pwm-puv3.c

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/*
 * linux/arch/unicore32/kernel/pwm.c
 *
 * Code specific to PKUnity SoC and UniCore ISA
 *
 *  Maintained by GUAN Xue-tao <[email protected]>
 *  Copyright (C) 2001-2010 Guan Xuetao
 *
 * 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.
 */

#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>
#include <mach/hardware.h>

struct puv3_pwm_chip {
    struct pwm_chip chip;
    void __iomem *base;
    struct clk *clk;
    bool enabled;
};

static inline struct puv3_pwm_chip *to_puv3(struct pwm_chip *chip)
{
    return container_of(chip, struct puv3_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 puv3_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
               int duty_ns, int period_ns)
{
    unsigned long period_cycles, prescale, pv, dc;
    struct puv3_pwm_chip *puv3 = to_puv3(chip);
    unsigned long long c;

    c = clk_get_rate(puv3->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 = OST_PWMDCCR_FDCYCLE;
    else
        dc = (pv + 1) * duty_ns / period_ns;

    /*
     * NOTE: the clock to PWM has to be enabled first
     * before writing to the registers
     */
    clk_prepare_enable(puv3->clk);

    writel(prescale, puv3->base + OST_PWM_PWCR);
    writel(pv - dc, puv3->base + OST_PWM_DCCR);
    writel(pv, puv3->base + OST_PWM_PCR);

    clk_disable_unprepare(puv3->clk);

    return 0;
}

static int puv3_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
    struct puv3_pwm_chip *puv3 = to_puv3(chip);

    return clk_prepare_enable(puv3->clk);
}

static void puv3_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
    struct puv3_pwm_chip *puv3 = to_puv3(chip);

    clk_disable_unprepare(puv3->clk);
}

static const struct pwm_ops puv3_pwm_ops = {
    .config = puv3_pwm_config,
    .enable = puv3_pwm_enable,
    .disable = puv3_pwm_disable,
    .owner = THIS_MODULE,
};

static int __devinit pwm_probe(struct platform_device *pdev)
{
    struct puv3_pwm_chip *puv3;
    struct resource *r;
    int ret;

    puv3 = devm_kzalloc(&pdev->dev, sizeof(*puv3), GFP_KERNEL);
    if (puv3 == NULL) {
        dev_err(&pdev->dev, "failed to allocate memory\n");
        return -ENOMEM;
    }

    puv3->clk = devm_clk_get(&pdev->dev, "OST_CLK");
    if (IS_ERR(puv3->clk))
        return PTR_ERR(puv3->clk);

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

    puv3->base = devm_request_and_ioremap(&pdev->dev, r);
    if (puv3->base == NULL)
        return -EADDRNOTAVAIL;

    puv3->chip.dev = &pdev->dev;
    puv3->chip.ops = &puv3_pwm_ops;
    puv3->chip.base = -1;
    puv3->chip.npwm = 1;

    ret = pwmchip_add(&puv3->chip);
    if (ret < 0) {
        dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
        return ret;
    }

    platform_set_drvdata(pdev, puv3);
    return 0;
}

static int __devexit pwm_remove(struct platform_device *pdev)
{
    struct puv3_pwm_chip *puv3 = platform_get_drvdata(pdev);

    return pwmchip_remove(&puv3->chip);
}

static struct platform_driver puv3_pwm_driver = {
    .driver = {
        .name = "PKUnity-v3-PWM",
    },
    .probe = pwm_probe,
    .remove = __devexit_p(pwm_remove),
};
module_platform_driver(puv3_pwm_driver);

MODULE_LICENSE("GPL v2");