arch/arm/mach-vt8500/pwm.c

   1 /*
   2  * arch/arm/mach-vt8500/pwm.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 static DEFINE_MUTEX(pwm_lock);
  30 static LIST_HEAD(pwm_list);
  31
  32 struct pwm_device {
  33         struct list_head        node;
  34         struct platform_device  *pdev;
  35
  36         const char      *label;
  37
  38         void __iomem    *regbase;
  39
  40         unsigned int    use_count;
  41         unsigned int    pwm_id;
  42 };
  43
  44 #define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
  45 static inline void pwm_busy_wait(void __iomem *reg, u8 bitmask)
  46 {
  47         int loops = msecs_to_loops(10);
  48         while ((readb(reg) & bitmask) && --loops)
  49                 cpu_relax();
  50
  51         if (unlikely(!loops))
  52                 pr_warning("Waiting for status bits 0x%x to clear timed out\n",
  53                            bitmask);
  54 }
  55
  56 int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
  57 {
  58         unsigned long long c;
  59         unsigned long period_cycles, prescale, pv, dc;
  60
  61         if (pwm == NULL || period_ns == 0 || duty_ns > period_ns)
  62                 return -EINVAL;
  63
  64         c = 25000000/2; /* wild guess --- need to implement clocks */
  65         c = c * period_ns;
  66         do_div(c, 1000000000);
  67         period_cycles = c;
  68
  69         if (period_cycles < 1)
  70                 period_cycles = 1;
  71         prescale = (period_cycles - 1) / 4096;
  72         pv = period_cycles / (prescale + 1) - 1;
  73         if (pv > 4095)
  74                 pv = 4095;
  75
  76         if (prescale > 1023)
  77                 return -EINVAL;
  78
  79         c = (unsigned long long)pv * duty_ns;
  80         do_div(c, period_ns);
  81         dc = c;
  82
  83         pwm_busy_wait(pwm->regbase + 0x40 + pwm->pwm_id, (1 << 1));
  84         writel(prescale, pwm->regbase + 0x4 + (pwm->pwm_id << 4));
  85
  86         pwm_busy_wait(pwm->regbase + 0x40 + pwm->pwm_id, (1 << 2));
  87         writel(pv, pwm->regbase + 0x8 + (pwm->pwm_id << 4));
  88
  89         pwm_busy_wait(pwm->regbase + 0x40 + pwm->pwm_id, (1 << 3));
  90         writel(dc, pwm->regbase + 0xc + (pwm->pwm_id << 4));
  91
  92         return 0;
  93 }
  94 EXPORT_SYMBOL(pwm_config);
  95
  96 int pwm_enable(struct pwm_device *pwm)
  97 {
  98         pwm_busy_wait(pwm->regbase + 0x40 + pwm->pwm_id, (1 << 0));
  99         writel(5, pwm->regbase + (pwm->pwm_id << 4));
 100         return 0;
 101 }
 102 EXPORT_SYMBOL(pwm_enable);
 103
 104 void pwm_disable(struct pwm_device *pwm)
 105 {
 106         pwm_busy_wait(pwm->regbase + 0x40 + pwm->pwm_id, (1 << 0));
 107         writel(0, pwm->regbase + (pwm->pwm_id << 4));
 108 }
 109 EXPORT_SYMBOL(pwm_disable);
 110
 111 struct pwm_device *pwm_request(int pwm_id, const char *label)
 112 {
 113         struct pwm_device *pwm;
 114         int found = 0;
 115
 116         mutex_lock(&pwm_lock);
 117
 118         list_for_each_entry(pwm, &pwm_list, node) {
 119                 if (pwm->pwm_id == pwm_id) {
 120                         found = 1;
 121                         break;
 122                 }
 123         }
 124
 125         if (found) {
 126                 if (pwm->use_count == 0) {
 127                         pwm->use_count++;
 128                         pwm->label = label;
 129                 } else {
 130                         pwm = ERR_PTR(-EBUSY);
 131                 }
 132         } else {
 133                 pwm = ERR_PTR(-ENOENT);
 134         }
 135
 136         mutex_unlock(&pwm_lock);
 137         return pwm;
 138 }
 139 EXPORT_SYMBOL(pwm_request);
 140
 141 void pwm_free(struct pwm_device *pwm)
 142 {
 143         mutex_lock(&pwm_lock);
 144
 145         if (pwm->use_count) {
 146                 pwm->use_count--;
 147                 pwm->label = NULL;
 148         } else {
 149                 pr_warning("PWM device already freed\n");
 150         }
 151
 152         mutex_unlock(&pwm_lock);
 153 }
 154 EXPORT_SYMBOL(pwm_free);
 155
 156 static inline void __add_pwm(struct pwm_device *pwm)
 157 {
 158         mutex_lock(&pwm_lock);
 159         list_add_tail(&pwm->node, &pwm_list);
 160         mutex_unlock(&pwm_lock);
 161 }
 162
 163 static int __devinit pwm_probe(struct platform_device *pdev)
 164 {
 165         struct pwm_device *pwms;
 166         struct resource *r;
 167         int ret = 0;
 168         int i;
 169
 170         pwms = kzalloc(sizeof(struct pwm_device) * VT8500_NR_PWMS, GFP_KERNEL);
 171         if (pwms == NULL) {
 172                 dev_err(&pdev->dev, "failed to allocate memory\n");
 173                 return -ENOMEM;
 174         }
 175
 176         for (i = 0; i < VT8500_NR_PWMS; i++) {
 177                 pwms[i].use_count = 0;
 178                 pwms[i].pwm_id = i;
 179                 pwms[i].pdev = pdev;
 180         }
 181
 182         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 183         if (r == NULL) {
 184                 dev_err(&pdev->dev, "no memory resource defined\n");
 185                 ret = -ENODEV;
 186                 goto err_free;
 187         }
 188
 189         r = request_mem_region(r->start, resource_size(r), pdev->name);
 190         if (r == NULL) {
 191                 dev_err(&pdev->dev, "failed to request memory resource\n");
 192                 ret = -EBUSY;
 193                 goto err_free;
 194         }
 195
 196         pwms[0].regbase = ioremap(r->start, resource_size(r));
 197         if (pwms[0].regbase == NULL) {
 198                 dev_err(&pdev->dev, "failed to ioremap() registers\n");
 199                 ret = -ENODEV;
 200                 goto err_free_mem;
 201         }
 202
 203         for (i = 1; i < VT8500_NR_PWMS; i++)
 204                 pwms[i].regbase = pwms[0].regbase;
 205
 206         for (i = 0; i < VT8500_NR_PWMS; i++)
 207                 __add_pwm(&pwms[i]);
 208
 209         platform_set_drvdata(pdev, pwms);
 210         return 0;
 211
 212 err_free_mem:
 213         release_mem_region(r->start, resource_size(r));
 214 err_free:
 215         kfree(pwms);
 216         return ret;
 217 }
 218
 219 static int __devexit pwm_remove(struct platform_device *pdev)
 220 {
 221         struct pwm_device *pwms;
 222         struct resource *r;
 223         int i;
 224
 225         pwms = platform_get_drvdata(pdev);
 226         if (pwms == NULL)
 227                 return -ENODEV;
 228
 229         mutex_lock(&pwm_lock);
 230
 231         for (i = 0; i < VT8500_NR_PWMS; i++)
 232                 list_del(&pwms[i].node);
 233         mutex_unlock(&pwm_lock);
 234
 235         iounmap(pwms[0].regbase);
 236
 237         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 238         release_mem_region(r->start, resource_size(r));
 239
 240         kfree(pwms);
 241         return 0;
 242 }
 243
 244 static struct platform_driver pwm_driver = {
 245         .driver         = {
 246                 .name   = "vt8500-pwm",
 247                 .owner  = THIS_MODULE,
 248         },
 249         .probe          = pwm_probe,
 250         .remove         = __devexit_p(pwm_remove),
 251 };
 252
 253 static int __init pwm_init(void)
 254 {
 255         return platform_driver_register(&pwm_driver);
 256 }
 257 arch_initcall(pwm_init);
 258
 259 static void __exit pwm_exit(void)
 260 {
 261         platform_driver_unregister(&pwm_driver);
 262 }
 263 module_exit(pwm_exit);
 264
 265 MODULE_LICENSE("GPL");