linux-imx

/*

 * linux/arch/unicore32/kernel/pwm.c

 *

 * Code specific to PKUnity SoC and UniCore ISA

 *

 *  Maintained by GUAN Xue-tao <gxt@mprc.pku.edu.cn>

 *  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;

};

​

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;