diff options
Diffstat (limited to 'nuttx/configs/px4io/src/up_hrt.c')
-rw-r--r-- | nuttx/configs/px4io/src/up_hrt.c | 664 |
1 files changed, 664 insertions, 0 deletions
diff --git a/nuttx/configs/px4io/src/up_hrt.c b/nuttx/configs/px4io/src/up_hrt.c new file mode 100644 index 000000000..d0c46bd26 --- /dev/null +++ b/nuttx/configs/px4io/src/up_hrt.c @@ -0,0 +1,664 @@ +/**************************************************************************** + * + * Copyright (C) 2012 PX4 Development Team. All rights reserved. + * + * 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 PX4 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. + * + ****************************************************************************/ + +/** + * @file High-resolution timer callouts and timekeeping. + * + * This can use any general or advanced STM32 timer. + * + * Note that really, this could use systick too, but that's + * monopolised by NuttX and stealing it would just be awkward. + * + * We don't use the NuttX STM32 driver per se; rather, we + * claim the timer and then drive it directly. + */ + +#include <nuttx/config.h> +#include <nuttx/arch.h> +#include <nuttx/irq.h> + +#include <sys/types.h> +#include <stdbool.h> + +#include <assert.h> +#include <debug.h> +#include <time.h> +#include <queue.h> +#include <errno.h> +#include <string.h> + +#include <arch/board/board.h> +#include <arch/board/up_hrt.h> + +#include "chip.h" +#include "up_internal.h" +#include "up_arch.h" + +#include "stm32_internal.h" +#include "stm32_gpio.h" +#include "stm32_tim.h" + +#ifdef CONFIG_HRT_TIMER + +/* HRT configuration */ +#if HRT_TIMER == 1 +# define HRT_TIMER_BASE STM32_TIM1_BASE +# define HRT_TIMER_POWER_REG STM32_RCC_APB2ENR +# define HRT_TIMER_POWER_BIT RCC_APB2ENR_TIM1EN +# define HRT_TIMER_VECTOR STM32_IRQ_TIM1CC +# define HRT_TIMER_CLOCK STM32_APB2_TIM1_CLKIN +# if CONFIG_STM32_TIM1 +# error must not set CONFIG_STM32_TIM1=y and HRT_TIMER=1 +# endif +#elif HRT_TIMER == 2 +# define HRT_TIMER_BASE STM32_TIM2_BASE +# define HRT_TIMER_POWER_REG STM32_RCC_APB1ENR +# define HRT_TIMER_POWER_BIT RCC_APB2ENR_TIM2EN +# define HRT_TIMER_VECTOR STM32_IRQ_TIM2 +# define HRT_TIMER_CLOCK STM32_APB1_TIM2_CLKIN +# if CONFIG_STM32_TIM2 +# error must not set CONFIG_STM32_TIM2=y and HRT_TIMER=2 +# endif +#elif HRT_TIMER == 3 +# define HRT_TIMER_BASE STM32_TIM3_BASE +# define HRT_TIMER_POWER_REG STM32_RCC_APB1ENR +# define HRT_TIMER_POWER_BIT RCC_APB2ENR_TIM3EN +# define HRT_TIMER_VECTOR STM32_IRQ_TIM3 +# define HRT_TIMER_CLOCK STM32_APB1_TIM3_CLKIN +# if CONFIG_STM32_TIM3 +# error must not set CONFIG_STM32_TIM3=y and HRT_TIMER=3 +# endif +#elif HRT_TIMER == 4 +# define HRT_TIMER_BASE STM32_TIM4_BASE +# define HRT_TIMER_POWER_REG STM32_RCC_APB1ENR +# define HRT_TIMER_POWER_BIT RCC_APB2ENR_TIM4EN +# define HRT_TIMER_VECTOR STM32_IRQ_TIM4 +# define HRT_TIMER_CLOCK STM32_APB1_TIM4_CLKIN +# if CONFIG_STM32_TIM4 +# error must not set CONFIG_STM32_TIM4=y and HRT_TIMER=4 +# endif +#elif HRT_TIMER == 5 +# define HRT_TIMER_BASE STM32_TIM5_BASE +# define HRT_TIMER_POWER_REG STM32_RCC_APB1ENR +# define HRT_TIMER_POWER_BIT RCC_APB2ENR_TIM5EN +# define HRT_TIMER_VECTOR STM32_IRQ_TIM5 +# define HRT_TIMER_CLOCK STM32_APB1_TIM5_CLKIN +# if CONFIG_STM32_TIM5 +# error must not set CONFIG_STM32_TIM5=y and HRT_TIMER=5 +# endif +#elif HRT_TIMER == 8 +# define HRT_TIMER_BASE STM32_TIM8_BASE +# define HRT_TIMER_POWER_REG STM32_RCC_APB2ENR +# define HRT_TIMER_POWER_BIT RCC_APB2ENR_TIM8EN +# define HRT_TIMER_VECTOR STM32_IRQ_TIM8CC +# define HRT_TIMER_CLOCK STM32_APB2_TIM8_CLKIN +# if CONFIG_STM32_TIM8 +# error must not set CONFIG_STM32_TIM8=y and HRT_TIMER=6 +# endif +#elif HRT_TIMER == 9 +# define HRT_TIMER_BASE STM32_TIM9_BASE +# define HRT_TIMER_POWER_REG STM32_RCC_APB1ENR +# define HRT_TIMER_POWER_BIT RCC_APB2ENR_TIM9EN +# define HRT_TIMER_VECTOR STM32_IRQ_TIM1BRK +# define HRT_TIMER_CLOCK STM32_APB1_TIM9_CLKIN +# if CONFIG_STM32_TIM9 +# error must not set CONFIG_STM32_TIM9=y and HRT_TIMER=9 +# endif +#elif HRT_TIMER == 10 +# define HRT_TIMER_BASE STM32_TIM10_BASE +# define HRT_TIMER_POWER_REG STM32_RCC_APB1ENR +# define HRT_TIMER_POWER_BIT RCC_APB2ENR_TIM10EN +# define HRT_TIMER_VECTOR STM32_IRQ_TIM1UP +# define HRT_TIMER_CLOCK STM32_APB1_TIM10_CLKIN +# if CONFIG_STM32_TIM10 +# error must not set CONFIG_STM32_TIM11=y and HRT_TIMER=10 +# endif +#elif HRT_TIMER == 11 +# define HRT_TIMER_BASE STM32_TIM11_BASE +# define HRT_TIMER_POWER_REG STM32_RCC_APB1ENR +# define HRT_TIMER_POWER_BIT RCC_APB2ENR_TIM11EN +# define HRT_TIMER_VECTOR STM32_IRQ_TIM1TRGCOM +# define HRT_TIMER_CLOCK STM32_APB1_TIM11_CLKIN +# if CONFIG_STM32_TIM11 +# error must not set CONFIG_STM32_TIM11=y and HRT_TIMER=11 +# endif +#else +# error HRT_TIMER must be set in board.h if CONFIG_HRT_TIMER=y +#endif + +/* + * HRT clock must be a multiple of 1MHz greater than 1MHz + */ +#if (HRT_TIMER_CLOCK % 1000000) != 0 +# error HRT_TIMER_CLOCK must be a multiple of 1MHz +#endif +#if HRT_TIMER_CLOCK <= 1000000 +# error HRT_TIMER_CLOCK must be greater than 1MHz +#endif + +/* + * Minimum/maximum deadlines. + * + * These are suitable for use with a 16-bit timer/counter clocked + * at 1MHz. The high-resolution timer need only guarantee that it + * not wrap more than once in the 50ms period for absolute time to + * be consistently maintained. + * + * The minimum deadline must be such that the time taken between + * reading a time and writing a deadline to the timer cannot + * result in missing the deadline. + */ +#define HRT_INTERVAL_MIN 50 +#define HRT_INTERVAL_MAX 50000 + +/* + * Period of the free-running counter, in microseconds. + */ +#define HRT_COUNTER_PERIOD 65536 + +/* + * Scaling factor(s) for the free-running counter; convert an input + * in counts to a time in microseconds. + */ +#define HRT_COUNTER_SCALE(_c) (_c) + +/* + * Timer register accessors + */ +#define REG(_reg) (*(volatile uint32_t *)(HRT_TIMER_BASE + _reg)) + +#define rCR1 REG(STM32_GTIM_CR1_OFFSET) +#define rCR2 REG(STM32_GTIM_CR2_OFFSET) +#define rSMCR REG(STM32_GTIM_SMCR_OFFSET) +#define rDIER REG(STM32_GTIM_DIER_OFFSET) +#define rSR REG(STM32_GTIM_SR_OFFSET) +#define rEGR REG(STM32_GTIM_EGR_OFFSET) +#define rCCMR1 REG(STM32_GTIM_CCMR1_OFFSET) +#define rCCMR2 REG(STM32_GTIM_CCMR2_OFFSET) +#define rCCER REG(STM32_GTIM_CCER_OFFSET) +#define rCNT REG(STM32_GTIM_CNT_OFFSET) +#define rPSC REG(STM32_GTIM_PSC_OFFSET) +#define rARR REG(STM32_GTIM_ARR_OFFSET) +#define rCCR1 REG(STM32_GTIM_CCR1_OFFSET) +#define rCCR2 REG(STM32_GTIM_CCR2_OFFSET) +#define rCCR3 REG(STM32_GTIM_CCR3_OFFSET) +#define rCCR4 REG(STM32_GTIM_CCR4_OFFSET) +#define rDCR REG(STM32_GTIM_DCR_OFFSET) +#define rDMAR REG(STM32_GTIM_DMAR_OFFSET) + +/* + * Specific registers and bits used by HRT sub-functions + */ +#if HRT_TIMER_CHANNEL == 1 +# define rCCR_HRT rCCR1 /* compare register for HRT */ +# define DIER_HRT GTIM_DIER_CC1IE /* interrupt enable for HRT */ +# define SR_INT_HRT GTIM_SR_CC1IF /* interrupt status for HRT */ +#elif HRT_TIMER_CHANNEL == 2 +# define rCCR_HRT rCCR2 /* compare register for HRT */ +# define DIER_HRT GTIM_DIER_CC2IE /* interrupt enable for HRT */ +# define SR_INT_HRT GTIM_SR_CC2IF /* interrupt status for HRT */ +#elif HRT_TIMER_CHANNEL == 3 +# define rCCR_HRT rCCR3 /* compare register for HRT */ +# define DIER_HRT GTIM_DIER_CC3IE /* interrupt enable for HRT */ +# define SR_INT_HRT GTIM_SR_CC3IF /* interrupt status for HRT */ +#elif HRT_TIMER_CHANNEL == 4 +# define rCCR_HRT rCCR4 /* compare register for HRT */ +# define DIER_HRT GTIM_DIER_CC4IE /* interrupt enable for HRT */ +# define SR_INT_HRT GTIM_SR_CC4IF /* interrupt status for HRT */ +#else +# error HRT_TIMER_CHANNEL must be a value between 1 and 4 +#endif + +/* + * Queue of callout entries. + */ +static struct sq_queue_s callout_queue; + +/* + * The time corresponding to a counter value of zero, as of the + * last time that hrt_absolute_time() was called. + */ +static hrt_abstime base_time; + +/* timer-specific functions */ +static void hrt_tim_init(int timer); +static int hrt_tim_isr(int irq, void *context); + +/* callout list manipulation */ +static void hrt_call_enter(struct hrt_call *entry); +static void hrt_call_reschedule(void); +static void hrt_call_invoke(void); + +/* + * Specific registers and bits used by PPM sub-functions + */ +#ifdef CONFIG_HRT_PPM +# include <arch/board/drv_ppm_input.h> + +/* + * If the timer hardware doesn't support GTIM_CCER_CCxNP, then we will work around it. + */ +# ifndef GTIM_CCER_CC1NP +# define GTIM_CCER_CC1NP 0 +# define GTIM_CCER_CC2NP 0 +# define GTIM_CCER_CC3NP 0 +# define GTIM_CCER_CC4NP 0 +# define PPM_EDGE_FLIP +# endif + +# if HRT_PPM_CHANNEL == 1 +# define rCCR_PPM rCCR1 /* capture register for PPM */ +# define DIER_PPM GTIM_DIER_CC1IE /* capture interrupt (non-DMA mode) */ +# define SR_INT_PPM GTIM_SR_CC1IF /* capture interrupt (non-DMA mode) */ +# define SR_OVF_PPM GTIM_SR_CC1OF /* capture overflow (non-DMA mode) */ +# define CCMR1_PPM 1 /* on TI1 */ +# define CCMR2_PPM 0 +# define CCER_PPM (GTIM_CCER_CC1E | GTIM_CCER_CC1P | GTIM_CCER_CC1NP) /* CC1, both edges */ +# define CCER_PPM_FLIP GTIM_CCER_CC1P +# elif HRT_PPM_CHANNEL == 2 +# define rCCR_PPM rCCR2 /* capture register for PPM */ +# define DIER_PPM GTIM_DIER_CC2IE /* capture interrupt (non-DMA mode) */ +# define SR_INT_PPM GTIM_SR_CC2IF /* capture interrupt (non-DMA mode) */ +# define SR_OVF_PPM GTIM_SR_CC2OF /* capture overflow (non-DMA mode) */ +# define CCMR1_PPM 2 /* on TI2 */ +# define CCMR2_PPM 0 +# define CCER_PPM (GTIM_CCER_CC2E | GTIM_CCER_CC2P | GTIM_CCER_CC2NP) /* CC2, both edges */ +# define CCER_PPM_FLIP GTIM_CCER_CC2P +# elif HRT_PPM_CHANNEL == 3 +# define rCCR_PPM rCCR3 /* capture register for PPM */ +# define DIER_PPM GTIM_DIER_CC3IE /* capture interrupt (non-DMA mode) */ +# define SR_INT_PPM GTIM_SR_CC3IF /* capture interrupt (non-DMA mode) */ +# define SR_OVF_PPM GTIM_SR_CC3OF /* capture overflow (non-DMA mode) */ +# define CCMR1_PPM 0 +# define CCMR2_PPM 1 /* on TI3 */ +# define CCER_PPM (GTIM_CCER_CC3E | GTIM_CCER_CC3P | GTIM_CCER_CC3NP) /* CC3, both edges */ +# define CCER_PPM_FLIP GTIM_CCER_CC3P +# elif HRT_PPM_CHANNEL == 4 +# define rCCR_PPM rCCR4 /* capture register for PPM */ +# define DIER_PPM GTIM_DIER_CC4IE /* capture interrupt (non-DMA mode) */ +# define SR_INT_PPM GTIM_SR_CC4IF /* capture interrupt (non-DMA mode) */ +# define SR_OVF_PPM GTIM_SR_CC4OF /* capture overflow (non-DMA mode) */ +# define CCMR1_PPM 0 +# define CCMR2_PPM 2 /* on TI4 */ +# define CCER_PPM (GTIM_CCER_CC4E | GTIM_CCER_CC4P | GTIM_CCER_CC4NP) /* CC4, both edges */ +# define CCER_PPM_FLIP GTIM_CCER_CC4P +# else +# error HRT_PPM_CHANNEL must be a value between 1 and 4 if CONFIG_HRT_PPM is set +# endif +#else +/* disable the PPM configuration */ +# define rCCR_PPM 0 +# define DIER_PPM 0 +# define SR_INT_PPM 0 +# define SR_OVF_PPM 0 +# define CCMR1_PPM 0 +# define CCMR2_PPM 0 +# define CCER_PPM 0 +#endif /* CONFIG_HRT_PPM */ + +/* + * Initialise the timer we are going to use. + * + * We expect that we'll own one of the reduced-function STM32 general + * timers, and that we can use channel 1 in compare mode. + */ +static void +hrt_tim_init(int timer) +{ + /* clock/power on our timer */ + modifyreg32(HRT_TIMER_POWER_REG, 0, HRT_TIMER_POWER_BIT); + + /* claim our interrupt vector */ + irq_attach(HRT_TIMER_VECTOR, hrt_tim_isr); + + /* disable and configure the timer */ + rCR1 = 0; + rCR2 = 0; + rSMCR = 0; + rDIER = DIER_HRT | DIER_PPM; + rCCER = 0; /* unlock CCMR* registers */ + rCCMR1 = CCMR1_PPM; + rCCMR2 = CCMR2_PPM; + rCCER = CCER_PPM; + rDCR = 0; + + /* configure the timer to free-run at 1MHz */ + rPSC = (HRT_TIMER_CLOCK / 1000000) - 1; /* this really only works for whole-MHz clocks */ + + /* run the full span of the counter */ + rARR = 0xffff; + + /* set an initial capture a little ways off */ + rCCR_HRT = 1000; + + /* generate an update event; reloads the counter, all registers */ + rEGR = GTIM_EGR_UG; + + /* enable the timer */ + rCR1 = GTIM_CR1_CEN; + + /* enable interrupts */ + up_enable_irq(HRT_TIMER_VECTOR); +} + +/* + * Handle the compare interupt by calling the callout dispatcher + * and then re-scheduling the next deadline. + */ +static int +hrt_tim_isr(int irq, void *context) +{ + uint32_t status; + + /* copy interrupt status */ + status = rSR; + + /* ack the interrupts we just read */ + rSR = ~status; + +#ifdef CONFIG_HRT_PPM + /* was this a PPM edge? */ + if (status & (SR_INT_PPM | SR_OVF_PPM)) { + + /* if required, flip edge sensitivity */ +# ifdef PPM_EDGE_FLIP + rCCER ^= CCER_PPM_FLIP; +# endif + + /* feed the edge to the PPM decoder */ + ppm_input_decode(status & SR_OVF_PPM, rCCR_PPM); + } +#endif + + /* was this a timer tick? */ + if (status & SR_INT_HRT) { + /* run any callouts that have met their deadline */ + hrt_call_invoke(); + + /* and schedule the next interrupt */ + hrt_call_reschedule(); + } + + return OK; +} + +/* + * Fetch a never-wrapping absolute time value in microseconds from + * some arbitrary epoch shortly after system start. + */ +hrt_abstime +hrt_absolute_time(void) +{ + static uint32_t last_count; + uint32_t count; + uint32_t flags = irqsave(); + + count = rCNT; + + //lldbg("count %u last_count %u\n", count, last_count); + + /* This simple test is made possible by the guarantee that + * we are always called at least once per counter period. + */ + if (count < last_count) + base_time += HRT_COUNTER_PERIOD; + + last_count = count; + + irqrestore(flags); + + return HRT_COUNTER_SCALE(base_time + count); +} + +/* + * Convert a timespec to absolute time + */ +hrt_abstime +ts_to_abstime(struct timespec *ts) +{ + hrt_abstime result; + + result = (hrt_abstime)(ts->tv_sec) * 1000000; + result += ts->tv_nsec / 1000; + + return result; +} + +/* + * Convert absolute time to a timespec. + */ +void +abstime_to_ts(struct timespec *ts, hrt_abstime abstime) +{ + ts->tv_sec = abstime / 1000000; + abstime -= ts->tv_sec * 1000000; + ts->tv_nsec = abstime * 1000; +} + +/* + * Initalise the high-resolution timing module. + */ +void +hrt_init(int timer) +{ + sq_init(&callout_queue); + hrt_tim_init(timer); +} + +/* + * Call callout(arg) after interval has elapsed. + */ +void +hrt_call_after(struct hrt_call *entry, hrt_abstime delay, hrt_callout callout, void *arg) +{ + entry->deadline = hrt_absolute_time() + delay; + entry->period = 0; + entry->callout = callout; + entry->arg = arg; + + hrt_call_enter(entry); +} + +/* + * Call callout(arg) at calltime. + */ +void +hrt_call_at(struct hrt_call *entry, hrt_abstime calltime, hrt_callout callout, void *arg) +{ + entry->deadline = calltime; + entry->period = 0; + entry->callout = callout; + entry->arg = arg; + + hrt_call_enter(entry); +} + +/* + * Call callout(arg) every period. + */ +void +hrt_call_every(struct hrt_call *entry, hrt_abstime delay, hrt_abstime interval, hrt_callout callout, void *arg) +{ + entry->deadline = hrt_absolute_time() + delay; + entry->period = interval; + entry->callout = callout; + entry->arg = arg; + + hrt_call_enter(entry); +} + +/* + * If this returns true, the call has been invoked and removed from the callout list. + * + * Always returns false for repeating callouts. + */ +bool +hrt_called(struct hrt_call *entry) +{ + bool result; + + irqstate_t flags = irqsave(); + result = (entry->deadline == 0); + irqrestore(flags); + + return result; +} + +/* + * Remove the entry from the callout list. + */ +void +hrt_cancel(struct hrt_call *entry) +{ + irqstate_t flags = irqsave(); + + sq_rem(&entry->link, &callout_queue); + entry->deadline = 0; + + /* if this is a periodic call being removed by the callout, prevent it from + * being re-entered when the callout returns. + */ + entry->period = 0; + + irqrestore(flags); +} + +static void +hrt_call_enter(struct hrt_call *entry) +{ + irqstate_t flags = irqsave(); + struct hrt_call *call, *next; + + call = (struct hrt_call *)sq_peek(&callout_queue); + + if ((call == NULL) || (entry->deadline < call->deadline)) { + sq_addfirst(&entry->link, &callout_queue); + //lldbg("call enter at head, reschedule\n"); + /* we changed the next deadline, reschedule the timer event */ + hrt_call_reschedule(); + } else { + do { + next = (struct hrt_call *)sq_next(&call->link); + if ((next == NULL) || (entry->deadline < next->deadline)) { + //lldbg("call enter after head\n"); + sq_addafter(&call->link, &entry->link, &callout_queue); + break; + } + } while ((call = next) != NULL); + } + + //lldbg("scheduled\n"); + irqrestore(flags); +} + +static void +hrt_call_invoke(void) +{ + struct hrt_call *call; + hrt_abstime deadline; + + while (true) { + /* get the current time */ + hrt_abstime now = hrt_absolute_time(); + + call = (struct hrt_call *)sq_peek(&callout_queue); + if (call == NULL) + break; + if (call->deadline > now) + break; + + sq_rem(&call->link, &callout_queue); + //lldbg("call pop\n"); + + /* save the intended deadline for periodic calls */ + deadline = call->deadline; + + /* zero the deadline, as the call has occurred */ + call->deadline = 0; + + /* invoke the callout (if there is one) */ + if (call->callout) { + //lldbg("call %p: %p(%p)\n", call, call->callout, call->arg); + call->callout(call->arg); + } + + /* if the callout has a non-zero period, it has to be re-entered */ + if (call->period != 0) { + call->deadline = deadline + call->period; + hrt_call_enter(call); + } + } +} + +/* + * Reschedule the next timer interrupt. + * + * This routine must be called with interrupts disabled. + */ +static void +hrt_call_reschedule() +{ + hrt_abstime now = hrt_absolute_time(); + struct hrt_call *next = (struct hrt_call *)sq_peek(&callout_queue); + hrt_abstime deadline = now + HRT_INTERVAL_MAX; + + /* + * Determine what the next deadline will be. + * + * Note that we ensure that this will be within the counter + * period, so that when we truncate all but the low 16 bits + * the next time the compare matches it will be the deadline + * we want. + * + * It is important for accurate timekeeping that the compare + * interrupt fires sufficiently often that the base_time update in + * hrt_absolute_time runs at least once per timer period. + */ + if (next != NULL) { + //lldbg("entry in queue\n"); + if (next->deadline <= (now + HRT_INTERVAL_MIN)) { + //lldbg("pre-expired\n"); + /* set a minimal deadline so that we call ASAP */ + deadline = now + HRT_INTERVAL_MIN; + } else if (next->deadline < deadline) { + //lldbg("due soon\n"); + deadline = next->deadline; + } + } + //lldbg("schedule for %u at %u\n", (unsigned)(deadline & 0xffffffff), (unsigned)(now & 0xffffffff)); + + /* set the new compare value */ + rCCR_HRT = deadline & 0xffff; +} + +#endif /* CONFIG_HRT_TIMER */ |