blob: 8e87b1848bb307931447cb74d5b908d74563143a [file] [log] [blame]
/*
* Copyright (c) 2018 omSquare s.r.o.
*
* SPDX-License-Identifier: Apache-2.0
*/
#define DT_DRV_COMPAT atmel_sam0_rtc
/**
* @file
* @brief Atmel SAM0 series RTC-based system timer
*
* This system timer implementation supports both tickless and ticking modes.
* In tickless mode, RTC counts continually in 32-bit mode and timeouts are
* scheduled using the RTC comparator. In ticking mode, RTC is configured to
* generate an interrupt every tick.
*/
#include <zephyr/init.h>
#include <soc.h>
#include <zephyr/drivers/clock_control.h>
#include <zephyr/drivers/timer/system_timer.h>
#include <zephyr/drivers/pinctrl.h>
#include <zephyr/sys_clock.h>
#include <zephyr/irq.h>
#include <zephyr/sys/util.h>
/* RTC registers. */
#define RTC0 ((RtcMode0 *) DT_INST_REG_ADDR(0))
#ifdef MCLK
#define RTC_CLOCK_HW_CYCLES_PER_SEC SOC_ATMEL_SAM0_OSC32K_FREQ_HZ
#else
#define RTC_CLOCK_HW_CYCLES_PER_SEC SOC_ATMEL_SAM0_GCLK0_FREQ_HZ
#endif
/* Number of sys timer cycles per on tick. */
#define CYCLES_PER_TICK (RTC_CLOCK_HW_CYCLES_PER_SEC \
/ CONFIG_SYS_CLOCK_TICKS_PER_SEC)
/* Maximum number of ticks. */
#define MAX_TICKS (UINT32_MAX / CYCLES_PER_TICK - 2)
#ifdef CONFIG_TICKLESS_KERNEL
/*
* Due to the nature of clock synchronization, reading from or writing to some
* RTC registers takes approximately six RTC_GCLK cycles. This constant defines
* a safe threshold for the comparator.
*/
#define TICK_THRESHOLD 7
BUILD_ASSERT(CYCLES_PER_TICK > TICK_THRESHOLD,
"CYCLES_PER_TICK must be greater than TICK_THRESHOLD for "
"tickless mode");
#else /* !CONFIG_TICKLESS_KERNEL */
/*
* For some reason, RTC does not generate interrupts when COMP == 0,
* MATCHCLR == 1 and PRESCALER == 0. So we need to check that CYCLES_PER_TICK
* is more than one.
*/
BUILD_ASSERT(CYCLES_PER_TICK > 1,
"CYCLES_PER_TICK must be greater than 1 for ticking mode");
#endif /* CONFIG_TICKLESS_KERNEL */
/* Helper macro to get the correct GCLK GEN based on configuration. */
#define GCLK_GEN(n) GCLK_EVAL(n)
#define GCLK_EVAL(n) GCLK_CLKCTRL_GEN_GCLK##n
/* Tick/cycle count of the last announce call. */
static volatile uint32_t rtc_last;
#ifndef CONFIG_TICKLESS_KERNEL
/* Current tick count. */
static volatile uint32_t rtc_counter;
/* Tick value of the next timeout. */
static volatile uint32_t rtc_timeout;
PINCTRL_DT_INST_DEFINE(0);
static const struct pinctrl_dev_config *pcfg = PINCTRL_DT_INST_DEV_CONFIG_GET(0);
#endif /* CONFIG_TICKLESS_KERNEL */
/*
* Waits for RTC bus synchronization.
*/
static inline void rtc_sync(void)
{
/* Wait for bus synchronization... */
#ifdef RTC_STATUS_SYNCBUSY
while (RTC0->STATUS.reg & RTC_STATUS_SYNCBUSY) {
}
#else
while (RTC0->SYNCBUSY.reg) {
}
#endif
}
/*
* Reads RTC COUNT register. First a read request must be written to READREQ,
* then - when bus synchronization completes - the COUNT register is read and
* returned.
*/
static uint32_t rtc_count(void)
{
#ifdef RTC_READREQ_RREQ
RTC0->READREQ.reg = RTC_READREQ_RREQ;
#endif
rtc_sync();
return RTC0->COUNT.reg;
}
static void rtc_reset(void)
{
rtc_sync();
/* Disable interrupt. */
RTC0->INTENCLR.reg = RTC_MODE0_INTENCLR_MASK;
/* Clear interrupt flag. */
RTC0->INTFLAG.reg = RTC_MODE0_INTFLAG_MASK;
/* Disable RTC module. */
#ifdef RTC_MODE0_CTRL_ENABLE
RTC0->CTRL.reg &= ~RTC_MODE0_CTRL_ENABLE;
#else
RTC0->CTRLA.reg &= ~RTC_MODE0_CTRLA_ENABLE;
#endif
rtc_sync();
/* Initiate software reset. */
#ifdef RTC_MODE0_CTRL_SWRST
RTC0->CTRL.bit.SWRST = 1;
while (RTC0->CTRL.bit.SWRST) {
}
#else
RTC0->CTRLA.bit.SWRST = 1;
while (RTC0->CTRLA.bit.SWRST) {
}
#endif
}
static void rtc_isr(const void *arg)
{
ARG_UNUSED(arg);
/* Read and clear the interrupt flag register. */
uint16_t status = RTC0->INTFLAG.reg;
RTC0->INTFLAG.reg = status;
#ifdef CONFIG_TICKLESS_KERNEL
/* Read the current counter and announce the elapsed time in ticks. */
uint32_t count = rtc_count();
if (count != rtc_last) {
uint32_t ticks = (count - rtc_last) / CYCLES_PER_TICK;
sys_clock_announce(ticks);
rtc_last += ticks * CYCLES_PER_TICK;
}
#else /* !CONFIG_TICKLESS_KERNEL */
if (status) {
/* RTC just ticked one more tick... */
if (++rtc_counter == rtc_timeout) {
sys_clock_announce(rtc_counter - rtc_last);
rtc_last = rtc_counter;
}
} else {
/* ISR was invoked directly from sys_clock_set_timeout. */
sys_clock_announce(0);
}
#endif /* CONFIG_TICKLESS_KERNEL */
}
void sys_clock_set_timeout(int32_t ticks, bool idle)
{
ARG_UNUSED(idle);
#ifdef CONFIG_TICKLESS_KERNEL
ticks = (ticks == K_TICKS_FOREVER) ? MAX_TICKS : ticks;
ticks = CLAMP(ticks - 1, 0, (int32_t) MAX_TICKS);
/* Compute number of RTC cycles until the next timeout. */
uint32_t count = rtc_count();
uint32_t timeout = ticks * CYCLES_PER_TICK + count % CYCLES_PER_TICK;
/* Round to the nearest tick boundary. */
timeout = DIV_ROUND_UP(timeout, CYCLES_PER_TICK) * CYCLES_PER_TICK;
if (timeout < TICK_THRESHOLD) {
timeout += CYCLES_PER_TICK;
}
rtc_sync();
RTC0->COMP[0].reg = count + timeout;
#else /* !CONFIG_TICKLESS_KERNEL */
if (ticks == K_TICKS_FOREVER) {
/* Disable comparator for K_TICKS_FOREVER and other negative
* values.
*/
rtc_timeout = rtc_counter;
return;
}
if (ticks < 1) {
ticks = 1;
}
/* Avoid race condition between reading counter and ISR incrementing
* it.
*/
unsigned int key = irq_lock();
rtc_timeout = rtc_counter + ticks;
irq_unlock(key);
#endif /* CONFIG_TICKLESS_KERNEL */
}
uint32_t sys_clock_elapsed(void)
{
#ifdef CONFIG_TICKLESS_KERNEL
return (rtc_count() - rtc_last) / CYCLES_PER_TICK;
#else
return rtc_counter - rtc_last;
#endif
}
uint32_t sys_clock_cycle_get_32(void)
{
/* Just return the absolute value of RTC cycle counter. */
return rtc_count();
}
static int sys_clock_driver_init(void)
{
int retval;
#ifdef MCLK
MCLK->APBAMASK.reg |= MCLK_APBAMASK_RTC;
OSC32KCTRL->RTCCTRL.reg = OSC32KCTRL_RTCCTRL_RTCSEL_ULP32K;
#else
/* Set up bus clock and GCLK generator. */
PM->APBAMASK.reg |= PM_APBAMASK_RTC;
GCLK->CLKCTRL.reg = GCLK_CLKCTRL_ID(RTC_GCLK_ID) | GCLK_CLKCTRL_CLKEN
| GCLK_GEN(DT_INST_PROP(0, clock_generator));
/* Synchronize GCLK. */
while (GCLK->STATUS.bit.SYNCBUSY) {
}
#endif
retval = pinctrl_apply_state(pcfg, PINCTRL_STATE_DEFAULT);
if (retval < 0) {
return retval;
}
/* Reset module to hardware defaults. */
rtc_reset();
rtc_last = 0U;
/* Configure RTC with 32-bit mode, configured prescaler and MATCHCLR. */
#ifdef RTC_MODE0_CTRL_MODE
uint16_t ctrl = RTC_MODE0_CTRL_MODE(0) | RTC_MODE0_CTRL_PRESCALER(0);
#else
uint16_t ctrl = RTC_MODE0_CTRLA_MODE(0) | RTC_MODE0_CTRLA_PRESCALER(0);
#endif
#ifdef RTC_MODE0_CTRLA_COUNTSYNC
ctrl |= RTC_MODE0_CTRLA_COUNTSYNC;
#endif
#ifndef CONFIG_TICKLESS_KERNEL
#ifdef RTC_MODE0_CTRL_MATCHCLR
ctrl |= RTC_MODE0_CTRL_MATCHCLR;
#else
ctrl |= RTC_MODE0_CTRLA_MATCHCLR;
#endif
#endif
rtc_sync();
#ifdef RTC_MODE0_CTRL_MODE
RTC0->CTRL.reg = ctrl;
#else
RTC0->CTRLA.reg = ctrl;
#endif
#ifdef CONFIG_TICKLESS_KERNEL
/* Tickless kernel lets RTC count continually and ignores overflows. */
RTC0->INTENSET.reg = RTC_MODE0_INTENSET_CMP0;
#else
/* Non-tickless mode uses comparator together with MATCHCLR. */
rtc_sync();
RTC0->COMP[0].reg = CYCLES_PER_TICK;
RTC0->INTENSET.reg = RTC_MODE0_INTENSET_OVF;
rtc_counter = 0U;
rtc_timeout = 0U;
#endif
/* Enable RTC module. */
rtc_sync();
#ifdef RTC_MODE0_CTRL_ENABLE
RTC0->CTRL.reg |= RTC_MODE0_CTRL_ENABLE;
#else
RTC0->CTRLA.reg |= RTC_MODE0_CTRLA_ENABLE;
#endif
/* Enable RTC interrupt. */
NVIC_ClearPendingIRQ(DT_INST_IRQN(0));
IRQ_CONNECT(DT_INST_IRQN(0),
DT_INST_IRQ(0, priority), rtc_isr, 0, 0);
irq_enable(DT_INST_IRQN(0));
return 0;
}
SYS_INIT(sys_clock_driver_init, PRE_KERNEL_2,
CONFIG_SYSTEM_CLOCK_INIT_PRIORITY);