drivers/pwm/pwm-vt8500.c

   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
  29 struct 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)
  37 static 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
  48 static 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
  86 static 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
  95 static 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
 103 static 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
 110 static 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
 145 static 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
 156 static 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
 165 static int __init pwm_init(void)
 166 {
 167         return platform_driver_register(&pwm_driver);
 168 }
 169 arch_initcall(pwm_init);
 170
 171 static void __exit pwm_exit(void)
 172 {
 173         platform_driver_unregister(&pwm_driver);
 174 }
 175 module_exit(pwm_exit);
 176
 177 MODULE_LICENSE("GPL");