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nuttx/arch/arm/src/sam34/sam4cm_oneshot.c
Nathan Hartman a5e643b0cd Fix typos in comments and documentation.
2020-03-16 20:01:11 -06:00

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/****************************************************************************
* arch/arm/src/sam34/sam4cm_oneshot.c
*
* Copyright (C) 2015 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* References:
*
* Atmel NoOS sample code.
*
* The Atmel sample code has a BSD compatible license that requires this
* copyright notice:
*
* Copyright (c) 2011, Atmel Corporation
*
* 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 names NuttX nor Atmel 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 <assert.h>
#include <errno.h>
#include <nuttx/irq.h>
#include <nuttx/clock.h>
#include "sam4cm_oneshot.h"
#include "sam4cm_freerun.h"
#ifdef CONFIG_SAM34_ONESHOT
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: sam_oneshot_handler
*
* Description:
* Timer interrupt callback. When the oneshot timer interrupt expires,
* this function will be called. It will forward the call to the next
* level up.
*
* Input Parameters:
* tch - The handle that represents the timer state
* arg - An opaque argument provided when the interrupt was registered
* sr - The value of the timer interrupt status register at the time
* that the interrupt occurred.
*
* Returned Value:
* None
*
****************************************************************************/
static void sam_oneshot_handler(TC_HANDLE tch, void *arg, uint32_t sr)
{
struct sam_oneshot_s *oneshot = (struct sam_oneshot_s *)arg;
oneshot_handler_t oneshot_handler;
void *oneshot_arg;
tmrinfo("Expired...\n");
DEBUGASSERT(oneshot && oneshot->handler);
/* The clock was stopped, but not disabled when the RC match occurred.
* Disable the TC now and disable any further interrupts.
*/
sam_tc_attach(oneshot->tch, NULL, NULL, 0);
sam_tc_stop(oneshot->tch);
/* The timer is no longer running */
oneshot->running = false;
/* Forward the event, clearing out any vestiges */
oneshot_handler = (oneshot_handler_t)oneshot->handler;
oneshot->handler = NULL;
oneshot_arg = (void *)oneshot->arg;
oneshot->arg = NULL;
#ifdef CONFIG_SAM34_FREERUN
oneshot->start_count = 0;
#endif
oneshot_handler(oneshot_arg);
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: sam_oneshot_initialize
*
* Description:
* Initialize the oneshot timer wrapper
*
* Input Parameters:
* oneshot Caller allocated instance of the oneshot state structure
* chan Timer counter channel to be used. See the TC_CHAN*
* definitions in arch/arm/src/sam34/sam_tc.h.
* resolution The required resolution of the timer in units of
* microseconds. NOTE that the range is restricted to the
* range of uint16_t (excluding zero).
*
* Returned Value:
* Zero (OK) is returned on success; a negated errno value is returned
* on failure.
*
****************************************************************************/
int sam_oneshot_initialize(struct sam_oneshot_s *oneshot, int chan,
uint16_t resolution)
{
uint32_t frequency;
uint32_t divisor;
uint32_t cmr;
int ret;
tmrinfo("chan=%d resolution=%d usec\n", chan, resolution);
DEBUGASSERT(oneshot && resolution > 0);
/* Get the TC frequency the corresponds to the requested resolution */
frequency = USEC_PER_SEC / (uint32_t)resolution;
/* The pre-calculate values to use when we start the timer */
ret = sam_tc_divisor(frequency, &divisor, &cmr);
if (ret < 0)
{
tmrerr("ERROR: sam_tc_divisor failed: %d\n", ret);
return ret;
}
tmrinfo("frequency=%lu, divisor=%lu, cmr=%08lx\n",
(unsigned long)frequency, (unsigned long)divisor,
(unsigned long)cmr);
/* Allocate the timer/counter and select its mode of operation
*
* CMR_TCCLKS - Returned by sam_tc_divisor
* TC_CMR_CLKI=0 - Not inverted
* TC_CMR_BURST_NONE - Not gated by an external signal
* TC_CMR_CPCSTOP=1 - Stop the clock on an RC compare event
* TC_CMR_CPCDIS=0 - Don't disable the clock on an RC compare event
* TC_CMR_EEVTEDG_NONE - No external events (and, hence, no edges
* TC_CMR_EEVT_TIOB - ???? REVISIT
* TC_CMR_ENET=0 - External event trigger disabled
* TC_CMR_WAVSEL_UPRC - TC_CV is incremented from 0 to the value of RC,
* then automatically reset on a RC Compare
* TC_CMR_WAVE - Waveform mode
* TC_CMR_ACPA_NONE - RA compare has no effect on TIOA
* TC_CMR_ACPC_NONE - RC compare has no effect on TIOA
* TC_CMR_AEEVT_NONE - No external event effect on TIOA
* TC_CMR_ASWTRG_NONE - No software trigger effect on TIOA
* TC_CMR_BCPB_NONE - RB compare has no effect on TIOB
* TC_CMR_BCPC_NONE - RC compare has no effect on TIOB
* TC_CMR_BEEVT_NONE - No external event effect on TIOB
* TC_CMR_BSWTRG_NONE - No software trigger effect on TIOB
*/
cmr |= (TC_CMR_BURST_NOTGATED | TC_CMR_CPCSTOP | TC_CMR_EEVTEDG_NONE |
TC_CMR_EEVT_TIOB | TC_CMR_WAVSEL_UPAUTO | TC_CMR_WAVE |
TC_CMR_ACPA_NONE | TC_CMR_ACPC_NONE | TC_CMR_AEEVT_NONE |
TC_CMR_ASWTRG_NONE | TC_CMR_BCPB_NONE | TC_CMR_BCPC_NONE |
TC_CMR_BEEVT_NONE | TC_CMR_BSWTRG_NONE);
oneshot->tch = sam_tc_allocate(chan, cmr);
if (!oneshot->tch)
{
tmrerr("ERROR: Failed to allocate timer channel %d\n", chan);
return -EBUSY;
}
/* Initialize the remaining fields in the state structure and return
* success.
*/
oneshot->chan = chan;
oneshot->running = false;
oneshot->handler = NULL;
oneshot->arg = NULL;
#ifdef CONFIG_SAM34_FREERUN
oneshot->start_count = 0;
#endif
return OK;
}
/****************************************************************************
* Name: sam_oneshot_max_delay
*
* Description:
* Determine the maximum delay of the one-shot timer (in microseconds)
*
****************************************************************************/
int sam_oneshot_max_delay(struct sam_oneshot_s *oneshot, uint64_t *usec)
{
DEBUGASSERT(oneshot && usec);
*usec = (0xffffull * USEC_PER_SEC) / (uint64_t)sam_tc_divfreq(oneshot->tch);
return OK;
}
/****************************************************************************
* Name: sam_oneshot_start
*
* Description:
* Start the oneshot timer
*
* Input Parameters:
* oneshot Caller allocated instance of the oneshot state structure. This
* structure must have been previously initialized via a call to
* sam_oneshot_initialize();
* handler The function to call when when the oneshot timer expires.
* arg An opaque argument that will accompany the callback.
* ts Provides the duration of the one shot timer.
*
* Returned Value:
* Zero (OK) is returned on success; a negated errno value is returned
* on failure.
*
****************************************************************************/
int sam_oneshot_start(struct sam_oneshot_s *oneshot,
struct sam_freerun_s *freerun,
oneshot_handler_t handler, void *arg,
const struct timespec *ts)
{
uint64_t usec;
uint64_t regval;
irqstate_t flags;
tmrinfo("handler=%p arg=%p, ts=(%lu, %lu)\n",
handler, arg, (unsigned long)ts->tv_sec, (unsigned long)ts->tv_nsec);
DEBUGASSERT(oneshot && handler && ts);
/* Was the oneshot already running? */
flags = enter_critical_section();
if (oneshot->running)
{
/* Yes.. then cancel it */
tmrinfo("Already running... cancelling\n");
sam_oneshot_cancel(oneshot, freerun, NULL);
}
/* Save the new handler and its argument */
oneshot->handler = handler;
oneshot->arg = arg;
/* Express the delay in microseconds */
usec = (uint64_t)ts->tv_sec * USEC_PER_SEC + (uint64_t)(ts->tv_nsec / NSEC_PER_USEC);
/* Get the timer counter frequency and determine the number of counts need to achieve the requested delay.
*
* frequency = ticks / second
* ticks = seconds * frequency
* = (usecs * frequency) / USEC_PER_SEC;
*/
regval = (usec * (uint64_t)sam_tc_divfreq(oneshot->tch)) / USEC_PER_SEC;
tmrinfo("usec=%llu regval=%08llx\n", usec, regval);
DEBUGASSERT(regval <= UINT16_MAX);
/* Set up to receive the callback when the interrupt occurs */
sam_tc_attach(oneshot->tch, sam_oneshot_handler, oneshot,
TC_INT_CPCS);
/* Set RC so that an event will be triggered when TC_CV register counts
* up to RC.
*/
sam_tc_setregister(oneshot->tch, TC_REGC, (uint32_t)regval);
/* Start the counter */
sam_tc_start(oneshot->tch);
#ifdef CONFIG_SAM34_FREERUN
/* The function sam_tc_start() starts the timer/counter by setting the
* bits TC_CCR_CLKEN and TC_CCR_SWTRG in the channel control register.
* The first one enables the timer/counter the latter performs an
* software trigger, which starts the clock and sets the counter
* register to zero. This reset is performed with the next valid edge
* of the selected clock. Thus it can take up USEC_PER_TICK microseconds
* until the counter register becomes zero.
*
* If the timer is canceled within this period the counter register holds
* the counter value for the last timer/counter run. To circumvent this
* the counter value of the freerun timer/counter is stored at each start
* of the oneshot timer/counter.
*
* The function up_timer_gettime() could also be used for this but it takes
* too long. If up_timer_gettime() is called within this function the problem
* vanishes at least if compiled with no optimisation.
*/
if (freerun != NULL)
{
oneshot->start_count = sam_tc_getcounter(freerun->tch);
}
#endif
/* Enable interrupts. We should get the callback when the interrupt
* occurs.
*/
oneshot->running = true;
leave_critical_section(flags);
return OK;
}
/****************************************************************************
* Name: sam_oneshot_cancel
*
* Description:
* Cancel the oneshot timer and return the time remaining on the timer.
*
* NOTE: This function may execute at a high rate with no timer running (as
* when pre-emption is enabled and disabled).
*
* Input Parameters:
* oneshot Caller allocated instance of the oneshot state structure. This
* structure must have been previously initialized via a call to
* sam_oneshot_initialize();
* ts The location in which to return the time remaining on the
* oneshot timer. A time of zero is returned if the timer is
* not running. ts may be zero in which case the time remaining
* is not returned.
*
* Returned Value:
* Zero (OK) is returned on success. A call to up_timer_cancel() when
* the timer is not active should also return success; a negated errno
* value is returned on any failure.
*
****************************************************************************/
int sam_oneshot_cancel(struct sam_oneshot_s *oneshot,
struct sam_freerun_s *freerun, struct timespec *ts)
{
irqstate_t flags;
uint64_t usec;
uint64_t sec;
uint64_t nsec;
uint32_t count;
uint32_t rc;
/* Was the timer running? */
flags = enter_critical_section();
if (!oneshot->running)
{
/* No.. Just return zero timer remaining and successful cancellation.
* This function may execute at a high rate with no timer running
* (as when pre-emption is enabled and disabled).
*/
ts->tv_sec = 0;
ts->tv_nsec = 0;
leave_critical_section(flags);
return OK;
}
/* Yes.. Get the timer counter and rc registers and stop the counter. If
* the counter expires while we are doing this, the counter clock will be
* stopped, but the clock will not be disabled.
*
* The expected behavior is that the counter register will freezes at
* a value equal to the RC register when the timer expires. The counter
* should have values between 0 and RC in all other cased.
*
* REVISIT: This does not appear to be the case.
*/
tmrinfo("Cancelling...\n");
count = sam_tc_getcounter(oneshot->tch);
rc = sam_tc_getregister(oneshot->tch, TC_REGC);
#ifdef CONFIG_SAM34_FREERUN
/* In the case the timer/counter was canceled very short after its start,
* the counter register can hold the wrong value (the value of the last
* run). To prevent this the counter value is set to zero if not at
* least on tick passed since the start of the timer/counter.
*/
if (count > 0 && freerun != NULL &&
sam_tc_getcounter(freerun->tch) == oneshot->start_count)
{
count = 0;
}
#endif
/* Now we can disable the interrupt and stop the timer. */
sam_tc_attach(oneshot->tch, NULL, NULL, 0);
sam_tc_stop(oneshot->tch);
oneshot->running = false;
oneshot->handler = NULL;
oneshot->arg = NULL;
leave_critical_section(flags);
/* Did the caller provide us with a location to return the time
* remaining?
*/
if (ts)
{
/* Yes.. then calculate and return the time remaining on the
* oneshot timer.
*/
tmrinfo("rc=%lu count=%lu usec=%lu\n",
(unsigned long)rc, (unsigned long)count, (unsigned long)usec);
/* REVISIT: I am not certain why the timer counter value sometimes
* exceeds RC. Might be a bug, or perhaps the counter does not stop
* in all cases.
*/
if (count >= rc)
{
/* No time remaining (?) */
ts->tv_sec = 0;
ts->tv_nsec = 0;
}
else
{
/* The total time remaining is the difference. Convert that
* to units of microseconds.
*
* frequency = ticks / second
* seconds = ticks * frequency
* usecs = (ticks * USEC_PER_SEC) / frequency;
*/
usec = (((uint64_t)(rc - count)) * USEC_PER_SEC) /
sam_tc_divfreq(oneshot->tch);
/* Each time the timer/counter is canceled the time calculated from
* the two registers (counter and REGC) is accurate up to an error
* between 0 and USEC_PER_TICK microseconds. To correct this error
* one tick which means USEC_PER_TICK microseconds are subtracted.
*/
usec = usec > USEC_PER_TICK ? usec - USEC_PER_TICK : 0;
/* Return the time remaining in the correct form */
sec = usec / USEC_PER_SEC;
nsec = ((usec) - (sec * USEC_PER_SEC)) * NSEC_PER_USEC;
ts->tv_sec = (time_t)sec;
ts->tv_nsec = (unsigned long)nsec;
}
tmrinfo("remaining (%lu, %lu)\n",
(unsigned long)ts->tv_sec, (unsigned long)ts->tv_nsec);
}
return OK;
}
#endif /* CONFIG_SAM34_ONESHOT */
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