chip);
    if (ret < 0)
        return ret;

    platform_set_drvdata(pdev, imx);
    return 0;
}

static int __devexit imx_pwm_remove(struct platform_device *pdev)
{
    struct imx_chip *imx;

    imx = platform_get_drvdata(pdev);
    if (imx == NULL)
        return -ENODEV;

    return pwmchip_remove(&imx->chip);
}

static struct platform_driver imx_pwm_driver = {
    .driver     = {
        .name   = "imx-pwm",
        .of_match_table = of_match_ptr(imx_pwm_dt_ids),
    },
    .probe      = imx_pwm_probe,
    .remove     = __devexit_p(imx_pwm_remove),
};

module_platform_driver(imx_pwm_driver);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Sascha Hauer <[email protected]>");