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/err.h>
  15 #include <linux/clk.h>
  16 #include <linux/io.h>
  17 #include <linux/pwm.h>
  18 #include <mach/hardware.h>
  19
  20
  21 /* i.MX1 and i.MX21 share the same PWM function block: */
  22
  23 #define MX1_PWMC    0x00   /* PWM Control Register */
  24 #define MX1_PWMS    0x04   /* PWM Sample Register */
  25 #define MX1_PWMP    0x08   /* PWM Period Register */
  26
  27
  28 /* i.MX27, i.MX31, i.MX35 share the same PWM function block: */
  29
  30 #define MX3_PWMCR                 0x00    /* PWM Control Register */
  31 #define MX3_PWMSAR                0x0C    /* PWM Sample Register */
  32 #define MX3_PWMPR                 0x10    /* PWM Period Register */
  33 #define MX3_PWMCR_PRESCALER(x)    (((x - 1) & 0xFFF) << 4)
  34 #define MX3_PWMCR_DOZEEN                (1 << 24)
  35 #define MX3_PWMCR_WAITEN                (1 << 23)
  36 #define MX3_PWMCR_DBGEN                 (1 << 22)
  37 #define MX3_PWMCR_CLKSRC_IPG_HIGH (2 << 16)
  38 #define MX3_PWMCR_CLKSRC_IPG      (1 << 16)
  39 #define MX3_PWMCR_EN              (1 << 0)
  40
  41
  42
  43 struct pwm_device {
  44         struct list_head        node;
  45         struct platform_device *pdev;
  46
  47         const char      *label;
  48         struct clk      *clk;
  49
  50         int             clk_enabled;
  51         void __iomem    *mmio_base;
  52
  53         unsigned int    use_count;
  54         unsigned int    pwm_id;
  55 };
  56
  57 int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
  58 {
  59         if (pwm == NULL || period_ns == 0 || duty_ns > period_ns)
  60                 return -EINVAL;
  61
  62         if (cpu_is_mx27() || cpu_is_mx3() || cpu_is_mx25()) {
  63                 unsigned long long c;
  64                 unsigned long period_cycles, duty_cycles, prescale;
  65                 u32 cr;
  66
  67                 c = clk_get_rate(pwm->clk);
  68                 c = c * period_ns;
  69                 do_div(c, 1000000000);
  70                 period_cycles = c;
  71
  72                 prescale = period_cycles / 0x10000 + 1;
  73
  74                 period_cycles /= prescale;
  75                 c = (unsigned long long)period_cycles * duty_ns;
  76                 do_div(c, period_ns);
  77                 duty_cycles = c;
  78
  79                 /*
  80                  * according to imx pwm RM, the real period value should be
  81                  * PERIOD value in PWMPR plus 2.
  82                  */
  83                 if (period_cycles > 2)
  84                         period_cycles -= 2;
  85                 else
  86                         period_cycles = 0;
  87
  88                 writel(duty_cycles, pwm->mmio_base + MX3_PWMSAR);
  89                 writel(period_cycles, pwm->mmio_base + MX3_PWMPR);
  90
  91                 cr = MX3_PWMCR_PRESCALER(prescale) |
  92                         MX3_PWMCR_DOZEEN | MX3_PWMCR_WAITEN |
  93                         MX3_PWMCR_DBGEN | MX3_PWMCR_EN;
  94
  95                 if (cpu_is_mx25())
  96                         cr |= MX3_PWMCR_CLKSRC_IPG;
  97                 else
  98                         cr |= MX3_PWMCR_CLKSRC_IPG_HIGH;
  99
 100                 writel(cr, pwm->mmio_base + MX3_PWMCR);
 101         } else if (cpu_is_mx1() || cpu_is_mx21()) {
 102                 /* The PWM subsystem allows for exact frequencies. However,
 103                  * I cannot connect a scope on my device to the PWM line and
 104                  * thus cannot provide the program the PWM controller
 105                  * exactly. Instead, I'm relying on the fact that the
 106                  * Bootloader (u-boot or WinCE+haret) has programmed the PWM
 107                  * function group already. So I'll just modify the PWM sample
 108                  * register to follow the ratio of duty_ns vs. period_ns
 109                  * accordingly.
 110                  *
 111                  * This is good enought for programming the brightness of
 112                  * the LCD backlight.
 113                  *
 114                  * The real implementation would divide PERCLK[0] first by
 115                  * both the prescaler (/1 .. /128) and then by CLKSEL
 116                  * (/2 .. /16).
 117                  */
 118                 u32 max = readl(pwm->mmio_base + MX1_PWMP);
 119                 u32 p = max * duty_ns / period_ns;
 120                 writel(max - p, pwm->mmio_base + MX1_PWMS);
 121         } else {
 122                 BUG();
 123         }
 124
 125         return 0;
 126 }
 127 EXPORT_SYMBOL(pwm_config);
 128
 129 int pwm_enable(struct pwm_device *pwm)
 130 {
 131         int rc = 0;
 132
 133         if (!pwm->clk_enabled) {
 134                 rc = clk_enable(pwm->clk);
 135                 if (!rc)
 136                         pwm->clk_enabled = 1;
 137         }
 138         return rc;
 139 }
 140 EXPORT_SYMBOL(pwm_enable);
 141
 142 void pwm_disable(struct pwm_device *pwm)
 143 {
 144         writel(0, pwm->mmio_base + MX3_PWMCR);
 145
 146         if (pwm->clk_enabled) {
 147                 clk_disable(pwm->clk);
 148                 pwm->clk_enabled = 0;
 149         }
 150 }
 151 EXPORT_SYMBOL(pwm_disable);
 152
 153 static DEFINE_MUTEX(pwm_lock);
 154 static LIST_HEAD(pwm_list);
 155
 156 struct pwm_device *pwm_request(int pwm_id, const char *label)
 157 {
 158         struct pwm_device *pwm;
 159         int found = 0;
 160
 161         mutex_lock(&pwm_lock);
 162
 163         list_for_each_entry(pwm, &pwm_list, node) {
 164                 if (pwm->pwm_id == pwm_id) {
 165                         found = 1;
 166                         break;
 167                 }
 168         }
 169
 170         if (found) {
 171                 if (pwm->use_count == 0) {
 172                         pwm->use_count++;
 173                         pwm->label = label;
 174                 } else
 175                         pwm = ERR_PTR(-EBUSY);
 176         } else
 177                 pwm = ERR_PTR(-ENOENT);
 178
 179         mutex_unlock(&pwm_lock);
 180         return pwm;
 181 }
 182 EXPORT_SYMBOL(pwm_request);
 183
 184 void pwm_free(struct pwm_device *pwm)
 185 {
 186         mutex_lock(&pwm_lock);
 187
 188         if (pwm->use_count) {
 189                 pwm->use_count--;
 190                 pwm->label = NULL;
 191         } else
 192                 pr_warning("PWM device already freed\n");
 193
 194         mutex_unlock(&pwm_lock);
 195 }
 196 EXPORT_SYMBOL(pwm_free);
 197
 198 static int __devinit mxc_pwm_probe(struct platform_device *pdev)
 199 {
 200         struct pwm_device *pwm;
 201         struct resource *r;
 202         int ret = 0;
 203
 204         pwm = kzalloc(sizeof(struct pwm_device), GFP_KERNEL);
 205         if (pwm == NULL) {
 206                 dev_err(&pdev->dev, "failed to allocate memory\n");
 207                 return -ENOMEM;
 208         }
 209
 210         pwm->clk = clk_get(&pdev->dev, "pwm");
 211
 212         if (IS_ERR(pwm->clk)) {
 213                 ret = PTR_ERR(pwm->clk);
 214                 goto err_free;
 215         }
 216
 217         pwm->clk_enabled = 0;
 218
 219         pwm->use_count = 0;
 220         pwm->pwm_id = pdev->id;
 221         pwm->pdev = pdev;
 222
 223         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 224         if (r == NULL) {
 225                 dev_err(&pdev->dev, "no memory resource defined\n");
 226                 ret = -ENODEV;
 227                 goto err_free_clk;
 228         }
 229
 230         r = request_mem_region(r->start, r->end - r->start + 1, pdev->name);
 231         if (r == NULL) {
 232                 dev_err(&pdev->dev, "failed to request memory resource\n");
 233                 ret = -EBUSY;
 234                 goto err_free_clk;
 235         }
 236
 237         pwm->mmio_base = ioremap(r->start, r->end - r->start + 1);
 238         if (pwm->mmio_base == NULL) {
 239                 dev_err(&pdev->dev, "failed to ioremap() registers\n");
 240                 ret = -ENODEV;
 241                 goto err_free_mem;
 242         }
 243
 244         mutex_lock(&pwm_lock);
 245         list_add_tail(&pwm->node, &pwm_list);
 246         mutex_unlock(&pwm_lock);
 247
 248         platform_set_drvdata(pdev, pwm);
 249         return 0;
 250
 251 err_free_mem:
 252         release_mem_region(r->start, r->end - r->start + 1);
 253 err_free_clk:
 254         clk_put(pwm->clk);
 255 err_free:
 256         kfree(pwm);
 257         return ret;
 258 }
 259
 260 static int __devexit mxc_pwm_remove(struct platform_device *pdev)
 261 {
 262         struct pwm_device *pwm;
 263         struct resource *r;
 264
 265         pwm = platform_get_drvdata(pdev);
 266         if (pwm == NULL)
 267                 return -ENODEV;
 268
 269         mutex_lock(&pwm_lock);
 270         list_del(&pwm->node);
 271         mutex_unlock(&pwm_lock);
 272
 273         iounmap(pwm->mmio_base);
 274
 275         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 276         release_mem_region(r->start, r->end - r->start + 1);
 277
 278         clk_put(pwm->clk);
 279
 280         kfree(pwm);
 281         return 0;
 282 }
 283
 284 static struct platform_driver mxc_pwm_driver = {
 285         .driver         = {
 286                 .name   = "mxc_pwm",
 287         },
 288         .probe          = mxc_pwm_probe,
 289         .remove         = __devexit_p(mxc_pwm_remove),
 290 };
 291
 292 static int __init mxc_pwm_init(void)
 293 {
 294         return platform_driver_register(&mxc_pwm_driver);
 295 }
 296 arch_initcall(mxc_pwm_init);
 297
 298 static void __exit mxc_pwm_exit(void)
 299 {
 300         platform_driver_unregister(&mxc_pwm_driver);
 301 }
 302 module_exit(mxc_pwm_exit);
 303
 304 MODULE_LICENSE("GPL v2");
 305 MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");