linux/drivers/pwm/pwm-vt8500.c
<<
>>
Prefs
   1/*
   2 * drivers/pwm/pwm-vt8500.c
   3 *
   4 *  Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
   5 *
   6 * This software is licensed under the terms of the GNU General Public
   7 * License version 2, as published by the Free Software Foundation, and
   8 * may be copied, distributed, and modified under those terms.
   9 *
  10 * This program is distributed in the hope that it will be useful,
  11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 * GNU General Public License for more details.
  14 */
  15
  16#include <linux/module.h>
  17#include <linux/kernel.h>
  18#include <linux/platform_device.h>
  19#include <linux/slab.h>
  20#include <linux/err.h>
  21#include <linux/io.h>
  22#include <linux/pwm.h>
  23#include <linux/delay.h>
  24
  25#include <asm/div64.h>
  26
  27#define VT8500_NR_PWMS 4
  28
  29struct vt8500_chip {
  30        struct pwm_chip chip;
  31        void __iomem *base;
  32};
  33
  34#define to_vt8500_chip(chip)    container_of(chip, struct vt8500_chip, chip)
  35
  36#define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
  37static inline void pwm_busy_wait(void __iomem *reg, u8 bitmask)
  38{
  39        int loops = msecs_to_loops(10);
  40        while ((readb(reg) & bitmask) && --loops)
  41                cpu_relax();
  42
  43        if (unlikely(!loops))
  44                pr_warn("Waiting for status bits 0x%x to clear timed out\n",
  45                           bitmask);
  46}
  47
  48static int vt8500_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
  49                int duty_ns, int period_ns)
  50{
  51        struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
  52        unsigned long long c;
  53        unsigned long period_cycles, prescale, pv, dc;
  54
  55        c = 25000000/2; /* wild guess --- need to implement clocks */
  56        c = c * period_ns;
  57        do_div(c, 1000000000);
  58        period_cycles = c;
  59
  60        if (period_cycles < 1)
  61                period_cycles = 1;
  62        prescale = (period_cycles - 1) / 4096;
  63        pv = period_cycles / (prescale + 1) - 1;
  64        if (pv > 4095)
  65                pv = 4095;
  66
  67        if (prescale > 1023)
  68                return -EINVAL;
  69
  70        c = (unsigned long long)pv * duty_ns;
  71        do_div(c, period_ns);
  72        dc = c;
  73
  74        pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 1));
  75        writel(prescale, vt8500->base + 0x4 + (pwm->hwpwm << 4));
  76
  77        pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 2));
  78        writel(pv, vt8500->base + 0x8 + (pwm->hwpwm << 4));
  79
  80        pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 3));
  81        writel(dc, vt8500->base + 0xc + (pwm->hwpwm << 4));
  82
  83        return 0;
  84}
  85
  86static int vt8500_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
  87{
  88        struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
  89
  90        pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 0));
  91        writel(5, vt8500->base + (pwm->hwpwm << 4));
  92        return 0;
  93}
  94
  95static void vt8500_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
  96{
  97        struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
  98
  99        pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 0));
 100        writel(0, vt8500->base + (pwm->hwpwm << 4));
 101}
 102
 103static struct pwm_ops vt8500_pwm_ops = {
 104        .enable = vt8500_pwm_enable,
 105        .disable = vt8500_pwm_disable,
 106        .config = vt8500_pwm_config,
 107        .owner = THIS_MODULE,
 108};
 109
 110static int __devinit pwm_probe(struct platform_device *pdev)
 111{
 112        struct vt8500_chip *chip;
 113        struct resource *r;
 114        int ret;
 115
 116        chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
 117        if (chip == NULL) {
 118                dev_err(&pdev->dev, "failed to allocate memory\n");
 119                return -ENOMEM;
 120        }
 121
 122        chip->chip.dev = &pdev->dev;
 123        chip->chip.ops = &vt8500_pwm_ops;
 124        chip->chip.base = -1;
 125        chip->chip.npwm = VT8500_NR_PWMS;
 126
 127        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 128        if (r == NULL) {
 129                dev_err(&pdev->dev, "no memory resource defined\n");
 130                return -ENODEV;
 131        }
 132
 133        chip->base = devm_request_and_ioremap(&pdev->dev, r);
 134        if (chip->base == NULL)
 135                return -EADDRNOTAVAIL;
 136
 137        ret = pwmchip_add(&chip->chip);
 138        if (ret < 0)
 139                return ret;
 140
 141        platform_set_drvdata(pdev, chip);
 142        return ret;
 143}
 144
 145static int __devexit pwm_remove(struct platform_device *pdev)
 146{
 147        struct vt8500_chip *chip;
 148
 149        chip = platform_get_drvdata(pdev);
 150        if (chip == NULL)
 151                return -ENODEV;
 152
 153        return pwmchip_remove(&chip->chip);
 154}
 155
 156static struct platform_driver pwm_driver = {
 157        .driver         = {
 158                .name   = "vt8500-pwm",
 159                .owner  = THIS_MODULE,
 160        },
 161        .probe          = pwm_probe,
 162        .remove         = __devexit_p(pwm_remove),
 163};
 164
 165static int __init pwm_init(void)
 166{
 167        return platform_driver_register(&pwm_driver);
 168}
 169arch_initcall(pwm_init);
 170
 171static void __exit pwm_exit(void)
 172{
 173        platform_driver_unregister(&pwm_driver);
 174}
 175module_exit(pwm_exit);
 176
 177MODULE_LICENSE("GPL");
 178
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.