runtime: update to avoid //go:volatile

There was exactly one change in the output of the smoke tests:
examples/test. However, it still runs just fine on a PCA10040.

src/runtime/runtime_atsamd21.go

@@ -6,6 +6,7 @@ import (
 	"device/arm"
 	"device/sam"
 	"machine"
+	"runtime/volatile"
 	"unsafe"
 )
 
@@ -230,10 +231,7 @@ var (
 	timerLastCounter uint64
 )
 
-//go:volatile
+var timerWakeup volatile.Register8
-type isrFlag bool
-
-var timerWakeup isrFlag
 
 const asyncScheduler = false
 
@@ -262,7 +260,7 @@ func ticks() timeUnit {
 
 // ticks are in microseconds
 func timerSleep(ticks uint32) {
-	timerWakeup = false
+	timerWakeup.Set(0)
 	if ticks < 30 {
 		// have to have at least one clock count
 		ticks = 30
@@ -280,7 +278,7 @@ func timerSleep(ticks uint32) {
 	// enable IRQ for CMP0 compare
 	sam.RTC_MODE0.INTENSET.SetBits(sam.RTC_MODE0_INTENSET_CMP0)
 
-	for !timerWakeup {
+	for timerWakeup.Get() == 0 {
 		arm.Asm("wfi")
 	}
 }
@@ -290,7 +288,7 @@ func handleRTC() {
 	// disable IRQ for CMP0 compare
 	sam.RTC_MODE0.INTFLAG.Set(sam.RTC_MODE0_INTENSET_CMP0)
 
-	timerWakeup = true
+	timerWakeup.Set(1)
 }
 
 func initUSBClock() {

src/runtime/runtime_nrf.go

@@ -6,6 +6,7 @@ import (
 	"device/arm"
 	"device/nrf"
 	"machine"
+	"runtime/volatile"
 )
 
 type timeUnit int64
@@ -79,14 +80,11 @@ func ticks() timeUnit {
 	return timestamp
 }
 
-//go:volatile
+var rtc_wakeup volatile.Register8
-type isrFlag bool
-
-var rtc_wakeup isrFlag
 
 func rtc_sleep(ticks uint32) {
 	nrf.RTC1.INTENSET.Set(nrf.RTC_INTENSET_COMPARE0)
-	rtc_wakeup = false
+	rtc_wakeup.Set(0)
 	if ticks == 1 {
 		// Race condition (even in hardware) at ticks == 1.
 		// TODO: fix this in a better way by detecting it, like the manual
@@ -94,7 +92,7 @@ func rtc_sleep(ticks uint32) {
 		ticks = 2
 	}
 	nrf.RTC1.CC[0].Set((nrf.RTC1.COUNTER.Get() + ticks) & 0x00ffffff)
-	for !rtc_wakeup {
+	for rtc_wakeup.Get() == 0 {
 		arm.Asm("wfi")
 	}
 }
@@ -103,5 +101,5 @@ func rtc_sleep(ticks uint32) {
 func handleRTC1() {
 	nrf.RTC1.INTENCLR.Set(nrf.RTC_INTENSET_COMPARE0)
 	nrf.RTC1.EVENTS_COMPARE[0].Set(0)
-	rtc_wakeup = true
+	rtc_wakeup.Set(1)
 }

src/runtime/runtime_qemu.go

@@ -7,6 +7,7 @@ package runtime
 
 import (
 	"device/arm"
+	"runtime/volatile"
 	"unsafe"
 )
 
@@ -36,12 +37,9 @@ func ticks() timeUnit {
 	return timestamp
 }
 
-//go:volatile
-type regValue uint32
-
 // UART0 output register.
-var stdoutWrite *regValue = (*regValue)(unsafe.Pointer(uintptr(0x4000c000)))
+var stdoutWrite = (*volatile.Register8)(unsafe.Pointer(uintptr(0x4000c000)))
 
 func putchar(c byte) {
-	*stdoutWrite = regValue(c)
+	stdoutWrite.Set(uint8(c))
 }

src/runtime/runtime_stm32f103xx.go

@@ -6,6 +6,7 @@ import (
 	"device/arm"
 	"device/stm32"
 	"machine"
+	"runtime/volatile"
 )
 
 func init() {
@@ -58,10 +59,7 @@ var (
 	timerLastCounter uint64
 )
 
-//go:volatile
+var timerWakeup volatile.Register8
-type isrFlag bool
-
-var timerWakeup isrFlag
 
 func initRTC() {
 	// Enable the PWR and BKP.
@@ -136,7 +134,7 @@ func ticks() timeUnit {
 
 // ticks are in microseconds
 func timerSleep(ticks uint32) {
-	timerWakeup = false
+	timerWakeup.Set(0)
 
 	// STM32 timer update event period is calculated as follows:
 	//
@@ -177,7 +175,7 @@ func timerSleep(ticks uint32) {
 	stm32.TIM3.CR1.SetBits(stm32.TIM_CR1_CEN)
 
 	// wait till timer wakes up
-	for !timerWakeup {
+	for timerWakeup.Get() == 0 {
 		arm.Asm("wfi")
 	}
 }
@@ -192,6 +190,6 @@ func handleTIM3() {
 		stm32.TIM3.SR.ClearBits(stm32.TIM_SR_UIF)
 
 		// timer was triggered
-		timerWakeup = true
+		timerWakeup.Set(1)
 	}
 }

src/runtime/runtime_stm32f407.go

@@ -6,6 +6,7 @@ import (
 	"device/arm"
 	"device/stm32"
 	"machine"
+	"runtime/volatile"
 )
 
 func init() {
@@ -114,10 +115,7 @@ var (
 	tickCount timeUnit
 )
 
-//go:volatile
+var timerWakeup volatile.Register8
-type isrFlag bool
-
-var timerWakeup isrFlag
 
 // Enable the TIM3 clock.(sleep count)
 func initTIM3() {
@@ -160,7 +158,7 @@ func ticks() timeUnit {
 
 // ticks are in microseconds
 func timerSleep(ticks uint32) {
-	timerWakeup = false
+	timerWakeup.Set(0)
 
 	// CK_INT = APB1 x2 = 84mhz
 	// prescale counter down from 84mhz to 10khz aka 0.1 ms frequency.
@@ -180,7 +178,7 @@ func timerSleep(ticks uint32) {
 	stm32.TIM3.CR1.SetBits(stm32.TIM_CR1_CEN)
 
 	// wait till timer wakes up
-	for !timerWakeup {
+	for timerWakeup.Get() == 0 {
 		arm.Asm("wfi")
 	}
 }
@@ -195,7 +193,7 @@ func handleTIM3() {
 		stm32.TIM3.SR.ClearBits(stm32.TIM_SR_UIF)
 
 		// timer was triggered
-		timerWakeup = true
+		timerWakeup.Set(1)
 	}
 }