dev: prevent intel 8254 timer counter events firing before startup

This change includes edits to Intel8254Timer to prevent counter events firing
before startup to comply with SimObject initialization call sequence.

Committed by: Nilay Vaish <nilay@cs.wisc.edu>

src/dev/alpha/tsunami_io.cc

@@ -288,6 +288,7 @@ void
 TsunamiIO::startup()
 {
     rtc.startup();
+    pitimer.startup();
 }
 
 TsunamiIO *

src/dev/intel_8254_timer.cc

@@ -89,13 +89,22 @@ Intel8254Timer::unserialize(const string &base, Checkpoint *cp,
     counter[2]->unserialize(base + ".counter2", cp, section);
 }
 
+void
+Intel8254Timer::startup()
+{
+    counter[0]->startup();
+    counter[1]->startup();
+    counter[2]->startup();
+}
+
 Intel8254Timer::Counter::Counter(Intel8254Timer *p,
         const string &name, unsigned int _num)
-    : _name(name), num(_num), event(this), initial_count(0),
-      latched_count(0), period(0), mode(0), output_high(false),
-      latch_on(false), read_byte(LSB), write_byte(LSB), parent(p)
+    : _name(name), num(_num), event(this), running(false),
+      initial_count(0), latched_count(0), period(0), mode(0),
+      output_high(false), latch_on(false), read_byte(LSB),
+      write_byte(LSB), parent(p)
 {
-
+    offset = period * event.getInterval();
 }
 
 void
@@ -179,7 +188,9 @@ Intel8254Timer::Counter::write(const uint8_t data)
         else
             period = initial_count;
 
-        if (period > 0)
+        offset = period * event.getInterval();
+
+        if (running && (period > 0))
             event.setTo(period);
 
         write_byte = LSB;
@@ -229,10 +240,10 @@ Intel8254Timer::Counter::serialize(const string &base, ostream &os)
     paramOut(os, base + ".read_byte", read_byte);
     paramOut(os, base + ".write_byte", write_byte);
 
-    Tick event_tick = 0;
+    Tick event_tick_offset = 0;
     if (event.scheduled())
-        event_tick = event.when();
-    paramOut(os, base + ".event_tick", event_tick);
+        event_tick_offset = event.when() - curTick();
+    paramOut(os, base + ".event_tick_offset", event_tick_offset);
 }
 
 void
@@ -248,12 +259,20 @@ Intel8254Timer::Counter::unserialize(const string &base, Checkpoint *cp,
     paramIn(cp, section, base + ".read_byte", read_byte);
     paramIn(cp, section, base + ".write_byte", write_byte);
 
-    Tick event_tick = 0;
-    if (event.scheduled())
-        parent->deschedule(event);
-    paramIn(cp, section, base + ".event_tick", event_tick);
-    if (event_tick)
-        parent->schedule(event, event_tick);
+    Tick event_tick_offset = 0;
+    assert(!event.scheduled());
+    paramIn(cp, section, base + ".event_tick_offset", event_tick_offset);
+    offset = event_tick_offset;
+}
+
+void
+Intel8254Timer::Counter::startup()
+{
+    running = true;
+    if ((period > 0) && (offset > 0))
+    {
+        parent->schedule(event, curTick() + offset);
+    }
 }
 
 Intel8254Timer::Counter::CounterEvent::CounterEvent(Counter* c_ptr)
@@ -302,3 +321,10 @@ Intel8254Timer::Counter::CounterEvent::description() const
 {
     return "Intel 8254 Interval timer";
 }
+
+Tick
+Intel8254Timer::Counter::CounterEvent::getInterval()
+{
+    return interval;
+}
+

src/dev/intel_8254_timer.hh

@@ -102,6 +102,8 @@ class Intel8254Timer : public EventManager
             void setTo(int clocks);
 
             int clocksLeft();
+
+            Tick getInterval();
         };
 
       private:
@@ -112,6 +114,9 @@ class Intel8254Timer : public EventManager
 
         CounterEvent event;
 
+        /** True after startup is called. */
+        bool running;
+
         /** Initial count value */
         uint16_t initial_count;
 
@@ -121,6 +126,9 @@ class Intel8254Timer : public EventManager
         /** Interrupt period */
         uint16_t period;
 
+        /** When to start ticking */
+        Tick offset;
+
         /** Current mode of operation */
         uint8_t mode;
 
@@ -181,6 +189,9 @@ class Intel8254Timer : public EventManager
          */
         void unserialize(const std::string &base, Checkpoint *cp,
                          const std::string &section);
+
+        /** Start ticking */
+        void startup();
     };
 
   protected:
@@ -246,6 +257,9 @@ class Intel8254Timer : public EventManager
      */
     void unserialize(const std::string &base, Checkpoint *cp,
                      const std::string &section);
+
+    /** Start ticking */
+    void startup();
 };
 
 #endif // __DEV_8254_HH__

src/dev/mips/malta_io.cc

@@ -146,6 +146,7 @@ void
 MaltaIO::startup()
 {
     rtc.startup();
+    pitimer.startup();
 }
 
 MaltaIO *

src/dev/x86/i8254.cc

@@ -89,6 +89,12 @@ X86ISA::I8254::unserialize(Checkpoint *cp, const std::string &section)
     pit.unserialize("pit", cp, section);
 }
 
+void
+X86ISA::I8254::startup()
+{
+    pit.startup();
+}
+
 X86ISA::I8254 *
 I8254Params::create()
 {

src/dev/x86/i8254.hh

@@ -111,6 +111,7 @@ class I8254 : public BasicPioDevice
 
     virtual void serialize(std::ostream &os);
     virtual void unserialize(Checkpoint *cp, const std::string &section);
+    virtual void startup();
 
 };