pwm-vt8500.c

Go to the documentation of this file.

/*
 * drivers/pwm/pwm-vt8500.c
 *
 *  Copyright (C) 2010 Alexey Charkov <[email protected]>
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * 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.
 */

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

#include <asm/div64.h>

#define VT8500_NR_PWMS 4

struct vt8500_chip {
    struct pwm_chip chip;
    void __iomem *base;
};

#define to_vt8500_chip(chip)    container_of(chip, struct vt8500_chip, chip)

#define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
static inline void pwm_busy_wait(void __iomem *reg, u8 bitmask)
{
    int loops = msecs_to_loops(10);
    while ((readb(reg) & bitmask) && --loops)
        cpu_relax();

    if (unlikely(!loops))
        pr_warn("Waiting for status bits 0x%x to clear timed out\n",
               bitmask);
}

static int vt8500_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
        int duty_ns, int period_ns)
{
    struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
    unsigned long long c;
    unsigned long period_cycles, prescale, pv, dc;

    c = 25000000/2; /* wild guess --- need to implement clocks */
    c = c * period_ns;
    do_div(c, 1000000000);
    period_cycles = c;

    if (period_cycles < 1)
        period_cycles = 1;
    prescale = (period_cycles - 1) / 4096;
    pv = period_cycles / (prescale + 1) - 1;
    if (pv > 4095)
        pv = 4095;

    if (prescale > 1023)
        return -EINVAL;

    c = (unsigned long long)pv * duty_ns;
    do_div(c, period_ns);
    dc = c;

    pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 1));
    writel(prescale, vt8500->base + 0x4 + (pwm->hwpwm << 4));

    pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 2));
    writel(pv, vt8500->base + 0x8 + (pwm->hwpwm << 4));

    pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 3));
    writel(dc, vt8500->base + 0xc + (pwm->hwpwm << 4));

    return 0;
}

static int vt8500_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
    struct vt8500_chip *vt8500 = to_vt8500_chip(chip);

    pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 0));
    writel(5, vt8500->base + (pwm->hwpwm << 4));
    return 0;
}

static void vt8500_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
    struct vt8500_chip *vt8500 = to_vt8500_chip(chip);

    pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 0));
    writel(0, vt8500->base + (pwm->hwpwm << 4));
}

static struct pwm_ops vt8500_pwm_ops = {
    .enable = vt8500_pwm_enable,
    .disable = vt8500_pwm_disable,
    .config = vt8500_pwm_config,
    .owner = THIS_MODULE,
};

static int __devinit pwm_probe(struct platform_device *pdev)
{
    struct vt8500_chip *chip;
    struct resource *r;
    int ret;

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

    chip->chip.dev = &pdev->dev;
    chip->chip.ops = &vt8500_pwm_ops;
    chip->chip.base = -1;
    chip->chip.npwm = VT8500_NR_PWMS;

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

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

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

    platform_set_drvdata(pdev, chip);
    return ret;
}

static int __devexit pwm_remove(struct platform_device *pdev)
{
    struct vt8500_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   = "vt8500-pwm",
        .owner  = THIS_MODULE,
    },
    .probe      = pwm_probe,
    .remove     = __devexit_p(pwm_remove),
};

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");