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