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Re: [Qemu-devel] [PATCH v3 6/9] arm: clarify the use of muldiv64()
From: |
Peter Crosthwaite |
Subject: |
Re: [Qemu-devel] [PATCH v3 6/9] arm: clarify the use of muldiv64() |
Date: |
Thu, 27 Aug 2015 13:23:56 -0700 |
On Thu, Aug 27, 2015 at 12:33 PM, Laurent Vivier <address@hidden> wrote:
> 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 <address@hidden>
Reviewed-by: Peter Crosthwaite <address@hidden>
> ---
> 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
>
>
- [Qemu-devel] [PATCH v3 0/9] remove useless muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 1/9] i6300esb: remove muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 2/9] rtl8139: remove muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 3/9] pcnet: remove muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 4/9] mips: remove muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 5/9] openrisc: remove muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 6/9] arm: clarify the use of muldiv64(), Laurent Vivier, 2015/08/27
- Re: [Qemu-devel] [PATCH v3 6/9] arm: clarify the use of muldiv64(),
Peter Crosthwaite <=
- [Qemu-devel] [PATCH v3 7/9] hpet: remove muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 8/9] bt: remove muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 9/9] net: remove muldiv64(), Laurent Vivier, 2015/08/27