arch/arm/plat-mxc/pwm.c

   1 /*
   2  * simple driver for PWM (Pulse Width Modulator) controller
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * Derived from pxa PWM driver by eric miao <eric.miao@marvell.com>
   9  */
  10
  11 #include <linux/module.h>
  12 #include <linux/kernel.h>
  13 #include <linux/platform_device.h>
  14 #include <linux/slab.h>
  15 #include <linux/err.h>
  16 #include <linux/clk.h>
  17 #include <linux/io.h>
  18 #include <linux/pwm.h>
  19 #include <mach/hardware.h>
  20
  21
  22 /* i.MX1 and i.MX21 share the same PWM function block: */
  23
  24 #define MX1_PWMC    0x00   /* PWM Control Register */
  25 #define MX1_PWMS    0x04   /* PWM Sample Register */
  26 #define MX1_PWMP    0x08   /* PWM Period Register */
  27
  28
  29 /* i.MX27, i.MX31, i.MX35 share the same PWM function block: */
  30
  31 #define MX3_PWMCR                 0x00    /* PWM Control Register */
  32 #define MX3_PWMSAR                0x0C    /* PWM Sample Register */
  33 #define MX3_PWMPR                 0x10    /* PWM Period Register */
  34 #define MX3_PWMCR_PRESCALER(x)    (((x - 1) & 0xFFF) << 4)
  35 #define MX3_PWMCR_CLKSRC_IPG_HIGH (2 << 16)
  36 #define MX3_PWMCR_CLKSRC_IPG      (1 << 16)
  37 #define MX3_PWMCR_EN              (1 << 0)
  38
  39
  40
  41 struct pwm_device {
  42         struct list_head        node;
  43         struct platform_device *pdev;
  44
  45         const char      *label;
  46         struct clk      *clk;
  47
  48         int             clk_enabled;
  49         void __iomem    *mmio_base;
  50
  51         unsigned int    use_count;
  52         unsigned int    pwm_id;
  53 };
  54
  55 int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
  56 {
  57         if (pwm == NULL || period_ns == 0 || duty_ns > period_ns)
  58                 return -EINVAL;
  59
  60         if (cpu_is_mx27() || cpu_is_mx3() || cpu_is_mx25() || cpu_is_mx51()) {
  61                 unsigned long long c;
  62                 unsigned long period_cycles, duty_cycles, prescale;
  63                 u32 cr;
  64
  65                 c = clk_get_rate(pwm->clk);
  66                 c = c * period_ns;
  67                 do_div(c, 1000000000);
  68                 period_cycles = c;
  69
  70                 prescale = period_cycles / 0x10000 + 1;
  71
  72                 period_cycles /= prescale;
  73                 c = (unsigned long long)period_cycles * duty_ns;
  74                 do_div(c, period_ns);
  75                 duty_cycles = c;
  76
  77                 writel(duty_cycles, pwm->mmio_base + MX3_PWMSAR);
  78                 writel(period_cycles, pwm->mmio_base + MX3_PWMPR);
  79
  80                 cr = MX3_PWMCR_PRESCALER(prescale) | MX3_PWMCR_EN;
  81
  82                 if (cpu_is_mx25())
  83                         cr |= MX3_PWMCR_CLKSRC_IPG;
  84                 else
  85                         cr |= MX3_PWMCR_CLKSRC_IPG_HIGH;
  86
  87                 writel(cr, pwm->mmio_base + MX3_PWMCR);
  88         } else if (cpu_is_mx1() || cpu_is_mx21()) {
  89                 /* The PWM subsystem allows for exact frequencies. However,
  90                  * I cannot connect a scope on my device to the PWM line and
  91                  * thus cannot provide the program the PWM controller
  92                  * exactly. Instead, I'm relying on the fact that the
  93                  * Bootloader (u-boot or WinCE+haret) has programmed the PWM
  94                  * function group already. So I'll just modify the PWM sample
  95                  * register to follow the ratio of duty_ns vs. period_ns
  96                  * accordingly.
  97                  *
  98                  * This is good enough for programming the brightness of
  99                  * the LCD backlight.
 100                  *
 101                  * The real implementation would divide PERCLK[0] first by
 102                  * both the prescaler (/1 .. /128) and then by CLKSEL
 103                  * (/2 .. /16).
 104                  */
 105                 u32 max = readl(pwm->mmio_base + MX1_PWMP);
 106                 u32 p = max * duty_ns / period_ns;
 107                 writel(max - p, pwm->mmio_base + MX1_PWMS);
 108         } else {
 109                 BUG();
 110         }
 111
 112         return 0;
 113 }
 114 EXPORT_SYMBOL(pwm_config);
 115
 116 int pwm_enable(struct pwm_device *pwm)
 117 {
 118         int rc = 0;
 119
 120         if (!pwm->clk_enabled) {
 121                 rc = clk_enable(pwm->clk);
 122                 if (!rc)
 123                         pwm->clk_enabled = 1;
 124         }
 125         return rc;
 126 }
 127 EXPORT_SYMBOL(pwm_enable);
 128
 129 void pwm_disable(struct pwm_device *pwm)
 130 {
 131         writel(0, pwm->mmio_base + MX3_PWMCR);
 132
 133         if (pwm->clk_enabled) {
 134                 clk_disable(pwm->clk);
 135                 pwm->clk_enabled = 0;
 136         }
 137 }
 138 EXPORT_SYMBOL(pwm_disable);
 139
 140 static DEFINE_MUTEX(pwm_lock);
 141 static LIST_HEAD(pwm_list);
 142
 143 struct pwm_device *pwm_request(int pwm_id, const char *label)
 144 {
 145         struct pwm_device *pwm;
 146         int found = 0;
 147
 148         mutex_lock(&pwm_lock);
 149
 150         list_for_each_entry(pwm, &pwm_list, node) {
 151                 if (pwm->pwm_id == pwm_id) {
 152                         found = 1;
 153                         break;
 154                 }
 155         }
 156
 157         if (found) {
 158                 if (pwm->use_count == 0) {
 159                         pwm->use_count++;
 160                         pwm->label = label;
 161                 } else
 162                         pwm = ERR_PTR(-EBUSY);
 163         } else
 164                 pwm = ERR_PTR(-ENOENT);
 165
 166         mutex_unlock(&pwm_lock);
 167         return pwm;
 168 }
 169 EXPORT_SYMBOL(pwm_request);
 170
 171 void pwm_free(struct pwm_device *pwm)
 172 {
 173         mutex_lock(&pwm_lock);
 174
 175         if (pwm->use_count) {
 176                 pwm->use_count--;
 177                 pwm->label = NULL;
 178         } else
 179                 pr_warning("PWM device already freed\n");
 180
 181         mutex_unlock(&pwm_lock);
 182 }
 183 EXPORT_SYMBOL(pwm_free);
 184
 185 static int __devinit mxc_pwm_probe(struct platform_device *pdev)
 186 {
 187         struct pwm_device *pwm;
 188         struct resource *r;
 189         int ret = 0;
 190
 191         pwm = kzalloc(sizeof(struct pwm_device), GFP_KERNEL);
 192         if (pwm == NULL) {
 193                 dev_err(&pdev->dev, "failed to allocate memory\n");
 194                 return -ENOMEM;
 195         }
 196
 197         pwm->clk = clk_get(&pdev->dev, "pwm");
 198
 199         if (IS_ERR(pwm->clk)) {
 200                 ret = PTR_ERR(pwm->clk);
 201                 goto err_free;
 202         }
 203
 204         pwm->clk_enabled = 0;
 205
 206         pwm->use_count = 0;
 207         pwm->pwm_id = pdev->id;
 208         pwm->pdev = pdev;
 209
 210         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 211         if (r == NULL) {
 212                 dev_err(&pdev->dev, "no memory resource defined\n");
 213                 ret = -ENODEV;
 214                 goto err_free_clk;
 215         }
 216
 217         r = request_mem_region(r->start, resource_size(r), pdev->name);
 218         if (r == NULL) {
 219                 dev_err(&pdev->dev, "failed to request memory resource\n");
 220                 ret = -EBUSY;
 221                 goto err_free_clk;
 222         }
 223
 224         pwm->mmio_base = ioremap(r->start, resource_size(r));
 225         if (pwm->mmio_base == NULL) {
 226                 dev_err(&pdev->dev, "failed to ioremap() registers\n");
 227                 ret = -ENODEV;
 228                 goto err_free_mem;
 229         }
 230
 231         mutex_lock(&pwm_lock);
 232         list_add_tail(&pwm->node, &pwm_list);
 233         mutex_unlock(&pwm_lock);
 234
 235         platform_set_drvdata(pdev, pwm);
 236         return 0;
 237
 238 err_free_mem:
 239         release_mem_region(r->start, resource_size(r));
 240 err_free_clk:
 241         clk_put(pwm->clk);
 242 err_free:
 243         kfree(pwm);
 244         return ret;
 245 }
 246
 247 static int __devexit mxc_pwm_remove(struct platform_device *pdev)
 248 {
 249         struct pwm_device *pwm;
 250         struct resource *r;
 251
 252         pwm = platform_get_drvdata(pdev);
 253         if (pwm == NULL)
 254                 return -ENODEV;
 255
 256         mutex_lock(&pwm_lock);
 257         list_del(&pwm->node);
 258         mutex_unlock(&pwm_lock);
 259
 260         iounmap(pwm->mmio_base);
 261
 262         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 263         release_mem_region(r->start, resource_size(r));
 264
 265         clk_put(pwm->clk);
 266
 267         kfree(pwm);
 268         return 0;
 269 }
 270
 271 static struct platform_driver mxc_pwm_driver = {
 272         .driver         = {
 273                 .name   = "mxc_pwm",
 274         },
 275         .probe          = mxc_pwm_probe,
 276         .remove         = __devexit_p(mxc_pwm_remove),
 277 };
 278
 279 static int __init mxc_pwm_init(void)
 280 {
 281         return platform_driver_register(&mxc_pwm_driver);
 282 }
 283 arch_initcall(mxc_pwm_init);
 284
 285 static void __exit mxc_pwm_exit(void)
 286 {
 287         platform_driver_unregister(&mxc_pwm_driver);
 288 }
 289 module_exit(mxc_pwm_exit);
 290
 291 MODULE_LICENSE("GPL v2");
 292 MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");