pwm-pxa.c

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/*
 * drivers/pwm/pwm-pxa.c
 *
 * 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.
 *
 * 2008-02-13   initial version
 *      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 <asm/div64.h>

#define HAS_SECONDARY_PWM   0x10
#define PWM_ID_BASE(d)      ((d) & 0xf)

static const struct platform_device_id pwm_id_table[] = {
    /*   PWM    has_secondary_pwm? */
    { "pxa25x-pwm", 0 },
    { "pxa27x-pwm", 0 | HAS_SECONDARY_PWM },
    { "pxa168-pwm", 1 },
    { "pxa910-pwm", 1 },
    { },
};
MODULE_DEVICE_TABLE(platform, pwm_id_table);

/* PWM registers and bits definitions */
#define PWMCR       (0x00)
#define PWMDCR      (0x04)
#define PWMPCR      (0x08)

#define PWMCR_SD    (1 << 6)
#define PWMDCR_FD   (1 << 10)

struct pxa_pwm_chip {
    struct pwm_chip chip;
    struct device   *dev;

    struct clk  *clk;
    int     clk_enabled;
    void __iomem    *mmio_base;
};

static inline struct pxa_pwm_chip *to_pxa_pwm_chip(struct pwm_chip *chip)
{
    return container_of(chip, struct pxa_pwm_chip, chip);
}

/*
 * period_ns = 10^9 * (PRESCALE + 1) * (PV + 1) / PWM_CLK_RATE
 * duty_ns   = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
 */
static int pxa_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
              int duty_ns, int period_ns)
{
    struct pxa_pwm_chip *pc = to_pxa_pwm_chip(chip);
    unsigned long long c;
    unsigned long period_cycles, prescale, pv, dc;
    unsigned long offset;
    int rc;

    offset = pwm->hwpwm ? 0x10 : 0;

    c = clk_get_rate(pc->clk);
    c = c * period_ns;
    do_div(c, 1000000000);
    period_cycles = c;

    if (period_cycles < 1)
        period_cycles = 1;
    prescale = (period_cycles - 1) / 1024;
    pv = period_cycles / (prescale + 1) - 1;

    if (prescale > 63)
        return -EINVAL;

    if (duty_ns == period_ns)
        dc = PWMDCR_FD;
    else
        dc = (pv + 1) * duty_ns / period_ns;

    /* NOTE: the clock to PWM has to be enabled first
     * before writing to the registers
     */
    rc = clk_prepare_enable(pc->clk);
    if (rc < 0)
        return rc;

    writel(prescale, pc->mmio_base + offset + PWMCR);
    writel(dc, pc->mmio_base + offset + PWMDCR);
    writel(pv, pc->mmio_base + offset + PWMPCR);

    clk_disable_unprepare(pc->clk);
    return 0;
}

static int pxa_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
    struct pxa_pwm_chip *pc = to_pxa_pwm_chip(chip);
    int rc = 0;

    if (!pc->clk_enabled) {
        rc = clk_prepare_enable(pc->clk);
        if (!rc)
            pc->clk_enabled++;
    }
    return rc;
}

static void pxa_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
    struct pxa_pwm_chip *pc = to_pxa_pwm_chip(chip);

    if (pc->clk_enabled) {
        clk_disable_unprepare(pc->clk);
        pc->clk_enabled--;
    }
}

static struct pwm_ops pxa_pwm_ops = {
    .config = pxa_pwm_config,
    .enable = pxa_pwm_enable,
    .disable = pxa_pwm_disable,
    .owner = THIS_MODULE,
};

static int __devinit pwm_probe(struct platform_device *pdev)
{
    const struct platform_device_id *id = platform_get_device_id(pdev);
    struct pxa_pwm_chip *pwm;
    struct resource *r;
    int ret = 0;

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

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

    pwm->clk_enabled = 0;

    pwm->chip.dev = &pdev->dev;
    pwm->chip.ops = &pxa_pwm_ops;
    pwm->chip.base = -1;
    pwm->chip.npwm = (id->driver_data & HAS_SECONDARY_PWM) ? 2 : 1;

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

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

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

    platform_set_drvdata(pdev, pwm);
    return 0;
}

static int __devexit pwm_remove(struct platform_device *pdev)
{
    struct pxa_pwm_chip *chip;

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

    return pwmchip_remove(&chip->chip);
}

static struct platform_driver pwm_driver = {
    .driver     = {
        .name   = "pxa25x-pwm",
        .owner  = THIS_MODULE,
    },
    .probe      = pwm_probe,
    .remove     = __devexit_p(pwm_remove),
    .id_table   = pwm_id_table,
};

static int __init pwm_init(void)
{
    return platform_driver_register(&pwm_driver);
}
arch_initcall(pwm_init);

static void __exit pwm_exit(void)
{
    platform_driver_unregister(&pwm_driver);
}
module_exit(pwm_exit);

MODULE_LICENSE("GPL v2");