runtime/rp2: handle RP2350 shared FIFO IRQ for GC (#5482)

* runtime/rp2: handle RP2350 shared FIFO IRQ for GC

---------

Co-authored-by: rdon <you@example.com>

src/runtime/runtime_rp2.go

@@ -8,7 +8,6 @@ import (
 	"internal/task"
 	"machine"
 	_ "machine/usb/cdc"
-	"runtime/interrupt"
 	"runtime/volatile"
 	"unsafe"
 )
@@ -140,14 +139,7 @@ func startSecondaryCores() {
 	// Enable the FIFO interrupt for the GC stop the world phase.
 	// We can only do this after we don't need the FIFO anymore for starting the
 	// second core.
-	intr := interrupt.New(sioIrqFifoProc0, func(intr interrupt.Interrupt) {
-		switch rp.SIO.FIFO_RD.Get() {
-		case 1:
-			gcInterruptHandler(0)
-		}
-	})
-	intr.Enable()
-	intr.SetPriority(0xff)
+	enableSIOFifoInterruptCore0()
 }
 
 var core1StartSequence = [...]uint32{
@@ -174,14 +166,7 @@ func runCore1() {
 	// the GC.
 	// Use the lowest possible priority (highest priority value), so that other
 	// interrupts can still happen while the GC is running.
-	intr := interrupt.New(sioIrqFifoProc1, func(intr interrupt.Interrupt) {
-		switch rp.SIO.FIFO_RD.Get() {
-		case 1:
-			gcInterruptHandler(1)
-		}
-	})
-	intr.Enable()
-	intr.SetPriority(0xff)
+	enableSIOFifoInterruptCore1()
 
 	// Now start running the scheduler on this core.
 	schedulerLock.Lock()

src/runtime/runtime_rp2040.go

@@ -4,9 +4,39 @@ package runtime
 
 import (
 	"device/rp"
+	"runtime/interrupt"
 )
 
 const (
 	sioIrqFifoProc0 = rp.IRQ_SIO_IRQ_PROC0
 	sioIrqFifoProc1 = rp.IRQ_SIO_IRQ_PROC1
 )
+
+// On RP2040, each core has its own SIO FIFO IRQ. Core0 enables
+// IRQ_SIO_IRQ_PROC0 and Core1 enables IRQ_SIO_IRQ_PROC1, so each handler can
+// use a fixed core ID.
+func enableSIOFifoInterruptCore0() {
+	intr := interrupt.New(sioIrqFifoProc0, handleSIOFifoInterruptCore0)
+	intr.Enable()
+	intr.SetPriority(0xff)
+}
+
+func enableSIOFifoInterruptCore1() {
+	intr := interrupt.New(sioIrqFifoProc1, handleSIOFifoInterruptCore1)
+	intr.Enable()
+	intr.SetPriority(0xff)
+}
+
+func handleSIOFifoInterruptCore0(intr interrupt.Interrupt) {
+	switch rp.SIO.FIFO_RD.Get() {
+	case 1:
+		gcInterruptHandler(0)
+	}
+}
+
+func handleSIOFifoInterruptCore1(intr interrupt.Interrupt) {
+	switch rp.SIO.FIFO_RD.Get() {
+	case 1:
+		gcInterruptHandler(1)
+	}
+}

src/runtime/runtime_rp2350.go

@@ -4,6 +4,7 @@ package runtime
 
 import (
 	"device/rp"
+	"runtime/interrupt"
 )
 
 const (
@@ -14,3 +15,25 @@ const (
 	sioIrqFifoProc0 = rp.IRQ_SIO_IRQ_FIFO
 	sioIrqFifoProc1 = rp.IRQ_SIO_IRQ_FIFO
 )
+
+var sioFifoInterrupt = interrupt.New(sioIrqFifoProc0, handleSIOFifoInterrupt)
+
+// On RP2350 both cores share IRQ_SIO_IRQ_FIFO, but the NVIC enable and
+// priority state is per-core. Each core must enable the shared IRQ on
+// its own NVIC, so both Core0 and Core1 call Enable()/SetPriority().
+func enableSIOFifoInterruptCore0() {
+	sioFifoInterrupt.Enable()
+	sioFifoInterrupt.SetPriority(0xff)
+}
+
+func enableSIOFifoInterruptCore1() {
+	sioFifoInterrupt.Enable()
+	sioFifoInterrupt.SetPriority(0xff)
+}
+
+func handleSIOFifoInterrupt(intr interrupt.Interrupt) {
+	switch rp.SIO.FIFO_RD.Get() {
+	case 1:
+		gcInterruptHandler(currentCPU())
+	}
+}