Break out of ISR if timespan to next event allows, instead of busy waiting and stealing CPU cycles from userland.

dok-net · dok-net · commit 0d96dc197aae · 2021-06-08T03:38:19.000+02:00
diff --git a/cores/esp8266/core_esp8266_waveform.cpp b/cores/esp8266/core_esp8266_waveform.cpp
@@ -312,7 +312,14 @@ static ICACHE_RAM_ATTR void timer1Interrupt() {
     waveform.nextEventCcy = isrStartCcy + MAXIRQTICKSCCYS;
   }
 
+  uint32_t now = ESP.getCycleCount();
+  uint32_t isrNextEventCcy = now;
   while (busyPins) {
+    if (static_cast<int32_t>(isrNextEventCcy - now) > IRQLATENCYCCYS + DELTAIRQCCYS) {
+      waveform.nextEventCcy = isrNextEventCcy;
+      break;
+    }
+    isrNextEventCcy = waveform.nextEventCcy;
     for (int pin = waveform.startPin; pin <= waveform.endPin; ++pin) {
       const uint32_t pinBit = 1UL << pin;
       // If it's not on, ignore
@@ -322,7 +329,6 @@ static ICACHE_RAM_ATTR void timer1Interrupt() {
       Waveform& wave = waveform.pins[pin];
 
       uint32_t waveNextEventCcy = (waveform.states & pinBit) ? wave.endDutyCcy : wave.nextPeriodCcy;
-      const uint32_t now = ESP.getCycleCount();
       if (WaveformMode::EXPIRES == wave.mode &&
         static_cast<int32_t>(waveNextEventCcy - wave.expiryCcy) >= 0 &&
         static_cast<int32_t>(now - wave.expiryCcy) >= 0) {
@@ -396,15 +402,19 @@ static ICACHE_RAM_ATTR void timer1Interrupt() {
             waveform.nextEventCcy = waveNextEventCcy;
           }
         }
+        else if (static_cast<int32_t>(isrNextEventCcy - waveNextEventCcy) > 0) {
+          isrNextEventCcy = waveNextEventCcy;
+        }
       }
+      now = ESP.getCycleCount();
     }
   }
 
   int32_t callbackCcys = 0;
   if (waveform.timer1CB) {
     callbackCcys = scaleCcys(microsecondsToClockCycles(waveform.timer1CB()));
   }
-  const uint32_t now = ESP.getCycleCount();
+  now = ESP.getCycleCount();
   int32_t nextTimerCcys = waveform.nextEventCcy - now;
   // Account for unknown duration of timer1CB().
   if (waveform.timer1CB && nextTimerCcys > callbackCcys) {

Original file line number	Diff line number	Diff line change
`@@ -312,7 +312,14 @@ static ICACHE_RAM_ATTR void timer1Interrupt() {`
`312`	`312`	`waveform.nextEventCcy = isrStartCcy + MAXIRQTICKSCCYS;`
`313`	`313`	`}`
`314`	`314`
	`315`	`+ uint32_t now = ESP.getCycleCount();`
	`316`	`+ uint32_t isrNextEventCcy = now;`
`315`	`317`	`while (busyPins) {`
	`318`	`+ if (static_cast<int32_t>(isrNextEventCcy - now) > IRQLATENCYCCYS + DELTAIRQCCYS) {`
	`319`	`+ waveform.nextEventCcy = isrNextEventCcy;`
	`320`	`+ break;`
	`321`	`+ }`
	`322`	`+ isrNextEventCcy = waveform.nextEventCcy;`
`316`	`323`	`for (int pin = waveform.startPin; pin <= waveform.endPin; ++pin) {`
`317`	`324`	`const uint32_t pinBit = 1UL << pin;`
`318`	`325`	`// If it's not on, ignore`
`@@ -322,7 +329,6 @@ static ICACHE_RAM_ATTR void timer1Interrupt() {`
`322`	`329`	`Waveform& wave = waveform.pins[pin];`
`323`	`330`
`324`	`331`	`uint32_t waveNextEventCcy = (waveform.states & pinBit) ? wave.endDutyCcy : wave.nextPeriodCcy;`
`325`		`- const uint32_t now = ESP.getCycleCount();`
`326`	`332`	`if (WaveformMode::EXPIRES == wave.mode &&`
`327`	`333`	`static_cast<int32_t>(waveNextEventCcy - wave.expiryCcy) >= 0 &&`
`328`	`334`	`static_cast<int32_t>(now - wave.expiryCcy) >= 0) {`
`@@ -396,15 +402,19 @@ static ICACHE_RAM_ATTR void timer1Interrupt() {`
`396`	`402`	`waveform.nextEventCcy = waveNextEventCcy;`
`397`	`403`	`}`
`398`	`404`	`}`
	`405`	`+ else if (static_cast<int32_t>(isrNextEventCcy - waveNextEventCcy) > 0) {`
	`406`	`+ isrNextEventCcy = waveNextEventCcy;`
	`407`	`+ }`
`399`	`408`	`}`
	`409`	`+ now = ESP.getCycleCount();`
`400`	`410`	`}`
`401`	`411`	`}`
`402`	`412`
`403`	`413`	`int32_t callbackCcys = 0;`
`404`	`414`	`if (waveform.timer1CB) {`
`405`	`415`	`callbackCcys = scaleCcys(microsecondsToClockCycles(waveform.timer1CB()));`
`406`	`416`	`}`
`407`		`- const uint32_t now = ESP.getCycleCount();`
	`417`	`+ now = ESP.getCycleCount();`
`408`	`418`	`int32_t nextTimerCcys = waveform.nextEventCcy - now;`
`409`	`419`	`// Account for unknown duration of timer1CB().`
`410`	`420`	`if (waveform.timer1CB && nextTimerCcys > callbackCcys) {`