From 84326092ab1b1d64cfac206cefcc9eeff380069a Mon Sep 17 00:00:00 2001
From: Drahoslav <drahoslav@yo2.cz>
Date: Sat, 1 Dec 2018 05:25:37 +0100
Subject: [PATCH] Disable gpio IRQ on Detect edge

---
 rpio.go      | 13 +++++++++++--
 rpio_test.go | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+), 2 deletions(-)

diff --git a/rpio.go b/rpio.go
index 7e8f28d..cd1afb1 100644
--- a/rpio.go
+++ b/rpio.go
@@ -372,12 +372,20 @@ func TogglePin(pin Pin) {
 //
 // Note that using this function might conflict with the same functionality of other gpio library.
 //
-// It also clears previously detected event of this pin if any.
+// It also clears previously detected event of this pin if there was any.
 //
 // Note that call with RiseEdge will disable previously set FallEdge detection and vice versa.
 // You have to call with AnyEdge, to enable detection for both edges.
 // To disable previously enabled detection call it with NoEdge.
+//
+// WARNING: this might make your Pi unresponsive, if this happens, you should either run the code as root,
+// or add `dtoverlay=gpio-no-irq` to `/boot/config.txt` and restart your pi,
 func DetectEdge(pin Pin, edge Edge) {
+	if edge != NoEdge {
+		// disable GPIO event interruption to prevent freezing in some cases
+		DisableIRQs(1<<49 | 1<<52) // gpio_int[0] and gpio_int[3]
+	}
+
 	p := uint8(pin)
 
 	// Rising edge detect enable register (19/20 depending on bank)
@@ -692,6 +700,8 @@ func memMap(fd uintptr, base int64) (mem []uint32, mem8 []byte, err error) {
 
 // Close unmaps GPIO memory
 func Close() error {
+	EnableIRQs(irqsBackup) // Return IRQs to state where it was before - just to be nice
+
 	memlock.Lock()
 	defer memlock.Unlock()
 	for _, mem8 := range [][]uint8{gpioMem8, clkMem8, pwmMem8, spiMem8, intrMem8} {
@@ -699,7 +709,6 @@ func Close() error {
 			return err
 		}
 	}
-	EnableIRQs(irqsBackup) // Return IRQs to state where it was before - just to be nice
 	return nil
 }
 
diff --git a/rpio_test.go b/rpio_test.go
index d534f5f..9797a9d 100644
--- a/rpio_test.go
+++ b/rpio_test.go
@@ -1,6 +1,7 @@
 package rpio
 
 import (
+	"fmt"
 	"os"
 	"testing"
 	"time"
@@ -15,6 +16,21 @@ func TestMain(m *testing.M) {
 	os.Exit(m.Run())
 }
 
+func TestInterrupt(t *testing.T) {
+	logIrqRegs(t)
+	EnableIRQs(1 << 49)
+	EnableIRQs(1 << 50)
+	EnableIRQs(1 << 51)
+	EnableIRQs(1 << 52)
+	logIrqRegs(t)
+	DisableIRQs(1 << 49)
+	DisableIRQs(1 << 50)
+	DisableIRQs(1 << 51)
+	DisableIRQs(1 << 52)
+	logIrqRegs(t)
+	EnableIRQs(irqsBackup)
+}
+
 func TestEvent(t *testing.T) {
 	src := Pin(3)
 	src.Mode(Output)
@@ -118,6 +134,33 @@ func TestEvent(t *testing.T) {
 
 	})
 
+	// If this fr⁽eezes your pi,
+	// add `dtoverlay=gpio-no-irq` to `/boot/config.txt` and restart your pi,
+	// or run as root.
+	t.Run("multiple edges", func(t *testing.T) {
+		EnableIRQs(15 << 49) // all 4 gpio_int[]
+		logIrqRegs(t)
+		src.High()
+		pin.Detect(FallEdge)
+
+		logIrqRegs(t)
+
+		for i := 0; i < 10000; i++ {
+			time.Sleep(time.Millisecond)
+			src.High()
+			time.Sleep(time.Millisecond)
+			src.Low()
+		}
+		logIrqRegs(t)
+		if !pin.EdgeDetected() {
+			t.Errorf("Edge not detected")
+		}
+		logIrqRegs(t)
+		pin.Detect(NoEdge)
+		logIrqRegs(t)
+		EnableIRQs(irqsBackup)
+	})
+
 }
 
 func BenchmarkGpio(b *testing.B) {
@@ -191,3 +234,12 @@ func BenchmarkGpio(b *testing.B) {
 	})
 
 }
+
+func logIrqRegs(t *testing.T) {
+	fmt.Printf("PENDING(% X) FIQ(% X) ENAB(% X) DISAB(% X)\n",
+		intrMem8[0x200:0x20C],
+		intrMem8[0x20C:0x210],
+		intrMem8[0x210:0x21C],
+		intrMem8[0x21C:0x228],
+	)
+}