machine/esp32s3: implement Pin.SetInterrupt for GPIO pin change interrupts

Add support for rising, falling, and toggle edge interrupts on all
ESP32-S3 GPIO pins (0-48). The GPIO peripheral interrupt is routed
to CPU interrupt 8 via the interrupt matrix. The ISR reads both
STATUS and STATUS1 registers to cover the full 49-pin range.

Signed-off-by: deadprogram <ron@hybridgroup.com>

src/machine/machine_esp32s3.go

@@ -5,7 +5,9 @@ package machine
 import (
 	"device/esp"
 	"errors"
+	"runtime/interrupt"
 	"runtime/volatile"
+	"sync"
 	"unsafe"
 )
 
@@ -303,6 +305,91 @@ func (p Pin) pinReg() *volatile.Register32 {
 	return (*volatile.Register32)(unsafe.Add(unsafe.Pointer(&esp.GPIO.PIN0), uintptr(p)*4))
 }
 
+const maxPin = 49
+const cpuInterruptFromPin = 8
+
+type PinChange uint8
+
+// Pin change interrupt constants for SetInterrupt.
+const (
+	PinRising PinChange = iota + 1
+	PinFalling
+	PinToggle
+)
+
+// SetInterrupt sets an interrupt to be executed when a particular pin changes
+// state. The pin should already be configured as an input, including a pull up
+// or down if no external pull is provided.
+//
+// You can pass a nil func to unset the pin change interrupt. If you do so,
+// the change parameter is ignored and can be set to any value (such as 0).
+// If the pin is already configured with a callback, you must first unset
+// this pins interrupt before you can set a new callback.
+func (p Pin) SetInterrupt(change PinChange, callback func(Pin)) (err error) {
+	if p >= maxPin {
+		return ErrInvalidInputPin
+	}
+
+	if callback == nil {
+		// Disable this pin interrupt
+		p.pinReg().ClearBits(esp.GPIO_PIN_INT_TYPE_Msk | esp.GPIO_PIN_INT_ENA_Msk)
+
+		if pinCallbacks[p] != nil {
+			pinCallbacks[p] = nil
+		}
+		return nil
+	}
+
+	if pinCallbacks[p] != nil {
+		// The pin was already configured.
+		// To properly re-configure a pin, unset it first and set a new
+		// configuration.
+		return ErrNoPinChangeChannel
+	}
+	pinCallbacks[p] = callback
+
+	onceSetupPinInterrupt.Do(func() {
+		err = setupPinInterrupt()
+	})
+	if err != nil {
+		return err
+	}
+
+	p.pinReg().Set(
+		(p.pinReg().Get() & ^uint32(esp.GPIO_PIN_INT_TYPE_Msk|esp.GPIO_PIN_INT_ENA_Msk)) |
+			uint32(change)<<esp.GPIO_PIN_INT_TYPE_Pos | uint32(1)<<esp.GPIO_PIN_INT_ENA_Pos)
+
+	return nil
+}
+
+var (
+	pinCallbacks          [maxPin]func(Pin)
+	onceSetupPinInterrupt sync.Once
+)
+
+func setupPinInterrupt() error {
+	esp.INTERRUPT_CORE0.SetGPIO_INTERRUPT_PRO_MAP(cpuInterruptFromPin)
+	return interrupt.New(cpuInterruptFromPin, func(interrupt.Interrupt) {
+		// Check status for GPIO0-31
+		status := esp.GPIO.STATUS.Get()
+		for i, mask := 0, uint32(1); i < 32; i, mask = i+1, mask<<1 {
+			if (status&mask) != 0 && pinCallbacks[i] != nil {
+				pinCallbacks[i](Pin(i))
+			}
+		}
+		// Check status for GPIO32-48
+		status1 := esp.GPIO.STATUS1.Get()
+		for i, mask := 32, uint32(1); i < maxPin; i, mask = i+1, mask<<1 {
+			if (status1&mask) != 0 && pinCallbacks[i] != nil {
+				pinCallbacks[i](Pin(i))
+			}
+		}
+		// Clear interrupt bits
+		esp.GPIO.STATUS_W1TC.SetBits(status)
+		esp.GPIO.STATUS1_W1TC.SetBits(status1)
+	}).Enable()
+}
+
 var DefaultUART = UART0
 
 var (