1 files changed, 103 insertions, 0 deletions
diff --git a/src/machine/machine_rp2_timer.go b/src/machine/machine_rp2_timer.go
new file mode 100644
index 000000000..a78ed70bb
--- /dev/null
+++ b/src/machine/machine_rp2_timer.go
@@ -0,0 +1,103 @@
+//go:build rp2040 || rp2350
+
+package machine
+
+import (
+	"device/arm"
+	"runtime/interrupt"
+	"runtime/volatile"
+)
+
+const numTimers = 4
+
+// Alarm0 is reserved for sleeping by tinygo runtime code for RP2040.
+// Alarm0 is also IRQ0
+const sleepAlarm = 0
+const sleepAlarmIRQ = 0
+
+// The minimum sleep duration in μs (ticks)
+const minSleep = 10
+
+type timerType struct {
+	timeHW   volatile.Register32
+	timeLW   volatile.Register32
+	timeHR   volatile.Register32
+	timeLR   volatile.Register32
+	alarm    [numTimers]volatile.Register32
+	armed    volatile.Register32
+	timeRawH volatile.Register32
+	timeRawL volatile.Register32
+	dbgPause volatile.Register32
+	pause    volatile.Register32
+	locked   [rp2350ExtraReg]volatile.Register32
+	source   [rp2350ExtraReg]volatile.Register32
+	intR     volatile.Register32
+	intE     volatile.Register32
+	intF     volatile.Register32
+	intS     volatile.Register32
+}
+
+// TimeElapsed returns time elapsed since power up, in microseconds.
+func (tmr *timerType) timeElapsed() (us uint64) {
+	// Need to make sure that the upper 32 bits of the timer
+	// don't change, so read that first
+	hi := tmr.timeRawH.Get()
+	var lo, nextHi uint32
+	for {
+		// Read the lower 32 bits
+		lo = tmr.timeRawL.Get()
+		// Now read the upper 32 bits again and
+		// check that it hasn't incremented. If it has, loop around
+		// and read the lower 32 bits again to get an accurate value
+		nextHi = tmr.timeRawH.Get()
+		if hi == nextHi {
+			break
+		}
+		hi = nextHi
+	}
+	return uint64(hi)<<32 | uint64(lo)
+}
+
+// lightSleep will put the processor into a sleep state a short period
+// (up to approx 72mins per RP2040 datasheet, 4.6.3. Alarms).
+//
+// This function is a 'light' sleep and will return early if another
+// interrupt or event triggers.  This is intentional since the
+// primary use-case is for use by the TinyGo scheduler which will
+// re-sleep if needed.
+func (tmr *timerType) lightSleep(us uint64) {
+	// minSleep is a way to avoid race conditions for short
+	// sleeps by ensuring there is enough time to setup the
+	// alarm before sleeping.  For very short sleeps, this
+	// effectively becomes a 'busy loop'.
+	if us < minSleep {
+		return
+	}
+
+	// Interrupt handler is essentially a no-op, we're just relying
+	// on the side-effect of waking the CPU from "wfe"
+	intr := interrupt.New(sleepAlarmIRQ, func(interrupt.Interrupt) {
+		// Clear the IRQ
+		timer.intR.Set(1 << sleepAlarm)
+	})
+
+	// Reset interrupt flag
+	tmr.intR.Set(1 << sleepAlarm)
+
+	// Enable interrupt
+	tmr.intE.SetBits(1 << sleepAlarm)
+	intr.Enable()
+
+	// Only the low 32 bits of time can be used for alarms
+	target := uint64(tmr.timeRawL.Get()) + us
+	tmr.alarm[sleepAlarm].Set(uint32(target))
+
+	// Wait for sleep (or any other) interrupt
+	arm.Asm("wfe")
+
+	// Disarm timer
+	tmr.armed.Set(1 << sleepAlarm)
+
+	// Disable interrupt
+	intr.Disable()
+}