From a4dd38de817d77cb282ddcc5a1203f75a4d50dc3 Mon Sep 17 00:00:00 2001
From: deadprogram <ron@hybridgroup.com>
Date: Fri, 17 Apr 2026 16:53:49 +0200
Subject: [PATCH] machine/esp32s3: use edge-triggered CPU interrupt for GPIO
 pin interrupts
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When SPI is configured via the GPIO Matrix, SPI signal transitions set
GPIO.STATUS bits on the routed pins. With a level-triggered CPU interrupt
(line 8), the ISR re-enters continuously as long as any STATUS bit is
asserted — causing user GPIO callbacks to fire spuriously.

Switch cpuInterruptFromPin to CPU interrupt 10, which is edge-triggered
(level 1) on the Xtensa LX7. This ensures the ISR fires once per GPIO
event rather than looping while SPI is active.

Also move STATUS_W1TC clears to before callback dispatch so that new
GPIO events arriving during handler execution generate a fresh edge, and
add writeINTCLEAR(active) in handleInterrupt to properly acknowledge
edge-triggered CPU interrupt pending bits via the INTCLEAR register.

Fixes GPIO interrupts firing constantly when SPI and pin interrupts are
used together.

Signed-off-by: deadprogram <ron@hybridgroup.com>
---
 src/examples/pininterrupt/xiao-esp32s3.go  |  2 +-
 src/machine/machine_esp32s3.go             | 22 ++++++++++++++++------
 src/runtime/interrupt/interrupt_esp32s3.go | 16 ++++++++++++++++
 3 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/src/examples/pininterrupt/xiao-esp32s3.go b/src/examples/pininterrupt/xiao-esp32s3.go
index 4173170c3..348b83f43 100644
--- a/src/examples/pininterrupt/xiao-esp32s3.go
+++ b/src/examples/pininterrupt/xiao-esp32s3.go
@@ -6,6 +6,6 @@ import "machine"
 
 const (
 	button          = machine.D1
-	buttonMode      = machine.PinInput
+	buttonMode      = machine.PinInputPullup
 	buttonPinChange = machine.PinFalling
 )
diff --git a/src/machine/machine_esp32s3.go b/src/machine/machine_esp32s3.go
index 78f5fd445..e7582688f 100644
--- a/src/machine/machine_esp32s3.go
+++ b/src/machine/machine_esp32s3.go
@@ -306,7 +306,12 @@ func (p Pin) pinReg() *volatile.Register32 {
 }
 
 const maxPin = 49
-const cpuInterruptFromPin = 8
+
+// cpuInterruptFromPin selects an edge-triggered CPU interrupt line for GPIO.
+// CPU interrupt 10 is edge-triggered level-1 on the Xtensa LX7, which prevents
+// the ISR from re-entering continuously when other peripherals (e.g. SPI via
+// the GPIO Matrix) keep GPIO.STATUS bits asserted.
+const cpuInterruptFromPin = 10
 
 type PinChange uint8
 
@@ -370,23 +375,28 @@ var (
 func setupPinInterrupt() error {
 	esp.INTERRUPT_CORE0.SetGPIO_INTERRUPT_PRO_MAP(cpuInterruptFromPin)
 	return interrupt.New(cpuInterruptFromPin, func(interrupt.Interrupt) {
-		// Check status for GPIO0-31
+		// Read and immediately clear interrupt status bits.
+		// Clearing before processing is critical for edge-triggered CPU
+		// interrupts: any new GPIO events that arrive during callback
+		// execution will set fresh STATUS bits, generating a new edge
+		// on the CPU interrupt line so they are not lost.
 		status := esp.GPIO.STATUS.Get()
+		status1 := esp.GPIO.STATUS1.Get()
+		esp.GPIO.STATUS_W1TC.Set(status)
+		esp.GPIO.STATUS1_W1TC.Set(status1)
+
+		// Check status for GPIO0-31
 		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()
 }
 
diff --git a/src/runtime/interrupt/interrupt_esp32s3.go b/src/runtime/interrupt/interrupt_esp32s3.go
index bfb55cb81..5fbaaea02 100644
--- a/src/runtime/interrupt/interrupt_esp32s3.go
+++ b/src/runtime/interrupt/interrupt_esp32s3.go
@@ -107,6 +107,12 @@ func handleInterrupt() {
 	enabled := readINTENABLE()
 	active := pending & enabled
 
+	// Clear edge-triggered pending bits before dispatching handlers so that
+	// new edges arriving during handler execution are not lost.  Writing to
+	// INTCLEAR is a no-op for level-triggered lines, so this is safe for all
+	// interrupt types.
+	writeINTCLEAR(active)
+
 	for i := firstCPUInt; i <= lastCPUInt; i++ {
 		if active&(1<<uint(i)) != 0 {
 			// callHandlers requires a compile-time constant, so we
@@ -212,6 +218,16 @@ func readINTERRUPT() uint32 {
 	return uint32(device.AsmFull("rsr {}, INTERRUPT", nil))
 }
 
+// writeINTCLEAR writes the INTCLEAR special register (SR 227).
+// Setting bit N clears CPU interrupt N if it is edge-triggered or
+// software-triggered.  Bits corresponding to level-triggered interrupts
+// are ignored by hardware.
+func writeINTCLEAR(val uint32) {
+	device.AsmFull("wsr {val}, INTCLEAR", map[string]interface{}{
+		"val": val,
+	})
+}
+
 // -- Interrupt matrix helpers -----------------------------------------------
 // The ESP32-S3 interrupt matrix has one mapping register per peripheral
 // source.  These are memory-mapped in the INTERRUPT_CORE0 peripheral.