systemc: Implement signal based resets.

The implementation is based on sc_event sensitivities.

Also of note is that the way reset works in the Accellera
implementation isn't consistent with the spec. That says that
wait(int n) is supposed to be equivalent to calling wait() n times,
assuming n is greater than 0.

Instead, Accellera stores that count and then doesn't wake up the
process until the count is 0, decrementing it otherwise.

That means that when the process is in reset, it won't actually reset
for those intermediate wait()s which it would if wait() was called
repeatedly. Also, oddly, when a reset becomes asserted, it will clear
the count to 0 explicitly. That may have been an attempt to make the
behavior of wait(int n) match the spec, but it doesn't handle cases
where the reset is already set when wait(int n) is called.

Change-Id: I92f8e9a128e6618af94dc048ce570a4436e17e4b
Reviewed-on: https://gem5-review.googlesource.com/c/13186
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/src/systemc/core/process.hh b/src/systemc/core/process.hh
index 9e85fc7cc..85a7a27a8 100644
--- a/src/systemc/core/process.hh
+++ b/src/systemc/core/process.hh
@@ -87,6 +87,8 @@ class Process : public ::sc_core::sc_process_b, public ListNode
     void syncResetOn(bool inc_kids);
     void syncResetOff(bool inc_kids);
 
+    void signalReset(bool set, bool sync);
+
     void incref() { refCount++; }
     void decref() { refCount--; }
 
@@ -100,6 +102,7 @@ class Process : public ::sc_core::sc_process_b, public ListNode
     void addStatic(StaticSensitivity *);
     void setDynamic(DynamicSensitivity *);
     void clearDynamic() { setDynamic(nullptr); }
+    void addReset(ResetSensitivity *);
 
     ScEvent timeoutEvent;
     void setTimeout(::sc_core::sc_time t);
@@ -119,13 +122,15 @@ class Process : public ::sc_core::sc_process_b, public ListNode
     bool hasStaticSensitivities() { return !staticSensitivities.empty(); }
     bool internal() { return _internal; }
     bool timedOut() { return _timedOut; }
-    bool syncReset() { return _syncReset; }
+    bool inReset() { return _syncReset || syncResetCount || asyncResetCount; }
 
     bool dontInitialize() { return _dontInitialize; }
     void dontInitialize(bool di) { _dontInitialize = di; }
 
     void joinWait(::sc_core::sc_join *join) { joinWaiters.push_back(join); }
 
+    void waitCount(int count) { _waitCount = count; }
+
   protected:
     void timeout();
 
@@ -170,12 +175,18 @@ class Process : public ::sc_core::sc_process_b, public ListNode
 
     bool _syncReset;
 
+    int syncResetCount;
+    int asyncResetCount;
+
+    int _waitCount;
+
     int refCount;
 
     size_t stackSize;
 
     StaticSensitivities staticSensitivities;
     DynamicSensitivity *dynamicSensitivity;
+    ResetSensitivities resetSensitivities;
 
     std::unique_ptr<::sc_core::sc_report> _lastReport;