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//go:build mimxrt1062
package runtime
import (
"device/arm"
"device/nxp"
"runtime/interrupt"
"runtime/volatile"
"unsafe"
)
type timeUnit int64
const (
lastCycle = SYSTICK_FREQ/1000 - 1
cyclesPerMicro = CORE_FREQ / 1000000
)
const (
pitFreq = OSC_FREQ // PIT/GPT are muxed to 24 MHz OSC
pitCyclesPerMicro = pitFreq / 1000000
pitSleepTimer = 0 // x4 32-bit PIT timers [0..3]
)
var (
tickCount volatile.Register64
cycleCount volatile.Register32
pitActive volatile.Register32
pitTimeout interrupt.Interrupt
)
var (
// debug exception and monitor control
DEM_CR = (*volatile.Register32)(unsafe.Pointer(uintptr(0xe000edfc)))
DWT_CR = (*volatile.Register32)(unsafe.Pointer(uintptr(0xe0001000)))
DWT_CYCCNT = (*volatile.Register32)(unsafe.Pointer(uintptr(0xe0001004)))
)
func ticksToNanoseconds(ticks timeUnit) int64 {
return int64(ticks) * 1000
}
func nanosecondsToTicks(ns int64) timeUnit {
return timeUnit(ns / 1000)
}
func initSysTick() {
const (
traceEnable = 0x01000000 // enable debugging & monitoring blocks
cycleCountEnable = 0x00000001 // cycle count register
)
// disable SysTick if already running
if arm.SYST.SYST_CSR.HasBits(arm.SYST_CSR_ENABLE_Msk) {
arm.SYST.SYST_CSR.ClearBits(arm.SYST_CSR_ENABLE_Msk)
}
// zeroize the counter
tickCount.Set(0)
arm.SYST.SYST_RVR.Set(lastCycle)
arm.SYST.SYST_CVR.Set(0)
arm.SYST.SYST_CSR.Set(arm.SYST_CSR_TICKINT | arm.SYST_CSR_ENABLE)
// set SysTick and PendSV priority to 32
nxp.SystemControl.SHPR3.Set((0x20 << nxp.SCB_SHPR3_PRI_15_Pos) |
(0x20 << nxp.SCB_SHPR3_PRI_14_Pos))
// turn on cycle counter
DEM_CR.SetBits(traceEnable)
DWT_CR.SetBits(cycleCountEnable)
cycleCount.Set(DWT_CYCCNT.Get())
// enable PIT, disable counters
nxp.PIT.MCR.Set(0)
for i := range nxp.PIT.TIMER {
nxp.PIT.TIMER[i].TCTRL.Set(0)
}
// register sleep timer interrupt
pitTimeout = interrupt.New(nxp.IRQ_PIT, timerWake)
pitTimeout.SetPriority(0x21)
pitTimeout.Enable()
}
func initRTC() {
if !nxp.SNVS.LPCR.HasBits(nxp.SNVS_LPCR_SRTC_ENV) {
// if SRTC isn't running, start it with default Jan 1, 2019
nxp.SNVS.LPSRTCLR.Set(uint32((0x5c2aad80 << 15) & 0xFFFFFFFF))
nxp.SNVS.LPSRTCMR.Set(uint32(0x5c2aad80 >> 17))
nxp.SNVS.LPCR.SetBits(nxp.SNVS_LPCR_SRTC_ENV)
}
}
//go:export SysTick_Handler
func tick() {
tickCount.Set(tickCount.Get() + 1)
cycleCount.Set(DWT_CYCCNT.Get())
}
func ticks() timeUnit {
mask := arm.DisableInterrupts()
tick := tickCount.Get()
cycs := cycleCount.Get()
curr := DWT_CYCCNT.Get()
arm.EnableInterrupts(mask)
var diff uint32
if curr < cycs { // cycle counter overflow/rollover occurred
diff = (0xFFFFFFFF - cycs) + curr
} else {
diff = curr - cycs
}
frac := uint64(diff*0xFFFFFFFF/cyclesPerMicro) >> 32
if frac > 1000 {
frac = 1000
}
return timeUnit(1000*tick + frac)
}
func sleepTicks(duration timeUnit) {
if duration >= 0 {
curr := ticks()
last := curr + duration // 64-bit overflow unlikely
for curr < last {
cycles := timeUnit((last - curr) / pitCyclesPerMicro)
if cycles > 0xFFFFFFFF {
cycles = 0xFFFFFFFF
}
if !timerSleep(uint32(cycles)) {
return // return early due to interrupt
}
curr = ticks()
}
}
}
func timerSleep(cycles uint32) bool {
pitActive.Set(1)
nxp.PIT.TIMER[pitSleepTimer].LDVAL.Set(cycles)
nxp.PIT.TIMER[pitSleepTimer].TCTRL.Set(nxp.PIT_TIMER_TCTRL_TIE) // enable interrupts
nxp.PIT.TIMER[pitSleepTimer].TCTRL.SetBits(nxp.PIT_TIMER_TCTRL_TEN) // start timer
for {
//arm.Asm("wfi") // TODO: causes hardfault! why?
if pitActive.Get() == 0 {
return true
}
if hasScheduler {
break // some other interrupt occurred and needs servicing
}
}
timerWake(interrupt.Interrupt{}) // clear and disable timer
return false
}
func timerWake(interrupt.Interrupt) {
pitActive.Set(0)
// TFLGn[TIF] are set to 1 when a timeout occurs on the associated timer, and
// are cleared to 0 by writing a 1 to the corresponding TFLGn[TIF].
nxp.PIT.TIMER[pitSleepTimer].TFLG.Set(nxp.PIT_TIMER_TFLG_TIF) // clear interrupt flag
nxp.PIT.TIMER[pitSleepTimer].TCTRL.Set(0) // disable timer/interrupt enable flags
}
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