From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46325) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZULt2-0004lg-Jn for qemu-devel@nongnu.org; Tue, 25 Aug 2015 17:36:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZULsy-0006wP-IU for qemu-devel@nongnu.org; Tue, 25 Aug 2015 17:36:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58742) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZULsy-0006w4-Dx for qemu-devel@nongnu.org; Tue, 25 Aug 2015 17:36:04 -0400 References: <1440535491-4511-1-git-send-email-lvivier@redhat.com> <1440535491-4511-5-git-send-email-lvivier@redhat.com> From: Laurent Vivier Message-ID: <55DCDFC1.2060703@redhat.com> Date: Tue, 25 Aug 2015 23:36:01 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 4/7] arm: remove muldiv64() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Crosthwaite Cc: Peter Maydell , "qemu-devel@nongnu.org Developers" On 25/08/2015 23:11, Peter Crosthwaite wrote: > On Tue, Aug 25, 2015 at 1:44 PM, Laurent Vivier wrote: >> muldiv64() is used to convert microseconds to nanoseconds. >> >> Use qemu_clock_get_ns() instead of qemu_clock_get_us() >> to avoid this operation. >> >> Signed-off-by: Laurent Vivier >> --- >> target-arm/helper.c | 9 +++------ >> 1 file changed, 3 insertions(+), 6 deletions(-) >> >> diff --git a/target-arm/helper.c b/target-arm/helper.c >> index 1568aa6..f5e8fd8 100644 >> --- a/target-arm/helper.c >> +++ b/target-arm/helper.c >> @@ -678,8 +678,7 @@ 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 = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); >> >> if (env->cp15.c9_pmcr & PMCRD) { >> /* Increment once every 64 processor clock cycles */ >> @@ -717,8 +716,7 @@ 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 = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); >> > > The long term goal here was to replace get_ticks_per_sec with a > parameterizable CPU frequency so ideally the math should remain. The > ARM CPU frequency == get_ticks_per_sec is the bigger issue. OK, I will remove this one from the series. Perhaps a comment in the original functions would help to understand what we are doing here... or something like that: #define ARM_CPU_FREQ 1000000000 /* FIXME: should be parameterizable */ #define NSEC_PER_SEC 1000000000 total_ticks = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL), ARM_CPU_FREQ, NSEC_PER_SEC); Laurent > Regards, > Peter > >> if (env->cp15.c9_pmcr & PMCRD) { >> /* Increment once every 64 processor clock cycles */ >> @@ -738,8 +736,7 @@ 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 = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); >> >> if (env->cp15.c9_pmcr & PMCRD) { >> /* Increment once every 64 processor clock cycles */ >> -- >> 2.1.0 >> >>