linux-imx

/*

 * ST Microelectronics SPEAr Pulse Width Modulator driver

 *

 * Copyright (C) 2012 ST Microelectronics

 * Shiraz Hashim <shiraz.linux.kernel@gmail.com>

 *

 * This file is licensed under the terms of the GNU General Public

 * License version 2. This program is licensed "as is" without any

 * warranty of any kind, whether express or implied.

 */

​

#include <linux/clk.h>

#include <linux/err.h>

#include <linux/io.h>

#include <linux/ioport.h>

#include <linux/kernel.h>

#include <linux/math64.h>

#include <linux/module.h>

#include <linux/of.h>

#include <linux/platform_device.h>

#include <linux/pwm.h>

#include <linux/slab.h>

#include <linux/types.h>

​

#define NUM_PWM     4

​

/* PWM registers and bits definitions */

#define PWMCR           0x00    /* Control Register */

#define PWMCR_PWM_ENABLE    0x1

#define PWMCR_PRESCALE_SHIFT    2

#define PWMCR_MIN_PRESCALE  0x00

#define PWMCR_MAX_PRESCALE  0x3FFF

​

#define PWMDCR          0x04    /* Duty Cycle Register */

#define PWMDCR_MIN_DUTY     0x0001

#define PWMDCR_MAX_DUTY     0xFFFF

​

#define PWMPCR          0x08    /* Period Register */

#define PWMPCR_MIN_PERIOD   0x0001

#define PWMPCR_MAX_PERIOD   0xFFFF

​

/* Following only available on 13xx SoCs */

#define PWMMCR          0x3C    /* Master Control Register */

#define PWMMCR_PWM_ENABLE   0x1

​

/**

 * struct spear_pwm_chip - struct representing pwm chip

 *

 * @mmio_base: base address of pwm chip

 * @clk: pointer to clk structure of pwm chip

 * @chip: linux pwm chip representation

 */

struct spear_pwm_chip {

    void __iomem *mmio_base;

    struct clk *clk;

    struct pwm_chip chip;

};

​

static inline struct spear_pwm_chip *to_spear_pwm_chip(struct pwm_chip *chip)

{

    return container_of(chip, struct spear_pwm_chip, chip);

}

​

static inline u32 spear_pwm_readl(struct spear_pwm_chip *chip, unsigned int num,

                  unsigned long offset)

{

    return readl_relaxed(chip->mmio_base + (num << 4) + offset);

}

​

static inline void spear_pwm_writel(struct spear_pwm_chip *chip,

                    unsigned int num, unsigned long offset,

                    unsigned long val)

{

    writel_relaxed(val, chip->mmio_base + (num << 4) + offset);

}

​

static int spear_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,

                int duty_ns, int period_ns)

{

    struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);

    u64 val, div, clk_rate;

    unsigned long prescale = PWMCR_MIN_PRESCALE, pv, dc;

    int ret;

​

    /*

     * Find pv, dc and prescale to suit duty_ns and period_ns. This is done

     * according to formulas described below:

     *

     * period_ns = 10^9 * (PRESCALE + 1) * PV / PWM_CLK_RATE

     * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE

     *

     * PV = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1))