[Qemu-devel] [PATCH v2 4/7] arm: clarify the use of muldiv64()

[Laurent Vivier <lvivier@redhat.com>]

muldiv64() is used to convert microseconds into CPU ticks.

But it is not clear and not commented. This patch uses macro
to clearly identify what is used: time, CPU frequency and ticks.
For an elapsed time and a given frequency, we compute how many ticks
 we have.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
v2: replace "arm: remove muldiv64()"
 target-arm/helper.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/target-arm/helper.c b/target-arm/helper.c
index 7df1f06..4455761 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -12,6 +12,8 @@
 #include <zlib.h> /* For crc32 */
 #include "exec/semihost.h"
 
+#define ARM_CPU_FREQ 1000000000 /* FIXME: 1 GHz, should be configurable */
+
 #ifndef CONFIG_USER_ONLY
 static inline bool get_phys_addr(CPUARMState *env, target_ulong address,
                                  int access_type, ARMMMUIdx mmu_idx,
@@ -678,8 +680,8 @@ void pmccntr_sync(CPUARMState *env)
 {
     uint64_t temp_ticks;
 
-    temp_ticks = muldiv64(qemu_clock_get_us(QEMU_CLOCK_VIRTUAL),
-                          get_ticks_per_sec(), 1000000);
+    temp_ticks = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
+                          ARM_CPU_FREQ, NANOSECONDS_PER_SECOND);
 
     if (env->cp15.c9_pmcr & PMCRD) {
         /* Increment once every 64 processor clock cycles */
@@ -717,8 +719,8 @@ static uint64_t pmccntr_read(CPUARMState *env, const ARMCPRegInfo *ri)
         return env->cp15.c15_ccnt;
     }
 
-    total_ticks = muldiv64(qemu_clock_get_us(QEMU_CLOCK_VIRTUAL),
-                           get_ticks_per_sec(), 1000000);
+    total_ticks = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
+                           ARM_CPU_FREQ, NANOSECONDS_PER_SECOND);
 
     if (env->cp15.c9_pmcr & PMCRD) {
         /* Increment once every 64 processor clock cycles */
@@ -738,8 +740,8 @@ static void pmccntr_write(CPUARMState *env, const ARMCPRegInfo *ri,
         return;
     }
 
-    total_ticks = muldiv64(qemu_clock_get_us(QEMU_CLOCK_VIRTUAL),
-                           get_ticks_per_sec(), 1000000);
+    total_ticks = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
+                           ARM_CPU_FREQ, NANOSECONDS_PER_SECOND);
 
     if (env->cp15.c9_pmcr & PMCRD) {
         /* Increment once every 64 processor clock cycles */
-- 
2.1.0