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-rw-r--r--bsp/env/freedom-e300-hifive1/init.c38
1 files changed, 27 insertions, 11 deletions
diff --git a/bsp/env/freedom-e300-hifive1/init.c b/bsp/env/freedom-e300-hifive1/init.c
index 167d652..61a1ae3 100644
--- a/bsp/env/freedom-e300-hifive1/init.c
+++ b/bsp/env/freedom-e300-hifive1/init.c
@@ -5,8 +5,6 @@
#include "platform.h"
#include "encoding.h"
-uint32_t cpu_freq = 0;
-
extern int main(int argc, char** argv);
extern void trap_entry();
@@ -116,21 +114,40 @@ static void use_default_clocks()
use_hfrosc(4, 16);
}
-void measure_cpu_freq(size_t n, size_t mtime_freq)
+static unsigned long __attribute__((noinline)) measure_cpu_freq(size_t n)
{
- uint32_t start_mtime = mtime_lo();
- uint32_t start_mcycle = mcycle_lo();
+ unsigned long start_mtime, delta_mtime;
+ unsigned long mtime_freq = get_timer_freq();
+
+ // Don't start measuruing until we see an mtime tick
+ unsigned long tmp = mtime_lo();
+ do {
+ start_mtime = mtime_lo();
+ } while (start_mtime == tmp);
+
+ unsigned long start_mcycle = read_csr(mcycle);
- while (mtime_lo() - start_mtime < n) ;
+ do {
+ delta_mtime = mtime_lo() - start_mtime;
+ } while (delta_mtime < n);
- uint32_t end_mtime = mtime_lo();
- uint32_t end_mcycle = mcycle_lo();
+ unsigned long delta_mcycle = read_csr(mcycle) - start_mcycle;
- cpu_freq = (end_mcycle-start_mcycle)/n*mtime_freq;
+ return (delta_mcycle / delta_mtime) * mtime_freq
+ + ((delta_mcycle % delta_mtime) * mtime_freq) / delta_mtime;
}
-uint32_t get_cpu_freq()
+unsigned long get_cpu_freq()
{
+ static uint32_t cpu_freq;
+
+ if (!cpu_freq) {
+ // warm up I$
+ measure_cpu_freq(1);
+ // measure for real
+ cpu_freq = measure_cpu_freq(10);
+ }
+
return cpu_freq;
}
@@ -178,7 +195,6 @@ void _init()
{
use_default_clocks();
use_pll(0, 0, 1, 31, 1);
- measure_cpu_freq(1000, 32768);
uart_init(115200);
printf("core freq at %d Hz\n", get_cpu_freq());