add support for CPU interrupts for ESP32-C3

src/runtime/runtime_esp32c3.go

@@ -5,6 +5,8 @@ package runtime
 import (
 	"device/esp"
 	"device/riscv"
+	"runtime/volatile"
+	"unsafe"
 )
 
 // This is the function called on startup after the flash (IROM/DROM) is
@@ -47,6 +49,9 @@ func main() {
 
 	clearbss()
 
+	// Configure interrupt handler
+	interruptInit()
+
 	// Initialize main system timer used for time.Now.
 	initTimer()
 
@@ -63,3 +68,28 @@ func abort() {
 		riscv.Asm("wfi")
 	}
 }
+
+// interruptInit initialize the interrupt controller and called from runtime once.
+func interruptInit() {
+	mie := riscv.DisableInterrupts()
+
+	// Reset all interrupt source priorities to zero.
+	priReg := &esp.INTERRUPT_CORE0.CPU_INT_PRI_1
+	for i := 0; i < 31; i++ {
+		priReg.Set(0)
+		priReg = (*volatile.Register32)(unsafe.Pointer(uintptr(unsafe.Pointer(priReg)) + uintptr(4)))
+	}
+
+	// default threshold for interrupts is 5
+	esp.INTERRUPT_CORE0.CPU_INT_THRESH.Set(5)
+
+	// Set the interrupt address.
+	// Set MODE field to 1 - a vector base address (only supported by ESP32C3)
+	// Note that this address must be aligned to 256 bytes.
+	riscv.MTVEC.Set((uintptr(unsafe.Pointer(&_vector_table))) | 1)
+
+	riscv.EnableInterrupts(mie)
+}
+
+//go:extern _vector_table
+var _vector_table [0]uintptr