Add optional support for real-time clint

This patch adds optional support clint timer incrementing at
real-time rate. This can be enabled by passing command line
parameter "--real-time-clint".

This feature can be used for:
1. Checking whether any code addition to Spike is slowing down
simulation too much
2. Comparing run-time for software on Spike with other functional
simulators (such as QEMU)

Signed-off-by: Anup Patel <anup.patel@wdc.com>

5 files changed, 35 insertions, 8 deletions

diff --git a/riscv/clint.cc b/riscv/clint.cc
index 20a9fca..d68f4cc 100644
--- a/riscv/clint.cc
+++ b/riscv/clint.cc
@@ -1,9 +1,16 @@
+#include <sys/time.h>
 #include "devices.h"
 #include "processor.h"
 
-clint_t::clint_t(std::vector<processor_t*>& procs)
-  : procs(procs), mtime(0), mtimecmp(procs.size())
+clint_t::clint_t(std::vector<processor_t*>& procs, uint64_t freq_mhz, bool real_time)
+  : procs(procs), freq_mhz(freq_mhz), real_time(real_time), mtime(0), mtimecmp(procs.size())
 {
+  struct timeval base;
+
+  gettimeofday(&base, NULL);
+
+  real_time_ref_secs = base.tv_sec;
+  real_time_ref_usecs = base.tv_usec;
 }
 
 /* 0000 msip hart 0
@@ -22,6 +29,7 @@ clint_t::clint_t(std::vector<processor_t*>& procs)
 
 bool clint_t::load(reg_t addr, size_t len, uint8_t* bytes)
 {
+  increment(0);
   if (addr >= MSIP_BASE && addr + len <= MSIP_BASE + procs.size()*sizeof(msip_t)) {
     std::vector<msip_t> msip(procs.size());
     for (size_t i = 0; i < procs.size(); ++i)
@@ -63,7 +71,16 @@ bool clint_t::store(reg_t addr, size_t len, const uint8_t* bytes)
 
 void clint_t::increment(reg_t inc)
 {
-  mtime += inc;
+  if (real_time) {
+   struct timeval now;
+   uint64_t diff_usecs;
+
+   gettimeofday(&now, NULL);
+   diff_usecs = ((now.tv_sec - real_time_ref_secs) * 1000000) + (now.tv_usec - real_time_ref_usecs);
+   mtime = diff_usecs * freq_mhz;
+  } else {
+    mtime += inc;
+  }
   for (size_t i = 0; i < procs.size(); i++) {
     procs[i]->state.mip &= ~MIP_MTIP;
     if (mtime >= mtimecmp[i])
diff --git a/riscv/devices.h b/riscv/devices.h
index aa4c050..130be3c 100644
--- a/riscv/devices.h
+++ b/riscv/devices.h
@@ -63,7 +63,7 @@ class mem_t : public abstract_device_t {
 
 class clint_t : public abstract_device_t {
  public:
-  clint_t(std::vector<processor_t*>&);
+  clint_t(std::vector<processor_t*>&, uint64_t freq_mhz, bool real_time);
   bool load(reg_t addr, size_t len, uint8_t* bytes);
   bool store(reg_t addr, size_t len, const uint8_t* bytes);
   size_t size() { return CLINT_SIZE; }
@@ -73,6 +73,10 @@ class clint_t : public abstract_device_t {
   typedef uint64_t mtimecmp_t;
   typedef uint32_t msip_t;
   std::vector<processor_t*>& procs;
+  uint64_t freq_mhz;
+  bool real_time;
+  uint64_t real_time_ref_secs;
+  uint64_t real_time_ref_usecs;
   mtime_t mtime;
   std::vector<mtimecmp_t> mtimecmp;
 };
diff --git a/riscv/sim.cc b/riscv/sim.cc
index 3d7cd88..96fd0b2 100644
--- a/riscv/sim.cc
+++ b/riscv/sim.cc
@@ -26,7 +26,8 @@ static void handle_signal(int sig)
 }
 
 sim_t::sim_t(const char* isa, const char* priv, const char* varch,
-             size_t nprocs, bool halted, reg_t initrd_start, reg_t initrd_end,
+             size_t nprocs, bool halted, bool real_time_clint,
+             reg_t initrd_start, reg_t initrd_end,
              reg_t start_pc, std::vector<std::pair<reg_t, mem_t*>> mems,
              std::vector<std::pair<reg_t, abstract_device_t*>> plugin_devices,
              const std::vector<std::string>& args,
@@ -65,7 +66,7 @@ sim_t::sim_t(const char* isa, const char* priv, const char* varch,
     }
   }
 
-  clint.reset(new clint_t(procs));
+  clint.reset(new clint_t(procs, CPU_HZ / INSNS_PER_RTC_TICK / 1000000, real_time_clint));
   bus.add_device(CLINT_BASE, clint.get());
 }
 
diff --git a/riscv/sim.h b/riscv/sim.h
index 44f2f92..a9d4923 100644
--- a/riscv/sim.h
+++ b/riscv/sim.h
@@ -22,7 +22,8 @@ class sim_t : public htif_t, public simif_t
 {
 public:
   sim_t(const char* isa, const char* priv, const char* varch, size_t _nprocs,
-        bool halted, reg_t initrd_start, reg_t initrd_end,
+        bool halted, bool real_time_clint,
+        reg_t initrd_start, reg_t initrd_end,
         reg_t start_pc, std::vector<std::pair<reg_t, mem_t*>> mems,
         std::vector<std::pair<reg_t, abstract_device_t*>> plugin_devices,
         const std::vector<std::string>& args, const std::vector<int> hartids,
diff --git a/spike_main/spike.cc b/spike_main/spike.cc
index f14ef87..1474a4c 100644
--- a/spike_main/spike.cc
+++ b/spike_main/spike.cc
@@ -51,6 +51,7 @@ static void help(int exit_code = 1)
   fprintf(stderr, "  --dump-dts            Print device tree string and exit\n");
   fprintf(stderr, "  --disable-dtb         Don't write the device tree blob into memory\n");
   fprintf(stderr, "  --initrd=<path>       Load kernel initrd into memory\n");
+  fprintf(stderr, "  --real-time-clint     Increment clint time at real-time rate\n");
   fprintf(stderr, "  --dm-progsize=<words> Progsize for the debug module [default 2]\n");
   fprintf(stderr, "  --dm-sba=<bits>       Debug bus master supports up to "
       "<bits> wide accesses [default 0]\n");
@@ -131,6 +132,7 @@ int main(int argc, char** argv)
   bool log = false;
   bool dump_dts = false;
   bool dtb_enabled = true;
+  bool real_time_clint = false;
   size_t nprocs = 1;
   size_t initrd_size;
   reg_t initrd_start = 0, initrd_end = 0;
@@ -241,6 +243,7 @@ int main(int argc, char** argv)
   parser.option(0, "dump-dts", 0, [&](const char *s){dump_dts = true;});
   parser.option(0, "disable-dtb", 0, [&](const char *s){dtb_enabled = false;});
   parser.option(0, "initrd", 1, [&](const char* s){initrd = s;});
+  parser.option(0, "real-time-clint", 0, [&](const char *s){real_time_clint = true;});
   parser.option(0, "extlib", 1, [&](const char *s){
     void *lib = dlopen(s, RTLD_NOW | RTLD_GLOBAL);
     if (lib == NULL) {
@@ -286,7 +289,8 @@ int main(int argc, char** argv)
     }
   }
 
-  sim_t s(isa, priv, varch, nprocs, halted, initrd_start, initrd_end, start_pc, mems, plugin_devices, htif_args,
+  sim_t s(isa, priv, varch, nprocs, halted, real_time_clint,
+      initrd_start, initrd_end, start_pc, mems, plugin_devices, htif_args,
       std::move(hartids), dm_config);
   std::unique_ptr<remote_bitbang_t> remote_bitbang((remote_bitbang_t *) NULL);
   std::unique_ptr<jtag_dtm_t> jtag_dtm(