[PATCH v2] MIPS - fix cycle counter timing calculations

[Simon Burge <simonb@NetBSD.org>]

The cp0_count_ns value is calculated from the CP0_COUNT_RATE_DEFAULT
constant in target/mips/cpu.c.  The cycle counter resolution is defined
per-CPU in target/mips/cpu-defs.c.inc; use this value for calculating
cp0_count_ns.  Fixings timing problems on guest OSs for the 20Kc CPU
which has a CCRes of 1.

Signed-off-by: Simon Burge <simonb@NetBSD.org>
---
 target/mips/cpu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/target/mips/cpu.c b/target/mips/cpu.c
index 4aae23934b..0766e25693 100644
--- a/target/mips/cpu.c
+++ b/target/mips/cpu.c
@@ -440,8 +440,9 @@ static void mips_cp0_period_set(MIPSCPU *cpu)
 {
     CPUMIPSState *env = &cpu->env;
 
+    /* env->CCRes isn't initialised this early, use env->cpu_model->CCRes. */
     env->cp0_count_ns = clock_ticks_to_ns(MIPS_CPU(cpu)->clock,
-                                          cpu->cp0_count_rate);
+                                          env->cpu_model->CCRes);
     assert(env->cp0_count_ns);
 }
 
-- 
2.33.0