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