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author | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2012-01-09 18:23:30 +0000 |
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committer | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2012-01-09 18:23:30 +0000 |
commit | 547156a0f3f375205e5302432598b83d26bed715 (patch) | |
tree | 73cafb13ede6e70f6d6fde334e234a34bb8c83f8 /nuttx/drivers/pwm.c | |
parent | 0bc978aa032d7bd2a60c577cc261ccdcb8dfd628 (diff) | |
download | px4-nuttx-547156a0f3f375205e5302432598b83d26bed715.tar.gz px4-nuttx-547156a0f3f375205e5302432598b83d26bed715.tar.bz2 px4-nuttx-547156a0f3f375205e5302432598b83d26bed715.zip |
Add basic support for pulse count in the PWM interface
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4285 42af7a65-404d-4744-a932-0658087f49c3
Diffstat (limited to 'nuttx/drivers/pwm.c')
-rw-r--r-- | nuttx/drivers/pwm.c | 254 |
1 files changed, 236 insertions, 18 deletions
diff --git a/nuttx/drivers/pwm.c b/nuttx/drivers/pwm.c index 455e72706..6a613f3b5 100644 --- a/nuttx/drivers/pwm.c +++ b/nuttx/drivers/pwm.c @@ -89,10 +89,16 @@ struct pwm_upperhalf_s { - uint8_t crefs; /* The number of times the device has been opened */ - bool started; /* True: pulsed output is being generated */ - sem_t sem; /* Supports mutual exclusion */ - struct pwm_info_s info; /* Pulsed output characteristics */ + 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 */ }; @@ -104,6 +110,7 @@ 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); /**************************************************************************** @@ -146,7 +153,7 @@ static int pwm_open(FAR struct file *filep) /* Get exclusive access to the device structures */ - ret = sem_wait(&upper->sem); + ret = sem_wait(&upper->exclsem); if (ret < 0) { ret = -errno; @@ -191,7 +198,7 @@ static int pwm_open(FAR struct file *filep) ret = OK; errout_with_sem: - sem_post(&upper->sem); + sem_post(&upper->exclsem); errout: return ret; @@ -215,7 +222,7 @@ static int pwm_close(FAR struct file *filep) /* Get exclusive access to the device structures */ - ret = sem_wait(&upper->sem); + ret = sem_wait(&upper->exclsem); if (ret < 0) { ret = -errno; @@ -248,7 +255,7 @@ static int pwm_close(FAR struct file *filep) ret = OK; //errout_with_sem: - sem_post(&upper->sem); + sem_post(&upper->exclsem); errout: return ret; @@ -283,6 +290,112 @@ static ssize_t pwm_write(FAR struct file *filep, FAR const char *buffer, size_t } /************************************************************************************ + * 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 */ + + 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: @@ -295,12 +408,20 @@ 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 = OK; - - /* Handle built-in ioctl commands */ + 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 @@ -318,13 +439,27 @@ static int pwm_ioctl(FAR struct file *filep, int cmd, unsigned long arg) 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; @@ -342,8 +477,14 @@ static int pwm_ioctl(FAR struct file *filep, int cmd, unsigned long 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; @@ -355,16 +496,19 @@ static int pwm_ioctl(FAR struct file *filep, int cmd, unsigned long arg) 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); - if (!upper->started) - { - ret = lower->ops->start(lower, &upper->info); - upper->started = true; - } + /* Start the pulse train */ + + ret = pwm_start(upper, filep->f_oflags); } break; @@ -382,6 +526,12 @@ static int pwm_ioctl(FAR struct file *filep, int cmd, unsigned long arg) { ret = lower->ops->stop(lower); upper->started = false; +#ifdef CONFIG_PWM_PULSECOUNT + if (upper->waiting) + { + upper->waiting = FALSE; + } +#endif } } break; @@ -396,6 +546,8 @@ static int pwm_ioctl(FAR struct file *filep, int cmd, unsigned long arg) } break; } + + sem_post(&upper->exclsem); return ret; } @@ -443,7 +595,10 @@ int pwm_register(FAR const char *path, FAR struct pwm_lowerhalf_s *dev) /* Initialize the PWM device structure (it was already zeroed by zalloc()) */ - sem_init(&upper->sem, 0, 1); + sem_init(&upper->exclsem, 0, 1); +#ifdef CONFIG_PWM_PULSECOUNT + sem_init(&upper->waitsem, 0, 0); +#endif upper->dev = dev; /* Register the PWM device */ @@ -452,4 +607,67 @@ int pwm_register(FAR const char *path, FAR struct pwm_lowerhalf_s *dev) 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; + + /* 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 */ |