Regularize timing code

Provide get_timer_value() and get_timer_freq() and use them.  On Arty,
they use mcycle and the known-fixed core frequency, whereas on HiFive1
they use mtime and the known-fixed mtime frequency.

5 files changed, 58 insertions, 13 deletions

diff --git a/bsp/env/freedom-e300-arty/init.c b/bsp/env/freedom-e300-arty/init.c
index 0a80cbb..35b1104 100644
--- a/bsp/env/freedom-e300-arty/init.c
+++ b/bsp/env/freedom-e300-arty/init.c
@@ -9,11 +9,30 @@
 extern int main(int argc, char** argv);
 extern void trap_entry();
 
-uint32_t get_cpu_freq()
+static unsigned long get_cpu_freq()
 {
   return 65000000;
 }
 
+unsigned long get_timer_freq()
+{
+  return get_cpu_freq();
+}
+
+uint64_t get_timer_value()
+{
+#if __riscv_xlen == 32
+  while (1) {
+    uint32_t hi = read_csr(mcycleh);
+    uint32_t lo = read_csr(mcycle);
+    if (hi == read_csr(mcycleh))
+      return ((uint64_t)hi << 32) | lo;
+  }
+#else
+  return read_csr(mcycle);
+#endif
+}
+
 static void uart_init(size_t baud_rate)
 {
   GPIO_REG(GPIO_IOF_SEL) &= ~IOF0_UART0_MASK;
diff --git a/bsp/env/freedom-e300-arty/platform.h b/bsp/env/freedom-e300-arty/platform.h
index 1f62956..d5d6dda 100644
--- a/bsp/env/freedom-e300-arty/platform.h
+++ b/bsp/env/freedom-e300-arty/platform.h
@@ -119,4 +119,7 @@
 #define HAS_BOARD_BUTTONS
 #include "hifive1.h"
 
+unsigned long get_timer_freq(void);
+uint64_t get_timer_value(void);
+
 #endif /* _SIFIVE_PLATFORM_H */
diff --git a/bsp/env/freedom-e300-hifive1/init.c b/bsp/env/freedom-e300-hifive1/init.c
index 61a1ae3..71e1659 100644
--- a/bsp/env/freedom-e300-hifive1/init.c
+++ b/bsp/env/freedom-e300-hifive1/init.c
@@ -8,16 +8,40 @@
 extern int main(int argc, char** argv);
 extern void trap_entry();
 
-uint32_t mtime_lo(void)
+static unsigned long mtime_lo(void)
 {
-  return *(volatile uint32_t *)(CLINT_BASE_ADDR + CLINT_MTIME);
+  return *(volatile unsigned long *)(CLINT_BASE_ADDR + CLINT_MTIME);
 }
 
-uint32_t mcycle_lo(void)
+#ifdef __riscv32
+
+static uint32_t mtime_hi(void)
+{
+  return *(volatile uint32_t *)(CLINT_BASE_ADDR + CLINT_MTIME + 4);
+}
+
+uint64_t get_timer_value()
+{
+  while (1) {
+    uint32_t hi = mtime_hi();
+    uint32_t lo = mtime_lo();
+    if (hi == mtime_hi())
+      return ((uint64_t)hi << 32) | lo;
+  }
+}
+
+#else /* __riscv32 */
+
+uint64_t get_timer_value()
+{
+  return mtime_lo();
+}
+
+#endif
+
+unsigned long get_timer_freq()
 {
-  uint32_t t;
-  asm volatile ("csrr %0, mcycle" : "=r" (t));
-  return t;
+  return 32768;
 }
 
 static void use_hfrosc(int div, int trim)
diff --git a/bsp/env/freedom-e300-hifive1/platform.h b/bsp/env/freedom-e300-hifive1/platform.h
index eca708e..63efc9e 100644
--- a/bsp/env/freedom-e300-hifive1/platform.h
+++ b/bsp/env/freedom-e300-hifive1/platform.h
@@ -126,6 +126,8 @@
 
 #include "hifive1.h"
 
-uint32_t get_cpu_freq();
+unsigned long get_cpu_freq(void);
+unsigned long get_timer_freq(void);
+uint64_t get_timer_value(void);
 
 #endif /* _SIFIVE_PLATFORM_H */
diff --git a/software/dhrystone/dhry_stubs.c b/software/dhrystone/dhry_stubs.c
index d3bd14c..0616f86 100644
--- a/software/dhrystone/dhry_stubs.c
+++ b/software/dhrystone/dhry_stubs.c
@@ -3,16 +3,13 @@
 /* The functions in this file are only meant to support Dhrystone on an
  * embedded RV32 system and are obviously incorrect in general. */
 
-// return the cycle counter as though it were the current time
 long time(void)
 {
-  long t;
-  asm volatile ("csrr %0, mcycle" : "=r" (t));
-  return t / (get_cpu_freq() / 1000);
+  return get_timer_value() / get_timer_freq();
 }
 
 // set the number of dhrystone iterations
 void __wrap_scanf(const char* fmt, int* n)
 {
-  *n = 1500000;
+  *n = 100000000;
 }