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