text: /****************************************************************************
   * drivers/pwm.c
   *
   *   Copyright (C) 2011-2013, 2016-2017 Gregory Nutt. All rights reserved.
   *   Author: Gregory Nutt <gnutt@nuttx.org>
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   * 3. Neither the name NuttX nor the names of its contributors may be
   *    used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
   * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
   * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   *
   ****************************************************************************/
  
  /****************************************************************************
   * Included Files
   ****************************************************************************/
  
  #include <nuttx/config.h>
  
  #include <sys/types.h>
  #include <stdint.h>
  #include <stdbool.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <string.h>
  #include <semaphore.h>
  #include <fcntl.h>
  #include <assert.h>
  #include <errno.h>
  #include <debug.h>
  
  #include <nuttx/arch.h>
  #include <nuttx/kmalloc.h>
  #include <nuttx/semaphore.h>
  #include <nuttx/fs/fs.h>
  #include <nuttx/drivers/pwm.h>
  
  #include <nuttx/irq.h>
  
  #ifdef CONFIG_PWM
  
  /****************************************************************************
   * Private Type Definitions
   ****************************************************************************/
  
  /* This structure describes the state of the upper half driver */
  
  struct pwm_upperhalf_s
  {
    uint8_t           crefs;    /* The number of times the device has been opened */
    volatile bool     started;  /* True: pulsed output is being generated */
  #ifdef CONFIG_PWM_PULSECOUNT
    volatile bool     waiting;  /* True: Caller is waiting for the pulse count to expire */
  #endif
    sem_t             exclsem;  /* Supports mutual exclusion */
  #ifdef CONFIG_PWM_PULSECOUNT
    sem_t             waitsem;  /* Used to wait for the pulse count to expire */
  #endif
    struct pwm_info_s info;     /* Pulsed output characteristics */
    FAR struct pwm_lowerhalf_s *dev;  /* lower-half state */
  };
  
  /****************************************************************************
   * Private Function Prototypes
   ****************************************************************************/
  
  static void    pwm_dump(FAR const char *msg,
                          FAR const struct pwm_info_s *info,
                          bool started);
  static int     pwm_open(FAR struct file *filep);
  static int     pwm_close(FAR struct file *filep);
  static ssize_t pwm_read(FAR struct file *filep, FAR char *buffer,
                          size_t buflen);
  static ssize_t pwm_write(FAR struct file *filep, FAR const char *buffer,
                           size_t buflen);
  static int     pwm_start(FAR struct pwm_upperhalf_s *upper,
                           unsigned int oflags);
  static int     pwm_ioctl(FAR struct file *filep, int cmd, unsigned long arg);
  
  /****************************************************************************
   * Private Data
   ****************************************************************************/
  
  static const struct file_operations g_pwmops =
  {
    pwm_open,  /* open */
    pwm_close, /* close */
    pwm_read,  /* read */
    pwm_write, /* write */
    0,         /* seek */
    pwm_ioctl  /* ioctl */
  #ifndef CONFIG_DISABLE_POLL
    , 0        /* poll */
  #endif
  };
  
  /****************************************************************************
   * Private Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: pwm_dump
   ****************************************************************************/
  
  static void pwm_dump(FAR const char *msg, FAR const struct pwm_info_s *info,
                       bool started)
  {
  #ifdef CONFIG_PWM_MULTICHAN
    int i;
  #endif
  
    pwminfo("%s: frequency: %d", msg, info->frequency);
  
  #ifdef CONFIG_PWM_MULTICHAN
    for (i = 0; i < CONFIG_PWM_NCHANNELS; i++)
      {
        pwminfo(" channel: %d duty: %08x",
                info->channels[i].channel, info->channels[i].duty);
      }
  #else
    pwminfo(" duty: %08x", info->duty);
  #endif
  
  #ifdef CONFIG_PWM_PULSECOUNT
    pwminfo(" count: %d\n", info->count);
  #endif
  
    pwminfo(" started: %d\n", started);
  }
  
  /****************************************************************************
   * Name: pwm_open
   *
   * Description:
   *   This function is called whenever the PWM device is opened.
   *
   ****************************************************************************/
  
  static int pwm_open(FAR struct file *filep)
  {
    FAR struct inode           *inode = filep->f_inode;
    FAR struct pwm_upperhalf_s *upper = inode->i_private;
    uint8_t                     tmp;
    int                         ret;
  
    pwminfo("crefs: %d\n", upper->crefs);
  
    /* Get exclusive access to the device structures */
  
    ret = nxsem_wait(&upper->exclsem);
    if (ret < 0)
      {
        goto errout;
      }
  
    /* Increment the count of references to the device.  If this the first
     * time that the driver has been opened for this device, then initialize
     * the device.
     */
  
    tmp = upper->crefs + 1;
    if (tmp == 0)
      {
        /* More than 255 opens; uint8_t overflows to zero */
  
        ret = -EMFILE;
        goto errout_with_sem;
      }
  
    /* Check if this is the first time that the driver has been opened. */
  
    if (tmp == 1)
      {
        FAR struct pwm_lowerhalf_s *lower = upper->dev;
  
        /* Yes.. perform one time hardware initialization. */
  
        DEBUGASSERT(lower->ops->setup != NULL);
        pwminfo("calling setup\n");
  
        ret = lower->ops->setup(lower);
        if (ret < 0)
          {
            goto errout_with_sem;
          }
      }
  
    /* Save the new open count on success */
  
    upper->crefs = tmp;
    ret = OK;
  
  errout_with_sem:
    nxsem_post(&upper->exclsem);
  
  errout:
    return ret;
  }
  
  /****************************************************************************
   * Name: pwm_close
   *
   * Description:
   *   This function is called when the PWM device is closed.
   *
   ****************************************************************************/
  
  static int pwm_close(FAR struct file *filep)
  {
    FAR struct inode           *inode = filep->f_inode;
    FAR struct pwm_upperhalf_s *upper = inode->i_private;
    int                         ret;
  
    pwminfo("crefs: %d\n", upper->crefs);
  
    /* Get exclusive access to the device structures */
  
    ret = nxsem_wait(&upper->exclsem);
    if (ret < 0)
      {
        goto errout;
      }
  
    /* Decrement the references to the driver.  If the reference count will
     * decrement to 0, then uninitialize the driver.
     */
  
    if (upper->crefs > 1)
      {
        upper->crefs--;
      }
    else
      {
        FAR struct pwm_lowerhalf_s *lower = upper->dev;
  
        /* There are no more references to the port */
  
        upper->crefs = 0;
  
        /* Disable the PWM device */
  
        DEBUGASSERT(lower->ops->shutdown != NULL);
        pwminfo("calling shutdown: %d\n");
  
        lower->ops->shutdown(lower);
      }
    ret = OK;
  
  //errout_with_sem:
    nxsem_post(&upper->exclsem);
  
  errout:
    return ret;
  }
  
  /****************************************************************************
   * Name: pwm_read
   *
   * Description:
   *   A dummy read method.  This is provided only to satisfy the VFS layer.
   *
   ****************************************************************************/
  
  static ssize_t pwm_read(FAR struct file *filep, FAR char *buffer,
                          size_t buflen)
  {
    /* Return zero -- usually meaning end-of-file */
  
    return 0;
  }
  
  /****************************************************************************
   * Name: pwm_write
   *
   * Description:
   *   A dummy write method.  This is provided only to satisfy the VFS layer.
   *
   ****************************************************************************/
  
  static ssize_t pwm_write(FAR struct file *filep, FAR const char *buffer,
                           size_t buflen)
  {
    return 0;
  }
  
  /****************************************************************************
   * Name: pwm_start
   *
   * Description:
   *   Handle the PWMIOC_START ioctl command
   *
   ****************************************************************************/
  
  #ifdef CONFIG_PWM_PULSECOUNT
  static int pwm_start(FAR struct pwm_upperhalf_s *upper, unsigned int oflags)
  {
    FAR struct pwm_lowerhalf_s *lower;
    irqstate_t flags;
    int ret = OK;
  
    DEBUGASSERT(upper != NULL);
    lower = upper->dev;
    DEBUGASSERT(lower != NULL && lower->ops->start != NULL);
  
    /* Verify that the PWM is not already running */
  
    if (!upper->started)
      {
        /* Disable interrupts to avoid race conditions */
  
        flags = enter_critical_section();
  
        /* Indicate that if will be waiting for the pulse count to complete.
         * Note that we will only wait if a non-zero pulse count is specified
         * and if the PWM driver was opened in normal, blocking mode.  Also
         * assume for now that the pulse train will be successfully started.
         *
         * We do these things before starting the PWM to avoid race conditions.
         */
  
        upper->waiting = (upper->info.count > 0) && ((oflags & O_NONBLOCK) == 0);
        upper->started = true;
  
        /* Invoke the bottom half method to start the pulse train */
  
        ret = lower->ops->start(lower, &upper->info, upper);
  
        /* A return value of zero means that the pulse train was started
         * successfully.
         */
  
        if (ret == OK)
          {
            /* Should we wait for the pulse output to complete?  Loop in
             * in case the wakeup form nxsem_wait() is a false alarm.
             */
  
            while (upper->waiting)
              {
                /* Wait until we are awakened by pwm_expired().  When
                 * pwm_expired is called, it will post the waitsem and
                 * clear the waiting flag.
                 */
  
                int tmp = nxsem_wait(&upper->waitsem);
                DEBUGASSERT(tmp == OK || tmp == -EINTR);
              }
          }
        else
          {
            /* Looks like we won't be waiting after all */
  
            pwminfo("start failed: %d\n", ret);
            upper->started = false;
            upper->waiting = false;
          }
  
        leave_critical_section(flags);
      }
  
    return ret;
  }
  #else
  static int pwm_start(FAR struct pwm_upperhalf_s *upper, unsigned int oflags)
  {
    FAR struct pwm_lowerhalf_s *lower;
    int ret = OK;
  
    DEBUGASSERT(upper != NULL);
    lower = upper->dev;
    DEBUGASSERT(lower != NULL && lower->ops->start != NULL);
  
    /* Verify that the PWM is not already running */
  
    if (!upper->started)
      {
        /* Invoke the bottom half method to start the pulse train */
  
        ret = lower->ops->start(lower, &upper->info);
  
        /* A return value of zero means that the pulse train was started
         * successfully.
         */
  
        if (ret == OK)
          {
            /* Indicate that the pulse train has started */
  
            upper->started = true;
          }
      }
  
    return ret;
  }
  #endif
  
  /****************************************************************************
   * Name: pwm_ioctl
   *
   * Description:
   *   The standard ioctl method.  This is where ALL of the PWM work is done.
   *
   ****************************************************************************/
  
  static int pwm_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
  {
    FAR struct inode           *inode = filep->f_inode;
    FAR struct pwm_upperhalf_s *upper = inode->i_private;
    FAR struct pwm_lowerhalf_s *lower = upper->dev;
    int                         ret;
  
    pwminfo("cmd: %d arg: %ld\n", cmd, arg);
  
    /* Get exclusive access to the device structures */
  
    ret = nxsem_wait(&upper->exclsem);
    if (ret < 0)
      {
        return ret;
      }
  
    /* Handle built-in ioctl commands */
  
    switch (cmd)
      {
        /* PWMIOC_SETCHARACTERISTICS - Set the characteristics of the next pulsed
         *   output.  This command will neither start nor stop the pulsed output.
         *   It will either setup the configuration that will be used when the
         *   output is started; or it will change the characteristics of the pulsed
         *   output on the fly if the timer is already started.
         *
         *   ioctl argument:  A read-only reference to struct pwm_info_s that provides
         *   the characteristics of the pulsed output.
         */
  
        case PWMIOC_SETCHARACTERISTICS:
          {
            FAR const struct pwm_info_s *info = (FAR const struct pwm_info_s *)((uintptr_t)arg);
            DEBUGASSERT(info != NULL && lower->ops->start != NULL);
  
            pwm_dump("PWMIOC_SETCHARACTERISTICS", info, upper->started);
  
            /* Save the pulse train characteristics */
  
            memcpy(&upper->info, info, sizeof(struct pwm_info_s));
  
            /* If PWM is already running, then re-start it with the new characteristics */
  
            if (upper->started)
              {
  #ifdef CONFIG_PWM_PULSECOUNT
                ret = lower->ops->start(lower, &upper->info, upper);
  #else
                ret = lower->ops->start(lower, &upper->info);
  #endif
              }
          }
          break;
  
        /* PWMIOC_GETCHARACTERISTICS - Get the currently selected characteristics of
         *   the pulsed output (independent of whether the output is start or stopped).
         *
         *   ioctl argument:  A reference to struct pwm_info_s to receive the
         *   characteristics of the pulsed output.
         */
  
        case PWMIOC_GETCHARACTERISTICS:
          {
            FAR struct pwm_info_s *info = (FAR struct pwm_info_s *)((uintptr_t)arg);
            DEBUGASSERT(info != NULL);
  
            memcpy(info, &upper->info, sizeof(struct pwm_info_s));
  
            pwm_dump("PWMIOC_GETCHARACTERISTICS", info, upper->started);
          }
          break;
  
        /* PWMIOC_START - Start the pulsed output.  The PWMIOC_SETCHARACTERISTICS
         *   command must have previously been sent.
         *
         *   ioctl argument:  None
         */
  
        case PWMIOC_START:
          {
            pwm_dump("PWMIOC_START", &upper->info, upper->started);
            DEBUGASSERT(lower->ops->start != NULL);
  
            /* Start the pulse train */
  
            ret = pwm_start(upper, filep->f_oflags);
          }
          break;
  
        /* PWMIOC_STOP - Stop the pulsed output.
         *
         *   ioctl argument:  None
         */
  
        case PWMIOC_STOP:
          {
            pwminfo("PWMIOC_STOP: started: %d\n", upper->started);
            DEBUGASSERT(lower->ops->stop != NULL);
  
            if (upper->started)
              {
                ret = lower->ops->stop(lower);
                upper->started = false;
  #ifdef CONFIG_PWM_PULSECOUNT
                if (upper->waiting)
                  {
                    upper->waiting = false;
                  }
  #endif
              }
          }
          break;
  
        /* Any unrecognized IOCTL commands might be platform-specific ioctl commands */
  
        default:
          {
            pwminfo("Forwarding unrecognized cmd: %d arg: %ld\n", cmd, arg);
            DEBUGASSERT(lower->ops->ioctl != NULL);
            ret = lower->ops->ioctl(lower, cmd, arg);
          }
          break;
      }
  
    nxsem_post(&upper->exclsem);
    return ret;
  }
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: pwm_register
   *
   * Description:
   *   This function binds an instance of a "lower half" timer driver with the
   *   "upper half" PWM device and registers that device so that can be used
   *   by application code.
   *
   *   When this function is called, the "lower half" driver should be in the
   *   reset state (as if the shutdown() method had already been called).
   *
   * Input parameters:
   *   path - The full path to the driver to be registered in the NuttX pseudo-
   *     filesystem.  The recommended convention is to name all PWM drivers
   *     as "/dev/pwm0", "/dev/pwm1", etc.  where the driver path differs only
   *     in the "minor" number at the end of the device name.
   *   dev - A pointer to an instance of lower half timer driver.  This instance
   *     is bound to the PWM driver and must persists as long as the driver
   *     persists.
   *
   * Returned Value:
   *   Zero on success; a negated errno value on failure.
   *
   ****************************************************************************/
  
  int pwm_register(FAR const char *path, FAR struct pwm_lowerhalf_s *dev)
  {
    FAR struct pwm_upperhalf_s *upper;
  
    /* Allocate the upper-half data structure */
  
    upper = (FAR struct pwm_upperhalf_s *)kmm_zalloc(sizeof(struct pwm_upperhalf_s));
    if (!upper)
      {
        pwmerr("Allocation failed\n");
        return -ENOMEM;
      }
  
    /* Initialize the PWM device structure (it was already zeroed by kmm_zalloc()) */
  
    nxsem_init(&upper->exclsem, 0, 1);
  #ifdef CONFIG_PWM_PULSECOUNT
    nxsem_init(&upper->waitsem, 0, 0);
  
    /* The wait semaphore is used for signaling and, hence, should not have priority
     * inheritance enabled.
     */
  
    nxsem_setprotocol(&upper->waitsem, SEM_PRIO_NONE);
  #endif
  
    upper->dev = dev;
  
    /* Register the PWM device */
  
    pwminfo("Registering %s\n", path);
    return register_driver(path, &g_pwmops, 0666, upper);
  }
  
  /****************************************************************************
   * Name: pwm_expired
   *
   * Description:
   *   If CONFIG_PWM_PULSECOUNT is defined and the pulse count was configured
   *   to a non-zero value, then the "upper half" driver will wait for the
   *   pulse count to expire.  The sequence of expected events is as follows:
   *
   *   1. The upper half driver calls the start method, providing the lower
   *      half driver with the pulse train characteristics.  If a fixed
   *      number of pulses is required, the 'count' value will be nonzero.
   *   2. The lower half driver's start() methoc must verify that it can
   *      support the request pulse train (frequency, duty, AND pulse count).
   *      If it cannot, it should return an error.  If the pulse count is
   *      non-zero, it should set up the hardware for that number of pulses
   *      and return success.  NOTE:  That is CONFIG_PWM_PULSECOUNT is
   *      defined, the start() method receives an additional parameter
   *      that must be used in this callback.
   *   3. When the start() method returns success, the upper half driver
   *      will "sleep" until the pwm_expired method is called.
   *   4. When the lower half detects that the pulse count has expired
   *      (probably through an interrupt), it must call the pwm_expired
   *      interface using the handle that was previously passed to the
   *      start() method
   *
   * Input parameters:
   *   handle - This is the handle that was provided to the lower-half
   *     start() method.
   *
   * Returned Value:
   *   None
   *
   * Assumptions:
   *   This function may be called from an interrupt handler.
   *
   ****************************************************************************/
  
  #ifdef CONFIG_PWM_PULSECOUNT
  void pwm_expired(FAR void *handle)
  {
    FAR struct pwm_upperhalf_s *upper = (FAR struct pwm_upperhalf_s *)handle;
  
    pwminfo("started: %d waiting: %d\n", upper->started, upper->waiting);
  
    /* Make sure that the PWM is started */
  
    if (upper->started)
      {
        /* Is there a thread waiting for the pulse train to complete? */
  
        if (upper->waiting)
          {
            /* Yes.. clear the waiting flag and awakened the waiting thread */
  
            upper->waiting = false;
            nxsem_post(&upper->waitsem);
          }
  
        /* The PWM is now stopped */
  
        upper->started = false;
      }
  }
  #endif
  
  #endif /* CONFIG_PWM */
  