nRF52 tickless RTC: fix timer not firing on edge case
The calls via RTC API weren't fast enough for the edge case of minimum counter value, resulting in the timer never expiring as the counter had already passed the compare value. This now uses direct register access functions and also gets the latest counter value in edge case.
This commit is contained in:
Matias N
Brennan Ashton
parent
27ac9a6948
commit
74e7e2b5b2
@ -93,6 +93,7 @@ static int nrf52_rtc_ackint(FAR struct nrf52_rtc_dev_s *dev, uint8_t s);
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static int nrf52_rtc_enableevt(FAR struct nrf52_rtc_dev_s *dev, uint8_t evt);
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static int nrf52_rtc_disableevt(FAR struct nrf52_rtc_dev_s *dev,
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uint8_t evt);
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static uint32_t nrf52_rtc_getbase(FAR struct nrf52_rtc_dev_s *dev);
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/****************************************************************************
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* Private Data
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@ -117,6 +118,7 @@ struct nrf52_rtc_ops_s nrf52_rtc_ops =
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.ackint = nrf52_rtc_ackint,
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.enableevt = nrf52_rtc_enableevt,
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.disableevt = nrf52_rtc_disableevt,
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.getbase = nrf52_rtc_getbase,
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};
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#ifdef CONFIG_NRF52_RTC0
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@ -724,6 +726,18 @@ errout:
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return ret;
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}
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/****************************************************************************
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* Name: nrf52_rtc_getbase
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****************************************************************************/
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static uint32_t nrf52_rtc_getbase(FAR struct nrf52_rtc_dev_s *dev)
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{
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FAR struct nrf52_rtc_priv_s *rtc = (FAR struct nrf52_rtc_priv_s *)dev;
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DEBUGASSERT(dev);
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return rtc->base;
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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@ -50,6 +50,15 @@
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#define NRF52_RTC_ACKINT(d, s) ((d)->ops->ackint(d, s))
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#define NRF52_RTC_ENABLEEVT(d, s) ((d)->ops->enableevt(d, s))
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#define NRF52_RTC_DISABLEEVT(d, s) ((d)->ops->disableevt(d, s))
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#define NRF52_RTC_GETBASE(d) ((d)->ops->getbase(d))
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/* These are defined for direct access to registers, which is needed in some
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* critical parts where access speed is important
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*/
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#define NRF52_RTC_GETCOUNTER_REG(base) (getreg32(base + NRF52_RTC_COUNTER_OFFSET))
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#define NRF52_RTC_SETCC_REG(base, ch, cc) (putreg32(cc, base + NRF52_RTC_CC_OFFSET(ch)))
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#define NRF52_RTC_GETCC_REG(base, ch) (getreg32(base + NRF52_RTC_CC_OFFSET(ch)))
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/****************************************************************************
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* Public Types
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@ -116,6 +125,10 @@ struct nrf52_rtc_ops_s
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CODE int (*enableevt)(FAR struct nrf52_rtc_dev_s *dev, uint8_t evt);
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CODE int (*disableevt)(FAR struct nrf52_rtc_dev_s *dev, uint8_t evt);
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/* Utility */
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CODE uint32_t (*getbase)(FAR struct nrf52_rtc_dev_s *dev);
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};
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/****************************************************************************
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@ -51,16 +51,6 @@
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# error "Support for RTC2 is not enabled"
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#endif
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/* TIMER configuration */
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#if (CONFIG_NRF52_SYSTIMER_RTC_INSTANCE == 0)
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# define NRF52_RTC_BASE NRF52_RTC0_BASE
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#elif (CONFIG_NRF52_SYSTIMER_RTC_INSTANCE == 1)
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# define NRF52_RTC_BASE NRF52_RTC1_BASE
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#elif (CONFIG_NRF52_SYSTIMER_RTC_INSTANCE == 2)
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# define NRF52_RTC_BASE NRF52_RTC2_BASE
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#endif
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#define NRF52_RTC_PERIOD (512)
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#define NRF52_RTC_MAX (0x00ffffff)
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#define NRF52_RTC_MAX_TIME (NRF52_RTC_MAX * 31)
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@ -111,7 +101,7 @@ struct nrf52_tickless_dev_s g_tickless_dev;
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* Private Functions
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****************************************************************************/
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static void rtc_counter_to_ts(uint32_t counter, struct timespec *now)
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static inline void rtc_counter_to_ts(uint32_t counter, struct timespec *now)
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{
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uint32_t usec;
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@ -129,42 +119,63 @@ static void rtc_prepare_alarm(void)
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uint32_t usec;
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uint32_t counter;
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uint32_t target_counter;
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const uint32_t rtc_base = NRF52_RTC_GETBASE(g_tickless_dev.rtc);
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/* get current counter and absolute time */
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/* Get current absolute time */
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NRF52_RTC_GETCOUNTER(g_tickless_dev.rtc, &counter);
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counter = NRF52_RTC_GETCOUNTER_REG(rtc_base);
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rtc_counter_to_ts(counter, &now);
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/* obtain relative time to alarm */
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/* Obtain relative time to alarm */
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clock_timespec_subtract(&g_tickless_dev.alarm, &now, &delta);
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usec = delta.tv_sec * USEC_PER_SEC + delta.tv_nsec / NSEC_PER_USEC;
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/* if the alarm is to expire within one RTC period, we can set the CC */
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/* Check if the alarm is to expire within one RTC period, if so we can set
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* the CC.
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*/
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if (usec < NRF52_RTC_PERIOD * USEC_PER_SEC)
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{
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/* usec is the time w.r.t. now, so we compute the counter compare value
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* from current counter. as this may be "behind" the counter, we wrap
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* around one full timer period
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/* Obtain absolute number of microseconds of alarm within current
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* RTC period.
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*/
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usec = (g_tickless_dev.alarm.tv_sec % NRF52_RTC_PERIOD) *
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USEC_PER_SEC + g_tickless_dev.alarm.tv_nsec / NSEC_PER_USEC;
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/* Compute counter value for that point in time */
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target_counter = USEC_TO_COUNTER(usec);
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if (target_counter < 2)
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{
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/* ensure counter fires, from nRF52832_PS_v1.4 (p. 245):
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* "If the COUNTER is N, writing N+2 to a CC register is
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* guaranteed to trigger a COMPARE event at N+2."
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*/
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/* Enable interrupt. First set CC to distant value to ensure
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* no match will be generated. Doing things this way we now that
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* once we write a CC value it should be ready to match.
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*/
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target_counter = 2;
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}
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target_counter = (counter + target_counter) % (NRF52_RTC_MAX + 1);
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NRF52_RTC_SETCC(g_tickless_dev.rtc, NRF52_RTC_CC0, target_counter);
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NRF52_RTC_SETCC_REG(rtc_base, 0, counter - 1);
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NRF52_RTC_ENABLEINT(g_tickless_dev.rtc, NRF52_RTC_EVT_COMPARE0);
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/* Set CC to desired value */
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NRF52_RTC_SETCC_REG(rtc_base, 0, target_counter);
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/* Ensure counter fires: from nRF52832_PS_v1.4 (p. 245) we know that
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* "If the COUNTER is N, writing N+2 to a CC register is
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* guaranteed to trigger a COMPARE event at N+2.", so anything
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* less than that is not guaranteed and it may not ever match.
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*
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* To ensure this, we check if CC < N + 2, and if so we set CC = N+2.
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* We repeat this until this is satisfied (as the counter may change
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* in between calculations).
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*/
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while (NRF52_RTC_GETCC_REG(rtc_base, 0) <
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NRF52_RTC_GETCOUNTER_REG(rtc_base) + 2)
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{
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NRF52_RTC_SETCC_REG(rtc_base, 0,
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NRF52_RTC_GETCOUNTER_REG(rtc_base) + 2);
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}
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}
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}
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@ -180,7 +191,7 @@ static int rtc_handler(int irq, void *context, void *arg)
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/* if the timer wrapped-around */
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if (getreg32(NRF52_RTC_BASE + NRF52_RTC_EVENTS_OVRFLW_OFFSET))
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if (NRF52_RTC_CHECKINT(g_tickless_dev.rtc, NRF52_RTC_EVT_OVRFLW))
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{
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/* ack interrupt */
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@ -200,7 +211,7 @@ static int rtc_handler(int irq, void *context, void *arg)
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/* if the compare event fired */
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if (getreg32(NRF52_RTC_BASE + NRF52_RTC_EVENTS_COMPARE_OFFSET(0)))
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if (NRF52_RTC_CHECKINT(g_tickless_dev.rtc, NRF52_RTC_EVT_COMPARE0))
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{
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struct timespec now;
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