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// SAMD21 timer interrupt scheduling
//
// Copyright (C) 2018 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include "board/irq.h" // irq_disable
#include "board/misc.h" // timer_read_time
#include "board/timer_irq.h" // timer_dispatch_many
#include "internal.h" // enable_pclock
#include "sched.h" // DECL_INIT
// Set the next irq time
static void
timer_set(uint32_t value)
{
TC4->COUNT32.CC[0].reg = value;
TC4->COUNT32.INTFLAG.reg = TC_INTFLAG_MC0;
}
// Return the current time (in absolute clock ticks).
uint32_t
timer_read_time(void)
{
return TC4->COUNT32.COUNT.reg;
}
// Activate timer dispatch as soon as possible
void
timer_kick(void)
{
timer_set(timer_read_time() + 50);
}
void
timer_init(void)
{
// Supply power and clock to the timer
enable_pclock(TC3_GCLK_ID, ID_TC3);
enable_pclock(TC4_GCLK_ID, ID_TC4);
// Configure the timer
TcCount32 *tc = &TC4->COUNT32;
irqstatus_t flag = irq_save();
tc->CTRLA.reg = 0;
tc->CTRLA.reg = TC_CTRLA_MODE_COUNT32;
NVIC_SetPriority(TC4_IRQn, 2);
NVIC_EnableIRQ(TC4_IRQn);
tc->INTENSET.reg = TC_INTENSET_MC0;
tc->COUNT.reg = 0;
timer_kick();
tc->CTRLA.reg = TC_CTRLA_MODE_COUNT32 | TC_CTRLA_ENABLE;
irq_restore(flag);
}
DECL_INIT(timer_init);
// IRQ handler
void __visible __aligned(16) // aligning helps stabilize perf benchmarks
TC4_Handler(void)
{
irq_disable();
uint32_t next = timer_dispatch_many();
timer_set(next);
irq_enable();
}
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