linux/drivers/pwm/pwm-pxa.c
<<
>>
Prefs
   1/*
   2 * drivers/pwm/pwm-pxa.c
   3 *
   4 * simple driver for PWM (Pulse Width Modulator) controller
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation.
   9 *
  10 * 2008-02-13   initial version
  11 *              eric miao <eric.miao@marvell.com>
  12 */
  13
  14#include <linux/module.h>
  15#include <linux/kernel.h>
  16#include <linux/platform_device.h>
  17#include <linux/slab.h>
  18#include <linux/err.h>
  19#include <linux/clk.h>
  20#include <linux/io.h>
  21#include <linux/pwm.h>
  22
  23#include <asm/div64.h>
  24
  25#define HAS_SECONDARY_PWM       0x10
  26
  27static const struct platform_device_id pwm_id_table[] = {
  28        /*   PWM    has_secondary_pwm? */
  29        { "pxa25x-pwm", 0 },
  30        { "pxa27x-pwm", HAS_SECONDARY_PWM },
  31        { "pxa168-pwm", 0 },
  32        { "pxa910-pwm", 0 },
  33        { },
  34};
  35MODULE_DEVICE_TABLE(platform, pwm_id_table);
  36
  37/* PWM registers and bits definitions */
  38#define PWMCR           (0x00)
  39#define PWMDCR          (0x04)
  40#define PWMPCR          (0x08)
  41
  42#define PWMCR_SD        (1 << 6)
  43#define PWMDCR_FD       (1 << 10)
  44
  45struct pxa_pwm_chip {
  46        struct pwm_chip chip;
  47        struct device   *dev;
  48
  49        struct clk      *clk;
  50        void __iomem    *mmio_base;
  51};
  52
  53static inline struct pxa_pwm_chip *to_pxa_pwm_chip(struct pwm_chip *chip)
  54{
  55        return container_of(chip, struct pxa_pwm_chip, chip);
  56}
  57
  58/*
  59 * period_ns = 10^9 * (PRESCALE + 1) * (PV + 1) / PWM_CLK_RATE
  60 * duty_ns   = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
  61 */
  62static int pxa_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
  63                          int duty_ns, int period_ns)
  64{
  65        struct pxa_pwm_chip *pc = to_pxa_pwm_chip(chip);
  66        unsigned long long c;
  67        unsigned long period_cycles, prescale, pv, dc;
  68        unsigned long offset;
  69        int rc;
  70
  71        offset = pwm->hwpwm ? 0x10 : 0;
  72
  73        c = clk_get_rate(pc->clk);
  74        c = c * period_ns;
  75        do_div(c, 1000000000);
  76        period_cycles = c;
  77
  78        if (period_cycles < 1)
  79                period_cycles = 1;
  80        prescale = (period_cycles - 1) / 1024;
  81        pv = period_cycles / (prescale + 1) - 1;
  82
  83        if (prescale > 63)
  84                return -EINVAL;
  85
  86        if (duty_ns == period_ns)
  87                dc = PWMDCR_FD;
  88        else
  89                dc = (pv + 1) * duty_ns / period_ns;
  90
  91        /* NOTE: the clock to PWM has to be enabled first
  92         * before writing to the registers
  93         */
  94        rc = clk_prepare_enable(pc->clk);
  95        if (rc < 0)
  96                return rc;
  97
  98        writel(prescale, pc->mmio_base + offset + PWMCR);
  99        writel(dc, pc->mmio_base + offset + PWMDCR);
 100        writel(pv, pc->mmio_base + offset + PWMPCR);
 101
 102        clk_disable_unprepare(pc->clk);
 103        return 0;
 104}
 105
 106static int pxa_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
 107{
 108        struct pxa_pwm_chip *pc = to_pxa_pwm_chip(chip);
 109
 110        return clk_prepare_enable(pc->clk);
 111}
 112
 113static void pxa_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 114{
 115        struct pxa_pwm_chip *pc = to_pxa_pwm_chip(chip);
 116
 117        clk_disable_unprepare(pc->clk);
 118}
 119
 120static struct pwm_ops pxa_pwm_ops = {
 121        .config = pxa_pwm_config,
 122        .enable = pxa_pwm_enable,
 123        .disable = pxa_pwm_disable,
 124        .owner = THIS_MODULE,
 125};
 126
 127static int pwm_probe(struct platform_device *pdev)
 128{
 129        const struct platform_device_id *id = platform_get_device_id(pdev);
 130        struct pxa_pwm_chip *pwm;
 131        struct resource *r;
 132        int ret = 0;
 133
 134        pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
 135        if (pwm == NULL) {
 136                dev_err(&pdev->dev, "failed to allocate memory\n");
 137                return -ENOMEM;
 138        }
 139
 140        pwm->clk = devm_clk_get(&pdev->dev, NULL);
 141        if (IS_ERR(pwm->clk))
 142                return PTR_ERR(pwm->clk);
 143
 144        pwm->chip.dev = &pdev->dev;
 145        pwm->chip.ops = &pxa_pwm_ops;
 146        pwm->chip.base = -1;
 147        pwm->chip.npwm = (id->driver_data & HAS_SECONDARY_PWM) ? 2 : 1;
 148
 149        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 150        pwm->mmio_base = devm_ioremap_resource(&pdev->dev, r);
 151        if (IS_ERR(pwm->mmio_base))
 152                return PTR_ERR(pwm->mmio_base);
 153
 154        ret = pwmchip_add(&pwm->chip);
 155        if (ret < 0) {
 156                dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
 157                return ret;
 158        }
 159
 160        platform_set_drvdata(pdev, pwm);
 161        return 0;
 162}
 163
 164static int pwm_remove(struct platform_device *pdev)
 165{
 166        struct pxa_pwm_chip *chip;
 167
 168        chip = platform_get_drvdata(pdev);
 169        if (chip == NULL)
 170                return -ENODEV;
 171
 172        return pwmchip_remove(&chip->chip);
 173}
 174
 175static struct platform_driver pwm_driver = {
 176        .driver         = {
 177                .name   = "pxa25x-pwm",
 178                .owner  = THIS_MODULE,
 179        },
 180        .probe          = pwm_probe,
 181        .remove         = pwm_remove,
 182        .id_table       = pwm_id_table,
 183};
 184
 185static int __init pwm_init(void)
 186{
 187        return platform_driver_register(&pwm_driver);
 188}
 189arch_initcall(pwm_init);
 190
 191static void __exit pwm_exit(void)
 192{
 193        platform_driver_unregister(&pwm_driver);
 194}
 195module_exit(pwm_exit);
 196
 197MODULE_LICENSE("GPL v2");
 198
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.