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px4-firmware/nuttx/drivers/pwm.c

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/****************************************************************************
* drivers/pwm.c
*
* Copyright (C) 2011 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.
*
****************************************************************************/
/****************************************************************************
* Compilation Switches
****************************************************************************/
/****************************************************************************
* 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/fs/fs.h>
#include <nuttx/arch.h>
#include <nuttx/pwm.h>
#include <arch/irq.h>
#ifdef CONFIG_PWM
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Debug ********************************************************************/
/* Non-standard debug that may be enabled just for testing PWM */
#ifdef CONFIG_DEBUG_PWM
# define pwmdbg dbg
# define pwmvdbg vdbg
# define pwmlldbg lldbg
# define pwmllvdbg llvdbg
#else
# define pwmdbg(x...)
# define pwmvdbg(x...)
# define pwmlldbg(x...)
# define pwmllvdbg(x...)
#endif
/****************************************************************************
* Private Type Definitions
****************************************************************************/
/* This structure describes the state of the upper half drivere */
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 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_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;
pwmvdbg("crefs: %d\n", upper->crefs);
/* Get exclusive access to the device structures */
ret = sem_wait(&upper->exclsem);
if (ret < 0)
{
ret = -errno;
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);
pwmvdbg("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:
sem_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;
pwmvdbg("crefs: %d\n", upper->crefs);
/* Get exclusive access to the device structures */
ret = sem_wait(&upper->exclsem);
if (ret < 0)
{
ret = -errno;
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);
pwmvdbg("calling shutdown: %d\n");
lower->ops->shutdown(lower);
}
ret = OK;
//errout_with_sem:
sem_post(&upper->exclsem);
errout:
return ret;
}
/************************************************************************************
* Name: pwm_read
*
* Description:
* A dummy read method. This is provided only to satsify 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 satsify 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 = upper->dev;
irqstate_t flags;
int ret = OK;
DEBUGASSERT(upper != NULL && lower->ops->start != NULL);
/* Verify that the PWM is not already running */
if (!upper->started)
{
/* Disable interrupts to avoid race conditions */
flags = irqsave();
/* 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 sem_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 = sem_wait(&upper->waitsem);
DEBUGASSERT(tmp == OK || errno == EINTR);
}
}
else
{
/* Looks like we won't be waiting after all */
pwmvdbg("start failed: %d\n", ret);
upper->started = false;
upper->waiting = false;
}
irqrestore(flags);
}
return ret;
}
#else
static int pwm_start(FAR struct pwm_upperhalf_s *upper, unsigned int oflags)
{
FAR struct pwm_lowerhalf_s *lower = upper->dev;
int ret = OK;
DEBUGASSERT(upper != 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;
pwmvdbg("cmd: %d arg: %ld\n", cmd, arg);
/* Get exclusive access to the device structures */
ret = sem_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);
#ifdef CONFIG_PWM_PULSECOUNT
pwmvdbg("PWMIOC_SETCHARACTERISTICS frequency: %d duty: %08x count: %d started: %d\n",
info->frequency, info->duty, info->count, upper->started);
#else
pwmvdbg("PWMIOC_SETCHARACTERISTICS frequency: %d duty: %08x started: %d\n",
info->frequency, info->duty, upper->started);
#endif
/* 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 recevie 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));
#ifdef CONFIG_PWM_PULSECOUNT
pwmvdbg("PWMIOC_GETCHARACTERISTICS frequency: %d duty: %08x count: %d\n",
info->frequency, info->duty, info->count);
#else
pwmvdbg("PWMIOC_GETCHARACTERISTICS frequency: %d duty: %08x\n",
info->frequency, info->duty);
#endif
}
break;
/* PWMIOC_START - Start the pulsed output. The PWMIOC_SETCHARACTERISTICS
* command must have previously been sent.
*
* ioctl argument: None
*/
case PWMIOC_START:
{
#ifdef CONFIG_PWM_PULSECOUNT
pwmvdbg("PWMIOC_START frequency: %d duty: %08x count: %d started: %d\n",
upper->info.frequency, upper->info.duty, upper->info.count,
upper->started);
#else
pwmvdbg("PWMIOC_START frequency: %d duty: %08x started: %d\n",
upper->info.frequency, upper->info.duty, upper->started);
#endif
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:
{
pwmvdbg("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:
{
pwmvdbg("Forwarding unrecognized cmd: %d arg: %ld\n", cmd, arg);
DEBUGASSERT(lower->ops->ioctl != NULL);
ret = lower->ops->ioctl(lower, cmd, arg);
}
break;
}
sem_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 registers 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 *)zalloc(sizeof(struct pwm_upperhalf_s));
if (!upper)
{
pwmdbg("Allocation failed\n");
return -ENOMEM;
}
/* Initialize the PWM device structure (it was already zeroed by zalloc()) */
sem_init(&upper->exclsem, 0, 1);
#ifdef CONFIG_PWM_PULSECOUNT
sem_init(&upper->waitsem, 0, 0);
#endif
upper->dev = dev;
/* Register the PWM device */
pwmvdbg("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).
* It 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;
pwmllvdbg("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;
sem_post(&upper->waitsem);
}
/* The PWM is now stopped */
upper->started = false;
}
}
#endif
#endif /* CONFIG_PWM */
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