From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34155) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZZIPa-0004Yi-Jq for qemu-devel@nongnu.org; Tue, 08 Sep 2015 08:54:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZZIPX-0005s2-8T for qemu-devel@nongnu.org; Tue, 08 Sep 2015 08:54:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52629) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZZIPX-0005qF-0m for qemu-devel@nongnu.org; Tue, 08 Sep 2015 08:54:07 -0400 References: <1440703987-29012-1-git-send-email-lvivier@redhat.com> <1440703987-29012-5-git-send-email-lvivier@redhat.com> From: Laurent Vivier Message-ID: <55EEDA6A.3000308@redhat.com> Date: Tue, 8 Sep 2015 14:54:02 +0200 MIME-Version: 1.0 In-Reply-To: <1440703987-29012-5-git-send-email-lvivier@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v3 4/9] mips: remove muldiv64() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, Aurelien Jarno , Leon Alrae ping ? On 27/08/2015 21:33, Laurent Vivier wrote: > Originally, timers were ticks based, and it made sense to > add ticks to current time to know when to trigger an alarm. > > But since commit: > > 7447545 change all other clock references to use nanosecond resolution accessors > > All timers use nanoseconds and we need to convert ticks to nanoseconds, by > doing something like: > > y = muldiv64(x, get_ticks_per_sec(), TIMER_FREQ) > > where x is the number of device ticks and y the number of system ticks. > > y is used as nanoseconds in timer functions, > it works because 1 tick is 1 nanosecond. > (get_ticks_per_sec() is 10^9) > > But as MIPS timer frequency is 100 MHz, we can also do: > > y = x * 10; /* 100 MHz period is 10 ns */ > > Signed-off-by: Laurent Vivier > --- > hw/mips/cputimer.c | 19 ++++++++----------- > 1 file changed, 8 insertions(+), 11 deletions(-) > > diff --git a/hw/mips/cputimer.c b/hw/mips/cputimer.c > index 577c9ae..a74ae5c 100644 > --- a/hw/mips/cputimer.c > +++ b/hw/mips/cputimer.c > @@ -25,7 +25,7 @@ > #include "qemu/timer.h" > #include "sysemu/kvm.h" > > -#define TIMER_FREQ 100 * 1000 * 1000 > +#define TIMER_PERIOD 10 /* 10 ns period for 100 Mhz frequency */ > > /* XXX: do not use a global */ > uint32_t cpu_mips_get_random (CPUMIPSState *env) > @@ -49,9 +49,8 @@ static void cpu_mips_timer_update(CPUMIPSState *env) > uint32_t wait; > > now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); > - wait = env->CP0_Compare - env->CP0_Count - > - (uint32_t)muldiv64(now, TIMER_FREQ, get_ticks_per_sec()); > - next = now + muldiv64(wait, get_ticks_per_sec(), TIMER_FREQ); > + wait = env->CP0_Compare - env->CP0_Count - (uint32_t)(now / TIMER_PERIOD); > + next = now + (uint64_t)wait * TIMER_PERIOD; > timer_mod(env->timer, next); > } > > @@ -79,8 +78,7 @@ uint32_t cpu_mips_get_count (CPUMIPSState *env) > cpu_mips_timer_expire(env); > } > > - return env->CP0_Count + > - (uint32_t)muldiv64(now, TIMER_FREQ, get_ticks_per_sec()); > + return env->CP0_Count + (uint32_t)(now / TIMER_PERIOD); > } > } > > @@ -95,9 +93,8 @@ void cpu_mips_store_count (CPUMIPSState *env, uint32_t count) > env->CP0_Count = count; > else { > /* Store new count register */ > - env->CP0_Count = > - count - (uint32_t)muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL), > - TIMER_FREQ, get_ticks_per_sec()); > + env->CP0_Count = count - > + (uint32_t)(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) / TIMER_PERIOD); > /* Update timer timer */ > cpu_mips_timer_update(env); > } > @@ -121,8 +118,8 @@ void cpu_mips_start_count(CPUMIPSState *env) > void cpu_mips_stop_count(CPUMIPSState *env) > { > /* Store the current value */ > - env->CP0_Count += (uint32_t)muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL), > - TIMER_FREQ, get_ticks_per_sec()); > + env->CP0_Count += (uint32_t)(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) / > + TIMER_PERIOD); > } > > static void mips_timer_cb (void *opaque) >