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pwm.c

/*
 * simple driver for PWM (Pulse Width Modulator) controller
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Derived from pxa PWM driver by eric miao <eric.miao@marvell.com>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/pwm.h>
#include <mach/hardware.h>


/* i.MX1 and i.MX21 share the same PWM function block: */

#define MX1_PWMC    0x00   /* PWM Control Register */
#define MX1_PWMS    0x04   /* PWM Sample Register */
#define MX1_PWMP    0x08   /* PWM Period Register */


/* i.MX27, i.MX31, i.MX35 share the same PWM function block: */

#define MX3_PWMCR                 0x00    /* PWM Control Register */
#define MX3_PWMSAR                0x0C    /* PWM Sample Register */
#define MX3_PWMPR                 0x10    /* PWM Period Register */
#define MX3_PWMCR_PRESCALER(x)    (((x - 1) & 0xFFF) << 4)
#define MX3_PWMCR_CLKSRC_IPG_HIGH (2 << 16)
#define MX3_PWMCR_CLKSRC_IPG      (1 << 16)
#define MX3_PWMCR_EN              (1 << 0)



00041 struct pwm_device {
      struct list_head  node;
      struct platform_device *pdev;

      const char  *label;
      struct clk  *clk;

      int         clk_enabled;
      void __iomem      *mmio_base;

      unsigned int      use_count;
      unsigned int      pwm_id;
};

int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
{
      if (pwm == NULL || period_ns == 0 || duty_ns > period_ns)
            return -EINVAL;

      if (cpu_is_mx27() || cpu_is_mx3() || cpu_is_mx25() || cpu_is_mx51()) {
            unsigned long long c;
            unsigned long period_cycles, duty_cycles, prescale;
            u32 cr;

            c = clk_get_rate(pwm->clk);
            c = c * period_ns;
            do_div(c, 1000000000);
            period_cycles = c;

            prescale = period_cycles / 0x10000 + 1;

            period_cycles /= prescale;
            c = (unsigned long long)period_cycles * duty_ns;
            do_div(c, period_ns);
            duty_cycles = c;

            writel(duty_cycles, pwm->mmio_base + MX3_PWMSAR);
            writel(period_cycles, pwm->mmio_base + MX3_PWMPR);

            cr = MX3_PWMCR_PRESCALER(prescale) | MX3_PWMCR_EN;

            if (cpu_is_mx25())
                  cr |= MX3_PWMCR_CLKSRC_IPG;
            else
                  cr |= MX3_PWMCR_CLKSRC_IPG_HIGH;

            writel(cr, pwm->mmio_base + MX3_PWMCR);
      } else if (cpu_is_mx1() || cpu_is_mx21()) {
            /* The PWM subsystem allows for exact frequencies. However,
             * I cannot connect a scope on my device to the PWM line and
             * thus cannot provide the program the PWM controller
             * exactly. Instead, I'm relying on the fact that the
             * Bootloader (u-boot or WinCE+haret) has programmed the PWM
             * function group already. So I'll just modify the PWM sample
             * register to follow the ratio of duty_ns vs. period_ns
             * accordingly.
             *
             * This is good enough for programming the brightness of
             * the LCD backlight.
             *
             * The real implementation would divide PERCLK[0] first by
             * both the prescaler (/1 .. /128) and then by CLKSEL
             * (/2 .. /16).
             */
            u32 max = readl(pwm->mmio_base + MX1_PWMP);
            u32 p = max * duty_ns / period_ns;
            writel(max - p, pwm->mmio_base + MX1_PWMS);
      } else {
            BUG();
      }

      return 0;
}
EXPORT_SYMBOL(pwm_config);

int pwm_enable(struct pwm_device *pwm)
{
      int rc = 0;

      if (!pwm->clk_enabled) {
            rc = clk_enable(pwm->clk);
            if (!rc)
                  pwm->clk_enabled = 1;
      }
      return rc;
}
EXPORT_SYMBOL(pwm_enable);

void pwm_disable(struct pwm_device *pwm)
{
      writel(0, pwm->mmio_base + MX3_PWMCR);

      if (pwm->clk_enabled) {
            clk_disable(pwm->clk);
            pwm->clk_enabled = 0;
      }
}
EXPORT_SYMBOL(pwm_disable);

static DEFINE_MUTEX(pwm_lock);
static LIST_HEAD(pwm_list);

struct pwm_device *pwm_request(int pwm_id, const char *label)
{
      struct pwm_device *pwm;
      int found = 0;

      mutex_lock(&pwm_lock);

      list_for_each_entry(pwm, &pwm_list, node) {
            if (pwm->pwm_id == pwm_id) {
                  found = 1;
                  break;
            }
      }

      if (found) {
            if (pwm->use_count == 0) {
                  pwm->use_count++;
                  pwm->label = label;
            } else
                  pwm = ERR_PTR(-EBUSY);
      } else
            pwm = ERR_PTR(-ENOENT);

      mutex_unlock(&pwm_lock);
      return pwm;
}
EXPORT_SYMBOL(pwm_request);

void pwm_free(struct pwm_device *pwm)
{
      mutex_lock(&pwm_lock);

      if (pwm->use_count) {
            pwm->use_count--;
            pwm->label = NULL;
      } else
            pr_warning("PWM device already freed\n");

      mutex_unlock(&pwm_lock);
}
EXPORT_SYMBOL(pwm_free);

static int __devinit mxc_pwm_probe(struct platform_device *pdev)
{
      struct pwm_device *pwm;
      struct resource *r;
      int ret = 0;

      pwm = kzalloc(sizeof(struct pwm_device), GFP_KERNEL);
      if (pwm == NULL) {
            dev_err(&pdev->dev, "failed to allocate memory\n");
            return -ENOMEM;
      }

      pwm->clk = clk_get(&pdev->dev, "pwm");

      if (IS_ERR(pwm->clk)) {
            ret = PTR_ERR(pwm->clk);
            goto err_free;
      }

      pwm->clk_enabled = 0;

      pwm->use_count = 0;
      pwm->pwm_id = pdev->id;
      pwm->pdev = pdev;

      r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
      if (r == NULL) {
            dev_err(&pdev->dev, "no memory resource defined\n");
            ret = -ENODEV;
            goto err_free_clk;
      }

      r = request_mem_region(r->start, r->end - r->start + 1, pdev->name);
      if (r == NULL) {
            dev_err(&pdev->dev, "failed to request memory resource\n");
            ret = -EBUSY;
            goto err_free_clk;
      }

      pwm->mmio_base = ioremap(r->start, r->end - r->start + 1);
      if (pwm->mmio_base == NULL) {
            dev_err(&pdev->dev, "failed to ioremap() registers\n");
            ret = -ENODEV;
            goto err_free_mem;
      }

      mutex_lock(&pwm_lock);
      list_add_tail(&pwm->node, &pwm_list);
      mutex_unlock(&pwm_lock);

      platform_set_drvdata(pdev, pwm);
      return 0;

err_free_mem:
      release_mem_region(r->start, r->end - r->start + 1);
err_free_clk:
      clk_put(pwm->clk);
err_free:
      kfree(pwm);
      return ret;
}

static int __devexit mxc_pwm_remove(struct platform_device *pdev)
{
      struct pwm_device *pwm;
      struct resource *r;

      pwm = platform_get_drvdata(pdev);
      if (pwm == NULL)
            return -ENODEV;

      mutex_lock(&pwm_lock);
      list_del(&pwm->node);
      mutex_unlock(&pwm_lock);

      iounmap(pwm->mmio_base);

      r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
      release_mem_region(r->start, r->end - r->start + 1);

      clk_put(pwm->clk);

      kfree(pwm);
      return 0;
}

static struct platform_driver mxc_pwm_driver = {
      .driver           = {
            .name = "mxc_pwm",
      },
      .probe            = mxc_pwm_probe,
      .remove           = __devexit_p(mxc_pwm_remove),
};

static int __init mxc_pwm_init(void)
{
      return platform_driver_register(&mxc_pwm_driver);
}
arch_initcall(mxc_pwm_init);

static void __exit mxc_pwm_exit(void)
{
      platform_driver_unregister(&mxc_pwm_driver);
}
module_exit(mxc_pwm_exit);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");

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