ARM: Detect and skip udelay() functions in linux kernel.

This change speeds up booting, especially in MP cases, by not executing
udelay() on the core but instead skipping ahead tha amount of time that is being
delayed.

1 files changed, 24 insertions, 0 deletions

diff --git a/src/arch/arm/linux/system.cc b/src/arch/arm/linux/system.cc
index 38024c058..7aff2b6ef 100644
--- a/src/arch/arm/linux/system.cc
+++ b/src/arch/arm/linux/system.cc
@@ -47,9 +47,11 @@
 #include "base/loader/object_file.hh"
 #include "base/loader/symtab.hh"
 #include "cpu/thread_context.hh"
+#include "kern/linux/events.hh"
 #include "mem/physical.hh"
 
 using namespace ArmISA;
+using namespace Linux;
 
 LinuxArmSystem::LinuxArmSystem(Params *p)
     : ArmSystem(p)
@@ -96,6 +98,24 @@ LinuxArmSystem::LinuxArmSystem(Params *p)
     if (!kernelPanicEvent)
         panic("could not find kernel symbol \'panic\'");
 #endif
+
+    // With ARM udelay() is #defined to __udelay
+    Addr addr = 0;
+    if (kernelSymtab->findAddress("__udelay", addr)) {
+        uDelaySkipEvent = new UDelayEvent(&pcEventQueue, "__udelay",
+                fixFuncEventAddr(addr), 1000, 0);
+    } else {
+        panic("couldn't find kernel symbol \'udelay\'");
+    }
+
+    // constant arguments to udelay() have some precomputation done ahead of
+    // time. Constant comes from code.
+    if (kernelSymtab->findAddress("__const_udelay", addr)) {
+        constUDelaySkipEvent = new UDelayEvent(&pcEventQueue, "__const_udelay",
+                fixFuncEventAddr(addr), 1000, 107374);
+    } else {
+        panic("couldn't find kernel symbol \'udelay\'");
+    }
 }
 
 void
@@ -115,6 +135,10 @@ LinuxArmSystem::initState()
 
 LinuxArmSystem::~LinuxArmSystem()
 {
+    if (uDelaySkipEvent)
+        delete uDelaySkipEvent;
+    if (constUDelaySkipEvent)
+        delete constUDelaySkipEvent;
 }
 
 LinuxArmSystem *