[PATCH v2 04/10] target/arm: Ignore PMCR.D when PMCR.LC is set

[Peter Maydell <peter.maydell@linaro.org>]

The architecture requires that if PMCR.LC is set (for a 64-bit cycle
counter) then PMCR.D (which enables the clock divider so the counter
ticks every 64 cycles rather than every cycle) should be ignored.  We
were always honouring PMCR.D; fix the bug so we correctly ignore it
in this situation.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/arm/helper.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 59e1280a9cd..f2bf1c52eb2 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -1172,6 +1172,17 @@ static void pmu_update_irq(CPUARMState *env)
             (env->cp15.c9_pminten & env->cp15.c9_pmovsr));
 }
 
+static bool pmccntr_clockdiv_enabled(CPUARMState *env)
+{
+    /*
+     * Return true if the clock divider is enabled and the cycle counter
+     * is supposed to tick only once every 64 clock cycles. This is
+     * controlled by PMCR.D, but if PMCR.LC is set to enable the long
+     * (64-bit) cycle counter PMCR.D has no effect.
+     */
+    return (env->cp15.c9_pmcr & (PMCRD | PMCRLC)) == PMCRD;
+}
+
 /*
  * Ensure c15_ccnt is the guest-visible count so that operations such as
  * enabling/disabling the counter or filtering, modifying the count itself,
@@ -1184,8 +1195,7 @@ static void pmccntr_op_start(CPUARMState *env)
 
     if (pmu_counter_enabled(env, 31)) {
         uint64_t eff_cycles = cycles;
-        if (env->cp15.c9_pmcr & PMCRD) {
-            /* Increment once every 64 processor clock cycles */
+        if (pmccntr_clockdiv_enabled(env)) {
             eff_cycles /= 64;
         }
 
@@ -1228,8 +1238,7 @@ static void pmccntr_op_finish(CPUARMState *env)
 #endif
 
         uint64_t prev_cycles = env->cp15.c15_ccnt_delta;
-        if (env->cp15.c9_pmcr & PMCRD) {
-            /* Increment once every 64 processor clock cycles */
+        if (pmccntr_clockdiv_enabled(env)) {
             prev_cycles /= 64;
         }
         env->cp15.c15_ccnt_delta = prev_cycles - env->cp15.c15_ccnt;
-- 
2.25.1